slower with 3.42s instead of 2.73s

**1998z28** · 05-21-2009, 10:50 AM

i went to the track last night and the best i could get out of my camaro was a 14.09 at 98.64. The best mph i could get was 99.14. that might not be that bad but with 2.73s in it last year i ran a 14.01 at 101 and was consistently 100mph. so i figured with 3.42s i should be running at least like a 13.6 at like 104-105. i had mickey thompsons on it so traction was not an issue. i think the problem was is that it was running 210 degrees and sometimes even more. it was also like 85 degrees and extremely humid. any suggestions on what my problem is. anybody else have this problem?

**vetteemt** · 05-21-2009, 10:59 AM

Is your car a4 or m6? If an A4 did you get the computer corrected for the different gears? Also being hot and humid well slow you down and an engine temp of over 210 well not help make horse power. Also what octane of gas were you running? Was it the same as the last time you ran? A final thought that the transmission or clutch might be slipping causing you to slow down.

**1998z28** · 05-21-2009, 11:03 AM

i have got a automatic and i was running 92 octane which is actually higher than last time. i haven't corrected the computer yet but i just thought it affected my speedo because everything else works fine. its not the tranny it works perfect.

**MNZ28** · 05-21-2009, 11:56 AM

I also changed from 2.73s to 3.42s and had my computer tuned after. and I have not brought it to the track, but it seems twice as fast . Where did you go rock falls. and where you running street tires because I bet alot of the problem your having could be fixed with a tune and better tires. I have 275/40s which are 10.5 inchs wide and I can do a burnout forever so I m guessing mainly traction issues.

**MNZ28** · 05-21-2009, 11:59 AM

sorry did not read first post entirely, got the part about mickeys. oops. get the computer tuned, do you have any other mods.

**1998z28** · 05-21-2009, 12:08 PM

i went to BIR for the wednesday night thing. and it is completely stock except for the 3.42s. I ran at rock falls with the 2.73s. can a tune really do that much? i think i have more of a temp problem then tune problem. i guess i just don't know a whole lot about tuning.

**shady milkman** · 05-21-2009, 12:20 PM

i wouldnt worry..if it was hot and humid then your going to run slow ..i think a .4 gain is a little much to expect ..

**00z28bubba** · 05-21-2009, 01:15 PM

Originally Posted by shady milkman

i wouldnt worry..if it was hot and humid then your going to run slow ..i think a .4 gain is a little much to expect ..

+1. And a tune after any mods will always help but if you can try to do more than one mod at a time it will be cheaper tune-wise

**chevvydean** · 05-21-2009, 01:33 PM

I was there last night too. It may seem like a stupid question but were you lettin off at the 1000' mark or quarter? I had to ask because I saw alot of cars doin that.

**VENOMOUS** · 05-21-2009, 01:58 PM

Yep, it's your tuning. You do have to change your computer for gears and not just to have an accurate speedo. Being an A4 your computer relies on ACTUAL speed to follow preset parameters in the computer such as shift points, line pressure and torque converter lockup. What you saw mostly was most likely due to early lockup and resulting slower times. Hopefully you are comparing times at the same track as well cause Density Altitude will affect times dramatically.

**67CamaroRSSS** · 05-21-2009, 02:27 PM

I went to 3.42's from 2.73's and picked up .15 sec from 13.60 to 13.45.

If you were at a track then you'd get a time slip which will tell you your trap speed. This has nothing to do with what your speedometer reads.

**1998z28** · 05-21-2009, 02:42 PM

Originally Posted by 67CamaroRSSS

I went to 3.42's from 2.73's and picked up .15 sec from 13.60 to 13.45.

If you were at a track then you'd get a time slip which will tell you your trap speed. This has nothing to do with what your speedometer reads.

yeah i know about the mph on my slip my speedo was saying 120 -130 which i know is way off. i thought i would gain more than that because i actually use third gear now. huh maybe your right.

**1998z28** · 05-21-2009, 02:43 PM

Originally Posted by chevvydean

I was there last night too. It may seem like a stupid question but were you lettin off at the 1000' mark or quarter? I had to ask because I saw alot of cars doin that.

no i have been there before and i knew to keep on it until you went past the signs.

**67CamaroRSSS** · 05-21-2009, 05:34 PM

I should have mentioned that while I picked up .15 sec my mph stayed the same.

Same thing happened when I installed my 3400 stall torque converter. ET is now 12.60's but mph is only 107 (it was 105 at 13.45).

**Y2KPewterSS** · 05-21-2009, 05:40 PM

The weather and your lack of tuning are the problems. Your shift points need to be corrected with the 3:42 gears. You aren't really gonna be any faster until you change the shift points.

**dfillmore827** · 05-21-2009, 05:46 PM

if u dont adjust the shift points, the computer doesnt know the right rpm to shift and the engine timing could be off from the wheel speed and wut the computer is programmed to read

**1998z28** · 05-21-2009, 06:13 PM

Originally Posted by Y2KPewterSS

The weather and your lack of tuning are the problems. Your shift points need to be corrected with the 3:42 gears. You aren't really gonna be any faster until you change the shift points.

When i was driving down the track i was manually shifting it, I would put it in the next gear at 6000rpm so i don't understand how the shift points could be off. i guess i am just a little confused.

**67CamaroRSSS** · 05-21-2009, 06:23 PM

Originally Posted by 1998z28

When i was driving down the track i was manually shifting it, I would put it in the next gear at 6000rpm so i don't understand how the shift points could be off. i guess i am just a little confused.

FYI: The computer can shift the tranny much faster and more precisely than you might think. I have my car set up to shift at 6000 with the rev limiter set at 6100. I just leave it in OD and it does the rest. I do my burnout in OD also. This allows the cars PCM to do it's job. You also don't misshift and/or overrev the engine. Bent pushrods are a PITA!

**shady milkman** · 05-22-2009, 05:16 AM

Originally Posted by 1998z28

When i was driving down the track i was manually shifting it, I would put it in the next gear at 6000rpm so i don't understand how the shift points could be off. i guess i am just a little confused.

Originally Posted by 67CamaroRSSS

FYI: The computer can shift the tranny much faster and more precisely than you might think. I have my car set up to shift at 6000 with the rev limiter set at 6100. I just leave it in OD and it does the rest. I do my burnout in OD also. This allows the cars PCM to do it's job. You also don't misshift and/or overrev the engine. Bent pushrods are a PITA!

yea dont manually shift...and even when manually shifting the computer still will look at several variables before it shifts anyways ..however i disagree with 67Camaro...i put it into 3rd and drive the 3 eliminates the OD and i believe it uses all of the clutches

**Firebirdjones** · 05-22-2009, 07:37 AM

I do just as 67Camaro describes. I also leave mine in OD and just run it,,,let the car do the rest. Has always worked for me. I used to run my Typhoon and Iroc the same way. Never had any ill affects from it.