Odd Fire TBI

[Willys43]

1028610287

[dave w]

I wonder about the IAC controls? I'm thinking only one ECM needs to control the IAC.

I wonder about reference voltages, like the 5 volts to the TPS. I wonder what each computer sees for a TPS voltage when the ECM's are tied together?

Do you plan to bench test this setup?

For the bench testing I've done with a 7747, I use an electric drill for spinning the distributor to send a reference pulse to the ECM. When bench testing, I use TunerPro RT to data log so I can play-back the test.


dave w

[lionelhutz]

I'm not sure if you want comments, or just posting because or what, but I see a few things that won't work.

You should use 1 ESC module with the output going to both ECMs. Alternatively, you will need 2 knock sensors if you want to use the 2 ESC modules.

You can't connect both ECMs to the IAC motor. You'll have to let one of them control it.

Your IGN relay is wrong, the pink should be on the right terminal.

You'll need a coolant temp sensor for each ECM.

I believe the TPS and MAP can be shared but I'm not sure you want to connect the sensor 5V terminals together. I think you'll want to use the 5V from one ECM for the TPS and MAP with the common and outputs going to both ECMs.

I highly doubt you can run closed loop which makes the O2 sensors rather pointless. The control loops get out of sync and the one ECM will be adding fuel via one injector while the other is trying to remove it via the other injector causing a big fuel imbalance.

[Willys43]

All constructive comments are appreciated. I would much rather change the schematic then try and diagnose problems. I originally tied all inputs and most outputs together thinking that if one computer has a problem that the other will continue to operate my limp home mode.

[Willys43]

I wonder about the IAC controls? I'm thinking only one ECM needs to control the IAC.

I wonder about reference voltages, like the 5 volts to the TPS. I wonder what each computer sees for a TPS voltage when the ECM's are tied together?

Do you plan to bench test this setup?

For the bench testing I've done with a 7747, I use an electric drill for spinning the distributor to send a reference pulse to the ECM. When bench testing, I use TunerPro RT to data log so I can play-back the test.


dave w
Dave I have the same thoughts about the IAC receiving conflicting instructions from both ECMs, I just hadn't made any decisions. I thought possibly about having separate IAC pigtails coming out of the harness at the IAC. I think bench testing will be a good think to do.

[Willys43]

I'm not sure if you want comments, or just posting because or what, but I see a few things that won't work.

You should use 1 ESC module with the output going to both ECMs. Alternatively, you will need 2 knock sensors if you want to use the 2 ESC modules.

You can't connect both ECMs to the IAC motor. You'll have to let one of them control it.

Your IGN relay is wrong, the pink should be on the right terminal.

You'll need a coolant temp sensor for each ECM.

I believe the TPS and MAP can be shared but I'm not sure you want to connect the sensor 5V terminals together. I think you'll want to use the 5V from one ECM for the TPS and MAP with the common and outputs going to both ECMs.

I highly doubt you can run closed loop which makes the O2 sensors rather pointless. The control loops get out of sync and the one ECM will be adding fuel via one injector while the other is trying to remove it via the other injector causing a big fuel imbalance.

I absolutely want feedback, just be prepared to explain yourself if I don't understand!
OK I'll buy 1 ESC, 1 Knock, and you're correct about the ignition relay pink.
I don't understand the need for 2 temp sensors, or what problem the second 5v ref feed. I have some research to do before commenting on the fueling
Craig

[lionelhutz]

To keep it simple, the CTS is a variable resistance and each ECM passes some current through it to measure the resistance. Add 2 ECMs onto one sensor and the reading will be wrong.

I'm not sure on the 5V but the 5V supply in each ECM may try to fight each other.

[Willys43]

Dave I have the same thoughts about the IAC receiving conflicting instructions from both ECMs, I just hadn't made any decisions. I thought possibly about having separate IAC pigtails coming out of the harness at the IAC. I think bench testing will be a good think to do.
Dave I will bench test a TPS and a MAP by putting a single reference voltage on it with a meter on the return "b" and see what the computer sees, then with two meters, then I'll do the same with 2 voltage reference voltage and see what the difference might be.
Craig

[Willys43]

That makes sense, I'll add a second
Craig

[Willys43]

Does anybody know how the ESC module works and what the knock sensor acually does electrically?

[Willys43]

Lhutz, after reviewing your comment on the dual 02 sensors I believe that for odd fire fuel delivery that both sensors are needed and I don't see any concern for any fuel imbalance, and I believe that each ECM should go into closed loop when all conditions are met. I also believe that your concerns are valid if I were planning on even fire fuel delivery, then only one would be needed, since only one ECM would be handling the fuel delivery using two injectors.As far as the MAP, TPS and ETC are concerned, they are all variable resistors, if one of them can be read properly by both ECMs I would assume that all 3 three could. The key word is assume. I'll bench test to find out.Craig

[Willys43]

I wonder about the IAC controls? I'm thinking only one ECM needs to control the IAC.

I wonder about reference voltages, like the 5 volts to the TPS. I wonder what each computer sees for a TPS voltage when the ECM's are tied together?

Do you plan to bench test this setup?

For the bench testing I've done with a 7747, I use an electric drill for spinning the distributor to send a reference pulse to the ECM. When bench testing, I use TunerPro RT to data log so I can play-back the test.


dave w

Dave, if I understand the 5 volt reference correctly, it is actually an output signal sent to the sensors, that signal is modified by a variable resistor in the sensor, then that modified signal is what the computer reads and bases it output to the other output devices. IOW the ECM reads the "B" terminal on the MAP and the TPS, then it uses the info from the sensors and the programming in the ECM to calculate how long of an injector pulse is needed in order to supply correct amount of fuel.

[lionelhutz]

The dual O2 with both ECMs in closed loop would work if the O2, ECM and injector are all used on one bank. I doubt it will work if the manifold is open so both injectors feed both banks or the runners in the manifold crossover so each injector feeds cylinders on both banks. Possibly, it would work using one O2 so both ECMs see the same rich or lean signal but not likely with dual O2 sensors in different locations where each O2 reads the fuel from the other ECM's injector.

Yes, all the sensors are variable resistors but the MAP and TPS are 3-wire which means they produce a varying output voltage. The CTS sensor is 2-wire meaning the ECM has to measure it's resistance. They're not the same thing.

