Corvette crash video

Corvette crash video

Postby RacingFrog » Mon Sep 01, 2014 1:05 am

So here is the video of my crash at Burke 2. I still haven't figured out what happened and I haven't had time to look at the car yet since last weekend.
I'll post more details if I figure out more things, but feel free to give your opinion!

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Re: Corvette crash video

Postby Challenger392 » Mon Sep 01, 2014 9:22 am

Curious as to why the GPS speed barely drops below 60 before the ditch but the obd2 indicated much lower than that. I know the GPS must be lagging. But I wonder if the obd2 speed is also incorrect. Could it be possible that the wheel speed sensor malfunctioned causing the car to think you had a lockup and accuating the ABS. The lack of tire marks could be due to the extra traction there was late in the day for those of us with hard compound tires. That was part of the reason I crashed (besides driver error). I had a lot more speed going into that corner than before, and used a later braking point.
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Re: Corvette crash video

Postby Rabbit Farmer » Mon Sep 01, 2014 10:06 am

I would think the speedometer speed sensor is on the transmission final drive while the ABS is based on wheel sensor.
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Re: Corvette crash video

Postby RacingFrog » Mon Sep 01, 2014 11:58 am

Challenger392 wrote:Curious as to why the GPS speed barely drops below 60 before the ditch but the obd2 indicated much lower than that. I know the GPS must be lagging. But I wonder if the obd2 speed is also incorrect. Could it be possible that the wheel speed sensor malfunctioned causing the car to think you had a lockup and accuating the ABS. The lack of tire marks could be due to the extra traction there was late in the day for those of us with hard compound tires. That was part of the reason I crashed (besides driver error). I had a lot more speed going into that corner than before, and used a later braking point.


The GPS speed is a moving average that's why there is so much lag in it. I just put it on the video to show the difference, but the OBD2 speed seems consistent with the impact. If I had been closer to the GPS speed, I would have completely crushed the car at that higher speed.
Note that the speed of the transmission is not necessarily the speed of the car if the tires are slipping. The weird thing is I never felt the ABS engaging except maybe at the moment of the impact but pedal feel there might have been due more to the impact than the ABS. As the whole ABS/Traction control thingy is linked together, I wonder if it's the computer that kept the engine high in the RPM when it was unsettled by my high RPM downshift (something got out of range and instead of cutting off the throttle for traction control, it would have kept it pinned). I need to read more about how that module works.
What I don't understand is why the car didn't turn in if I had extra traction. It is really plowing straight.
Was I on a slippery line? Didn't put enough steering? Wasn't looking enough to the left?
I am unloading the car now, will see if I get more answers after I inspect the car!
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Re: Corvette crash video

Postby walterclark » Mon Sep 01, 2014 1:04 pm

This is not to say that they are all directly related but there were 2 other offs at that same location. Basically the same thing. Car went straight under braking. You might recall Don and I were at the Ambulance pull-off / check 5 right above you, having just recently recovered the blue BMW (I think Sam Catalano was driving) from the same exact spot. And Seth had something similar..I am pretty sure in the afternoon, but maybe before either of you had your incident...but he was able to get the car turned before it went completely off.
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Re: Corvette crash video

Postby RacingFrog » Mon Sep 01, 2014 1:49 pm

A fellow on the Corvette forum pointed me to what is likely to be the cause, it's a gremlin called 'ice mode' that is hardwired in the ABS system.
"Ice mode occurs when a wheel stops a lot faster than it could if it was on pavement. The computer knows how fast you should be able to stop and what rate of deceleration is within the possible (at least it thinks it does). If you have a wheel in the air, or if you are sliding sideways, and you apply the brakes, the wheel is going to stop essentially instantaneously, or at least a lot faster than it could if it was in contact with pavement and was slowing the car down. The computer then thinks the car is on ice and it limits the amount of brake pressure to give you about .1 or .2 g of deceleration. The only way to disengage ice mode is to recycle the brake pedal, and then you will get full stopping power. If you are going sideways and have your foot on the brake it's going to stop the wheel very quickly and that could invoke ice mode. Difficult thing to do when you are sliding backwards, but if you ever feel the car isn't slowing down like it should you need to recycle the brake pedal.
Yes, you have it on your 2004, all Corvettes have had it since 1986.
Nothing is displayed on the dic, the car just doesn't stop worth a darn when it is in ice mode."

