Add Highway mode to LT1

[NomakeWan]

Cool. Not everyone is looking for that. For ignition there are DIY solutions currently under active development which cost the user $200 or less to go to coil-per-cylinder, and the computer system in $EE is far from inferior. In addition as pointed out in the video I linked at the beginning of this thread the 0411 PCM doesn’t have this function built in either. The way you can do it with an 0411 is the same way you would do it with $EE. And if steveo, kur4o, or any other entrepreneuring individual wished there is the distinct possibility of patching that feature into $EE.

I’m glad you had such good results with your swap. Me personally, I enjoy having invested less than $300 total into tuning two Corvettes. ;)

[Fast355]

Cool. Not everyone is looking for that. For ignition there are DIY solutions currently under active development which cost the user $200 or less to go to coil-per-cylinder, and the computer system in $EE is far from inferior. In addition as pointed out in the video I linked at the beginning of this thread the 0411 PCM doesn’t have this function built in either. The way you can do it with an 0411 is the same way you would do it with $EE. And if steveo, kur4o, or any other entrepreneuring individual wished there is the distinct possibility of patching that feature into $EE.

I’m glad you had such good results with your swap. Me personally, I enjoy having invested less than $300 total into tuning two Corvettes. ;)

Its built into the 0411. It only has to be enabled. I enabled it with HP Tuners. Its also built into the later 2003 1-meg PCM I am running. It was also in the 05 6.0L truck PCM my friend has in his Chevelle.

Just have to change the platform designation to Holden, copy the system options to the Holden line, adjust the lean cruise settings and flash the PCM. I use Write Entire just to make sure the changes are correctly made to the calibration. No custom code work needed. Its already there.

Once it is enabled, the vehicle will command a leaner air/fuel mixture when the parameters are met to enter lean cruise.

[spfautsch]

Its built into the 0411.

That's all well and good, and I've been there and done that on a 0411 equipped vehicle back when gas was $4.50 a gallon. NomakeWan's point is the entry fee to put a 24x based ecu in a gen 2 LT-1 is about $800-$1200 if you're really creative. Considerably more if you want to click the "buy now" button, bolt stuff on and go. To quote facetious Bill Gates from the Simpon's season 8, episode 14, "I didn't get rich by writing a lot of checks".

[steveo]

its weird to pollute a thread about hacking an lt1 with 'just get a better ecm' especially in a forum full of TBI tuners.

isn't this an ecm tuning and hacking forum?

i fully object. beating up old ECMs to do what we want is what we do here.

i call BS that massive torque gains come from an ECM swap. one ECM was just better tuned than the other, that's all that happened there.

[Fast355]

its weird to pollute a thread about hacking an lt1 with 'just get a better ecm' especially in a forum full of TBI tuners.

isn't this an ecm tuning and hacking forum?

i fully object. beating up old ECMs to do what we want is what we do here.

i call BS that massive torque gains come from an ECM swap. one ECM was just better tuned than the other, that's all that happened there.

It was not the PCM swap that gave the gains. It was the coil per cylinder ignition and hotter spark from the D585 coils. The way I had to mount the D585 coils, I even retained the high performance L31 wires. It had Davis Unified stuff on it prior as well. The Davis Unified Ignition stuff had small gains across most of the powerband compared to the stock stuff as well. I put the Davis Unified Ignition stuff on the 305 in my 99 Tahoe after and it ran better as well. With the DUI stuff on the Vortec you can run a 0.060" plug gap vs the 0.035" GM has revised as the spec for the stock ignition. There is a GM TSB stating to close the gap because they found the Vortec engines often misfired with the wider gap. Closing the gap was worth 10 hp on my Express van with the stock ignition.

The newer PCM just operates more quickly and performs more calculations in the same amount of time.

Both the black box and 0411 had good tunes in them. The same timing map and held the same air/fuel ratio. The 0411 had better driveability. They both got the job done. The engine ran and made good power. The 0411 just flat ran better. Adding 8 ignition coils gave the ignition system a boost, resulting in more cylinder pressure and more power. Like starting a fire with a match vs a torch. At higher rpm you get more dwell time to recharge the spark which means hotter spark. Where the single coil drops off, 8 individual coils are still working perfectly. The L31 uses the same coil and module as the later LT1.