The knock sensor is basically a piezoelectric microphone and the ESC takes it's AC signal and produces a DC signal to send to the ECM when there is knock. Hence using one knock module to feed one ESC module to feed both ECMs.

[Willys43]

After thinking about how the IAC actually works I think that it could be possible to leave both ECMs hooked up to the IAC and have it work. At best it would be an assumption and trying to bench test it would be close to impossible, also it would be less complicated using one ECM controlling the idle. I'll change the IAC control to the primary ECM.

[lionelhutz]

Yes, do it that way. The ECM keeps track of the IAC position so having 2 ECMs on the same IAC will unsync the IAC from the position each ECM thinks it is at. That is assuming both ECM's can move it at the same time. Drive both coils at the same time and it won't even move.

[1project2many]

Actually, only one ECM should control the IAC. ECM gets no feedback about IAC position. It only knows what it has commanded for counts. A sticking or unresponsive IAC or in this case, and ecm sending opposite commands, will cause the IAC to move out of synchronization with the ECM's expected position.

I do not believe I would use only one 5V line. However, the resistance type sensors are part of a resistor network with a terminating resistor in the ecm. Adding a second terminating resistor can alter the total current through the sensor and therefor the voltage reading at the ecm. There are a few people that have published the results of trying to use dual pcm's. I can remember one individual using a 7749 for engine control and a 7427 for trans control in a Syclone and I seem to remember some sensor had to be duplicated. I'll have to see if I can find the information he posted.

The stock dual plane manifold is divided left and right bank. Each side should have it's own injector. I would expect no trouble with individual bank fuel trim. What would be interesting to me is, after enough time tuning, if VE and/or spark tables end up slightly different between L and R banks.

[Willys43]

Actually, only one ECM should control the IAC. ECM gets no feedback about IAC position. It only knows what it has commanded for counts. A sticking or unresponsive IAC or in this case, and ecm sending opposite commands, will cause the IAC to move out of synchronization with the ECM's expected position.

I do not believe I would use only one 5V line. However, the resistance type sensors are part of a resistor network with a terminating resistor in the ecm. Adding a second terminating resistor can alter the total current through the sensor and therefor the voltage reading at the ecm. There are a few people that have published the results of trying to use dual pcm's. I can remember one individual using a 7749 for engine control and a 7427 for trans control in a Syclone and I seem to remember some sensor had to be duplicated. I'll have to see if I can find the information he posted.

The stock dual plane manifold is divided left and right bank. Each side should have it's own injector. I would expect no trouble with individual bank fuel trim. What would be interesting to me is, after enough time tuning, if VE and/or spark tables end up slightly different between L and R banks.

i am going to use 1ECM for the IAC control, but I wonder about feedback. If there is no feedback why does each winding in the IAC have its own return wire back to the ECM instead of sharing 1 Wire. We all know that the GM doesn't add unnecessary wires if they can get by without it. Just think how much money they can save by deleting that wire.(Hah).As far as getting the proper sensor reading I'm going to bench test them all and verify that the readings are within the required parameters for proper ECM operation.
Craig

[Willys43]

Here are a couple of questions I have.
1. Does the ECM read sensor voltage or current
2. Why does the MAP and the TPS have the extra ground wire
3. Which way does the current flow thru the CTS/ECT? Neg to Pos? What should the resisted value parameters be?
4. I have read there is a 5 volt ref signal output from ECM to ECT, but that doesn't make sense to me. I Am unaware of how the ECM would be able to read the resisted value

[Willys43]

1P,
Thought you might be interested to hear the even bank went dead again. I checked the spark with the timing light and still had good clean spark, on the even wires. I went and got the pump spray bottle with gasoline and shot a couple of pumps into even bank of carb, "Viola" the even bank runs again. I went and ordered a carb kit cause something is plugged up tight.
Craig

[1project2many]

Here are a couple of questions I have.
1. Does the ECM read sensor voltage or current
2. Why does the MAP and the TPS have the extra ground wire
3. Which way does the current flow thru the CTS/ECT? Neg to Pos? What should the resisted value parameters be?
4. I have read there is a 5 volt ref signal output from ECM to ECT, but that doesn't make sense to me. I Am unaware of how the ECM would be able to read the resisted value

1) ECM will monitor voltage.
2) Extra? Both of those sensors can be thought of as potentiometers. The 5V reference is "split" between ground and the signal wires. When the resistance between the signal wire and power is high, the signal voltage is low. When resistance between 5V and signal is low, signal voltage is high. Open the ground circuit and the signal line will go to near 5V.
3) Hmmm... Current always flows from negative to positive (although many of us were taught otherwise in school). There are charts on the internet and in the factory service manual which match up resistance to temperature.
4) The ecm reads the voltage on the positive wire to CTS. As the resistance through the sensor changes so does the voltage between the supply line and ground. Both the two and three wire sensors require a roughly equivalent strategy for the ecm to detect voltage sensor. The temp sensor is only two wires due to the nature of the sensor.


If there is no feedback why does each winding in the IAC have its own return wire back to the ECM instead of sharing 1 Wire.
The ecm needs to be able to switch the direction of current flow through each coil in order to make the motor work in both directions.


Just think how much money they can save by deleting that wire.
They've gone to low voltage for many circuits today and tried to combine as many control circuits as possible with CAN communications. They're running things so tight that we see problems with terminal overheating and connector failure when a component draws just 2-3A over specification!



I went and ordered a carb kit cause something is plugged up tight.
That there is some baaad luck.

[Willys43]

1) ECM will monitor voltage.
2) Extra? Both of those sensors can be thought of as potentiometers. The 5V reference is "split" between ground and the signal wires. When the resistance between the signal wire and power is high, the signal voltage is low. When resistance between 5V and signal is low, signal voltage is high. Open the ground circuit and the signal line will go to near 5V.
3) Hmmm... Current always flows from negative to positive (although many of us were taught otherwise in school). There are charts on the internet and in the factory service manual which match up resistance to temperature.
4) The ecm reads the voltage on the positive wire to CTS. As the resistance through the sensor changes so does the voltage between the supply line and ground. Both the two and three wire sensors require a roughly equivalent strategy for the ecm to detect voltage sensor. The temp sensor is only two wires due to the nature of the sensor.


