SC_Highlander

This may be more appropriate for the under-the-hood forum, but I figured that racers would probably be the only people that might have experienced anything similar...

On Saturday, my co-driver spun the car on his first run at about 60-65mph. He went two-feet in, and kept the motor from stalling. While rolling backward slightly, he selected first gear, and let the clutch out, but something felt bound in the driveline, prevented the car from moving forward and the motor stalled. He re-fired the motor, which made some very unhappy sounds, clacking and rattling like crazy was captured on the video, but he doesn't remember it sounding off. The really strange thing, though, is that upon selecting first gear and letting out the clutch slowly, the car wanted to move _backwards_. Perplexed, he selected reverse, and the car wanted to move forward. In both cases, the motion was not a normal 'freely rotating' sensation (IE, not drivable). He said it felt bound up, like it was trying to move but the wheels were chocked or something. With the trans in neutral, they were able to push the car freely off course, and we towed it back to grid. Thinking we were done for the event after 1/4 of one run, I hopped in and fired it up, tested gears 1, 2, 3, and reverse, and they all worked fine. We ran the rest of the weekend (a total of 11 runs of ~57s each) with no issues. Garrett confirms that the spin was driver-induced, not caused by anything mechanical.

Relevant car information:
AP2 motor (24k miles)
AP1 transmission (50k miles) -- of note: after the F22 swap last year, we have been unable to select 6th gear in this transmission. It's as if there's no gate for 6th. Not a problem on an autocross car, so I never investigated.
AP1 differential -- PuddyMod reinforcements, Carbonetics carbon LSD, have been in the car for over 3 years. One year ago, 2 or 3 of the LSD clutches were replaced. Two days before this competition, the final drive was changed from 4.1 to 3.63 by Ben @ PuddyMod. He gave the diff a clean bill of health.

On my to-do list are to drain fluids from both the trans and the diff and see if anything strange shows up, and to use my inspection camera to get a look at the clutch/pressure plate. Based on how the car performed on Sunday, I don't think that anything was damaged permanently, but I'm also out of ideas for what to check before writing it off as just a random weirdness and moving on.

So, my questions are: WTF happened? Speculation among some of the other competitors is that the transmission was somehow engaged in multiple gears. Has anyone ever experienced anything similar? Are there any other places that I should investigate?

Here's the video: http://youtu.be/77qXRbSfj7o

GT Motoring

From the description, it seems like the motor somehow was spinning in the opposite direction than it normally does. If this is the case, it might be possible that the motor was breaking through the exhaust and exhaust was exiting through the intake.

**Edit** After watching the video a few times, I pretty strongly believe this is the issue. It kinda sounds to me like an unnatural blowing sound coming from the front of the car - maybe exhaust coming out of the intake? If the motor was running in reverse, your oil pump was sucking and not pumping, along with a whole host of other issues.

My theory is Bias Ply slicks + car rolling backwards in a forward gear and clutch popped triggered the motor to run in reverse. Too much grip to allow slip at the tires, so the motor did what the situation made it do.

dan_uk

I've seen someone mess up valves rolling backwards in gear like that

SC_Highlander

The problems I see with that theory are:

1. He's clutch-in by the time the car gets sideways, and has pulled the shifter out of gear (~19seconds on the video), well before it goes backwards.
2. Though the car was rolling backwards, it was not doing so at any meaningful speed, and the transmission is in neutral. When he selects first gear, and releases the clutch, the car started to move forward before it stalled. I agree that the slow backward rotation, while in 1st gear, when the cluch was released might have caused the stall. At that point, though, you can hear the throttle blip right before clutch release cause the revs to increase. The motor sounds completely normal at that point, except that it stalls.
3. Even assuming that the backward roll caused the motor to stall, at that point the motor isn't spinning anymore. Engaging the starter would force the motor to spin in the correct direction. I believe that at the re-fire, the motor is spinning the correct direction.
4. The 'first gear moves the car backwards' behavior occurred after the motor was re-fired

GT Motoring

I failed to see the car moving forward before it died, I see it now.

It is still possible, even if the motor was cranked over with the starter which initiated the rotation in the proper direction, that once fired, the motor spun in reverse. This happens on diesel motors occasionally when everthing is set just right for it to happen. Based on the fact that it ran poorly, sounded like poo with possible air pushing from the front of the car (specuation) and the gears were reversed, I still think the perfect combination of all variables caused the motor to run in a reverse rotation.

psychoazn

It sounds like the motor was "running backwards"...