3V - Is this A/F Safe

Gray02GT · Jun 3, 2005

http://forums.bradbarnett.net/index.php?act=Attach&type=post&id=21648

Not sure if you guys can see that, but basically over 2500 RPM it's 13.5-13.00. Is that safe for a n/a motor or should I try to get it more around 12.5'ish? Just wondering if I need to get a new tune for the car after getting the Magnaflow xpipe and catback (these damn cars are really picky computerwise when compared to the 2v)

SilverGTV8 · Jun 4, 2005

Yes that is safe, just a tad rich.

Kilgore Trout · Jun 4, 2005

I think your a/f ratio curve should be a lot flatter across the rpm range. Also, there is a 3V forum where you may find more accurate information for your car. I never go there so I am not sure of the quality of if though...

chimchim · Jun 4, 2005

267 RWHP from an x-pipe and catback!!! Go somewheres else and axe your questions.

Give Me TP · Jun 4, 2005

Kilgore Trout said:
I think your a/f ratio curve should be a lot flatter across the rpm range. Also, there is a 3V forum where you may find more accurate information for your car. I never go there so I am not sure of the quality of if though...

He's correct, it should be flatter than what is shown. Do you have a flash tuner?

DBMSTNG · Jun 4, 2005

it should be 12.5-13.0.

Jakes · Jun 4, 2005

I was/am under the impression the optimum A/F ratio (I think it's called "stoich" or something like that) is 14.??. This is where there is a near prefect match between the number of oxygen molecules and gas/fuel molecules to max the burn and power output. But everyone here, and on other boards, talk about 11 - 13 being ideal. When I got mine tuned after the KB went on, they set my A/F to 11.8 and backed off the timming as well. The rational was to protect the engine from detonation, but that seems awfully rich to me. What's up? Please help an old fart understand all this new fangled technology.

Oh yeah... during the dyno sessions one run was made at an A/F of 12.5 and gave about 20 more hp (390rwhp) than I have now (365rwhp).

Gray02GT · Jun 4, 2005

Give Me TP said:
He's correct, it should be flatter than what is shown. Do you have a flash tuner?

I don't, I am really trying to decide if I need one which is my main reason for asking. I dont particularly want to flash my computer and void the warranty (basically) unless it's necessary.

Kilgore Trout · Jun 4, 2005

Flash will not void if you unflash when you take it in. Also, the warranty will be up soon enough anyway, the car is built well, and the dealer will try to deny warranty claim half the time anyway. Do not let a stupid warranty stop you from enjoying your car!

Gray02GT · Jun 4, 2005

Kilgore Trout said:
Flash will not void if you unflash when you take it in. Also, the warranty will be up soon enough anyway, the car is built well, and the dealer will try to deny warranty claim half the time anyway. Do not let a stupid warranty stop you from enjoying your car!

Haha, well it's part that I don't want to spend another $500 already too

ADRENLN · Jun 4, 2005

wow you have a kb at 10psi and your only putting down 365? guys that have it set at 9psi are getting 400 rwhp. i know you said it was rich for safty, but man i dont know if that sounds right.

SilverGTV8 · Jun 4, 2005

Jakes said:
I was/am under the impression the optimum A/F ratio (I think it's called "stoich" or something like that) is 14.??. This is where there is a near prefect match between the number of oxygen molecules and gas/fuel molecules to max the burn and power output. But everyone here, and on other boards, talk about 11 - 13 being ideal. When I got mine tuned after the KB went on, they set my A/F to 11.8 and backed off the timming as well. The rational was to protect the engine from detonation, but that seems awfully rich to me. What's up? Please help an old fart understand all this new fangled technology.

Oh yeah... during the dyno sessions one run was made at an A/F of 12.5 and gave about 20 more hp (390rwhp) than I have now (365rwhp).

You want to be about 12.5-13.0, 14.0 is rich, the power drop is probably a result of backing out the timing. They probably packed out the timing to reduce the posibilty of detnonation with the leaner A/F ratio.

Also peak numbers mean nothing in reality. It is the curve that matters. They may have tuned the car so it had a better curve, but resulted in a lower peak number.

You will have to look at the graphs and see if there is a difference.

SilverGTV8 · Jun 4, 2005

Kilgore Trout said:
Flash will not void if you unflash when you take it in. Also, the warranty will be up soon enough anyway, the car is built well, and the dealer will try to deny warranty claim half the time anyway. Do not let a stupid warranty stop you from enjoying your car!

The dealer is capable of seeing if the computer has been reflashed and how many times it has been flashed.

DBMSTNG · Jun 4, 2005

Jakes said:
I was/am under the impression the optimum A/F ratio (I think it's called "stoich" or something like that) is 14.??. This is where there is a near prefect match between the number of oxygen molecules and gas/fuel molecules to max the burn and power output. But everyone here, and on other boards, talk about 11 - 13 being ideal. When I got mine tuned after the KB went on, they set my A/F to 11.8 and backed off the timming as well. The rational was to protect the engine from detonation, but that seems awfully rich to me. What's up? Please help an old fart understand all this new fangled technology.

Oh yeah... during the dyno sessions one run was made at an A/F of 12.5 and gave about 20 more hp (390rwhp) than I have now (365rwhp).

stoich (14.7:1) is only for idle and part throttle. for WOT you want to be at 12.5-13.0 n/a and 11.5-12.0 for forced induction.

running the car lean can make more power, but it's dangerous.

DBMSTNG · Jun 4, 2005

SilverGTV8 said:
You want to be about 12.5-13.0, 14.0 is rich, the power drop is probably a result of backing out the timing. They probably packed out the timing to reduce the posibilty of detnonation with the leaner A/F ratio.

Also peak numbers mean nothing in reality. It is the curve that matters. They may have tuned the car so it had a better curve, but resulted in a lower peak number.

You will have to look at the graphs and see if there is a difference.

14.0:1 is lean, not rich.

Jakes · Jun 5, 2005

ADRENLN said:
wow you have a kb at 10psi and your only putting down 365? guys that have it set at 9psi are getting 400 rwhp. i know you said it was rich for safty, but man i dont know if that sounds right.

Ask to see their dyno sheets. Also, dyno #'s will vary from dyno to dyno - operator to operator - and atmospheric conditions. One man's 400 is another man's 390. I'm also pushing an auto with stock gears and MAF on stock tires in a daily driver. I get into (and out of) enough trouble with what I have. I'm happy....... for now.

Jakes · Jun 5, 2005

DBMSTNG said:
stoich (14.7:1) is only for idle and part throttle. for WOT you want to be at 12.5-13.0 n/a and 11.5-12.0 for forced induction.

DBMSTNG.....Thanks for the explaination.

SILVER.... I'm with DBMSTNG on this one. A higher A/F = a leaner mix. Remember it's an AIR to fuel ratio so the first number is air. A 14:1 A/F is leaner than 12:1.

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