I am working on a supercharged 05 GT. The car has 3:73s, headers, FRPP axle back, and a Vortech base kit making 5-6 psi. When the car was NA it ran 13.7@103 mph with the above mods plus a JLT cold air on normal street tires and heavy FR-500 chrome wheels. I did not get the car dyno'd but I would guess it made in the 260-270 range at that time. We added the Vortech and with a safe tune the car made 360 to the tires. Not killer power but not bad for a mild tune. Took it for a spin and the trans shifted way too early and often on the street. Changed the shift schedule and it seemed much better. Took it to the track and it spun bad on the first pass so I put some drag radials on it. Staged the car and ran a 2.09 60 foot and a 14.0@98 mph. Car seemed like it was shifting way early so I changed tunes and it seemed better and went 13.8@99 mph. Finally I tried manually shifting the trans at 6000 and it went a 13.7@99 mph. The car is just FLAT. It has no pull at all, especially when it shifts to 4th gear. On the manually shifted pass it felt pretty good in the first three gears but when it shifted to 4th it just straight up fell flat on its face. The car made decent power and I figured should at least go in the 13.0 range at 100 mph. I had this kit on a 5 speed car before and it ran 12.40s@114 the first time out with it on the same drag radials. Anyone have any insight here?

 

Something is not working right...SC'd cars should do better than that...stock they run 13.5....Your tune may be the culprit...

 

I woiuld run a stall speed converter.
I have a 3200 RPM Level 10 billett converter and I have been getting 1.6 60" times with ET Streets.

 

2.09 is not a good 60' for drag radials. There's a lot more to be had there. That said, something is definitely wrong with the tune. You're trapping way too low. a Vortech charged car should be trapping a lot higher than that. My first time ever racing with a few bolt-ons I put down a 13.5@104 with a 2.139 60' on stock rubber. And that's with 3.31's. What RPM is it shifting at? Do you have any dyno graphs?

 

The 60' does suck but seems like you have bigger problems with the fallout in 4th gear. Also it is odd that you're running faster when manually shifting the car instead of letting the auto do the work. I would guess (again just guessing) that the shift schedule and torque converter lockup portion of the tune needs adjusted. Get a good tune from Brenspeed or Bama and give it a try before you spend anymore money on parts.

 

I am well aware something is not right and the car should trap higher. I am looking for opinions on what might be the problem. A converter would be great but it should be much faster as it is. 2.09 is not a great 60 foot but it is not bad for a stock converter either.

 

I talked to Brenspeed about a tune before and he wanted delete plates on it with the blower which I really did not want to get into. If Bamatunes or Brenspeed can get me a good program with the stock plates I am all ears.

 

What are the 1/8 mi times? We need to see if you are starting out well, but just falling off at the end. Don't worry about the 60' yet, your trap is way too low.

I'm betting it's a tune problem.

 

Just curious why you do not want delete plates? If they fail on you with FI, you will quickly have problems.

 

Delete plates are an easy install (1 hour) and Brent has a used set that he'll sell you cheap.... just saying, its a good mod that's affordable and works well on FI setups such as yours.

 

I thought you had to use the delete plates with the centris anyway? Why didn' you put any on? What's your aversion to them?

 

Not having delete plates is not the problem with the car. I very well might add them to the car but for now I want to find out what the problem is without throwing more parts at it. Not running deletes is not causing the car to trap at 99 mph but something else is and I am trying to find out what it is.

 

Just a guess here, but it sounds like maybe your torque converter is not ever locking up. You probably got good numbers on the dyno because they locked the tranny in 4th gear with the TC locked. Now that you're running on the regular tranny computer the TC maybe isn't locking up so you're never transferring full power to the wheels.

I think it's definitely the tune since the TC lockout can be computer controlled. I would hope that Brent or Doug can get you a good auto tranny tune that doesn't require delete plates to test it out.

 

Thanks Jaiasmit. That definately sounds like a possibility.

I checked and I don't have any timeslips. IIRC my 1/8th mile speed was around 79 which I thought was on the low side as well.

 

This is kinda ironic but not really on topic, well sorta. I just raced an 07 auto gt with a saleen sc. This guy had to have a bogus tune or low boost or something because we were dead even up to third gear... While we were racing I was thinking in my head " this guy is supercharged, you gotta be kidding me", I felt really bad because this guy looked ****ed after we raced and we had a pretty nice conforsation before the race. He told me before the race he had headers and the saleen s/c and tune. I could also def he the s/c because it was right in my ear. I was trying to ask him how much boost he was running and who did his install but he wanted nothing to do with me after the race. Just drove the other direction...

Ok back to the topic, I just had to share that because it just happened and I just got on my computer and this was the first thread I saw...

 

Sounds to me like maybe your belt is slipping bad.

 

Belt shouldn't be slipping at 5-6 psi, and the dyno numbers seem right on. It's got to be something to do with the changes made in the tune for the auto tranny.

 

Doug at Bamachips won't sent me a tune for a blower car. Is there anyone else you guys would reccomend? Brenspeed lists a blower tune but $185 is a bit steep for a mail order tune when everyone else is $75-85.

 

Eric Brooks/Diagostino Racing (sp?) will send you a blower tune.

 

Call Brent and talk to him...... otherwise you could try JDM too.