The ecm needs to be able to switch the direction of current flow through each coil in order to make the motor work in both directions.


They've gone to low voltage for many circuits today and tried to combine as many control circuits as possible with CAN communications. They're running things so tight that we see problems with terminal overheating and connector failure when a component draws just 2-3A over specification!



That there is some baaad luck.
It's what you get buying something that has been sitting for five years

[Willys43]

That's what you get when you buy a 72 year old vehicle with a 54 year old engine that's been sitting in abarn for 5 years. Almost 0 rust, I'll fix the problems. I don't think I've ever seen a potentiometer that wasn't sitting on a metal frame, that's why I didn't understand the extra wire, and the voltage split.

[Willys43]

Couldn't the ECM reverse the direction of current flow even if the windings had a common ground?
Is the 5 volt ref positive or negative?
If car mfg is anything like building construction the standards have changed so much in the past 30 years? Because of better and more engineering the the materials we used keep getting lighter and lighter yet carrying the same load.

[1project2many]

I don't think I've ever seen a potentiometer that wasn't sitting on a metal frame, that's why I didn't understand the extra wire, and the voltage split.
http://fddrsn.net/pcomp/examples/potentiometers.html
Potentiometer and description of operation. A would be 5V, B would ground, W would be connected to the signal.
This is exactly what a TPS is. For basic understanding you can think of a MAP as being the same thing.


Couldn't the ECM reverse the direction of current flow even if the windings had a common ground?
Yes, it could be done that way with added complexity. GM has chosen to isolate both ends of the stepper motor coil.


Is the 5 volt ref positive or negative?
It is positive.


Because of better and more engineering the the materials we used keep getting lighter and lighter yet carrying the same load.
Exactly. The 2015 and up F150 is primarily aluminum.


That's what you get when you buy a 72 year old vehicle with a 54 year old engine that's been sitting in abarn for 5 years.
If that's the only surprise then you've got a good rig.

[Willys43]

That's how I thought they worked for allowing the signal voltage, I just didn't realize that the remainder of the ref voltage went to ground. That was an excellent description. What confuses me is that the direction of current travel seems backward.
Is the W - or +?

[delcowizzid]

may i ask why 2 ecus as far as i know there is a buick oddfire hei type reluctor dizzy availiable that could run the gm 8 pin ignition module and one ecu

[1project2many]

What confuses me is that the direction of current travel seems backward.
Is the W - or +?

Well, now, that's a fine question. The ecm measures between W and GND so the voltage it sees will never be negative. But it could look negative if you measure between 12V and W. This measurement would show higher resistance if the wiper is at the +5V side of the pot, and it would show a full 12V when the wiper goes to ground.


why 2 ecus as far as i know there is a buick oddfire hei type reluctor dizzy availiable that could run the gm 8 pin ignition module and one ecu

oddfire engine has unequal pulse times between cylinders. ECM calculates rpm based on number of cylinders and time between reference pulses. Varying time between pulses would work out to rapidly increasing and decreasing RPM.

[Willys43]

"Look negative" wow that's loaded. I thought the ECM measured between W and the 5 volt ref? If the ECM measures between W And Ground, why the ref voltage.

Delco,
If you'll look at the Willys43 introduction thread, you will see how and why we ended up with 2 ECMs
Craig

[1project2many]

If the ECM measures between W And Ground, why the ref voltage.

Measuring between REF and GND gives a "known" or reference voltage. Second measurement between W and GND gives signal voltage. Then ECM can be programmed with max and min allowed values so if signal = REF or signal = GND a code is set.

[Willys43]

OK, then is the ref signal basically for comparison purposes to allow the ECM to calculate a corrected voltage for when then system voltage varies?

[dave w]

Best method to measure voltages / current / resistances, is with a test bench setup.:thumbsup:

dave w

[Willys43]

I agree Dave, test bench is built and wired, I just have to double check the wiring, and get it hooked up to a computer and I off and running. Actually it will probably be off and crashing at first, but I'll get thru it. Even wilth a test bench understanding what your seeing can be pretty confusing at times.
You did a write up on VE tables, how will I have to adjust mine, going from a 4.3 6 Cyl to a 3.2 dual ECM 6 Cyl? Set each ECM for a 1.6 3 Cyl ?

[lionelhutz]

I'll write about the TPS. The TPS is basically a potentiometer. The 5V reference is used so there is a constant fixed voltage for the sensor. That way, when the TPS is at 1/4 travel the output voltage is exactly 1.25V, when the TPS is at 1/2 travel the output is exactly 2.5V and when the TPS is at 3/4 travel the output is exactly 3.75V. Well, theoretically anyways.

It's be much harder to use these sensors if the reference voltage wasn't a fixed voltage. Say you tried to just use the battery voltage. Well, that can vary 1-2V and also contains all the switching noise and alternator ripple and other stuff such as that which means you have to constantly try to filter and correct for those variations. So, regulate it down to 5V and filter it so you have a nice steady voltage for the sensor and then you can just read the sensor output and know what it means without worrying about the reference voltage fluctuating. Same reason a dedicated negative wire is run from the sensor back to the ECM. It eliminates system noise and chassis ground connection issues. You'll see that the early systems used the exhaust system for the negative of the O2 sensor and then later systems used a dedicated wire and that change would have been for the same reason.

[Eds]

Craig, Anything new with your project? Hope things are moving forward.

[Willys43]

Hi Eds,
Things are still moving forward, I'm working on the test bench with dual computers, I've eliminated a few bugs, burned a couple of chips, and now I'm working on data logging so I can check to see if the ECMs are getting the same, correct signals from the sensors. This stuff is all new to me so it takes awhile to figure it out.
Craig

[Willys43]

It looks like everything is working right. TPS,MAP,ETC signals look good. Both computers are outputting spark signals and injector signals. I'm unable to tell if the spark and injector signals are staggered from even to odd cylinders because they're too close together. The RPMs look right. I am able to create and flag errors by manually varying input signals. Fuel pump relay works properly. Computer seems to be adjusting the timing. Guess maybe it's time to start setting up the harness I'm gonna use.

[Six_Shooter]

I also have to question the dual ECMs...

You're just setting yourself up for a world of hair pulling nightmares trying to run two ECMs on a single engine. As Delcowizzid was saying there's an HEI module that already does everything you need in sending puleses at corrected times to the ECM, while providing the oddfile spark.

