Using a 0411 PCM to run a TBI?

I know this is very redneck, arguably, lazy way to do a setup, but it also has to do with what I have laying around. With all the fantastic work that has been done on LSDroid, I think the usability of the LS1 PCM could be further exploited. My theory is, that one could modify a TBI distributor to work as a crank sensor. I know you wouldn't have a cam sensor, but I don't think that you would need it either. As for injectors, my thought is to wire up 1 of the TBI's connected to half of the injectors, with the other TBI connected to the other half. Spark would be handled by using the old vortec engine distributor config (already an option in the LS OS).

Would this work? Please throw stones about things I haven't thought about. I have no problem with using all the existing tooling to scan and re-burn chips, but was hoping that this option might be more appealing to those with old TBI engines.

Your kinda late to the party.

Dual trigger (cam / crank) '0411 low resolution distributor.

EIGHT Injectors REQIRED!

dave w

Attachment 15690

Attachment 15691

dave,

That looks pretty slick. Is there no way to keep the TBI injector setup? I know the performance of the TBI is not the greatest, but was hoping for a more "bolt on" setup. There was a guy over on the EFILive forum who rigged up a 0411 to run a 4 cylinder engine by not connecting 1/2 of the injectors. Believe he also just turned off the codes for those injectors, and it seemed to work.

Looking at the TBI wiring diagrams, it looks like the very important crank sensor signal actual comes from the spark module. I think it is called "reference" on the TBI diagrams and comes in on pin B5. Does anyone know what this signal looks like? is it 5V? 12V? Square wave?

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Originally Posted by turbo_bu

dave,

That looks pretty slick. Is there no way to keep the TBI injector setup? I know the performance of the TBI is not the greatest, but was hoping for a more "bolt on" setup. There was a guy over on the EFILive forum who rigged up a 0411 to run a 4 cylinder engine by not connecting 1/2 of the injectors. Believe he also just turned off the codes for those injectors, and it seemed to work.

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It might be possible to use the '0411 with TBI, but seem highly illogical to me. It might be more logical to replace the 2 injector TBI system with an 8 injector TPI / MPFI system using a "Bolt On" dual trigger distributor.

Perhaps the Learning Curve investment for LS Droid is better spend on an 8 injector TPI / MPFI system?

dave w

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Originally Posted by turbo_bu

Looking at the TBI wiring diagrams, it looks like the very important crank sensor signal actual comes from the spark module. I think it is called "reference" on the TBI diagrams and comes in on pin B5. Does anyone know what this signal looks like? is it 5V? 12V? Square wave?

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The attached picture is NOT a TBI computer! TBI computers use an identical ignition module system.:thumbsup: The attached picture shows the ignition module converts the distributor pickup coil AC signal to a DC square wave. The voltage is likely less than 5 volts. The ECM is using the DC square wave FREQUENCY as a RPM reference.

Attachment 15693

dave w

Thanks for sharing that excellent diagram of whats going on with the ignition control module. I realize that it is not a TBI computer, but I am just hoping to figure out what signals are going into / coming out of the TBI ECM. If I can figure out what it uses, then maybe I can determine if there is a way to make a 0411 work with those existing signals.

The TBI reference signal looks very similar to what the crankshaft sensor would put out. The first question that comes to mind is voltage. The 0411 uses a 12 volt hall effect sensor for the CKP. The ignition module most likely is only kicking out a 5 V signal. I went ahead and fired up my 0411 bench PCM and modified my CKP signal from 12 volts to 5 volts. Lo and be hold, the PCM still was able to show a meaningful RPM signal when it was getting only a 5 V square wave! This is promising.

I guess the next thing is to figure out is what kind of signal a 0411 uses to control spark .... I kind of understand how it does the coil packs, but never looked into how it is used on the old 5.7 vortec engines with distributors. Did those engines still have some form of ignition control module? I know that they had actual crank and camshaft sensors.

Here's a pic of the module and coil used on the vortec engines.

do you happen to have a wiring diagram for this setup?

I'm sure I do somewhere lol but will take less time to find via google. :thumbsup: 1996-1999 truck 5.7L and 7.4L

Other challenges of reverse engineering a '0411 / TBI system include:
Low impedance injectors (TBI) vs. high impedance injectors (native to the '0411).
Injector firing, TBI injectors are firing every Distributor Reference Pulse (DRP) vs. '0411 firing injectors sequentially using the cam position sensor to signal when #1 cylinder is at TDC.
The '0411 Spark Tables (low octane / high octane / optimal) bases timing on grams per second flow (from the MAF sensor) vs. RPM. The TBI spark table timing is Kpa (MAP Sensor) vs. RPM's.

I'm not against the R&D developing an '0411 / TBI system. I'm challenged with the effort vs. net gain?

I wonder about the possibilities using an '411 with the 8 injectors and dual trigger distributor, see pic below.
https://www.ebay.com/p/11017003857
https://www.enginemaster.com.au/prof...fuel-injection
dave w

Attachment 15721

Found a copy of the ignition wiring diagram over on lt1swap.com. Guess now I just need to get my head wrapped around what kind of signals are being sent to / from the different type of ignition modules. I am optimistic that GM didn't change things too much.

dave - I don't deny that your method would be more ideal, I am just trying to make something work. You can blame it on my mind wandering too much these days, and the fact that I have an old 91' TBI engine still running the stock ECM. This combined with me playing with / having the 0411 stuff laying around, and it makes me wonder if I could just do a quick and dirty swap. I have swapped other LS stuff, so I am familiar with making the 0411 stuff work in standalone-ish type environments. Granted this was done using my EFILive ... but that learning has shown me how to dig into the OS, and doing CAX's for things not supported.

As for the fueling side, I understand the differences between high / low impedence and am familar with how the TBI fueling works compared to say a Vortec / LS. My hope is that an old school method of either adding resistors in series would suffice, or maybe just wiring 4 of the injectors together into one of the TBI injectors would also work.

The different tables / maps are not a big deal. The 0411 can be made to work in SD mode. Yes, the tables are little goofy if you haven't worked with them before, but its not a show stopper.

I did some more thinking on the fueling part. With no cam position sensor, the 0411 will be in batch fire mode. This means that it will try to fire each bank 1 time in 2 crankshaft revs. To get more pulses, I was thinking about hooking up an injector from each bank to the same TBI injector. Not ideal, but would at least get you 2 pulses ever 2 revs instead of just 1 pulse in 2 revs. I believe that the TBI system is designed to do 8 pulses in 2 crankshaft revs, but need somebody to confirm this.

Does anyone know if hooking up the injector wires to the same TBI injector will cause any issues? The plan would be to solder in resistors to compensate for low impedence TBI injectors.

This isnt going to work for a number of reasons. The biggest obstacle, the TBI injectors are low impedance. The 0411 injector drivers are high impedance only.

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Originally Posted by mecanicman

This isnt going to work for a number of reasons. The biggest obstacle, the TBI injectors are low impedance. The 0411 injector drivers are high impedance only.

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Put 4 high impedance injectors in parallel and check the ohms :thumbsup: More importantly is that they are not driven peak and hold method but saturated circuit. Maybe that can be changed in the software, never looked or cared, lol.