I am surprised I haven't hit that mode earlier since I have done a bunch of braking on very bumpy surfaces at hillclimbs but as I didn't pump the brake pedal, if I was in that mode that could be the cause. Still not sure why the RPMs would still be stuck at the rev limiter though but that is a plausible cause.
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Re: Corvette crash video

Postby sdwarf36 » Mon Sep 01, 2014 2:28 pm

Take a look at how much steering input you have in the wheel-the run where you make the turn you have the wheel turned almost 180 *-the accident less than 90*.

There was nothing on the corner-I was on my hands+ knees checking it out.
All three and 1/2* incidents started early enough that Karen + I had time to go "oh shi...." before any off roading started. All started braking too late. Seth just missed his turn in-the BMW panic locked the brakes and went straight -and the Vette didnt slow or turn. Looking hard back at it, all three were very far to the right side of the road. (but i can't picture if other cars were that far over to that side also.)

*We also we going "ut-oh" for Luke-didn't sound like he was going to make the turn. He did-and got thru the corner noticeable faster than earlier. But what happens when you exit a corner faster than ever before? You carry more speed than ever into the next turn. (also see " I was on my best run ever" ;) )

Micheles theory was that everyone was used to stopping for Karen at the start-and when they saw her at turn 4 and decided to stop there. :lol:
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Re: Corvette crash video

Postby sachilles » Mon Sep 01, 2014 8:30 pm

My theory doesn't make it any more flattering for myself.
I contend that corner was more slick than previous visits. Sadly I knew this on Saturday. The corner felt off to me. Maybe I had more speed than before, who knows. However, I know I commented on it on Saturday.
I finally got comfortable with its level of grip, and that is when I went a little long. :oops:
I had a tire chirp like I locked the tires briefly, then let off to get control back(I have no abs).
I do feel like that corner was more slick than previous visits, but I knew that on the run I went off and still pushed it too far.
It is a very very fine line we walk on, it doesn't take much. We are are talking a fraction of a second between having your best run ever, or going agricultural.
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Re: Corvette crash video

Postby RacingFrog » Mon Sep 01, 2014 10:19 pm

sdwarf36 wrote:Take a look at how much steering input you have in the wheel-the run where you make the turn you have the wheel turned almost 180 *-the accident less than 90*.


Yes, when a car understeers it usually doesn't help to put more steering input. The rack is pretty short, even with 90 degrees of steering the car should have turned way more than it did.
I would have pushed it I would have no problem with taking all the blame, but I really was super conservative on my braking point, it looks like I had my foot on the brakes but it really felt like I had no brakes and I had no pulse from the ABS.
In my 3rd run on Sunday were I did a 2:19.82, I was really pushing it and I did brake way deeper than that without any issue (the telemetry shows that I did brake ~20ft later for the same speed). If you tell me that the road was perfectly clean, then I don't get why I would not have had time to slow down for the turn.
What I also don't get is why the car got stuck to the rev limiter until the impact.
I looked at the car today and didn't find anything besides a broken upper control arm due to the impact. I just hope it was just me and not something wrong with the car that will happen again because I misdiagnosed it the first time.
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Re: Corvette crash video

Postby sdwarf36 » Mon Sep 01, 2014 11:11 pm

I checked the road out at a microscopic level-at first just for really getting to know a turn for my own info. There are 3 little bumps to the very right side of the road. (Seth's chirps?) And the right edge of the road kinda turns in towards the left. (what got the BMW-wheels got into the dirt).

Is it possible that since you were hard braking--and I'm guessing EXTRA hard braking since it wasn't slowing-and you were (I presume) heel/toeing for the downshift-that your heel or the side of your foot caught the edge of the gas pedal just a bit?
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