Another, better option than going dual ECM is to go to an aftermarket ECM that WILL run oddfire, such as a Megasquirt. You'll spend less money and time in the end just going with something that will be known to work than trying to make some frankenstein of a mishmash of parts to get something that will likely only work marginally at best.

Like has been said, the closed loop fueling will be fighting each other. unless each bank is COMPLETELY isolated from one another, and treated as two separate engines, no no chance of fuel that is commanded by one ECM ever being read by the O2 sensor feeding the other ECM.

Regarding the IAC, yes, one ECM will control it, and you only want one ECM to control it, however, the ECM that has no IAC connected will not like that very much when it commands an idle speed change and doesn't see it. Keep in mind that just because both will be the same ECM and will have the same BIN file does not mean that they will be in sync, that would take communication between them, which is not possible, since they were not designed with that in mind.

The only successful dual ECM applications I have seen are where each bank or sets of cylinders have been completely isolated from each other in both fuel delivery AND spark, where each section was connected as it's own independent engine that just happens to share a common crank with another engine. Trying to split the ignition control like this will just be a night mare.

[1project2many]

It looks like everything is working right. TPS,MAP,ETC signals look good. Both computers are outputting spark signals and injector signals. I'm unable to tell if the spark and injector signals are staggered from even to odd cylinders because they're too close together. The RPMs look right. I am able to create and flag errors by manually varying input signals. Fuel pump relay works properly. Computer seems to be adjusting the timing. Guess maybe it's time to start setting up the harness I'm gonna use.

Congratulations! I think you'd need a scope or another tool to display the spark signals and be able to tell if they're spaced appropriately. But if they're coming from different pickup coils then they should be timed differently. Have you made any changes to the calibration yet? Like changing the number of cylinders in the chip?

Any pictures?


unless each bank is COMPLETELY isolated from one another, and treated as two separate engines
There are several technical reasons why this is being treated as two separate engines on a common crank. If you are interested, they are here (http://www.gearhead-efi.com/Fuel-Injection/showthread.php?5267-Willys43).

[Willys43]

Right now they are firing off of the same pickup coil that has had 3 points of the 6 pickup points ground off. Basically a 3 cylinder engine. The odd cylinder Chip is programmed for 3 cylinders at 0 degrees base spark. The even cylinder chip is programmed for 3 cylinders with 90 degrees base spark advance. The base BPW has been reduced from 181 down to 135. The Bin is from a 4.3, the 198 fireball is a 3.2 which is 25% smaller. I decreased th BPW from 181 x .75 to get to BPW of 135. If the single pickup doesn't work I'll take the factory pickup coil out and put two pickup coils in at 45 degrees. Anything else you can think of that I will need to change in the programming for start up? I'll post up a couple of pictures, it's kinda messy because I rolled up wires and tied them instead of cutting the longer wires I may need.

Six, I really really really like the last line on all of your posts��

[Willys43]

103911039210393
Here are 2 pictures of my test board, The throttle body has been removed because it just sitting loose, and one picture of the adapter I have to make for the throttle body.

[Six_Shooter]

I'm all for oddball things, but somethings you just need to step back and look at and realize that they just aren't worth the hassle.

I'm sure you get the engine to run, but I see it being severely limited in the way it performs. It'll be a nightmare to tune, dual emulators would help there, which I know works for Nissan applications, but not sure if there's anything special in the XDFs to allow for that, or if you just need to enable the setting in Tuner Pro. I'm still not sure why you wouldn't just try using a single ECM on your engine and see how it runs before complicating things. The magic of oddfire happens in the ICM, not the ECM.

[Willys43]

[Partial QUOTE=Six_Shooter;58697] but I see it being severely limited in the way it performs. It'll be a nightmare to tune[/QUOTE]
Six, I would really like to see some documentation that supports this statement.

[Willys43]

Here are some pictures of a two computer harness ready for installation onto the Willys. I will cut and solder the wires on the engine side after they are properly routed and connected so the lengths will be right, and I'll wrap them up after its up and running to make sure I haven't left anything out. I used a donor harness out of a late 80's full size Astro van, retaining the factory grommet shown in the middle picture.
. 104621046310464

[Willys43]

I wonder about the IAC controls? I'm thinking only one ECM needs to control the IAC.

I wonder about reference voltages, like the 5 volts to the TPS. I wonder what each computer sees for a TPS voltage when the ECM's are tied together?

Do you plan to bench test this setup?

For the bench testing I've done with a 7747, I use an electric drill for spinning the distributor to send a reference pulse to the ECM. When bench testing, I use TunerPro RT to data log so I can play-back the test.


dave w
The bench testing worked slick, Both ECMs "see" the same voltage from the 5v reference and the sensors provided the same out put with one or two ECMs hooked up, except for the ECT which required two sensors.

[Six_Shooter]

There's no real documentation for dual ECMs like you're trying to do. The only dual ECM engines I know of run each half of the engine COMPLETELY independent of one another. The ONLY common part is the crack, which each half of the engine just happens to share. Those ECMs are also designed with this setup in mind. The ECMs you are using are not.

On the bench is one thing, where signals and conditions are perfect, it's a very different thing on a running engine where syncing of each set of cylinders will a nightmare.

What you're trying to do is just over complicating the situation simply for the sake of over complicating it.

I ask again; Why have you not tried to use a single ECM? I think you'll be pleasantly surprised that it will likely work right with the right ignition module that takes into account the odd fire.

As I have already said the ECMs will not be in sync and when one ECM, sees an out of spec condition it will throw a code, our worse go into LHM. It won't take much for this to happen, a simple command in idle RPM change that it's not seen will cause the ECM to start doing other things, like changing spark timing to further compensate, which will then make the engine fight itself.

I just think you're over complicating what needs to Hadrian and there are far better ways to put EFI on an odd fire engine.

[lionelhutz]

The only way a singe even fire ECM could work on an odd fire engine is by not doing timing with the ECM. I this this has been well established.

