Disappointing track day

[widebody911]

I instructed @ Thunderhill today with TrackMasters Racing Club. This was my first outing with the new home made roll cage , fiberglass hard top, lexan windows, etc, etc.

The good: The car ran great. The only things that even remotely resembled mechanical issues were some excess brake fluid resevoir overflow, and an errant bolt, that doesn't even look like it goes to the car, became lodged under the clutch pedal and wouldn't let the pedal come back up. After a couple of tire pressure tweaks, the car was sticking like like on it's new Kumhos, which I had mounted literally minutes before I left for the track. With the new cage, the car was much tighter and responsive, and much easier to drive. The fiberglass top "worked" great, no squeaks or rattles, despite having zero weatherstripping. My po' man's interior door handles worked well, and were easy for students to figure out. I put down 190 track miles in one day; in the afternoon, I drove 3 sessions back to back for 75 straight minutes of track time. In keeping with the April 15th theme, my ass is sore...

The bad? As hard as I tried, I couldn't break 2:10

More pix @ http://rennlight.com/cgi-bin/search.cgi?string=Thunderhill+2004-04-15

[Tyson Schmidt]

Dude, that is some sick rake on your rear wing. Doesn't it push like crazy like that?

[smstcoach]

Thom,
I knew I lost something on that ride along. That was definitely different.
It was awesome to see what serious weight reduction can do for our cars. Mine felt like a fat pig in the last session. I'm ready to pull out a hack saw and chop my roof off.
-Jeff

[Jack Olsen]

Well, judging by the pictures, you looked the business out there.

And in my (limited) experience, that track has fast days and slow days. We should do another event where he trade cars for a session. It might be useful to see where the handling characteristics are different -- a kind of perspective check.

[widebody911]

Originally posted by Tyson Schmidt
Dude, that is some sick rake on your rear wing. Doesn't it push like crazy like that?

It pushed a little, but I dropped a couple lbs of air out of the fronts and it seemed to work OK. I had no clue as to where to set the angle, so I just WAG'd it and went from there. I'm on the steep side of the learning curve.

OTOH, nobody could touch me in turns 2 and 3.

[smstcoach]

Jack,
I'll trade with you if Thom won't
-Jeff

[ted]

Looks awesome in the corner.
What is the sweet spot for the banana wing, 7 to 12 degrees?
The photo looks like you have more.
A front splitter would seem to balance the added rear down force?
Car looks very good, compared to all the skillful time consuming improvements you have made a basic front spoiler would be simple.
I’d really like to try T hill and Sears this year.
When you coming down to Big Willow or Cal Speedway?

[Jack Olsen]

We've tried to get Thom down to Willow for a while now. One day, he'll see what a fast track is like.

[Tyson Schmidt]

Originally posted by widebody911
It pushed a little, but I dropped a couple lbs of air out of the fronts and it seemed to work OK. I had no clue as to where to set the angle, so I just WAG'd it and went from there. I'm on the steep side of the learning curve.

OTOH, nobody could touch me in turns 2 and 3.

Yeah, you're aproaching the stall angle there. I'd just try backing it off one notch.

[widebody911]

I'm also thinking about lowering the whole assembly about 1"

[mjshira]

Thom, I love your car man, MadMax meets 911.ROCKS!

[PorscheGuy79]

Thom, how did those holes work out? Notice any reduction in temps or maybe noticeable drag?

[widebody911]

Originally posted by PorscheGuy79
Thom, how did those holes work out? Notice any reduction in temps or maybe noticeable drag?

Oil temps were normal, and I can't really tell about the drag, with the new wing, different top, etc. Apples to tractors. I'm only getting up to 130 on the front straight, but that could be a factor of the incorrect wing angle.

[Jack Olsen]

In my opinion, the rear holes aren't going to do anything for you. You've got a high pressure area above the decklid, and a low-pressure area behind it. Part of your rear downforce is generated by the disparity between the two. The engine blower also relies on the high pressure air up top as a source for cooling air. The low pressure region in back is only going to be pulling air away from the blower. In a worst-case scenario, you're now reducing rear downforce, and diverting cooling air from above the decklid to behind it, reducing the volume of air for cooling the engine.

(Of course, my opinion should be taken with a large grain of salt, as I'm the furthest thing from an expert on aero.)

I think it's a different story down by the muffler.

And that's one of the coolest-looking rear ends you're going to find on a 911.

[kycarguy 935]

I found this aerodynamic wind tunnel simulator if anyone is interested. It may answer some questions about high/low pressure and downforce.

I havent tried it and have no affiliations.

http://www.kineticart.co.uk/WindStudioSimulator.asp