Got a couple of questions trying to figure out why my mph/ET seems to be suffering on the big end of the track. Car is a fairly mild lsvtec making 207/152 on a dyno jet and at the moment, the best run is 12.901@103.9xx. Now the car leaves great pulling 1.80 flat all day long and some dips into 1.75's on 22x8x13 slicks. No squat, just grabs and goes (this is on a T&T night, no track prep) and carries good speed to the 1/8 averaging 8.19-24 at around 85 mph. It just seems to slow down after that and the big end times aren't matching what the small end says it should be. I am revving the car to 9400 (that's where the car makes power to on the dyno so I am not over revving it) and in 4th when it rolls through the traps its around 8500 so it's still "feels" like it pulling hard. Am I missing something here or is the damn thing just slow?


I have spent a good bit of time with a couple of guys tuning at the track and on the dyno but it just doesn't seem to want to go any faster down the big end. Hell when the car was on a street tune and only made 183 whp, it went 12.92 at 102 but the 1/8 was down by more than 2 tenths. I expected the car to drop to the 12.60ish range with the improvements made and how well the car felt. Just doesn't seem to be happening.

Can anyone feed me ideas here on where to start next to try and get the power on the big end?


I know, it's a bit rediculous to ask this BUT, I am kinda confused since I have tried all the things I know what to do/could help short of a rear diffuser.

 

whats the weight w/ driver?

 

Honestly I am not sure. The only weight reduction on the car is the lack of back seats. I am 200 lbs so I would guess mid 2300's.

Last night I was thinking and came up with something rediculous. Duckbill??? It is a long shot but with the car not pulling timing or anything like that, I can only come up with aerodynamics issues since it's slowing down once it get's a good speed going. I am headed back to the track tonight if it doesn't rain so I will yank off the duck bill and throw the stock peice back on just to see.

I know it's a long shot but it just doesn't make sense to me to only gain 18-19 mph on the big end.

 

how much power does it make?

 

207/152.

 

seems to be right on track based on this : http://www.tunercalcs.com/

 

It's all motor. 1st and 2nd feels strong then 3rd and 4th feels a bit lacking.

 

Well, I did two things and went back to the track. I yanked the headlight and put in the headlight intake ****, and removed the duckbill and put the stock back on "just in case". NO OTHER CHANGES!




Didn't do to bad. I could have gone faster I think but I couldn't get the 60 down. Track wasn't prepped since it was T&T night and they weren't stressing it and it wouldn't hold more than a 7k launch. I can't wait to go back when there is an even going on and get the 60 back into the 1.70's. Maybe see some .30's on motor. Actually went 110 once but that was .02 slower so I posted the fastest slip.

 

wow thats a big difference

 

duck bills will cause major areo dynamic problems i once cracked mine on the highway and half of it came off the car actually started pulling really hard like i had bent something in the front end, stopped and ripped off the leftover peice and it was all good

 

Yeah man, I was very happy. The first pass getting the feel for track prep got me a 12.80 at 107 and I almost **** myself lol.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AllMotorMark &raquo;</TD></TR><TR><TD CLASS="quote">duck bills will cause major areo dynamic problems i once cracked mine on the highway and half of it came off the car actually started pulling really hard like i had bent something in the front end, stopped and ripped off the leftover peice and it was all good </TD></TR></TABLE>


After tonight, I can believe that 100% without even thinking twice.