Now I don't want a bunch of B.S. in this thread, so leave out anything having to do with 42# injectors and 2.7" pulley. Right now I'm tuned at 12.1 and have no detonation at all. Reading 0* knock all thru. My tuner say the car wants to run closer to 13.1. He says that the GM stage 2 tune is set at 13.1. Is it safe?????

Right now I'm running intake, 2.7" pulley, 42# injectors and 1 step colder plugs. Keep in mind I'm at 5600' here in Albuquerque.

Third gear pull netted me 257hp/236tq.


My tuner thinks that 13.1 will net me closer to 280hp/240tq.

Stock tune I ran 217hp/189tq and I was at nearly 14.1 then it dropped to 12.5.1

Personally, I don't think I would want my car over 12.5:1. Running leaner will increase your HP numbers, but it comes with risks. If your car is running well now and your happy, you should just leave it the way it is!

I shoot for 12.5 to 1.



You think you are going to get that much power from leaning it out 1 afr pt.

I shoot for 12.5 to 1.



You think you are going to get that much power from leaning it out 1 afr pt.


It went from 217 down to 205 when he took the stock tune from12.5.1 down to 11.8.1

I shoot for 12.5 to 1.



You think you are going to get that much power from leaning it out 1 afr pt.


Exactly your risking so much for so little, and the 2.7 with 42#'s :nono: It would be in you, and your cars best intrest to upgrade.

Here is the issue I see, you are giving up a margine of safety for performance. That might be fine, but you then your car isn't a daily driver anymore.

Just watch out for knock :)

Exactly your risking so much for so little, and the 2.7 with 42#'s :nono: It would be in you, and your cars best intrest to upgrade.


Once agian I said I didn't want to here the old 2.7/2.8 and 42# injectors bullshit!

If you must here are my numbers.
Currentyl 12.1 A/F and only 81% duty cycle. Its 42* here and atmosphereic pressure puts us at about 3600' instead of the actual of 5600'. I will post up graphs and all that jazz later.
So STFU about the 2.7/2.8 and 42# injectors already, they are more than enough for me and my current setup.

It went from 217 down to 205 when he took the stock tune from12.5.1 down to 11.8.1

I donnu I should believe that man, sounds too much, I mean that and you cant gain 20whp from going 1.0 AFR leaner, thats just insane. Too much power, I mean thats what people get with Water INjection.

I don't have a wide band, but I like to keep mine in the low 12s, like 12.2 - 12.5 any leaner your just waiting to burn a piston.

I donnu I should believe that man, sounds too much, I mean that and you cant gain 20whp from going 1.0 AFR leaner, thats just insane. Too much power, I mean thats what people get with Water INjection.


Thats not 20 thats 12, and I didn't say this, my tuner did..... I do know a little about the laws of combustion though, and too wet (i.e. too much fuel) effects combustion much more than too much air (I mean they both hinder the process, but it takes much more air to start to hinder combustion of any solvent than it does fuel in the same settings)..... just a thought.

13.1 A/F ratio is perfectly fine to run. Just try and monitor the knock. In now way is 13.1 lean. Anything above 14.7 is going to be considered lean. 12.5 in just a mark that has been set to be perfectly safe when doing high performance mods. Also anything under 12.5 is not good. Eventhough people may think it is better, if you go below this, lets say in the 11's then you run the risk of wasing the cylinders with gas. Thats not good for the motor. I have done many dyno runs on many diff vehicles (v8, v6, 4, turbo, supercharged whatever. Most of the airfuel ratios were right at 13.1. So I have to say 13.1 is fine just try and keep an eye on the knock.:cssNET:

Once agian I said I didn't want to here the old 2.7/2.8 and 42# injectors bullshit!

If you must here are my numbers.
Currentyl 12.1 A/F and only 81% duty cycle. Its 42* here and atmosphereic pressure puts us at about 3600' instead of the actual of 5600'. I will post up graphs and all that jazz later.
So STFU about the 2.7/2.8 and 42# injectors already, they are more than enough for me and my current setup.


Ok, its your car. No need to get your panites in a bunch, but hey you know it all so.

Oh, I forgot to mention, I also went with a step colder plugs....

Oh, I forgot to mention, I also went with a step colder plugs....


Right now I'm running intake, 2.7" pulley, 42# injectors and 1 step colder plugs. Keep in mind I'm at 5600' here in Albuquerque.

Right now I'm running intake, 2.7" pulley, 42# injectors and 1 step colder plugs. Keep in mind I'm at 5600' here in Albuquerque.


Oops!!!

Wow you guys really like it on the lean side
We always tune our cars to 11.5 a/f for turbo and 11.8-12a/f for the supercharged cars including the cobalts
Going to 13 a/f is plain Crazy I think you should find another tuner Unless you want new pistons and or a head gasket
We tune all motor Cars to 13.1-2 at the most


Coming from a turbo car, 11.2-11.5 is what I am used to, thats why this thread was made in the first place. I was absolutely amazed when he pulled up the GM stage 2 tune and it showed 13.1.

Wow you guys really like it on the lean side
We always tune our cars to 11.5 a/f for turbo and 11.8-12a/f for the supercharged cars including the cobalts
Going to 13 a/f is plain Crazy I think you should find another tuner Unless you want new pistons and or a head gasket
We tune all motor Cars to 13.1-2 at the most


Dont bother explaining, no one wants to listen until they break something. :lol:

Alright, new numbers for the night.

265hp/236tq thats just from adjusting the A/F from 12.1 to 12.5.1.


Tuning resumes in the morning.

I asked Rob, and he said for a daily driver tune a good AFR would be 12.2-12.5 and for the track 12.8-13.0

I shoot personally for 12:1 and at the track go a bit leaner.