[Six_Shooter]

Well established by whom? There are (single) ECMs that will run an oddfire engine without issue, definitely in the aftermarket, and I'm sure the same could be done with an OEM ECM as well with the right ICM set-up... If I cared enough about injecting an oddfire engine I think I'd use an 8 cylinder reluctor (or how ever many it would take to get even pulses between firing events), so that the pulses were even and just used the dizzy cap towers that are needed for the engine to run. Boom, one ECM, even pulses for the ECM to read, and odd fire at the ignition with timing control. Yes the RPM will read a bit high, but with a simple edit of the ADX it could be made to show accurate. No sync issues between ECMs, no ECM trying to control something it can't or isn't connected to and throwing a fit.

I'm sure I could come up with a more elegant way if I really wanted to as well. Actually that more elegant way would be an ECM that will run an oddfire engine natively without any trickery, save the headaches.

[fastacton]

I'd have to agree with Six_Shooter on this. I don't see why an odd-fire HEI distributor (which I understand is based on a V8 HEI with two dummy posts and a 6 point reluctor) couldn't be used along with a 7 or 8 pin ignition module to run TBI fairly easily. I'm relatively sure I've read about this being done on another forum. If I had an odd-fire motor here, I'd certainly give it a try. Has anyone here actually tried this?

[lionelhutz]

Odd fire V6 firing angles as you go through 720 degrees of crank revolution firing the 6 cylinders
0 90 240 330 480 570 720

Even fire V8 crank angles as you go through 720 degrees of crank revolution firing the 8 cylinders
0 90 180 270 360 450 540 630 720

As you can see, only the first 2 ignition events of the V6 engine fall at the same crank angles as the V8 engine. Hence, the V8 even firing 90* angle reluctor will not work on this engine. Period. End of story. Well established by the almost 40 years history of the engine.

[fastacton]

So, for the odd-fire HEI, they must have used a V8 sized distributor, but with a more specialized reluctor and distributor cap. What were the results when someone tried to use a 7 or 8 pin module and a TBI setup?

[1project2many]

The ignition module does not care what engine it is used on. It's not the problem. In bypass mode it only knows pulse out, pulse in. The problem is how the ecm interprets signals from the ICM. The code is built around the idea that the distributor pulses are equally spaced in time, and that the amount of time between pulses represents RPM. When the time is changing rapidly the ecm will calculate rapid increases and decreases in RPM. Since the odd-fire pickup coil pulses are unequally spaced to match the odd-fire firing intervals, the time between pulses will be unequal. This is not the best solution to deliver accurate ignition timing. It is possible to use a single stock ecm with odd fire. But it would require custom code and a cam position sensor. Most folks are not ready to write custom code. IMO the dual ecm solution is not a bad one.

I know of a couple of successful dual ecm project vehicles. Way back in the DIY-EFI days an individual known as "TedSCJ" used dual 7730's on a Jag V12. Following that, a member of DIY-EFI and the SyTy community piggybacked a 7749 and a 7427 in a Syclone in order to use a 4L60E. Although both solutions seemed less than ideal, they still worked. Both applications used similar combinations of shared sensors. MAP, TPS, and REF can be shared but two wire passive resistance sensors such as CTS and IAT cannot as the resistor network it creates changes the voltage the ecm will see.

The odd fire engine did use a V8 cap but it only had six terminals. Two of the six terminals had "long" contacts on the rotor side. They extended through the area where the missing V8 terminals would normally be. That was the only way to ensure spark reached the correct cylinder without making a completely new cap.

[lionelhutz]

What were the results when someone tried to use a 7 or 8 pin module and a TBI setup?

I've never read about anyone trying it, but it wouldn't work because the ECM would have a hard time figuring out the rpm and the timing advance would be completely out of whack.

[fastacton]

I've never read about anyone trying it, but it wouldn't work.

Sometimes theory and math don't prove out in the real world. Based on what 1project2many explained about the time between pulses being how RPM is calculated (I didn't know that), it might not work very well. But without actually testing it, I wouldn't write it off completely.

[lionelhutz]

Sometimes theory and math don't prove out in the real world. Based on what 1project2many explained about the time between pulses being how RPM is calculated (I didn't know that), it might not work very well. But without actually testing it, I wouldn't write it off completely.

Sigh, this was discussed multiple times already...

The ECM takes the reference pulse from the previous cylinder and adds a time equal to the correct crankshaft rotation to fire the next cylinder. All the GM even fire ECM's do this by delaying the ignition signal to the ICM by either (90*-advance*) or (120*-advance*) of delay after each reference pulse.

I'll try to make a simple timeline of how a V8 engine works for you to understand this. Assume the base timing is set to 0* and the ECM is currently running the timing at 25* BTDC.
0* -> ICM sends #1 reference pulse to ECM.
65* -> ECM has taken #1 reference pulse and added the delay to send pulse to ICM to fire the coil for #8.
90* -> ICM sends #8 reference pulse to ECM.
155* -> ECM has taken #8 reference pulse and added the delay to send pulse to ICM to fire the coil for #4.
180* -> ICM sends #4 reference pulse to ECM.
245* -> ECM has taken #4 reference pulse and added the delay to send pulse to ICM to fire the coil for #3.
270* -> ICM sends #3 reference pulse to ECM.
335* -> ECM has taken #3 reference pulse and added the delay to send pulse to ICM to fire the coil for #6.
etc, etc

See how the firing of each cylinder is based off the reference pulse for the previous cylinder? Now, can you get why it won't work? Even if the ECM can somehow interpret the ICM pulses and calculate rpm correctly, the delayed pulses it sends back to the ICM to fire the coil will result in completely wrong timing advance. The odd fire with a combination of 90* and 150* will simply be completely off.

[Willys43]

Sometimes theory and math don't prove out in the real world. Based on what 1project2many explained about the time between pulses being how RPM is calculated (I didn't know that), it might not work very well. But without actually testing it, I wouldn't write it off completely.

At least 1 megasquirt system has a software provision for "degrees of offset" for odd fire engines, GM never fuel injected an odd fire engine, Tunerpro doesn't have any provision for offsetting ignition firing. I'm kinda cheating using a second ECM using the Base timing in tunerpro to offset the ignition for 3 cylinders by 90*. The Ecms are using some shared sensors only to try and provide the same signals to both ECMs in order to produce similar output. I could have used two complete sets of sensors, I just didn't see the need. If need be I can change 1 wire and run the all fuel off of one ECM. If this works I will have gained tremendously over an aftermarket system, simply because I have GM's programming for a 90*V6 engine. The aftermarket requires borrowing someone elses programming or starting from scratch. I'm using 6 cylinder odd fire HEI with three pickups ground off, feeding two 8 pin modules. Each module supplies 1 ECM with distributor pulses. 1 ECM is set to 0* base timing, 1 is advanced 90* base timing, which creates the odd fire timing. It ought to work, time will tell.

