I messed up my OEM bumper, and had it replaced with a AP2 bumper.

I would (at certian times when the road is clear) race my friends STi... he usually pulls away from 60 to 100... not by much 1/2 to 1 car. my only mods then, were a spoon style snokel, K&N filter, and removed resonator.

last night or i guess today early morning (2am) we had a chance... with my new bumper, and suprisingly i pulled everytime.
from 45 - 100 i got about 1 car length...
from 60 to 100 i pulled about half a car lenght.

I did some reading this morning, and read that the AP2 had improved aerodynamics. The new bumper had much better aerodynamics. But i didn't know it would make that much difference!!!

Any input on this, are there any Cd data available.

 

you mean you replaced it with an AP2 bumper, right?

 

o yeah AP2 bumper, i just change it for you

 

I wonder if it is the time of day that made the difference... NA cars are heavly dependent on ambient temp for denser air to generate more power... where turbo cars will benefit less b/c the turbo will heat up the air to have intercooler cool it down again (and intercoolers cool the air down in %, so the effect of cool air diminishes as air gets cooler)... or it could be aerodynamics, but if it was aerodynamics only, i'd imagine you getting ahead more as speed increases.

 

yeah it could be the cooler weather. the other times we races was during the summer, but always late at night (early morning). here in hawaii its about 10 F difference from summer to fall temperatures.

according to this honda press release, the aerodynamics were improved by 5%, due to the redesigned bumper. it is stated in the spec comparision section under aerodynamics.

2004 Honda S2000 -- Introduction Part 1

To me that's a pretty big improvement. it's like gaining hp at higher speeds.

 

My gripe with Honda is why does the TSX get under body aero and we dont! The S2000s rear needs a diffuser to spice things up out back. IMO the rear design is too plain.

 

the only explanation i can come to is the difference of drivers, since it was 2am, he could have been somewhat tired and his shifts were not as accurate.

i very much doubt that the simple switching of bumpers will get that much gain. Sure, it might help the straight line stability, but i dont see it giving the gains you stated.

 

yeah i didn't think my new bumper will make much of a difference, we were just messing around.

 

At speeds under 100 mph, a 5% decrease in Cd will barely be felt. There are likely many factors that contributed to your gaining on him on those latter runs.

An STi (STI now) should walk an S2000 on average. Can't deny dynamics.