How to make a car consistent?

I have a friend with a gto, I've been tweaking his tune a little here and there trying to make it run more consistent. It was dyno tuned before he bought the car but it won't run same times to save its life. He uses it for bracket racing. I made a few changes and was able to run the exact same times 4 times in a row hot lapping. But during normal racing he has long breaks between runs. It will run same same for a while and suddenly jump .1 in the 1/8th. Which can cause a break out and a loss.

Only thing I can think of is the maf. He does randomly get maf fail CEL every once in a while some times at the track some times on the street. It's been cleaned and what not.

I'm on my phone so I'll post some logs and tune later. It's an 04 gto ls1 auto. He does run drag radials and it's basically a stock motor with long tubes and an intake. He isn't looking for power so much as just being consistent.

To me this is much more than just a tune thing here.

There is so much more involved here. A better launch or a 60 foot will can make it faster, the cooler motor and what the track is like when he takes off will effect the times.

That's some of my thinking too. But he makes sure the car is warmed up before each run. He does pop the hood between runs to cool it down but in the lanes he doesn't shut it off. All the logs I have the eng temp is the same. 196?. The changes have been getting worse with the cool weather. Obviously it's going faster and I told him that's just what it's going to do. But the other day it got faster as it got warmer. I was just told he get the Maf code more often than what he was leading me to believe. A normal day at the track the car will go .005 -.010 with in its times. Then there is a random .100 speed up lol.

IAT location on a 04 GTO sucks. Look for differences in IAT values between runs and what it might be changing tune wise.

especially with what iat's and ect's may be doing to your timing ;)

has he tried dialing a bit soft, cutting a good light, and then using the brakes at the top end?

I took out all the changes for timing for ect and iat in the areas he runs as per the data logs. The "dyno" tune was all over the place with numbers so I tried to smooth things out best I could. He likes to deep stage and with stock stall he brings it up to 1500rpm. He has broke out while on the brakes hard enough to get an abs light. I told him to change brake fluid if that happened. I'm sure it's stock 10 years old too. There is no knock in the logs timing stays steady. It just randomly goes fast lmao. Can I unplug his maf with out going 100% line pressure on the trans? I know some OS's liked to do that on the older stuff.

When he first got the car it wouldn't run the near the same times ever run. It was always out to lunch. The rev limit was only 100rpm from the shift point so it would smack that every few runs. Trans is "built" I think it's just a stock trans with a shift kit.

I got busy with my own project last night and didn't get to upload the tune and logs.
Anybody know if the beta can take a v6 e40 and make it a trailblazer v8 e40? I'm stuffing a 5.3 into a Colorado and need to run the e40 computer. (Off topic)

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Originally Posted by 4.8t

When he first got the car it wouldn't run the near the same times ever run. It was always out to lunch. The rev limit was only 100rpm from the shift point so it would smack that every few runs. Trans is "built" I think it's just a stock trans with a shift kit.

I got busy with my own project last night and didn't get to upload the tune and logs.
Anybody know if the beta can take a v6 e40 and make it a trailblazer v8 e40? I'm stuffing a 5.3 into a Colorado and need to run the e40 computer. (Off topic)

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Fix the MAF sensor (replace it), and then if it's still hard to keep it consistent, take some power out of it so it's easier to drive...consistency is more important to him than overall ET right? So pull a couple degrees of timing out of it and fatten it up a little.

Compare run to run the IAT and ECT going down the track.

As for the V6 PCM, I already replied on your other thread, but that's not an E40, it's a P05. It looks just like an E40, and has the same connectors, but it's not the same PCM inside and can't run E40 code.

Also make sure there's enough room between the shift point and rev limiter that it's absolutely never hitting the limiter. Some vehicles will load up the converter a little differently on launch than from a roll, and it can cause them to hit the limiter on the 1-2 shift when launched really hard.