Is stock tune "safe" (not optimized) with mild bolt-ons ?
 

Is the stock tune “SAFE” (not optimized) with mild bolt-ons based upon the following.

I understand with a tune you can get rid of CEL, AFM, set thermostat parameters, optimize fuel and advance etc., but I don’t have any of those issues.
The stock tune goes into COT which dumps fuel and causes extreme rich conditions....so don’t most tuners actually lean the fuel…gaining a few hp in the process.
The stock tune has relatively mild ignition advance setting and a really fast timing retard for knock for protection....so don't most tuners actually advance the timing....gaining a few hp in the process.

What am I missing….as far as a stock tune being “safe” (not optimized) with bolt-ons?

My mods are - CAI Halltech/TRIC, ported TB/snout/blower, main cat delete pipes, Corsa X, 170 F thermostat, inter cooler 1.7 gal extra tank, 2.30” upper pulley, Aeroforce Tech Interceptor gauge with O2 wideband (right bank 18” from exhaust manifold)

With 93 octane and Lambda set for 14.7:1, I have read the following AFR versus RPM on the street recording with the Interceptor gauge;
2nd gear – 12.7 (2,600 rpm) down to 11.2 (5,500 rpm) spinning
3rd gear – 12.1 (4,300 rpm) down to 10.6 (6,200 rpm)
4th gear – 10.6 (5,200 rpm) down to 10.1 (6,200 rpm)

Notes –
I drive the car very easy with occasional street hits and 1/8 mile runs when I use Torco Accelerator.
I have stock MPSS tires so it spins pretty easy which should help save the transmission.
It is almost as if some GM engineer threw us a bone with the COT so we could mod without a tune....
Hit me with your best shot…I’m ready to take a beating on this one.

Whenever you increase airflow to an engine, you should absolutely get a calibration to adjust for fuel. Letting the stock ECU try to deal with it is a bad idea.

:iagree:

Once you add a pulley and more boost, it would be MUCH safer to help out the computer and add some additional fuel, that's what we did....
Yes, your A/f does not look bad, but most would say you have to tune. I would certainly get on a dyno asap, see what a/f looks like there if you have not already...'

I really had NO choice on my 2017, the tune is not as forgiving as the 15 & 16s...

All we really did was add fuel, we did not change timing or take away the safety features built into the tune. I also run Torco and Meth, car runs GREAT!!!

"All we really did was add fuel, we did not change timing or take away the safety features built into the tune."



Where did they add fuel? My stock tune is pig rich within 1 second once WOT. Run 14.2-15.1 down the road at 23 mpg....

The only mod you did that intrigues me and the fact you ran with a stock tune is the upper pulley. There are a lot of owners that have (CAI, Ported ______, X pipe, Exhaust on 93 octane). You are the first with an upper pulley that I've seen that is running without a tune.

I've said it before and I'll say it again: swapping the pulley does not require a tune.

While the majority of your driving will be below 4,500 rpm's, you do not need a tune with your mods OP. However, you can maximize your setup with a pro dyno tune. More power is good. :cheers:

That's pretty ridiculous advice to be spreading. IMO

What do you base this statement on..actual tuning parameter measurements on a LT4?

We did it on the dyno, at WOT, in my case the car was going lean... We added fuel through out the power band...

May I ask
1. What AFR it went to on the lean side at WOT, and
2. What AFR did it get tuned to at WOT?

Ok, let play this through;

You listen to what speedforhire says. You decide, "Screw it. I've spent $3,000 on modifications for my car I don't care to spend another $500 on a tune." You drive around, 4-6 months the car drives great and feels fast. Then the unthinkable happens, you get a bad tank of gas and the ECU can't do enough to save the engine. You now go to GM with an engine full of modifications and they tell you that they won't replace anything under warranty. You're shit out of luck with a $12,000 bill. You really can't say anything, you can't say Well look what this guy on the forum said! He said it would be fine! Is speedforhire going to pay for your engine? No. He is not liable for anything you own or any decision you make. So to give "advice" like that is dangerous and if you're asking this sort of question, you should do a bit more research on tuning strategy, how engines work, and detonation.

As much as an advocate as I am for getting a real tune... I do see/understand your point.

