Need help with 383 TBI

[1project2many]

There are notes that instruct the user to make a change to the conversion math. You can use those notes to make sure the math in your file is set up for zero degrees distributor angle.

There are two values that need to be set for your engine, Initial Advance and Injector Flow. Initial Advance: After loading A217 $0D TP5 v250.adx into your definitions menu, and opening, go to the Acquisition menu and open Edit Definition. Click on the + sign beside the word Values. An expanded menu will open. Drop down and click on Spark Advance. Then click on the Conversion tab at the bottom of the screen. Next click on the Set button at the top and change the last number in the equation to the Initial Spark Advance. This can be found at 4133 in the bin file. The Initial Spark Advance should match the advance set at the distributor. This will correct the Spark Advance display. If you decide to leave this as is, then you will need to add the appropriate amount of Spark Advance to the displayed amount when viewing, as the definition is set-up for 0 Initial Advance

[Hellbilly]

There are notes that instruct the user to make a change to the conversion math. You can use those notes to make sure the math in your file is set up for zero degrees distributor angle.

Thanks! I missed that, somehow, I'll check it out this evening

[Hellbilly]

I cant figure out the ignition issue... when it first starts up the advance is normal. As it starts to warm up and lower RPM, it starts flashing back and forth between normal and over 23000 degrees advance. By the time it gets up to normal temp, it never shows a normal advance. I've tried replacing distributor with the one out of my old engine and also the original coil. I've reburned chips, even tried the original calibration with nothing changed except engine constants. I checked for spark at each cylinder, and put fresh plugs in. I'm running out of ideas. When it shows a normal advance value, it runs pretty decent, but once the advance goes haywire, it starts missing and backfiring if you try to give it throttle to fast or Rpm go above 3000. Both the old, Known good parts and the brand new parts act the exact same way. I do have a knock sensor fault but I think it might be the wrong one... if you look it up on Summit, it shows like 3 different ones and doesn't say what the difference is. I can swap that out with my old one but I don't see a knock sensor causing this problem. I can try another temp sensor, but temps seem to be working correctly. No other data is going haywire like advance is so I'm at a loss with what would cause this. The PCM shouldn't even be able to calculate that range, right?

[Hellbilly]

These are the files I'm using
383 4.9 timing 79Fuel.adx

383 start up.BIN
Advanced [ATTACH=CONFIG]18867[/ATTACH]D TP5 v251.xdf
383 4.9 timing 79Fuel.adx

[Fast355]

I cant figure out the ignition issue... when it first starts up the advance is normal. As it starts to warm up and lower RPM, it starts flashing back and forth between normal and over 23000 degrees advance. By the time it gets up to normal temp, it never shows a normal advance. I've tried replacing distributor with the one out of my old engine and also the original coil. I've reburned chips, even tried the original calibration with nothing changed except engine constants. I checked for spark at each cylinder, and put fresh plugs in. I'm running out of ideas. When it shows a normal advance value, it runs pretty decent, but once the advance goes haywire, it starts missing and backfiring if you try to give it throttle to fast or Rpm go above 3000. Both the old, Known good parts and the brand new parts act the exact same way. I do have a knock sensor fault but I think it might be the wrong one... if you look it up on Summit, it shows like 3 different ones and doesn't say what the difference is. I can swap that out with my old one but I don't see a knock sensor causing this problem. I can try another temp sensor, but temps seem to be working correctly. No other data is going haywire like advance is so I'm at a loss with what would cause this. The PCM shouldn't even be able to calculate that range, right?

What you are seeing is the result of a bad mathematical equation in the scanner definition file. It is a known issue that has been floating around for a while. When you are seeing that 23000 value the commanded timing is actually negative. Nothing is wrong with the actual PCM, distributor or anything like that. A knock sensor fault can cause the PCM to command less timing. Most modified engines are going to run like poop if the timing is negative.

[Hellbilly]

What you are seeing is the result of a bad mathematical equation in the scanner definition file. It is a known issue that has been floating around for a while. When you are seeing that 23000 value the commanded timing is actually negative. Nothing is wrong with the actual PCM, distributor or anything like that. A knock sensor fault can cause the PCM to command less timing. Most modified engines are going to run like poop if the timing is negative.

Ok, that makes sense I guess. I'll get the knock sensor taken care of and see what happens.

[Fast355]

Ok, that makes sense I guess. I'll get the knock sensor taken care of and see what happens.

Given that the PCM has to be able to make the engine knock to test the knock sensor, I am not sure I would mess with it yet. Those non swirl port aluminum heads need a good chunk more timing than the stock cast iron swirl ports. I would start with putting an appropriate advance curve in the engine.

[Hellbilly]

Given that the PCM has to be able to make the engine knock to test the knock sensor, I am not sure I would mess with it yet. Those non swirl port aluminum heads need a good chunk more timing than the stock cast iron swirl ports. I would start with putting an appropriate advance curve in the engine.

Maybe I haven't drank enough coffee yet. If the knock sensor fault is going to cause PCM to pull timing, which it has been showing 4-5* knock retard at any given RPM, then what is adding timing to the main spark table going to do?
Just trying to understand this better before I go mess with it, because there's obviously something I'm missing or don't understand (that I thought I knew lol).

