Bad/slipping clutch effect 1/4 mile time?

[SMRGTI]

I took my car to the drag strip recently and noted my 1/4 mile times were a full second slower. Its been more than a year ago since I've last been to the drag strip.

I was stage 2 back then running mid 14s on 19" TSWs and now stage 2+ on stock 17" with new tires and running slower (mid 15s). I noticed a lot of clutch slipping during cooler weather in gears 3-6 between 3-5k rpm but no slipping noticed on the 1/4 mile. Would the clutch be causing this issue? No boost leaks.

 

[Goingnowherefast]

What kind of tires do you have now and then, also what we're the outside temps?

 

[The Fed]

Weight of the wheels? Wheelspin?

 

[SMRGTI]

Temps were around the same, both with passenger, both with Continentals. Unsure of the weight of the wheels.

 

[Goingnowherefast]

What were your trap speeds?

 

[T0neyDanza]

Ummm. WHy are you hitting 6th gear? What track? Firebird or Speedworld?

 

[Red5pade]

Could be a number of things. Though a clutch don't help, wheel weight, traction, etc. what was the 60' and trap speed?


Sent from my iPhone

 

[Bunnspeed]

If your trap speed is more than a mph or two lower than last year, that would indicate you're probably down on power; either that or your clutch is slipping continuously and you aren't getting all your power to the wheels or able to load the engine enough to build/ hold as much boost. If your trap speeds are about the same, then your car is probably running fine aside from the clutch issues.

I'd bet your 60ft times are worse, probably due to clutch slip softening your launch by a lot. Your 60ft has a *huge* impact on your elapsed times. Every tenth added to the 60ft adds about 1.5 tenths to your E.T. For example if you had, say, a 2.5 second 60ft this year instead of a 2.2 second 60ft, your car would end up about half a second slower at the end of the run. After that, you'd add more tenths every time you shifted gears, as power gets used up on slipping the clutch instead of accelerating... I could see all those variables adding at least a half second to your E.T., maybe even a full second? :iono:

What are your 60ft times, elapsed times and trap speeds of your best runs, last year and this year? We really need those details to help you diagnose your problem.

 

[Bunnspeed]

I just re- read your post. If you didn't notice your clutch slipping, I don't think clutch slip would account for a whole second added to your times. We definitely need a more detailed breakdown of the variables, including what kinds of tires you ran, then and now, and, most importantly, your specific times, 60ft's, and trap speeds, especially your most recent info even if you can't dig up last year's slips. Enough of us have been to the strip with similar setups to tell you if your numbers look ok or if you are down on power or not getting traction.

 

[SMRGTI]

Damn I was so pissed that night I just tossed the slips away. I'll need to do a dyno test and take it back to Firebird with a new stronger clutch and see if anything changes. I haven't noticed any power loss over the years. My boost is still peaking where it should.

Although I can say it feels like the car has always been quicker during rolls than off the line when there isn't clutch slippage. Maybe it's my performance cuz a buddy of mine ran 14.1 1/4 mile times consistently in his MKIV gti and I pulled on him every time from a 20-30mph roll.

Unsure of the trap speed, but I remembered being around mid 15s @ ~95mph. My better times in Jan 2010 were usually around 14.7 @ 97-97.5mph

Only performance I added since was Forge twintercooler and APR HPFP.