Mine is set at 11.8 at 7K.

20-21* timing.
11.5 AFR
car runs mint.

I'd say 11.5-12 max. This is a boosted car, not N/A where a 13:1 would be great. A little bit more fuel will save the car from going to lean and boom. Just my thoughts from seeing tunes on other boosted car forums and discussions amongst the local tuners.

13.1 A/F ratio is perfectly fine to run. Just try and monitor the knock. In now way is 13.1 lean. Anything above 14.7 is going to be considered lean. 12.5 in just a mark that has been set to be perfectly safe when doing high performance mods. Also anything under 12.5 is not good. Eventhough people may think it is better, if you go below this, lets say in the 11's then you run the risk of wasing the cylinders with gas. Thats not good for the motor. I have done many dyno runs on many diff vehicles (v8, v6, 4, turbo, supercharged whatever. Most of the airfuel ratios were right at 13.1. So I have to say 13.1 is fine just try and keep an eye on the knock.:cssNET:
hahaha i hope people take what you say with a grain of salt. I dabbled in in the 12.8 from 5800 on till 6450's and it took some time and car ran hard but the motor finally started to fall apart from constantly running it at that a/f. If the injector can give enough fuel to leave you in the low 12's high 11's i would suggest the person stay in that range. my cars at 12.3 right now i doubt i'll go any leaner ever again. 12.3 put me at 243WHP back in the day and 12.8 put me at 250whp. 7extra whp wasn't worth my motor.

Ummmm... first off, the GM Stage 2 is tuned for around 11.8 at WOT IIR. If there is 13.1 in there somewhere, I'm betting it is for crusing. For F/I engines you want more fuel. 13a/f ratios are only good for N/A engines. If you try running a S/C... or even worse a T/C car at that ratio as a daily driver you are going to blow it up bad.

12~12.5 is what I would look at with a S/C setup. Closer to 12 if you don't have any cooling mods, closer to 12.5 if you have a high performance heat exchanger/water injection/etc.

You cant tell people anything these days : (

Hmmmmmm.............



Interesting.....

Thats not 20 thats 12, and I didn't say this, my tuner did..... I do know a little about the laws of combustion though, and too wet (i.e. too much fuel) effects combustion much more than too much air (I mean they both hinder the process, but it takes much more air to start to hinder combustion of any solvent than it does fuel in the same settings)..... just a thought.

Maybe so but you're talking about in a moderate case and things change much more when you're messing with high density air than naturally aspirated engines and things change when you're raising the pressure from vacuum to above atmospheric.

There are degrees of everything. Honestly, 12:1 is fine and from the injector duty cycle you gave earlier, that is perfect. Like zinner said, it's a weigh between safety and power. If you're safer at 12:1 ratio but you're losing say 12 HP, it's worth it in the end cause you could be making 0 HP when your engine detonates (this is in an extreme case but just something you should think about).

Now when you say too much fuel and too much air, I think you're thinking in the wrong state of mind. You need to think of the effects of both and how they weigh as far as possible outcome between having too much fuel and not enough fuel. Too much fuel will lead you to run richer and in worse case scenario you'll flood your engine. Damage with flooding engine: Damaging catalytic converter, ruining your 1st O2 sensor, replacing fuel injectors (to a better size if the case was that they are too big) and replacing spark plugs. Hundreds of dollars in changes. Damage from detonating: Possibly causing your head or piston to crack, melting of the pistons, damaging spark plugs, possibly damaging your valves and the list goes on. This will result in possibly thousands of dollars in replacing or upgrading parts and not even including labor if you're sending the engine to a professional.

These are the things you have to weigh. Is it worth it just to gain a mesley few more HP?

Judges? *Buzzer*

wow you guys Are Crazy
The Gm stage 2 tune isn't that lean and never has been
Better get a Shovel and a broom for the pistons ..


Jim the pistons don't fly out of the engine, they just crack and stay neatly inside the cylinder wall, so no messy clean up. :lol:

well, from what i gather, several people who have been tuned are dropping #4 cyl. probably because that particular cylinder gets less fuel flow, so it runs leaner...

you have to remember, that wbo2 in your bung hole is just an average of all 4 cyl, not just one.

im not looking for a flame here...just an opinion from a person who actually knows the difference between their ass and a hole in the ground...such as zinner or NJHK.....i got my car dynoed a few weeks ago and the AF reading was at approx 15 until about 4krpm then fell to approx 12....i have a 2.2 and know that i cant tune that yet, but what should i try to achieve once HPT gives me support?

im not looking for a flame here...just an opinion from a person who actually knows the difference between their ass and a hole in the ground...such as zinner or NJHK.....i got my car dynoed a few weeks ago and the AF reading was at approx 15 until about 4krpm then fell to approx 12....i have a 2.2 and know that i cant tune that yet, but what should i try to achieve once HPT gives me support?

If you're naturally aspirated, running 12 isn't necessary. The boosted guys do it for safety reasons because when you're boosted Combustion chamber temperatures raise higher than an n/a 4 cylinder would. Fuel in their case is not only for ignition purposes but for a "cooling" purpose. Fuel helps lower the temperatures in the combustion chamber and keeping things at a good temperature and from overheating from this process.

Why do the temps raise much higher than an n/a engine? Simple. They are using either compressed air or "stacked" air that is highly pressurized...compressed air is hotter than the air that your engine would naturally vacuum in.

So what a/f should you aim for? You could run 14s and be alright N/A.

thank you....that actually cleared up some stuff that i read on other threads too

thank you....that actually cleared up some stuff that i read on other threads too

Good. If you have anymore questions, feel free to ask. If I don't know, I can atleast point you in the right direction.