Hey folks, so three years ago I went to the drag strip and consistently put down low 14's on the quarter mile.
Tonight I decided for old times sake to hit the strip one last time. All my mods remain unchanged, with the exception of replacing the OEM resonator with a magnaflow version.
Tonight has been absolutely miserable. Best time was 14.8, worst time was 15.5. Consistent 15's all night.
I've kept up all my maintenance to the best of my knowledge. I'm suspecting possible bad mounts but I really don't know. Oil is at 100% and tranny fluid is clear and within levels.

Can anyone speculate on such a large change in quarter mile time? My vehicle mileage on my best runs was around 120k miles. Today's drag times my car has 161k miles.

 

What 60' have you done now vs before? What outside temperature now vs before? His your car tuned?

 

I did FORGET to mention, I swapped out my CAI for a short ram. But I cant imagine that making .5 sec difference.

Not tuned. The temp 3 years ago was high 40's, with 39% humidity. This was the best run I made. 10/19/14
60' ... 2.037
330'... 6.0000
1/8... 9.0945
1000'... 11.740
1/4 ... 14.066
Mph... 99
The run a few nights ago was 78F and 40% humidity.
60ft ----2.32
1/4 mile 15.079

 

eww at short ram

 

You'll most likely be better off trashing the short ram and going back to the stock factory CAI.

 

ok the answer is pretty clear cold day vs hot day... and .3 difference at start (60')... 0.1 difference in 60' for my car means a 0.3 difference at the end of the line sometimes so you had a 0.3 diff now meaning a 0.9 sec at the end... so your car is the same as before, let's get this car tuned and you will reach the 13s on a cold 40f day for sure and better mpg... and knock free car...

 

I'm not happy about it either. I sucked water into my motor on thanksgiving two years ago during a bad thunderstorm. Never again. Although Vtec sounds pretty awesome, the stock set-up is where I'm headed.

 

I love getting educated, thank you. However that will be the end for this car. I'm picking up a 6MT Type-S from another member on here and have big plans for it!

 

I never bought into the "x reduction in 60' results in x times 2" or whatever in the quarter. I've made probably 300 passes in my life with various cars/bikes and always scrutinized my slips. IME, 1/10 reduction in 60' has always resulted in 1/10 reduction in the 1/8 or 1/4, give or take a couple hundredths.

That said, a rough estimate is to subtract 1/10 for every 10 degrees ambient temp, all else being equal. So 40's to 70's will slow you down an easy 3/10 with no other changes. Then the additional miles and heat soak from the SRI could have cost you 3-4/10 (although I doubt the additional miles hurt much). And finally, 3/10 slower on the 60 adds up to around a full second.

You really need to use a DA calculator to keep things uniform. Obviously, track prep and weather are two variables that change drastically, even at the same track. And if you're comparing runs from different tracks, forget it.

I'd lose the SRI. Heat is a major killer. When I ran my 12.3 back in May, it was the first run of the day; decent weather, temps low 60's. Subsequent runs kept dropping to 12.4, 12.5, 12.6 after sitting in line idling. Turbo BMWs are horrible when it comes to heat soak. Good news is, I can now monitor intake air temps on my phone with the JB4 Bluetooth module/app. When they're up around 150F, The car feels noticeably more sluggish than when they're around 100F.

 

While you are absolutely correct, I've found it difficult to teach non-pilots how wrap their brains around the whole Density Altitude concept.

 

Air temp and elevation will be the biggest variable also take into note back then you might visit the track more often and your reaction time was on the dot.

 

A better indicator is your trap speed, not your ET. If you were trapping 99 then and slower now, that's an indication of lost horsepower.