With disregard to any of the other improvements associated with a tune, based on what your AFR trends are, I would think your engine could survive on your current stock tune... However you are solely relying on COT to fuel it... It does "work", however, we all know its not correct to do it.

If you are staying away from tuning because of the warranty, well you already have a good amount of aftermarket stuff on there so....You've basically voided it anyway.


So as many have posted, its best to do a real tune, turn off COT all together and build a good fuel curve...

Remember, there is a lot more to melting pistons then just the AFR...You can have a rich AFR and still detonate.




Playing "Devils Advocate" here but....
I think you'll be fine as long as you don't get stupid and make 1 mile pulls on it etc... I think at a minimum, I'd throw it on a dyno with its stand alone wideband (tail pipe sniffer) and at least verify what your Aeroforce wideband is reading..

I would think that your IATS are probably so high that the PCM is taking all the timing out of it anyway...plus the regular KR they normally get. With how aggressive the factory tune is for pulling timing for IAT, ECT, KR and I'm sure a lot of other metrics, I'd bet it will keep you alive, albeit with a lot less power.





BUT..... I would take it and get it tuned.:leaving:

FWIW.... My stock car with only a Haltech CAI will pull 5* KR going down the track on a 50* night with coolant temps around 200*... So they are very prone to knock (or at least false knock) on the stock tune.... So with you adding 2-3 psi more boost, I can imagine its knocking pretty bad.

Safe != Not Optimized

Remember with knock sensors and oxygen sensors it's not like the "olden days" where you could dial in a harry tune running on the ragged edge of knock or lean. Today's tune is already optimal, as it would have to be in order to pass emissions and avoid the gas guzzler tax (at least in the M7).

You could potentially add timing, but we're already pretty knock sensitive once the air gets warm, so I don't see a lot of gains there.

If you're adding boost, honestly the best advice I can give you (besides getting it retuned, I suppose) would be to increase octane. Throw in a half can or Torco or something so that the factory advance curve remains compatible with your increased air mass.

Thanks guys for your comments...

"However you are solely relying on COT to fuel it... It does "work", however, we all know its not correct to do it." Point well taken!

I do want to have the car tuned not only for safe power but also for things like getting rid of the V4/V8 AFM.

Issue I have with a tune, is I live in NW Alabama and there are no reptable LT4 tuners with dyno near by....traveling to Atlanta or Houston seems to be my only options in the near term. Can anyone recommend a reptable LT4 tuner/dyno near the NW Alabama area?

Lots of jealous folks out there on the interweb......some can't read or comprehend. However, It's good to see some that actually know what a combustible engine is and how it works.

Good luck on your endeavors wagoetzmann. Be careful with your tuner selection. :cheers:

You will find many opinions about tuning.
Based on the information you provided I would say your knowledge of how the modern PCM works is above average.

It takes many hours, if not years of study to understand the modern PCM and how it addresses fuel and spark (timing) let alone the torque tables.

My point is the answer you are looking for will rest in your knowledge and understanding of how the modern PCM works. Your knowledge will allow you to feel comfortable (or not) running without a tune.

That being said.

1. There are folks running similar set ups to you without tunes and they haven't had any issues.
2. Your AFR confirms what you already knew would be the case....and that you are well within safe parameters.
3. You have taken one of the most important safety steps when modifying......That is to monitor AFR so you know exactly when you are approaching dangerous levels.

Is a tune a good idea? Of course it is, hell its a good idea on a completely stock car isn't it?

But lets not kid ourselves, in your case a tune would be for the purposes of picking up any additional power left on the table by optimizing for your set up. Same as tuning a stock factory car.
Optimizing is always best and usually rewards you with some additional hp.

But your question was if your car is safe running the factory tune with your current set up? And you Sir have already answered that question with the information you provided.

I saw things heading toward the 13 Plus range, and we back out of it and added more fuel then we had already...

My tuner and I are both on the same page, NICE and SAFE...

We simply added fuel, along with a steady flow of meth, via the alky system that deliver based on air flow readings from the MAF, and put the fuel system back to right around 11.1/stock #s...

I have found in tuning both my C6 and C5, both have Meth, that running a little rich is not only safer, and leaves no power on the table. Sometimes, the car makes more power sitting just a tad rich when meth is involved...

We did not touch timing or some of the other things built into the stock tune...