DIY LTCC or similar system for LT1s

[Fast355]

You are one of the few that had a relatively easy time. There are a lot of pro tuners that have had nothing but headaches. While the conversion isn't overly difficult, getting the tune right can be extremely time consuming. There have been some consistent problems, especially with the LT1/4's. The novice tuner will need some good assistance from those of us that have their stuff dialed in.

Biggest issue I have seen and this was fixing what a "PRO" screwed up was getting the injectors & coils in the right order at the PCM and then correcting the injector bank assignment and firing order in the tune. If you go by a Gen3 wiring diagram on the coils and injectors it will be wrong 100% of the time on a traditional small block. It all has to match or it will run terribly. It also had the left and right o2 sensors swapped and when the PCM tried to go into closed loop, one LT fuel trim went to 125% and the other 75%. Then getting good injector data is a MUST! Finally the trickiest part I have found tuning anything with the Blackbox and the 0411 has to be the way the PCM handles fuel enrichment for AE and the idle air stuff. I have found leaving the tune a little on the rich side helps the driveability tremendously with the bigger cammed setups.

Then again I have tuned far bigger challenges. A 232/240 @ .050 cam cut on a 110° LSA in a heavily modified TPI 383 running the 7730 speed density ECM. That one was fun just to get it leaned out enough so it would idle and you could drive it and tune it.

The LT1 I tuned was a 396 with 42 lb/hr junk bosch injectors and a GM 847 cam. Luckily I had injector data from my buddies 6.0L truck that has the same JUNK bosch injectors in it. The 0411 does not like Bosch injectors much and both still occasionally get codes for open injectors. Moral of the story there don't buy cheap Ebay garbage injectors if you want the thing to run well.

I like the Gen3 PCMs because you can do alot of cool stuff like add an Ethanol Flex Fuel sensor and run anything from straight gasoline to E85 and have the PCM adjust both the spark map and fuel delivery to secondary values you can set. I gained a good bit of power running E85 with no engine changes. The next engine in my Express van will be a 383 in the 11.5:1 range with aluminum heads and run E85 for power. Goal is 500 ft/lbs @ 3,500 from a small block. 383+ moded TPI is how you get there. Should still be able to get 400 hp out of it as well.

[Tom B.]

I agree with you about some of the so called "Pros". As far as the average tinkerer goes, one example for the trials and tribulations of the LT/LS swap that can screw up a tune is the injection timing. Stock LS1 engines have no overlap, LT1's have varying degrees of overlap, if it isn't corrected you get a false rich condition when the engine is actually lean. You have the injectors spraying into an open intake valve while the exhaust valve is still open.
Most novice tuners trying to DIY, wouldn't know that and will be chasing their tail trying to get their VE corrected. This is just a single example, there are many other parameters that need to be addressed. My philosophy is to the best of my ability, to make the car hobby more enjoyable than frustrating for all involved. Sometimes the time and expense of these various upgrades is just not worth doing. Sensible, cost effective solutions on a case basis are usually the best way to proceed.

[Fast355]

I agree with you about some of the so called "Pros". As far as the average tinkerer goes, one example for the trials and tribulations of the LT/LS swap that can screw up a tune is the injection timing. Stock LS1 engines have no overlap, LT1's have varying degrees of overlap, if it isn't corrected you get a false rich condition when the engine is actually lean. You have the injectors spraying into an open intake valve while the exhaust valve is still open.
Most novice tuners trying to DIY, wouldn't know that and will be chasing their tail trying to get their VE corrected. This is just a single example, there are many other parameters that need to be addressed. My philosophy is to the best of my ability, to make the car hobby more enjoyable than frustrating for all involved. Sometimes the time and expense of these various upgrades is just not worth doing. Sensible, cost effective solutions on a case basis are usually the best way to proceed.

The overlap is really a non-issue with these PCMs. I have run the same values on 4 different cams. The factory Vortec 5.7 Express van tune offers a great starting point for most LT1 setups.

FWIW the LS1 engines DO have overlap. It just happens to be at lower valve lifts than the LT.

I see your point though.

I also have a history table I setup to log gms/cyl vs RPM vs KPA and can recreate any Map based spark map in the LS controller. I run a Ramjet 350 crate engine based timing map in my Express van.

[vilefly]

Finding the right chips to talk together is annoying, especially when a toddler is constantly attacking you and your paperwork. I may have to rework a few counting strategies.
LT1_distributor_optical_disk.jpg
My 8 channel analog multiplexer/demultiplexer chip had to be switched to a 16 channel one, due to a different counting strategy. (all low inputs make a count, leaving me with 7 outputs, not 8 to use with my ripple counter) The 24 pin dip version is obsolete and no one stocks it. So, I will use the CD74HCT4067-Q1 chip.
cd74hct4067-q1 pinout.pngcd74hct4067-q1 logic table.png
You can see how I tie in the ripple counter. To the uninitiated, a binary counter turns on certain output pins on the chip to express a number. a 7 would use 3 pins, 1+2+4. So, it should be a small matter to tie the proper value pins together from the counter directly to this chip. (basically, an electronic rotary switch).
I am being attacked again. be back when I can.

[spfautsch]

FWIW the LS1 engines DO have overlap. It just happens to be at lower valve lifts than the LT.

Valve overlap is purely a function of cam timing (lobe separation angle), duration, and lobe ramp rates. You and Tom B should take your LS vs LT p###ng contest elsewhere, it's not contributing to the essence of what the OP is trying to accomplish, which is cooler than you're capable of comprehending.

vilefly: - killer idea. I can't wait to see how it pans out.

[Tom B.]

Hey now! We did get a little off topic for a minute. Anyways, I am committed to help you guys find a good, reliable, economical solution. I'm sure Fast 355 will be just as generous with his time and expertise. (P.S. we know exactly how camshafts function).

[spfautsch]

(P.S. we know exactly how camshafts function).

Then you should know it has nothing whatsoever to do with the engine it's installed in. It doesn't matter how many cylinders there are, if it's an inline or v60 or crossplane v90. In a four stroke engine the intake stroke occurs immediately after the exhaust stroke. End of discussion.

This is a thread discussing the possibility of interfacing a cop setup to a PCM designed for for a distributor. Let's get away from the LS swap economics discussion. The subject has been beaten to death. Let it rest in peace.

[Tom B.]

I will say this once and then I am done with it. Valve overlap has a lot to do with the way it affects how an engine runs. If your position is to the contrary, I can only surmise you are less experienced than some of us that know better. You and I don't know each other or our personal abilities and experience, so lets not to try to play school teacher.
Back to the subject at hand. As far as this project goes, Andy should have the convertor box I sent him dissected in a timely fashion, and he and Vilefly will have a viable solution.