[steveo]

oh yeah coil per cylinder is great. im glad you did that for yourself

now lets talk about highway lean cruise on the lt1 again

[Fast355]

oh yeah coil per cylinder is great. im glad you did that for yourself

now lets talk about highway lean cruise on the lt1 again

I am sure some code could be written to easily do it.

However that hotter ignition system I mentioned does wonders in lean cruise. You can run the engine leaner before it starts to misfire. 17:1 air/fuel ratio is misfire free with a hot ignition system. The stock system starts to really struggle around 16:1. You will get alot of misfires and even more partial misfires. Which is why I brought it up in the first place. With the distributor you are also limited in how much timing advance you can run. In lean cruise my engine wants 52° of timing at 2,800 rpm. You are not able to get within 10° of that with a LT1 or L31 distributor because the spark will jump to the wrong cylinder because of rotor phasing. If you cannot compensate for the slower burn you will be losing torque and be shooting yourself in the foot trying to run that lean because you will have more airflow which means more fuel.

[steveo]

theres nothing easy about fundamental fuel system patching. lots can go wrong

just like the tbi engines with lean cruise handle it within reason

by your logic you should swap to direct injection engine that can go even leaner. things have come a very long way since the lt1 came out

i prefer challenging myself with what i have

this guy does too im sure

should he throw a modern ecm on his l98 too?

why dont we all throw our ecms in the garbages and get 0411s?

although you are correct that individual coils are superior to a distributor, you have no idea why we do what we do here, and you aren’t helping this thread at all.

[Fast355]

theres nothing easy about fundamental fuel system patching. lots can go wrong

just like the tbi engines with lean cruise handle it within reason

by your logic you should swap to direct injection engine that can go even leaner. things have come a very long way since the lt1 came out

i prefer challenging myself with what i have

this guy does too im sure

should he throw a modern ecm on his l98 too?

why dont we all throw our ecms in the garbages and get 0411s?

although you are correct that individual coils are superior to a distributor, you have no idea why we do what we do here, and you aren’t helping this thread at all.

I do know what your are doing. I have done code work on TBI ECMs and a little in the TBI PCM as well. I wrote flex fuel code for my TPI years ago. Then ended up swapping it to an 0411.

I also like a challenge. Hence why my Express van did not have a LS but had all the LS management including drive by wire. To add in an even bigger challenge was to base the engine off a L31 and still make head/cam LS power from it.

[Fast355]

Its just hard to ignore the benifits. I tuned a F-car a year or so ago that was 1 meg PCM EFI Connection swapped. We built a custom 4" air induction with a 100mm MAF. The car had a 58mm throttle body and ported intake manifold. Upgraded the springs and put 1.7 rockers on it with guide plates and hardened pushrods. Mid-length headers and a catback. On E85 it made 330 rwhp through a T56 and drove like a new car. With lean cruise on E85 it was still getting 25 mpg.

By that point...Why stop with a direct injected V8. Swap in the new Silverado turbo 4 and that 8 speed automatic. It runs on 2 cylinders on the highway and has good power. It is just begging for a good tune to wake it up too. The turbo 4 cylinder Camaros and Mustangs are out running big block race cars these days.

Even the shared port head 3.6 V6 in the Camaro and Challenger are begging for twin turbos. Single exhaust port heads would be stupid easy to turbo.

Just making a point.

[Fast355]

If you could somehow advance the optispark you could run more ignition advance FWIW. The TPI Corvettes used 6° initial to get to 48° total advance on the aluminum head engines. Distributor is limited to 42° advance.

[kur4o]

Blackbox and 0411 pcm runs the same processors and use almost identical strategies in spark and fuel calculations. So the only difference will be coil on plug and fine tunning with the later code.
Better spark can always increase fuel economy and power.

Lean cruise can be patched easily from the 94 v6 pcm as a template, but I have no interest in doing it.
I don`t see any real gains in fuel economy vs perfectly tuned lt1 engine in closed loop. The most efficient combustion is at stoich where engine makes best power. Leaning the mixture reduce engine power and the map jumps, leading to least efficient engine and you have crap running engine with less power and worse fuel economy.

