Will the car run ok will it be ok to race?

 

I say yes it will be fine. I ran headers on my vette for two years before I got it tuned. Done some racing also. Got 30mpg on the highway. Some people say they run rich after headers but I don't think it's a real problem. There are alot of people driving around with untuned cammed cars and that would be ALOT worse.

 

You will be fine. I did it for a while and ran the car hard with no problems.

 

i put on long tubes and now i'm running lean... :shrug

 

You'll be fine. I ran her with LTs for 3 years and yeah it was lean too. 339hp 347tq is what the dyno showed on dyno day

 

I wouldn't.

 

i am about to find out tomorrow if it is ok, wink wink

 

why would you now? long tubes do not effect drivablility. Tune is just to get max hp.

 

yeah, its okay to run #7 even leaner than the factory.

 

Now I'm really confused. I used to hear on this forum that putting headers on will make them run rich just because of the O2s being placed further back and not getting as hot as they would with manifolds. Also when I finally got my vette tuned the tuner even leaned it down from what it was stock. He even said running untuned with headers will make it run rich. So now I don't know what to think.

 

Iv also heard that LT's make thesecars run rich. Doesnt make sense to me. It seems like almost any mod you do is to increase the amount of flow through the motor, so more air going through should mean its going to need more fuel also. might be wrong, but that just makes sense to me.

 

you have to understand the PCM's in these cars.. on a very basic level.. there is a system in the PCM that was designed to adjust the tune for weather and altitude changes too keep the AFR at 14.7 during part throttle. this system compensates during part throttle and can do +/- 25% fuel to the base tune. you will hear this referred as the trims ot LTFT or STFTs. Usually with mods the cars base tune becomes off and the PCM starts adds fuel to the base tune. So in regards to the Base tune the car is actually Lean and the PCM is adding fuel to compensate but there is a twist.. the PCM will add whatever + fuel trim it calculates during part throttle driving to the WOT fueling.

example.. lets say I modded my car. now the PCM is adding 10% more fuel on top of the base tune to keep the nice 14.7 afr at part throttle. I go WOT. the PCM moves to the WOT table (factory tune is a very rich 11.5-11.7 AFR) then will add another 10% on that it calculated from the part throttle driving making for a super rich WOT. so 11.7 afr + 10% more fuel during WOT. so really its lean but the WOT will be rich.

The PCM compensates great at part throttle hence people thinking the car doesn't need a tune but at WOT you are loosing a lot of power because of the rich factory WOT setting and the additional fuel added by the PCM on top of that.

that is in Short and there is a LOT more going on than that but its just the very basics..

 

this subject is one that really confuses people..some people will tell you to get a tune after longtubes while others will tell you not to sweat it..i went along and got a tune couple months after i did my longtubes..you never know if your running rich or lean and i guess it serves as a piece of mind..i dont regret getting it tune..my car runs better now..also i only payed 250 with free updates so i wont be charge again when the bottle goes in

 

i'm waitin till i install my cam to get a tune . . . couple weeks but still you never know what could happen if you run lt's with no tune

 

My car ran rich without a tune for the headers. I just waited until I acquired a cam to tune it. Im not sure its worth getting a tune for them unless your done modding.

 

These cars USUALLY run rich after headers but they can make them run lean. Kind of like dirty injectors can cause rich or lean. Regardless, you will run harder after headers, both WOT and part throttle. You also, 98% of the time or more, will not get your max benefit (WOT or part throttle) without a tune. It's also about 98% likely, or more, that you won't hurt a thing. The only small possibilities are: IF you are already lean on #7 and headers lean you out further - as has been mentioned. If you are already rich and the headers make it richer, you will kill your cats (and MPG). Small possibilities but very real. If your tuner offers the full price and then $70-100 each one after, I'd do it. If it's 300-500 each time, I'd wait until I added more mods.

 

Thanks guys for the input..I'll do the tune..

 

If you want to get any HP out of headers, the car needs to be tunned for them. If you throw a Code, which you will, the PCM goes into safe or limp mode and retards timming & adds extra fuel.

My car gained no rwhp from headers until after the tune. Did before & after Dyno & after tune.

 

My car has been Dyno'd before and after every mod on the car.

 

False. I could tell a difference the first time i took my car out after long tubes, a very noticable difference, and I dont see why you would definatelly throw a code unless you got rid of your cats or installed something wrong. Dont listen to this guy hes an idiot.