Short Story

Ran my car at the track 15.0-15.2 @ 91-93MPH 2.3 60 foot

1 Month later I thought the car felt weak and I took it back to the same track with almost the same weather conditions and what do you know

Ran my car a month later 15.8-15.9 @ 83 MPH 2.3 60 foot

I have an R56 Cooper S automatic but it now can't mile an hour a stock Corolla.

I took it into my dealer and told them feels dead after 40 MPH they said don't see nothing wrong. I for a second thought it could be my imagination and that is why I went to the track

I now have a decision - do I use the time slips as proof. I makes things obvious but may give them an excuse.

 

if you give them time slips, i can see this now. the dealer will say its been raced and not honor your warranty. is the engine light on? if there are no driveabilty issues like stalling,bucking etc. have the dealer at least check for stored dtc's or fault codes. if nothing is found at least it will be documented.
DONT GIVE THEM THE TIMESLIPS!!

 

The best way to test the health of your motor is to run a compression and leakdown test. Leakdown will show cylinder leakage, and a compression test will show variances between cylinder compression, and could shed some light on potential engine damage. Timeslips mean nothing. Temperature, wind, track conditions, weather, etc can all effect 1/4 mile times.

 

It's true that *elapsed times* in the 1/4-mile can vary pretty significantly, even from run to run, but trap speeds are much more resistant to variations.

Regardless, a 10 MPH difference in trap speeds is roughly a 50 horsepower difference when you're talking about a 2900-pound car/driver combination.

Since both measurements were done at the same track within a month of each other, I'd say that he's correct in thinking that something's wrong.

Still not a good idea to show the dealer the timeslips, though. Take it to a dyno shop and find out for certain what's wrong before approaching the dealer with the dyno charts.