LT-1 EXPERTS HELP!
Thread Starter
Pro
Joined: Sep 2001
Posts: 685
Likes: 19
From: Houston, TX
LT-1 EXPERTS HELP!
Let me tell you what all i have first.
I have a 1994 Corvette lt-1 with auto.
the stock rear end ration was a 2:59. I recently swapped in some 3:75 richmond gears. At this time i changed the programming to accept the gears..but the only option was 3:70 on the programmer. I also guessed at the tire height..they are 285-35-18's so i programmed in 26 inches exactly. I am also running the shift firmness option and power tuning. The car has gutted cats and no resonators and 2 two chamber flowmasters.
NOW!..when i give it 3/4 throttle ...it will accelerate and hit the rev limiter! somtimes even when i floor it? i didnt alter the shift points on the programmer at all. But i am curious how it can be hitting the rev limiter? anyone know what is cuasing this? and if it is the difference in what gears i have and what is programmed...can i manipulate this with a different tire hieght? i am not capable of doing the math accurately if this is the case though
any ideas? btw my rev limiter is set at 6200
I have a 1994 Corvette lt-1 with auto.
the stock rear end ration was a 2:59. I recently swapped in some 3:75 richmond gears. At this time i changed the programming to accept the gears..but the only option was 3:70 on the programmer. I also guessed at the tire height..they are 285-35-18's so i programmed in 26 inches exactly. I am also running the shift firmness option and power tuning. The car has gutted cats and no resonators and 2 two chamber flowmasters.
NOW!..when i give it 3/4 throttle ...it will accelerate and hit the rev limiter! somtimes even when i floor it? i didnt alter the shift points on the programmer at all. But i am curious how it can be hitting the rev limiter? anyone know what is cuasing this? and if it is the difference in what gears i have and what is programmed...can i manipulate this with a different tire hieght? i am not capable of doing the math accurately if this is the case though
any ideas? btw my rev limiter is set at 6200
Drifting
Joined: Dec 2000
Posts: 1,255
Likes: 50
From: Clayton, NC north carolina
Re: LT-1 EXPERTS HELP! (Torquem)
what RPM does the revlimiter kick in? is it eratic? does it do it all the time? any specific gear?when was the last time the opti was changed?how many miles are on the injectors? :confused:
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: LT-1 EXPERTS HELP! (Torquem)
The difference between 3.70 gears and 3.75 is very small. For example, at 6000 rpms in 5th gear with 3.70 gears you would be going 166 MPH, where as with the 3.75's you would be going 164. Being that the amount of error increases with speed, you are alright at any sane speed. Absolute worst case you will be off by 3 MPH at 6500 RPM in 6th gear, so I wouldn't worry about that too much.
285/35/17's should be 25.85 inches tall, you might try to change that and see if it helps your problem, but even that doesn't seem like it should be much of an issue.
Yeah I just ran those numbers as well, with the car thinking 3.70 gears instead of 3.75 AND it thinking the tires are 26 inches instead of 25.85, you are still only looking at an error of 5 mph at 6500 RPM's in 6th gear. Shouldn't be enough to matter at all.
BTW, if you have access to Microsoft Excel, I've got a real nice spreadsheet that calculates it all out for you. I can e-mail it to you if you would like.
[Modified by Nathan Plemons, 7:27 AM 3/29/2002]
285/35/17's should be 25.85 inches tall, you might try to change that and see if it helps your problem, but even that doesn't seem like it should be much of an issue.
Yeah I just ran those numbers as well, with the car thinking 3.70 gears instead of 3.75 AND it thinking the tires are 26 inches instead of 25.85, you are still only looking at an error of 5 mph at 6500 RPM's in 6th gear. Shouldn't be enough to matter at all.
BTW, if you have access to Microsoft Excel, I've got a real nice spreadsheet that calculates it all out for you. I can e-mail it to you if you would like.
[Modified by Nathan Plemons, 7:27 AM 3/29/2002]
Team Owner
Joined: Nov 1999
Posts: 32,782
Likes: 11
From: Former NCM Drag Racing coordinator, National director Corvette Challenge Spring Hill, Tennessee: Whiting, New Jersey
Cruise-In VI Veteran
Cruise-In VII Veteran
Re: LT-1 EXPERTS HELP! (Torquem)
Set the rev limiter as high as you can get it.
What are you afraid of missing a shift?????????????
It's an A4, you'll be fine and then thats on less thing to worry about.
What are you afraid of missing a shift?????????????
It's an A4, you'll be fine and then thats on less thing to worry about.
Le Mans Master
Joined: Oct 1999
Posts: 9,713
Likes: 3
From: Sachse Texas
Cruise-In I Veteran
Cruise-In II Veteran
Re: LT-1 EXPERTS HELP! (Torquem)
Try putting the programming back to stock and see if you have the same issues. Or, do as Mackey suggested...set it to 6500 or more.
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: LT-1 EXPERTS HELP! (Torquem)
Just one thing about the Hypertech shift firmness option, so far heard of two that have blown their trannys while running with that option programmed in. I think Glock94 did (i thought I read a post to that effect...) and there's a local guy here with a '96 Impala SS LT1 that credits the shift firmness option for killing reverse and 1st gear in his car.
Advanced
Joined: Jan 2002
Posts: 80
Likes: 0
From: Clarksville Tn
Re: LT-1 EXPERTS HELP! (Vette92)
If you remove the hpp3 program from the computer and it does not shift correctly then it is because of the gears. I have heard of auto's having problems accepting gear changes before. What i've seen people do is get the pcm reprogrammed to shift at a mph instead of a certain rpm. Good luck trying to fix the problem, this is just one more reason why i hate autos.
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