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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
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.
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.
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.
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
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.
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
That makes sense, I'll add a second
Craig
Does anybody know how the ESC module works and what the knock sensor acually does electrically?
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
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.
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.
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.
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.
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
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
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
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.Quote:
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.
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!Quote:
Just think how much money they can save by deleting that wire.
That there is some baaad luck.Quote:
I went and ordered a carb kit cause something is plugged up tight.
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.
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.
http://fddrsn.net/pcomp/examples/potentiometers.htmlQuote:
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.
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.
Yes, it could be done that way with added complexity. GM has chosen to isolate both ends of the stepper motor coil.Quote:
Couldn't the ECM reverse the direction of current flow even if the windings had a common ground?
It is positive.Quote:
Is the 5 volt ref positive or negative?
Exactly. The 2015 and up F150 is primarily aluminum.Quote:
Because of better and more engineering the the materials we used keep getting lighter and lighter yet carrying the same load.
If that's the only surprise then you've got a good rig.Quote:
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.
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 +?
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
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.Quote:
What confuses me is that the direction of current travel seems backward.
Is the W - or +?
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.Quote:
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
"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
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.Quote:
If the ECM measures between W And Ground, why the ref voltage.
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?
Best method to measure voltages / current / resistances, is with a test bench setup.:thumbsup:
dave w
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 ?
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.
Craig, Anything new with your project? Hope things are moving forward.
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
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.
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.
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?Quote:
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.
Any pictures?
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.Quote:
unless each bank is COMPLETELY isolated from one another, and treated as two separate engines
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
Attachment 10391Attachment 10392Attachment 10393
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.