[parish8]

in the LS world it seem like everyone was comfortable in the 11.6-11.8 range.

in the LT world I see some people still at 11.6-11.8 and others that are going all the way up to 12.6-12.8. A guy I know that tunes a couple of cars a day is telling me 12.6-12.8 is what he recommends.

does anyone have any info on this?

on the dyno does it make more power richer or leaner?

how about with low boost levels like below 7psi?

how about on e85, we would have to talk lambda not actual a/f ratio but you know what I am asking?

now on to timing. in the LS world I was always happy to keep my timing around 15deg max and get all the power I wanted with more boost. we tried a little more timing a few times and had issues but the motors always liked more boost. how about the LT motors? what kind of wot timing should we be looking at?

[JoeAyalaM]

The only comment I have seen here on boost tuning is from Ted Janetty, he mentioned in his F.I. Q/A thread, of using a Lambda of 0.8, or 11.76 AFR.

No word on Spark Advance.

Anybody has more info or other recommendations?

[Ryephile]

Typically on DI engines you can run less rich as the chemical quench is much higher at a given lambda than a PFI setup.

For perspective, some VAG engines run Lambda 1.0 100% of operation, however this is a particular application and not going to be smart for a boosted LT1.

In any case, peak torque is almost always between 0.87 and 0.90 lambda, however that's usually only wise on naturally aspirated. Most OEM GDI boosted setups run Stoich at low RPM to increase EGT and get the turbo spooled up, then transition to peak torque around peak BMEP, and then transition to rich (roughly 0.75 to 0.8 lambda) at high RPM for good cooling effect.

My advice would be to look into the lambda the LT4 engine is running, and emulate that, biasing on the rich side for safety.

[Speedy1975]

I don't know about that 12+ AFR and boost. Ted seems to really know his stuff and he said NO WAY, 11.8 is where it's at and I'd trust his judgement.

On timing, that's a more tricky one. Nearly all engines are just that little bit different. Now there may be some base timing that works for 99% of use cases and it's on the uber safe side. However, a custom tune will get the most out of a car.

When we tuned my Challenger, we got the fuel dialed in first and kept he timing VERY low, 10 or 11 degrees. Then we started adding timing a little at a time and monitoring the knock sensors until we found the sweet spot, then backed off .5. I get exactly .5° of STKR in a couple spots at WOT telling me I'm at the right place and the knock sensors are also doing their job.

[JoeAyalaM]

From someone who has tuned many, many boosted LT1s succesfully:

Post cat AFR's usually are 12.0
Spark with good fuel is in the 14-16 range.

[parish8]

Originally Posted by Ryephile

Typically on DI engines you can run less rich as the chemical quench is much higher at a given lambda than a PFI setup.

For perspective, some VAG engines run Lambda 1.0 100% of operation, however this is a particular application and not going to be smart for a boosted LT1.

In any case, peak torque is almost always between 0.87 and 0.90 lambda, however that's usually only wise on naturally aspirated. Most OEM GDI boosted setups run Stoich at low RPM to increase EGT and get the turbo spooled up, then transition to peak torque around peak BMEP, and then transition to rich (roughly 0.75 to 0.8 lambda) at high RPM for good cooling effect.

My advice would be to look into the lambda the LT4 engine is running, and emulate that, biasing on the rich side for safety.

hmm. I have 2 z06 files here. both are 1.16-1.18 gas and 1.15-1.18 alcohol.

1.16 is 12.67 and 1.18 is 12.45. crazy, I didn't expect that. that is about the same as a stock na lt1.

I also looked at a port injected 2010 ctsv and the pe numbers are in the 1.26-1.33 range. much richer. 1.33 is 11.05/1

i am leaning toward coping the z06 table for now. once i get port injection and start turning it up let it go richer.

i would really like to hear some real world testing and reasons why a tuner goes one way or the other with this. maybe i should post up in the jenetty thread and see if he can share any experience.

[parish8]

Originally Posted by JoeAyalaM

From someone who has tuned many, many boosted LT1s succesfully:

Post cat AFR's usually are 12.0
Spark with good fuel is in the 14-16 range.

what would that be no cat?

[JANNETTYRACING]

Originally Posted by parish8

hmm. I have 2 z06 files here. both are 1.16-1.18 gas and 1.15-1.18 alcohol.

1.16 is 12.67 and 1.18 is 12.45. crazy, I didn't expect that. that is about the same as a stock na lt1.

I also looked at a port injected 2010 ctsv and the pe numbers are in the 1.26-1.33 range. much richer. 1.33 is 11.05/1

i am leaning toward coping the z06 table for now. once i get port injection and start turning it up let it go richer.

i would really like to hear some real world testing and reasons why a tuner goes one way or the other with this. maybe i should post up in the Jannetty thread and see if he can share any experience.

When viewing EQ ratio in GM PE tables you must divide that in to the Stoich value.

Stoich values in the E-92 computer is 14.10, taking into account 10% ethanol for the USA, so 14.10/1.16 = 12.15 AFR.

Now if you set you AFR Gauge to 10% ethanol you will see 12.67, Confusing to say the least.

The main reason why I switched over to strictly lambda 1.0 is Stoich for any fuel, .85 for PE on NA cars, and .78 on Boosted cars on pump fuel

I have moved the AFR/Lambda all over the place with the Boosted LT-1 and found .78-.80 to be the Happy Place on pump fuel.

Remember a portion of the fuel is used for cooling especially when boosting on poor quality pump gas.

On Race gas I would be more inclined to run PE at .82 Boosted.

Timing varies widely depending on which F/I you are using and how much boost you are running.

Timing is not a Flat value, it varies with cylinder filling/pressure.

Start low and creep up on it monitoring everything.

Note you can run more timing on a short pull than you can on a long pull.

Ted.

[EFI Tuning]

Great post Ted.

I'll be posting a thread later on today showing the Plex Knock Monitor unit I purchased in action. This is an expensive tool but if you are going to be tuning for FI or N20 it should be part of the arsenal. Once you begin changing things on the engine the factory knock sensors cannot be trusted to be accurate.

As stated... don't use AFR. Switch to...



Tim

[Perdieu]

^^^^^^ lmao nice picture Tim

[parish8]

I use lambda but have to convert it to gas a/f for it to mean anything. Kind of like running he 1/8th mile. I have I convert to a 1/4 to relate.

That being said it appears the factory is commanding .86-.84 lambda and probably getting .86-.84 lambda when running e10 in a zo6. That is at 9.5psi but less compression.

I appreciate the sharing of experience. What diferences are seen between the rich side and lean side? More power rich? Less knock rich?

[JANNETTYRACING]

Originally Posted by parish8

I use lambda but have to convert it to gas a/f for it to mean anything. Kind of like running he 1/8th mile. I have I convert to a 1/4 to relate.

That being said it appears the factory is commanding .86-.84 lambda and probably getting .86-.84 lambda when running e10 in a zo6. That is at 9.5psi but less compression.

I appreciate the sharing of experience. What diferences are seen between the rich side and lean side? More power rich? Less knock rich?

It is really simple you only need to remember 1.0 .85 or .78

Both

[ADM PERFORMANCE]

We also use the plex dual knock canbus system on our dyno and it really tells the truth about LT1 engines timing and Airfuel.

We run 12.9-13.0 on C-16 and 12.6-12.8 on 93 Texas fuel. All readings are before the catalytic.

You can always tell a 91-93 octane tune by how jagged the graph is due to a lower than happy timing map.

Race gas and nice timing make for smooth graph

[Speedy1975]

I'd be curious what Ted thinks about a near 13 AFR. Way different than what I'm accustomed to.