What would you expect to loose?

[turbov6joe]

Last night I took the TTA to the track with the following changes:
Switched from Nitto DR's (245/50/16) to MT's steet ET's (26/11.5/16), and installed a set of subframe connectors. Two weeks ago at the same state of tune, the car was running 118 MPH off of a 4 psi launch and 60's in the 2.0-1.9 range. Last night the best I could get out of it was 113 MPH at the same boost. I've always heard that switching from a hard radial to a slick type tire will cause a lose in MPH, but does this seem normal to you all? Somewhere in the time frame of 2 weeks the car dropped 3 MPH in the 1/8, and 3-5 MPH in the 1/4??? The only positive side of this was that the car turned it's best ever 1/8 and 1/4 mile ET's on much to be desired 1.87 short times. The overall picture of things as far as ET's were concerned looked good, it was just the MPH that was down! Any thoughts???

 

[19TTA89]

I had the same type of loss in MPH..When I asked About it,It was Best described to me this way....The less time you have to accelerate,The lower your MPH will Be...Your times were quicker...so you were actually on the gas for a shorter period of time..Make sence????HTH..Shawn

 

[GTABurnout]

I have heard that slicks cause a loss in MPH. The less tire spin you get the lower the MPH will be. I didn have this problem I acctually went faster with my ET streets 12.9 at 108 as oppsed to a 13.2 at 107 so who knows.

 

[turbov6joe]

I agree there is to be some kind of lose, but 5-6 MPH seems a bit much IMO. Best I can come up with was that there were numerous things going against me that day: 22º warmer out, switching to those tires, running pig fat, and low boost launches due to an overly rich condition that's being addressed as we speak.

 

[Razor]

Originally posted by turbov6joe
I agree there is to be some kind of lose, but 5-6 MPH seems a bit much IMO. Best I can come up with was that there were numerous things going against me that day: 22º warmer out, switching to those tires, running pig fat, and low boost launches due to an overly rich condition that's being addressed as we speak.

Ya answered your own question..rich, temp increase, tune.. bada bing..

Most cars MPH 1-3 when they blow the tires on the line....now a 1.88 60 foot..looks like ya need to practice your launch and burnout.

Get the tires at 14 lbs, heat them till smoke clearly comes from both wheel wells..make sure your not in the water box while doing your burnout, pull up to the line..pump your brake hard a couple times..push it down hard..pull up on your e-brake hard..mash the gas pedal..when the needle hits 15lbs "GO"

Guaranteed 1.6 every single time.

 

[turbov6joe]

No need for all that mash the brakes hard and pull up on the E brake stuff.....mechnical T brake Problem was that the old programming in the chip was purposly rich down low to avoid killing the Nittos; softened up the launch per se. Now with the good tires and suspension mods, traction is not such a problem. I'm having my chip dude lean it out down low for a harder launch. As for the rest of the programming, I finger that the leaner mid range will also get the fluttering boost under control a bunch. As of tommorow I'll have a good exhaust system, so that end of the equation will be addressed as well. With any luck at all, the new state of tune should produce some MPH that I can be happy with....say 122 @ 25 psi!

 

[Razor]

I had initially installed a stagerite in my tranny, and for some reason my car went down in trap speed. I tell you that it took me a month and a half..6 trips to the track to figure my MPH loss was attributed to the stagerite.

See I did the art carr shift kit and SR brake at the same time...went back to the track and lost 2 MPH from a car that consistently been trapping 112 went to 109. After I took the SR out..it went back to 112. Dunno..I must of installed and reinstalled it a bunch of times.. Direct Scan is what finally let me in on the tranny problem..My accelleration rate was coming way down past the 1000 ft mark

Anyways..back under my rock

Maybe I had a defective SR, maybe my tranny was on its way out,maybe maybe..My tranny 5 months latter needed to be built..but the SR I attributed to the problem. My .02

If ya can do 122 with a 1.5 60 foot low 11's are yours..worst case is 11.3-11.4

Cheers