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View Full Version : Do I really need a tune?


Motorhead350
08-31-2008, 04:15 PM
I was wondering if it's really worth the time and money to "tune" my car when I put the drag radials on it. I'm pretty happy with the 1/4 mile time, but the racing tires are 1.5 inches shorter than the stock rears. Does/will it really make a difference?
sd8683
08-31-2008, 04:26 PM
I would, you'll probably hit the rev limiter before it shifts, I could be wrong though, I frequently am!

Sean
KillJoy
08-31-2008, 04:28 PM
What do you think?

:dunno:

KillJoy
Motorhead350
08-31-2008, 05:41 PM
Steve it's been fine for over a year, so I say no. I want to know what the "experts" think.
KillJoy
08-31-2008, 05:46 PM
Steve it's been fine for over a year, so I say no. I want to know what the "experts" think.

Ok then...

YES, you need to re-tune for shorter tires, otherwise you will be banging off the Rev Limiter.

:up:

KillJoy
ctrlraven
09-01-2008, 02:35 AM
Yes, yes and yes.
chader
09-01-2008, 07:43 AM
it should be easy to do,the SCT has a spot to chance the tire revs
ChiTownMaraud3r
09-01-2008, 09:05 AM
Chader, does the tuner allow you to change tire revs for each tire individually?
chader
09-01-2008, 06:11 PM
ya as far as know,you have to find the revs for the specicic tire you want to run and enter it in
ImpalaSlayer
09-01-2008, 07:02 PM
13.72 with basic bolt ons should tell you yes it will help
ctrlraven
09-02-2008, 10:20 AM
13.72 with basic bolt ons should tell you yes it will help

Indeed, also helped my 3500 stall work a whole lot better. 4.10s are going to scoot me down the track even better.


You can change revs per mile in the tuner but you want a tune with shift points adjusted to match those revs per mile or all you do is confusing the PCM even more since it will have the shift points of such said stock rear tire.
red
09-07-2008, 01:59 PM
There is WOT RPM-based shift scalar which provides a commanded shift point in addition to the TP-MPH based shift schedule. Assuming these tires are just for the strip, using the handheld parameters for revs per mile and WOT shift point should serve him well (I've been doing this for some time). If you're bouncing off the rev limiter, then back off a MPH or two using the tuner. If you're missing any of these parameters, then your dealer needs to enable them. Obviously, this is not say there will be no gains from tuning, but if you've already had a good tune and are just planning to retune for the change in tire size, I say there's no need. As always, you should be logging to verify actuals and make sure you have a useful rev limiter set (not 7k!).