[1project2many]

At least 1 megasquirt system has a software provision for "degrees of offset" for odd fire engines

Is there a cam sensor or synchronizing sensor involved?

[Willys43]

Is there a cam sensor or synchronizing sensor involved?
Crank trigger, cam sensor, either or both, it looks to be software selectable, it is software selectable for 2 or 4 stroke, or rotary, 2,3,4,5,6,8,12,16 Cyl, 7 or 9 Cyl radial. It looks to be able to work with any brand vehicle while leaving vehicle OEM ECM in place, tons of features, it does have some base programs. It has a 300 hundred page manual. Specified not for street, probably because of emissions. It looks really sweet, I'd love to play with one. List price $1200. That price would total the Willys.

[Six_Shooter]

That sounds like the MS3Pro, which while it is a great system, is the most expensive version and is WAY overkill for any TBI set-up. An MS2 will have more than you need, but I think is the cheaapest MS that will run odd-fire. MS2 systems can be had for about $300 from diyautotune.com.

[1project2many]

I learned that Maserati's approach to odd fire was to use dual coils connected to a single distributor. The 225 will likely never see the same RPM as the Maserati and will likely never have a dwell issue. But we have a solution should there be a need for 5k+ rpm revs in the old Willys.

It appears the MS2 code can use an option bit for odd fire engines and a user entered value for "small angle" to help differentiate the pulses. However, this solution is not universal. Several posters on the msextra board used dual pickups in a single distributor and a special input mode in MS that took the input from the dual pickups. One poster even ran dual MS systems.

GMECM's actually average the crank pulse signal some. It may be possible to rewrite the GM code so it will do the same. There are also changes needed to the dwell computation to account for small / large time variations. I suppose we could determine a window of time representing maximum possible engine acceleration and determine that any substantial change in time less than that window must represent the switch from "large" to "small." It would follow that the next pulse is a "small" to "large" transition. I really wish I had time to play with this stuff. It would be an interesting excercise.

[Willys43]

That sounds like the MS3Pro, which while it is a great system, is the most expensive version and is WAY overkill for any TBI set-up. An MS2 will have more than you need, but I think is the cheaapest MS that will run odd-fire. MS2 systems can be had for about $300 from diyautotune.com.
It is the Ms3Pro, I didn't see any documentation for odd fire in the other models, but that doesn't mean it isn't supported. I think the Ms3 pro is primarily directed at racing. Cool system.

[Willys43]

I learned that Maserati's approach to odd fire was to use dual coils connected to a single distributor. The 225 will likely never see the same RPM as the Maserati and will likely never have a dwell issue. But we have a solution should there be a need for 5k+ rpm revs in the old Willys.

It appears the MS2 code can use an option bit for odd fire engines and a user entered value for "small angle" to help differentiate the pulses. However, this solution is not universal. Several posters on the msextra board used dual pickups in a single distributor and a special input mode in MS that took the input from the dual pickups. One poster even ran dual MS systems.

GMECM's actually average the crank pulse signal some. It may be possible to rewrite the GM code so it will do the same. There are also changes needed to the dwell computation to account for small / large time variations. I suppose we could determine a window of time representing maximum possible engine acceleration and determine that any substantial change in time less than that window must represent the switch from "large" to "small." It would follow that the next pulse is a "small" to "large" transition. I really wish I had time to play with this stuff. It would be an interesting excercise.
It's not even a 225, it's a 198 Fireball, just too damn cool to throw out. I checked my gear ratio chart and the highest RPM I used was 4000 to get 82 mph, which it will never see with this nut behind the wheel. I'm going to try to use two ign modules and 1 HEI coil and see if it will work. Do you think I'll have a dwell issue? I thought dwell was adjust in respect to fuel burn time in each Cyl rather than when the Cyl burns it(odd fire). The Odd fire HEI distributor didn't have any provision for adjusting the dwell,(outside of the initial setting). Please shed some light on this. While reading in the MsPro manual I found a very good explaination of IAC stepper motor operation, I understand the 4 wire system now.

[Six_Shooter]

It is the Ms3Pro, I didn't see any documentation for odd fire in the other models, but that doesn't mean it isn't supported. I think the Ms3 pro is primarily directed at racing. Cool system.

Yes it is, I have one sitting here to go into a friend's car where we're replacing the FAST system that never worked right. The engine in s a built Pontiac 496. We're also going from TBI to MPFI.


It's not even a 225, it's a 198 Fireball, just too damn cool to throw out. I checked my gear ratio chart and the highest RPM I used was 4000 to get 82 mph, which it will never see with this nut behind the wheel. I'm going to try to use two ign modules and 1 HEI coil and see if it will work. Do you think I'll have a dwell issue? I thought dwell was adjust in respect to fuel burn time in each Cyl rather than when the Cyl burns it(odd fire). The Odd fire HEI distributor didn't have any provision for adjusting the dwell,(outside of the initial setting). Please shed some light on this. While reading in the MsPro manual I found a very good explaination of IAC stepper motor operation, I understand the 4 wire system now.

Dual ICMs and single coil will not work. Keep in mind how a coil is triggered. The negative side of the primary is held low to charge the coil and sparks on the secondary when that signal is removed. Using dual ICMs in the way you propose will cause the negative to always be held low or possibly spark at the wrong time. Shortening dwell (which is not something normally supported in tuning software for GM ECMs) MIGHT make it work ok, but as the RPM rises I see it being more of an issue. This is one of the big reasons why I've been saying stay away from the dual ECM route. You need two completely separate ignition systems, and isolate the fuel and air intake of each sets of cylinders COMPLETELY to make this work, like I said treating it like two completely independent engines that happen to share a common crank.

To even give it a chance of working you will need two coils and a dual coil isolator (usually found in endurance and NASCAR racing}. The isolators are usually used to switch from one ignition system to another in the case of an ignition failure situation, but I don't see why it can't be used with two active ignitions systems.

