Fun times at Thunderhill with Hooked on Driving event a few weeks ago. An example would be my son's stint while taking Turn 1 in the 914 turbo; "minor" downshift issue approaching at about 120 but nice recovery!
Of course I was was going no where near that fast at my turn at the wheel. He was Group C but I was in Group A. ;o)

http://www.vholdr.com/video/thunderhill-t1-fubar-1-30-10

Nice save!


You need to mount the camera higher, 2/3 of the screen is the damn dash right now ...
Andy

I hear you for sure - I misplaced the freakin' mount so we had to mount it to his helmet - not the best placement! (Well we did all see his hands at work!)

Besides moving the camera up, you can add a pair of lights where the ash tray sits and use an old ash tray as a guide. One yellow light can be plugged into the brake light wire with a splice connector. It will come on when the brakes are pressed. The other is green and runs from a switch that is mounted on the floor board next to the pedal stop and will come on at full throttle only. Use a multi connector plug behind the dash so you can remove it and put the stock ash tray back in. One or the other of the lights should be on unless in the pits or on pace/warm up laps otherwise you are wasting time.....

nice save! especially because the track looks pretty wet

Yep it was a morning run and the track was still just a little wet. Dried off nice in the afternoon.

Wasting time doing what? Having a record of some fun laps? The recording was not intended to be a learning tool - we save that effort for the Formula Mazda races. ;o)

Tom:

Ah yes, another HEART-STOPPING moment of appreciating the meaning of LOW POLAR MOMENT OF INERTIA! I don't think ANY car is harder to catch in the wet than a 914.....great job of staying ahead of it and staying on the (wet) black stuff!

Enjoy those Track-Days,

Terry

An odd place to get out of shape. Trail braking in the wet is a good way to eat it.....even when assuming the brake balance is up to snuff. A 914 is not forgiving of such behavior.

Tom I have looked at that video 20+ times and stopped it along the way....

when the car started to slide the tach was still down, he hadn't completed the downshift at that point...
No big yank on the wheel either...
very strange...maybe he got loose on the white blend line between the hotpit lane and the track?

with it being wet out, it could be almost anything...
with out telemetry read out it is hard to say for sure, but I would put my bet on a bit too aggressive brake application on turn entry...
Possibly check your brake balance. A bit too much rear bias for those conditions.

Think I agree. Looks like a braking issue. You can see RPM's drop a little
at start of trouble indicating lack of traction and they stayed down while car was sliding straight - need to tune the butt to feel that happening when your driving in the wet. Also wheel was pointed ever so slightly in direction of the intial spin favoring left hand on wheel only direction, Once right hand came up car was already spinning. Probably a tad too much rear brake bias for wet too but its probably perfect for dry events. I was always dragging rears into turns in the dry with my 914 but thats the way I liked it.

If there was a shift perhaps not enough throttle blip and overly aggressive braking for conditions? Curious if the car has LSD or not as well.

And I have a theory about low polar point of inertia and 914's as being cause for crazy uncontrollable spins. Most 914's on the track have a fairly significant rear weight bias. That big heavy tranny and support structures behind rear axles are a lot different than many other mid engine cars with transverse mounted motors I have always suspected poor rear suspension that cant hold alignment spec under hard lateral loads being bigger cause of uncontrollable spins in 914s than low polar but thats just a feeling with no science or data behind it. I especially think that now that I drive a Boxster that is much easier to reel in from a spin than my 914 ever was.

Hi all:
Thanks for the analysis/input - I'll show them to my son.
As I recall he said he was in fifth approaching entry and downshifted from fifth to third (don't ask me why) and locked up the rear end. The track was not super wet but it had rained a little the evening before and of course that did not help the situation. ;o)
After looking at the video again I see his notes in the video and I see his right hand drop off the wheel for the downshift and almost simultaneously a BIG drop in engine revs so I think a 5th to 3rd shift and a subsequent lockup (and possible trailing throttle brake application?) was the culprit.

5th to 3rd would give a monster *jump up* in revs....unless he has very quick feet.

Now I see it.......the revs jump just as he starts to counter steer.

Yupp, you can see it just for a second then the steering wheel and hands get in the way ...

Good save.

Spin or mechanical over rev, not good either way.

Was it driver error or mechanical error causing the the shift gate to move?

The infamous BMW money shift comes to mind...

Hey guys, Tom's son here. I just thought I'd stop by real quick to clear things up.

This was completely the result of my own rare spell of carelessness paired with still getting acquainted with an unfamiliar (and IMO completely wonky-feeling) gearbox. I had meant to grab 4th and SURPRISE, what I got was 3rd. Physics and tire friction coefficients take over. Chaos ensues. The end. Trust me. Every driver gets one bonehead mistake allowance per season right? lol

Track conditions were cold and slightly damp. This was around the middle of the 2nd session of the morning and it rained the night before so by this time there was a little bit of dry line developing. But yes, it was still pretty damp everywhere else off line.

- Matt

EDIT: And ya the camera position sucked. This particular helmet-mount is great for the formula car stuff but not so great in a street car with a big ol' dashboard.

Curious how do you get 3rd going for 4th from 5th gear? I could see 2nd but not 3rd? Is this a 901 tranny and standard shifter?

Or were you pulling tricky "i'll skip 4th to 3rd" shift from 5th? Just not a typical mishift which makes this even more interesting.

Now hitting 2nd would definitly lock things up nicely!

Good question! lol It wasn't a *typical* mis-shift as in, say, going forward toward 4th and accidentally sliding into 2nd. It was more of something like, thinking ahead about another turn, a 3rd gear turn, and *intentionally* going for 3rd instead of 4th as if it's the correct gear for the corner. Yay. Like I said, just a bonehead space-cadet move. And at the same time since I was getting used to the shift pattern and trying to go real easy on the "imprecise" and grind-happy gearbox... I think these things just helped to get me all mixed up.

I'm not in any way trying to place blame on the car/gearbox though; it was all me.

Hey Tom,

As I've mentioned before downshifting in ONE down shift to the right gear for the corner is a great time saver, allowing more time to focus on corner entry..... Assuming 3rd gear was the right one in this case. If it weren't the right one, OOPS, it's tough being human!

However, an issue here is also how SMOOTH was the down shift? Does your son Double-clutch his downshifts?......and even better is Heal-and-Toe braking and downshifting. These a vital skills to driving smoother, faster laps and being kind to the equipment at the same time. Learning doesn't take too much time, just be sure to have a soft steering wheel to bounce off.

A great book I recommend to everyone as a fun and informative read is Mark Donohue's THE UNFAIR ADVANTAGE. Mark was the 1st True RACE ENGINEER on top of being a great driver. In the book, he talks about analyzing why the BRITS were so much faster in the WET than Americans and what he observed was a difference in driving technique. Americans tend to TRAIL-BRAKE big time, while the BRITS use the "traditional" Brake, release, then turn into the corner style. The BRIT technique pays off greatly when the track get slippery. So when things get wet, I make a conscious decision the change my braking technique.

Other great reads: The Technique of Motor Racing, Piero Tiruffi and Driving in Competition by Allen Johnson.

Enoy those track days with your son, a day couldn't be better! I had many track days with my Dad and cherish the experience.

Terry

Stew, keep reading. My posts address this.

Nice job. Jerry does nice work.

I should have my project on the track by the end of March.
I have done mine a little different.

Ron

Cool setup. Easy access to the turbo! heh With that external wastegate I take it you don't plan on running stock boost levels?