Why is my MPH so Slow

[TryMeGT]

Went to the track this weekend for fun, came home very disappointed. Car went 13.6 @ 99mph. This is around 6-7mph slower than last year. Only difference: Put on a Hooker Cat Back system w/ Aerochambers this winter, and I used the test pipe supplied in the kit. Last year, I had a Flowcrapper 2 into 1 out to 2, but I had a test pipe with removable cap. I always ran with it open at the track. Is running it through mufflers going to slow me down that much. If so, the other test pipe is going back on. Just frustrated that I added a second to the car. Boost was 20-21lbs, with a useless 2.1 60ft on slicks.

 

[UNGN]

My guess is that it is too rich. What is your Fuel Pressure?

 

[TryMeGT]

Fuel Pressure was 44-45 line off

 

[ledzeppac]

Even his 1/4 seems slow given he is running 21lb boost.

 

[5ltretr]

do you have any info from your scantool ?

 

[TryMeGT]

O2's were 840ish. Other than that IAC is 17-20 at idle and TPS is .46. Had 110 Octane fuel and I did not get any knock on the run. Launch was at about 5lbs boost. The run actually felt good, but the timeslip was disappointing

 

[5ltretr]

no blm problems? somethings up?

 

[Paul Clark]

What was your boost, your FP, and your 02s at the lights at the end of the track?

 

[TryMeGT]

I did not glance at the guages or scanmaster as I crossed the line. FP guage is under the hood so it is not readily accessible at the end of the track

 

[Paul Clark]

I think (someone correct me if I'm wrong) that your boost can be pretty high in the first 2 gears, but what counts is when it is 3rd (or maybe 4th) at the finish line. That's when it puts the most load on the engine.
Your fuel pressure should equal your boost plus the pressure you initially had with the line removed.
Your 02 readings really count (no pun intended) at the finish line also.
Again - those of you who know correct me if this is not correct.

 

[Turbo6inKY]

Did it feel like it was falling on its face towards the tops of the gears?

Could be coilpack.
What do the plugs look like? Check the gap. If they're worn, they'll misfire at high cylinder pressures.
has your gas mileage slipped at all?
You could be floating valves too. How old are the valvesprings?

 

[XLR8]

Valvesprings? With O2's at 840 you are rich - my car seems to like it best around 780 at the big end. I don't thing adding the Hooker system caused your problems. My times are with the Hooker Cat back system closed - both times that I opened the dump on my THDP, I lost 1 mph so now i keep it closed.

 

[TryMeGT]

I am starting to lean towards the car running too rich. FP was 44-45 line off. With Red's race chip, he suggests 42.5 +/- 1. His chips run rich to begin with and mid 800 02's suggest rich anyway. The valve springs are comp cams and have less that 8000 miles on them. I know what it is like when it falls on it's face at 4500rpm. That's why those were replaced. O2 crosscounts are strong and the denso 02 seems to be working very well. Next pass at the track I am really going to watch the numbers on the scanmaster at the end of the run.

 

[oehm]

Originally posted by TryMeGT
The run actually felt good, but the timeslip was disappointing

It is possible that the timing equipment at the track was off. Did you only run the car once? Were the times consistant?

 

[murphster]

What were the 1/8 mi time and mph? Also, what was the full timeslip from last year? I would think this would help diagnose the problem whether it was down on power, top end problems, etc.

I would assume same boost and chip as last year, as long as exactly same fuel. Weather any different?

I know I'd be wondering what the heck was up.