[Fast355]

Maybe I haven't drank enough coffee yet. If the knock sensor fault is going to cause PCM to pull timing, which it has been showing 4-5* knock retard at any given RPM, then what is adding timing to the main spark table going to do?
Just trying to understand this better before I go mess with it, because there's obviously something I'm missing or don't understand (that I thought I knew lol).

It may sound crazy, but you can actually get spark knock from having too little timing. Less timing causes the engine to run hotter, especially the cylinder heads, which can actually lead to more real knock.

Years ago before I was tuning, I put a TBI setup on top of a 305 that had 601 casting non swirl port heads on it. To get it to run well on the stock TBI tuning took 10* initial advance at the distributor. The swirl port heads have a drastically different burn rate than any other head. They burn more quickly than even Vortec heads. Those aluminum heads will want at least 30* of timing in my experience and maybe as much as 34-38*. The calibration for the TBI heads might have 20-24* of timing at high rpm and actually goes negative in places from the factory. Too little timing can cause drivability issues not limited to overheating, no power, backfiring into the intake and more. Best to get the timing curve closer to where you need it to be then work on fueling. Timing changes will affect the fueling on a speed density system anyway. I broad brush more fuel into the tune to make sure there is enough fuel, let the 02 sensors trim out what is not needed while tuning the VE tables.

I have a feeling you will also likely have to lie to the computer on injector size. You have an engine that is probably capable of more than 100% VE near peak torque. You will need to tell the computer that the injectors are smaller than they actually are to get the pulsewidth up enough to be able to control the fuel with the VE table. VE table maxes at 100%.

[Fast355]

Those AFR Enforcers are the same Chinese casting that I had LLoyd Elliot port for my 11:1 383 in my Express van. I am very familiar with the timing they require and can give you a few points to work the timing table around. On 91 octane this is where I am.

Idle 16-18*

Cruise timing @ 50 kpa
RPM Advance
1200 27
1600 31
2000 32
2400 33
2800 35
3200+ 37

WOT 90-100 KPA (remember the stock PE adder adds 2-4* to the main timing table)
RPM Advance
800 6
1200 14
1600 19
2000 24
2400 27
2800 28
3200+ 29

Moderate throttle 75 KPA
RPM Advance
800 8
1200 14
1600 20
2000 24
2400 27
2800 29
3200+ 29

[Hellbilly]

It may sound crazy, but you can actually get spark knock from having too little timing. Less timing causes the engine to run hotter, especially the cylinder heads, which can actually lead to more real knock.

Years ago before I was tuning, I put a TBI setup on top of a 305 that had 601 casting non swirl port heads on it. To get it to run well on the stock TBI tuning took 10* initial advance at the distributor. The swirl port heads have a drastically different burn rate than any other head. They burn more quickly than even Vortec heads. Those aluminum heads will want at least 30* of timing in my experience and maybe as much as 34-38*. The calibration for the TBI heads might have 20-24* of timing at high rpm and actually goes negative in places from the factory. Too little timing can cause drivability issues not limited to overheating, no power, backfiring into the intake and more. Best to get the timing curve closer to where you need it to be then work on fueling. Timing changes will affect the fueling on a speed density system anyway. I broad brush more fuel into the tune to make sure there is enough fuel, let the 02 sensors trim out what is not needed while tuning the VE tables.

I have a feeling you will also likely have to lie to the computer on injector size. You have an engine that is probably capable of more than 100% VE near peak torque. You will need to tell the computer that the injectors are smaller than they actually are to get the pulsewidth up enough to be able to control the fuel with the VE table. VE table maxes at 100%.

Thanks for the detailed info. I guess I was being conservative when I tried adding timing, because of knowing the knock sensor not working, was scared of hurting it that way. I'll go over what you've said and try to come up with something. I've never started this from the ground up and guess I didn't expect it to be that far off from a stock calibration. Live and learn I guess.
I really appreciate the help man. I'll try to get back on here tonight with an update

[Hellbilly]

ok, so after a little playing around, the truck actually makes enough power to drive... not WOT yet or anything crazy. I'll try to put the file and log here if anyone wants to look at it and make suggestions. its obviously gonna be way off in some areas still

[Fast355]

ok, so after a little playing around, the truck actually makes enough power to drive... not WOT yet or anything crazy. I'll try to put the file and log here if anyone wants to look at it and make suggestions. its obviously gonna be way off in some areas still

I adjusted the whole spark map, brought down the injector size to give you more room in your VE table. Should get it more to drink with the injector size being programmed smaller. As such I roughed in a VE table that is smoother than a plateau of 100%. I also disabled the EGR since the AFR Enforcers do not have EGR passageways to feed the valve.

Test carefully while listening for audible pinging.

[Fast355]

I just noticed something else. Is your distributor set at 5* BTDC with the EST wire disconnected? That is what the Initial Timing Value is set at in your .bin file and I did not alter it.

[Fast355]

If your distributor is at 5* BTDC use the one above, if it is at TDC or Zero, use this one. Having the initial value in the BIN not matching your initial value at the distributor, offsets the timing advance by that amount. They should match.