[1project2many]

Dual ICMs and single coil will not work.
They should as long as RPM isn't too high. Minimum angle between cylinders is 90 degrees just like a V8. Six cylinder dwell is 30-35 degrees so if spark advance is limited to 30-35 degrees max I would not expect a problem.


two coils and a dual coil isolator
Years ago I tried to build a non-computerized HEI for high RPM use. I used a high voltage diode in each coil wire. Each coil was controlled by an independent HEI module connected to a four cylinder pickup coil. It seemed to work ok.

[Willys43]

It started this morning. Yehaaaa. Hittin on all six

[skandolis]

what route did you end up taking?

[Willys43]

Two 1227747 (tel:1227747) computers, both modified for chip flashing, one controlling odd # cyls and IAC, initial spark set to 0* in computor, the other one controls even # cyl without IAC, with initial spark set to 90*, 1 odd fire hei distributor with three of six pickup points ground off, 2 ignition modules, all shared sensors except engine temp and O2 sensors

[dave w]

Two 1227747 (tel:1227747) computers, both modified for chip flashing, one controlling odd # cyls and IAC, initial spark set to 0* in computor, the other one controls even # cyl without IAC, with initial spark set to 90*, 1 odd fire hei distributor with three of six pickup points ground off, 2 ignition modules, all shared sensors except engine temp and O2 sensors

:wtg:

dave w

[lionelhutz]

:thumbsup::thumbsup:

[1project2many]

Congratulations!!! How long before you can start driving and tuning?

[Willys43]

Congratulations!!! How long before you can start driving and tuning?
2nd fuel regulator is bad, 11lbs. New adjustable regulator due in about Wed or Thur. Hope to try driving maybe this weekend. I'd hate to proceed knowing the fuel pressure was marginal.

[dave w]

I'm curious about your data logging and tuning plans? Identical VE Tables in both '7747's? Identical Spark Table in both 7747's? Two Laptops with two ALDL cables? One Laptop with two TunerPro RT sessions running?

dave w

[skandolis]

Very interested, lots of cool factor. what's the firing strategy,IE: will tach signals be right? is three cylinder firing possible on 7747? curious to learn how those things are gonna share fueling/mapping. I love oddball stuff, especially bringing it into the modern age........ :thumbsup:

[Willys43]

Im planning on staying with idntical tables, spark and ve. The laptop i have isnt much. I'll start without the ability to compare one ecu to the other. The harness has an extra injctor wire in it so I can change 1 wire and run both injectors off the same ecu if nescesary. I'm probably just going to drive the same route twice and log both just for grins and see what I get. Really accurate comparison isnt it? I lke the idea of 1 laptop, 2 cables, running to copies of Tunerpro RT. I just hate to buy another laptop. I could tune it ith 1 ECU controlling the fuel the prgram both ECUs the same and switch the injector back. Actually I don't think it should matter much which way I do it.

[Willys43]

Very interested, lots of cool factor. what's the firing strategy,IE: will tach signals be right? is three cylinder firing possible on 7747? curious to learn how those things are gonna share fueling/mapping. I love oddball stuff, especially bringing it into the modern age........ :thumbsup:
Tach signal is picked up off of the distributor which still has six pulses so i think it will work. 1227747 ECU is software programmable for 3 cyl engine. I am using mapping for a stock 4.3. My 198 is a 3.2 which is almost exactly 74% of a 4.3 so I've reduced the base fuel pulse width of the 4.3 to 74%. It starts and I haven't got the foggyest idea what will happen next. Time will tell.

[lionelhutz]

It starts and I haven't got the foggyest idea what will happen next.

I love the 1 step at a time approach. No matter what system you're working with you've got to get it running before you can worry about doing anything more. It's the only way to learn and you're doing a good job on such an oddball system.

[Six_Shooter]

I'm curious about your data logging and tuning plans? Identical VE Tables in both '7747's? Identical Spark Table in both 7747's? Two Laptops with two ALDL cables? One Laptop with two TunerPro RT sessions running?

dave w

Two sessions of Tuner Pro is possible, but not connected to two separate devices from each session. Only one session at a time can be connected to external hardware. This can be a bit annoying when you are trying to connect with a second session and forget that the first session is still "connected" (hardware not released) when trying to quickly switch back and forth. This goes for both emulation and datalogging. Got caught on that one a few times. :/

There is dual emulator support for in TunerPro RT used with Nissans that use split VE tables, but not sure if that is locked to Nissan applications or not. Whole tables should be uploaded to both Ostrichs, but Mark (that writes TunerPro) would know better how it's configured. But by the time you buy two Ostrich 2.0s and get everything set up, a Megasquirt 2 that will natively run an odd fire engine would be more cost effective and work better in the end. *shrug* '7747s are not known for high speed calculations, so staying in sync between a pair of them I still believe is going to be an issue when the engine gets some load on it.

[1project2many]

I love the 1 step at a time approach. No matter what system you're working with you've got to get it running before you can worry about doing anything more. It's the only way to learn and you're doing a good job on such an oddball system.

Agreed. Getting it to run is a good plateau to rest on. Fuel pressure at 12-13 psi is good. I'd aim for as much common ground between the two systems as possible. Do you have the info to change the number of cylinders to three? I can dig that up...

[dave w]

Agreed. Getting it to run is a good plateau to rest on. Fuel pressure at 12-13 psi is good. I'd aim for as much common ground between the two systems as possible. Do you have the info to change the number of cylinders to three? I can dig that up...When I change the cylinder select value, Hex address 0016 changes. I think changing the Hex value to 03 would be the correct value?

See attached screen shot for an example of a 3 cylinder BPW (1.9 liters is half of a 3.8 liter V6 / figuring two 45 lb TBI injectors).

dave w

[1project2many]

knumcyl is a divisor and lower number of cylinders results in a higher value. Three cylinder is 96d or 60h.

[dave w]

knumcyl is a divisor and lower number of cylinders results in a higher value. Three cylinder is 96d or 60h.Interesting; see attached.

dave w

[Willys43]

Well gents I have never been able to stabilize the secondary computor. I finally abandoned the spark control and put an HEI dist with mechanically advanced spark. Starts and runs, first time every time.

[dave w]

Thanks for the update.:thumbsup:

dave w

[1project2many]

Interesting to note. Are you talking about the AFR? Or the spark timing?

[Six_Shooter]

Interesting to note. Are you talking about the AFR? Or the spark timing?

