402 / L92 / L76 Tune Help (Need speedometer help too)

[exco]

Hey all--

I think i have it *close* attached are the logs and tune for my 2006 GTO. Here are the specs:

SLP 402ci stroker
L92 Heads (ported)
40# injectors
cam is 228*/240* .614/.610 115 LSA

The timing seemed a little high to me at cruising speed. (~45*) -Also, this isn't a finish tune, it's a "break-in" - im getting it tuned on the dyno Friday. I just want to make sure this tune is "safe" until friday.

I'm also having trouble tuning the speedometer to be right... the computer is right, but not the speedometer. I have 275/30/19 on the rear. and 3.91 gears..



Thanks in advance!!!!!


--chris

[BBA]

The way to get the speedo right is by using a portable GPS and modifying the calculation values until it reads right.

Also, set speedo to use calculated values instead of GM-LAN if you have that setting (I know a 2007 TBSS has the option under system but a 2006 does not).

[BBA]

Oh, and get rid of the negative timing values in all the timing table cells. Seems to work wonders for off the line response.

[exco]

well that works all fine and good - but there must be some kind of formula :-P

[exco]

Oh, and get rid of the negative timing values in all the timing table cells. Seems to work wonders for off the line response.

lol... those negative numbers came from when the car wasn't started at all. ignore those

[BBA]

lol... those negative numbers came from when the car wasn't started at all. ignore those

You might want to do some logging of that stop light to WOT pedal stomp airflow values...look at the timing histogram when you do it.

Makes perfect sense and it actually works.

So there!!!

[BBA]

Oh, the formula for correcting speedo error, simple, divide the reading MPH by the actual MPH and multiply or divide the resulting ratio by the gear ratio setting value in the tune to find the new value that will correct the speed error.

That or just experiment with small changes until it read right. It's all common sense...

[exco]

Oh, the formula for correcting speedo error, simple, divide the reading MPH by the actual MPH and multiply or divide the resulting ratio by the gear ratio setting value in the tune to find the new value that will correct the speed error.

That or just experiment with small changes until it read right. It's all common sense...

well yea......is there a way to change it while you're moving? it's a pain in the ass

[BBA]

well yea......is there a way to change it while you're moving? it's a pain in the ass

That I don't think so. It's just going to be a PITA.

[EC_Tune]

Give me your tire rollout and I'll fix your speedo for you.
Rollout is the distance for 1 tire revolution. You can do 2 to get it even more accurate.