Help me understand what happened here....

[GRFox]

I went to the strip for the first time on June 9th.

2003 Mach 1, 5 Speed
K&N CAI
Magnaflow Catted X-Pipe and Cat Back
Diablo Predator 93 Octane Flash Tune
Semi Bald 275 Summitomos

The car went:
13.807 @ 102.74 / 2.186 60'
13.733 @ 103.15 / 2.241 60'

This past week, I put on Nitto 555r DR had 4.10s installed with 31 spline Mosers and a Cobra differential. Went back to the same track yesterday with a car that feels significantly faster with the 4.10s and hooks up hard on 275 DRs.

I had 6 Solid runs:
13.781 @ 100.81 / 2.04 60'
13.784 @ 100.97 / 2.06 60'
13.858 @ 101.37 / 2.12 60'
13.748 @ 101.39 / 2.10 60'
13.847 @ 100.66 / 2.08 60'
13.802 @ 100.89 / 2.01 60'

You could argue driver mod, I am not going to say i am a professional driver but I drive the car pretty well, power shifting every run, and Im not really sure you could shift any faster or harder with out ripping the sifter off the transmission. All of the runs above I varied the launch any where from 3000rpm to 4500rpm, slipped the clutch, dumped the clutch, I hooked hard with the radials no matter what I did, and based on the consistency.... I don't think its me thats the problem. I shifted the car around 6500RPM on every pass.

I would have expected the car to be in the very low 13s possibly high 12s based on all the other Mach 1s out there. I am going to try and get the car on the dyno this week for a tune and see if there is an issue.

The car only has 52k miles on it. Any ideas guys?

Thanks in advance.

 

[Tommy Z]

Wish I could shed some light on this. I, too would like to know what happened since your 60 foots were better. My guess is it has something to do with the gears.

 

[2007ShelbyCobra]

2.0 60fts arent hooking hard, thats pretty bad especially with a 4.10 gear, should be in the 1.8s. With that mph, the car has to be lacking a lot of power. Id take the tune off, put it back to stock and see what it does. An intake/exhaust set up doesnt really need a tune, a lot of the pre programmed tunes on hand helds are junk. Are they 245 or 275 nittos? How did you do your burnouts? (what gear, how long, what tire pressure) Where are you shifting in each gear? Are you trapping in 3rd or 4th?

 

[4v_mach1]

I was going to mention about those predator tunes that come with the hand tuner are junk.. out dated. You can get a better tune through vmp or even a dyno.

 

[GRFox]

2.0 60fts arent hooking hard, thats pretty bad especially with a 4.10 gear, should be in the 1.8s. With that mph, the car has to be lacking a lot of power. Id take the tune off, put it back to stock and see what it does. An intake/exhaust set up doesnt really need a tune, a lot of the pre programmed tunes on hand helds are junk. Are they 245 or 275 nittos? How did you do your burnouts? (what gear, how long, what tire pressure) Where are you shifting in each gear? Are you trapping in 3rd or 4th?

After watching a video last night (cell phone video) it looks like the car was bogging pretty bad at the launch, I got almost no wheel spin at all coming off the line. They are 275 Nittos and I ran them at both 20lbs and then at 14 lbs and had the same times, 60', and trap speed either way. I shifted at 6500rpm every shift and went through the traps in 4th gear ( stayed in 3rd through the traps with the stock rear.)

 

[GRFox]

Burnouts went through the water box and I spun until I could see good smoke and then let off. 1st gear.

When I went to the radial the car feels like it struggles to break the tires loose in 1st on dry pavement. The car must be really lacking power.

 

[4v_mach1]

The car must be really lacking power.

check plugs, change fuel filter, check cops, and try your stock tune & see how it runs..

 

[CrispyBacon]

Sounds like you may need to try and launch at a higher rpm

 

[Roots-type]

Possibly clutch slipping?

 

[GRFox]

Burnouts went through the water box and I spun until I could see good smoke and then let off. 1st gear.

When I went to the radial the car feels like it struggles to break the tires loose in 1st on dry pavement. The car must be really lacking power.

Possibly clutch slipping?

No. Clutch has about 1500 miles on it.

 

[GRFox]

Ok, so I reset the car back to stock tune. It feels like I picked up some power but its hard to tell. The car is SUBSTANTIALLY quieter with the stock tune. I mean a huge difference in sound, is that normal for just a tune?

 

[watman02]

no the sound really shouldnt change unless timing changed substantually.
what rpm are you launching at? check out my sig for my best times on street tires and mods.
my trap speed what alot higher than urs are u at high altitude? really hot humid weather?

 

[GRFox]

no the sound really shouldnt change unless timing changed substantually.
what rpm are you launching at? check out my sig for my best times on street tires and mods.
my trap speed what alot higher than urs are u at high altitude? really hot humid weather?

It was very hot and humid. I launched as high as 4500 rpm.