It's been a while since I read about the physical connections in this thread, but IIRC he was using one ECM for both spark and fuel and the second ECM for spark only. I can see how keeping the second ECM in sync would be an issue, especially where spark timing is so critical. fuel could literally be dumped in at pretty much any time, especially when it comes to TBI fueling and still run without a noticeable issue... *shrug*

[Six_Shooter]

Well gents I have never been able to stabilize the secondary computor. I finally abandoned the spark control and put an HEI dist with mechanically advanced spark. Starts and runs, first time every time.

Have you tried swapping ECMs from "main" to "secondary" and visa-versa to see if it's an ECM issue?

[Willys43]

There secondary computor didnt have the ability to advance the spark 90 degrees even though the software would let you change the field to 89.65 degrees. The original schematic was incorrect. Only 1 ignition control module can be used. I could get 1 or 2 sparks out of the second computor then nothing. Changing cyl count to 3, and reducing fuel bpw to 137 resultd in 50% of required fuel. Using cyl count of 6 th fuel pulse of once per rev reduced fuel pulse to every other rev- 50% short. Fuel was still immaterial since I only had sprk on 1,3,5. Excellant excercise, project wasn t completed the way iI had hoped, but I have learned enough that I will never have a problem diagnosing Efi systems. Willys is running very well with 4.3 bin with bpw reduced to 137, havn t even logged it yet. That will come in time. Thanks for ll your help!

Craig

[Six_Shooter]

I thought you were using dual triggers and dual ICMs? That would mean that you wouldn't need to change the trigger angle, because the ECM wouldn't know about the other ECM controlling the other 3 cylinders.

If you were trying to trigger two ICMs off a single trigger, yeah that wouldn't work, because of a lack of isolation between the inputs causing them to interfere with each other.

[Willys43]

I thought you were using dual triggers and dual ICMs? That would mean that you wouldn't need to change the trigger angle, because the ECM wouldn't know about the other ECM controlling the other 3 cylinders.

If you were trying to trigger two ICMs off a single trigger, yeah that wouldn't work, because of a lack of isolation between the inputs causing them to interfere with each other.


I was using single trigger and dual ICM. The reason twoICM wouldn't work is becuse the ICM provides a continuos path to ground except when it breaks that ground to cause the coil to fire. Two ICMs, each breaking the ground path to fire the coil at 90 spread = a continuos ground path and no break in the ground. When I removed one ICM I had fire at 1,3,5 and a couple 2,4,6, then nothing at 2,4,6. Two triggers set at 90* might work for the spark, then the fueling is still gonna be goofier than I wanted to bite into.

[Willys43]

I just walked outside, 11 degrees in KC, willys started 1st attemp. I still havent changed any programming

[jschatte]

old thread I know, but its the closest I could find to a potential project I want to pursue. Hopefully some of you guys are still around!

I am looking to do an EFI conversion to a Delorean. Odd-fire 90deg V6, with mechanical fuel injection.
I am very experienced with LS swaps, especially the 0411 ecu.
I intially wanted to run spark and fuel, but it seems obvious to me that spark is not going to work. I am fairly confident I can just leave the stock distributor, coil, and ignition module in place and ignition will be sorted. Works for the carb conversion guys.
So with regards to the fuelling. Run a 2001 or 2002 s10 or similar 4.3 calibration on a 0411. I would retrofit a crank position sensor (3 tooth), as well as all the other sensors (MAP, MAF, CTS, IAT, IAC, TPS, O2s) and plumb in injectors in place of the old mechanical ones. i would omit the cam position sensor as I understand this is solely for use with the ignition side of things.

From here, I have a few concerns.
-How well will the ecu work without any ignition being involved? Will it be ok with omiting this after i clear all the codes?
-Will the ECU fire sequentially or in batch? It needs to fire batch as I understand or anything past the first two cylinders in the firing order will not get fuel when they need. i could perhaps only wire up injectors to the first two outputs, but I think it would be asking too much of the drivers.
-Finally, a much smaller concern, do the 4.3 calibrations have e-fan control.

I know I could easily use a MS2, but the idea of having a MAF based, fuel trim enabled setup with OBD2 support is all too enticing to me.

[1project2many]

I have not tried to operate an OBDII controller without spark. With no further information I would suspect the spark outputs will not affect fuel outputs. Batch fueling is the default when the CAM sensor signal is not present. the ECM number chosen could determine whether or not electric fans are an option.

So:
Disable all transmission codes.
Disable any ignition output codes.
Disable any misfire codes.
Disable any catalytic converter codes.
Disable any Post Cat O2 codes.
Set cam signal codes to "Type C" or "Type D" to ensure batch fire becomes active.
Ensure injectors are correct type and set flow accordingly
Set cylinder volume accordingly.
Adjust fuel delivery during priming, cranking, and low speed operation

I would expect to tune the speed density tables as they are used for cranking and low speed engine operation and may be used for acceleration enrichment. You may need to adjust the MAF transfer curve to provide optimum performance.

It is possible to use a 16197427 OBDI ecm with MAF if you use modified code. Maybe that is not a useful alternative?

[jschatte]

I have not tried to operate an OBDII controller without spark. With no further information I would suspect the spark outputs will not affect fuel outputs. Batch fueling is the default when the CAM sensor signal is not present. the ECM number chosen could determine whether or not electric fans are an option.

So:
Disable all transmission codes.
Disable any ignition output codes.
Disable any misfire codes.
Disable any catalytic converter codes.
Disable any Post Cat O2 codes.
Set cam signal codes to "Type C" or "Type D" to ensure batch fire becomes active.
Ensure injectors are correct type and set flow accordingly
Set cylinder volume accordingly.
Adjust fuel delivery during priming, cranking, and low speed operation

I would expect to tune the speed density tables as they are used for cranking and low speed engine operation and may be used for acceleration enrichment. You may need to adjust the MAF transfer curve to provide optimum performance.

It is possible to use a 16197427 OBDI ecm with MAF if you use modified code. Maybe that is not a useful alternative?

I have since tested a P01 with a v6 calibration on the bench and even without a cam sensor it still fires sequentially.
I gave up and ran a microsquirt.

[1project2many]

Interesting. Factory service literature says otherwise so thanks for the feedback. I don't blame you for stopping the fight.