back from the track, need help

pontiacfreak142 · #1 (**permalink**) 04-25-2008, 07:52 PM

Well i havent been on for a while, But i drive a 96 firebird.
the complete mod list is
custom P&P heads, abbott N/A cam, pacesetter headers, magnaflow 2.5 in catback, corvette servo, 3500 stall, torsen posi, 3.73 gears, "custom" ram air (very crappy design and am trying to find something better), A/C delete, spare tire and jack!, rear speakers and seatbelts!.

Anyways, Last season (before i took out the A/C and other random things), the car got a best of a 14.1 at 95 mph, i also took it out on the last sunday NTR was open (it was like mid 40's that day) and ran 14.4's all day on 2.2 or worse 60's at 94 mph. so after this i decided it was time for some DR's (best 60 on the street tires was a 1.990)

I ended up getting 225 50R16's on the DR's while my street tires are 225 60R16's. I had been told by a few people on another board that because they were smaller they would cause problems with the speedo and and shift points.
I finally got a chance to try them out 2 nights ago at NTR again. The best the car ran was a 14.5 at 92 mph with a 2.00 60'. the rest of the runs were in between 14.5-7 at 91-2 mph with 2.0 or worse 60's. I tried to swap my street tires for a pass, but it didnt do anything because it spun bad off the line and ended up with a near 2.4 60 and ran a 15.1 at 91.

now what i need help with. ive also posted up about needing help on 2 other boards. on one board, i have everyone telling me that a getting the PCM tuned for the smaller tires would help alot, but on the other board, they are saying it wouldnt do that much to get it tuned. what do you guys think?

I know the car needs a tune bad anyways. I had it tuned by intense a little over a year ago and made only 222 rwhp and 225 without the high stall. I did later find out that a few of the valve guides in the heads were messed up, and i was also still using the stock length pushrods with a bigger cam and ported heads, but i never got it tuned again after i got that all fixed.

There are also guys on another board running the same or better times than i am, with stock heads and the same cam i have. I have been told that some of my problem is my 2.5 inch exaust, and the fact that im still on stock fuel injectors. What do you guys think about this? Ive also been told that is possible that my heads are causing power loss, is that possible?

sorry about all of the questions, im just really confused and getting frustrated with this car.

SleeperLS · #2 (**permalink**) 04-25-2008, 09:24 PM

really, I would get some MT street slicks and never turn back...you should be able to yield a 1.7 60 foot on those especially with a rwd set-up. I don't know about this smaller tire situation...I wouldn't think it would matter that much. As long as the pcm is tuned for the motor, the tire size shouldn't kill it much at all unless you put larger tires and wheels on.

If your pushrods were not the correct length, that can cause a lot of hp loss on its own.

When you got it tuned the first time were you maxing out your injectors? If you are maxing out the injectors, then upgrade those before your next tune.

The only power loss I have heard from porting out heads is a loss of torque on the low end but still better power up top.

Hopefully you figure out what is going on with the tune situation. Bigger injectors and a better air intake might help you out.

pontiacfreak142 · #3 (**permalink**) 04-25-2008, 11:52 PM

yea they were to long, and after we got the new valve guides put in and got shorter psuhrods, you could deffinatly notice a difference.

as for the injectors, i dont know. tim is the one that tuned it and he didnt say, so im assuming they didnt, but then again with the power loss that i had, it may not have been enough to max them. im just going by a few others guys i know that have the same cam i do along with intake and exaust with stock heads and they were maxing their injectors.

and also with the tires, its not that the ones i have are bad (hoosiers that DR's that are basically slicks), i just dont know what is goin on. my best 60 on the street tires is a 1.990, but no matter what i did the other night, the best i would get was a 2.0, even with stalling it up and launching it. id always thought that smaller tires would help more to which is what is confusing me so much. i got better and smaller tires and did some weight reduction from last year, id think that would account for something.

and i know i probably sound dumb about this stuff, i am lol. ive never built a motor or a race car for that matter, and all this is confusing me, cause ive got quite a few people telling me i should be in the 13's pretty easily with what i have done, which makes sense cause there are people with less than me running faster.

SleeperLS · #4 (**permalink**) 04-26-2008, 12:13 PM

yup, I would upgrade the injectors then...I don't think it is a bad idea to mod according to what other people have done in similar fasion, it is just smart really. You no longer have to do the trial and error, just slap it all in and try to tune and launch it better than the other person.

So your best 60 foot on your DR is a 2 flat? What is your process like when you warm up the tires and then before the launch and during the launch through the 60 foot? Just describe as much as you can.

The launch is rediculously crucial in getting a good 1/4 mile time. I have seen alot of people with consistent 2.2-2.3 60 foot times on street tires and the 1.9-2.0 60 foot times with DR's and that hurts big time(ever.1 off of your launch = twice that down the track). I haven't had much of a problem with launching, but IMO I would say you really need to get used to working that gas pedal off of the line, I never go WOT until about 20ish.

Most people just get in and hammer, but get used to what rpms you can be stalled out at off the the line without breaking the tires loose. Don't give it any extra gas at this point, just dial in how high you can stall comfortably without the tires squeeling right off the get-go. Once you get this baseline, you know where to start at the line and just get the feel of how much gas you can keep giving it until it breaks them loose. Usually this part happens quick so be ready to give it more and more gas quickly if your tires are holding.

On one of my better launches I stalled out at 2500 and once I reached about 15-20 I just hammered it b/c my tires gripped hard off of the initial start. that yielded me a sub 2 60 foot on some not good street tires. Really It is all about getting the feel for what your car can do without tearing the tires apart.

SUPER_GTP · #5 (**permalink**) 04-26-2008, 12:44 PM

Well I don't just want to sound like a sales man but I'm selling 42# injectors FS: 42# Injectors and some ET streets Wheels and Slicks! - GOClubGP.

pontiacfreak142 · #6 (**permalink**) 04-26-2008, 04:39 PM

yep a 2 flat. Well since i havent had much time to really experiment around with them yet, all my launches have just been from idle, which is also how i got my 1.990 on the street tires. I did try to stall it up once but i think i only let it get to about 1500 before i went. with my burnouts i pretty much rolled through the water box and did like a 6-7 second burnout. on one run though i just rolled through the box and stomped it real quick to basically just get the water and rocks off, but ended up with a 2.093 60 on that one.

SleeperLS · #7 (**permalink**) 04-27-2008, 12:53 PM

It sounds to me like it might just be your launch that is the prob...do you ease into the throttle? or hammer it? Really the best way to do it is just feel how far down you can put your foot without spinning the tires. Ride on that thin line the entire time and you should get that nice 60 foot time.

pontiacfreak142 · #8 (**permalink**) 04-27-2008, 04:58 PM

Quote:

Originally Posted by SleeperLS

It sounds to me like it might just be your launch that is the prob...do you ease into the throttle? or hammer it? Really the best way to do it is just feel how far down you can put your foot without spinning the tires. Ride on that thin line the entire time and you should get that nice 60 foot time.

yea im goin to. its lookin like its gonna be nice wednsday night so, im just gonna use that to play around with it. Ive also been told to maybe put a little more air in the tires (on 25 psi right now), and see what that does.

and if anyone has any other idea's i should try let me know, im willing to give anything a shot at this point lol.