Not to mention the extra heat produced that put enormous stress on the engine components. Burned valves is usual and not that hard to get a melted catalyst.

I made alot of experiments with a 3.4 camaro running lean cruise. I couldn`t measure any better fuel economy. The overheating catalyst alarm was always on, moving the afr down to 12 to cool down the mixture.

The most important place to tune for fuel economy is the spark advance around on / off idle conditions. The transition must be perfectly dialed.
The other place is the maf pumpshot scalar.
General rule is to tune for higher engine vacuum. More vacuum equals less fuel needed and more power being made.

[Fast355]

Blackbox and 0411 pcm runs the same processors and use almost identical strategies in spark and fuel calculations. So the only difference will be coil on plug and fine tunning with the later code.
Better spark can always increase fuel economy and power.

Lean cruise can be patched easily from the 94 v6 pcm as a template, but I have no interest in doing it.
I don`t see any real gains in fuel economy vs perfectly tuned lt1 engine in closed loop. The most efficient combustion is at stoich where engine makes best power. Leaning the mixture reduce engine power and the map jumps, leading to least efficient engine and you have crap running engine with less power and worse fuel economy.

Not to mention the extra heat produced that put enormous stress on the engine components. Burned valves is usual and not that hard to get a melted catalyst.

I made alot of experiments with a 3.4 camaro running lean cruise. I couldn`t measure any better fuel economy. The overheating catalyst alarm was always on, moving the afr down to 12 to cool down the mixture.

The most important place to tune for fuel economy is the spark advance around on / off idle conditions. The transition must be perfectly dialed.
The other place is the maf pumpshot scalar.
General rule is to tune for higher engine vacuum. More vacuum equals less fuel needed and more power being made.

You do realize that stoich burns at the highest combustion temps. Once you get leaner the EGTs drop. The oil temps and engine temps actually drop as well. In air cooled air plane engines running 50°F lean of peak EGT results in slightly less power, much cooler cylinder temps and several gallons per hour fuel burn reduction. It also generates less carbon. Valves and pistons are not harmed at all. My Express van gets 2 MPG better in lean cruise. My friends 6.0L Chevelle went from 25 to 29 mpg highway and thats with a 4L80E and 4.10s.

[NomakeWan]

Indeed. Lean of peak you should be burning cooler, though ignition advance is certainly a factor to look out for. Fortunately swapping to coils fulfills that, but even stock being able to get a little more out of the engine MPG-wise should be great. We’re only talking about maintaining a fixed speed at fixed load, so we need a fraction of the power the engine could otherwise make. It’s not like we want lean cruise to affect acceleration.

Also I looked into HPTuners; a $300 piece of hardware you need to buy credits for in order to tune with? Yet more unnecessary cost. steveo already put it very well, but let me drill it home with numbers. I bought a $70 cable and am using free-as-in-beer software. For coils I spent $150 total, plus less than $50 for the controller and its associated parts. That is under $300 to be able to do whatever I want with the LT1, plus convert to coil-near-plug. 24X and 0411 and HPTuners is a very expensive proposition to a much simpler problem than you realize.

[LeMarky Dissod]

LT1 Swap to LS 411 pcm

Although the video is 32min long for some reason, the gist of it is:
he converted his OBD1 LT1 into an OBD2 LT1 with a 96/97 front timing cover and added wiring for the OBD2 crank sensor
he repinned his harness into an 0411 pcm
he basically runs his OBD2 LT1 as an OBD2 L31

Of note, both the L31 & the LT1 both need only one coil to run.

In terms of inputs and outputs between the pcm and either engine, the distinctions between an OBD2 L31 and an OBD2 LT1 lack any meaningful differences.

Can't think of a cheaper way to use an 0411 pcm to run an LT1 - even though I'm not as imaginative and resourceful as y'all.

That said, if an OBD1 LT1 pcm can be coerced into reliably exceeding 29 highway MpG in an LT1 Caprice Roadmaster or Fleetwood without hypermiling, I'll be impressed regardless of how it's achieved, in inverse proportion to the cost, and not just because it would be novel.