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      09-14-2020, 11:46 PM   #1
OldCrow7xx
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Burnout for drag strip

So I am very new to all of this, but my car makes pretty decent power now and I want to take it to a strip and let it run wide open.

I was trying to understand how a burnout with an automatic transmission could work. I would want to do a quick one to clean the tires.

If I have the brake pedal 100% down, the the calipers will be squeezing the disks not allowing it to rotate.

If I have the crankshaft rev'd up and spinning at 3/4/5 thousand rpm, and thats engaged to the tranny, and the tranny is trying to spin the wheel, but the brake is holding the wheel, how is that possible?

Wouldn't it snap the drive train parts or seize the motor from spinning? If the crankshaft is spinning and the whees aren't I just cant understand how the force would be stored or dissipated. Seems like gears and transmission plates would grind.

My car doesn't have a trans brake, I am assuming the trans brake is the answer to this but obviously thats not an option in my commuter car/ grocery getter.

I know the zf8 has a "launch mode" maybe that plays into all this. My car is converted to rear wheel drive as well.

Thanks for any advice, detailed answers are much appreciated.
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      09-15-2020, 06:50 AM   #2
KennyFSU
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Unless you have DRs or slicks you don't need to do a burnout for the drag strip.

Turn xdrive back on when you're at the track, it will have much more traction than RWD.

I did 2 passes; 1 using LC, 1 without and both were consistent.
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      09-15-2020, 07:07 AM   #3
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Yeah, right. You're not looking to hoon about doing burnouts, just wanting to responsibly clean off those tires for a good data run. Suuuure. And if it happens in a Dunkin donuts parking lot in front of a bunch of onlookers, well, no accounting for coincidence. If you want to really crush in the drags you will go back to AWD and put on a set of drag radials, perhaps with some rubber conditioner to soften them up a bit (I hear there are also some common household chemicals that will make for a nice smokey 'tire cleaning').

The answer to your Q is called a torque converter, kind of a hydraulic clutch; keep exploring this new world of burnouts and you'll learn a lot more about these than you ever wanted to (you're on target with that 'snap and seize' part). It lets the $15000 motor spin wildly while the $9000 drivetrain sits there held in place; then you engage it suddenly and hope that it is the tire contact patches that give up and create a burnout. Trans brakes just do the holding in the tranny, instead of with the brakes - what you crave is a line lock (and a '70's Camaro).
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      09-15-2020, 08:33 AM   #4
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Quote:
Originally Posted by Maynard View Post
Yeah, right. You're not looking to hoon about doing burnouts, just wanting to responsibly clean off those tires for a good data run. Suuuure. And if it happens in a Dunkin donuts parking lot in front of a bunch of onlookers, well, no accounting for coincidence. If you want to really crush in the drags you will go back to AWD and put on a set of drag radials, perhaps with some rubber conditioner to soften them up a bit (I hear there are also some common household chemicals that will make for a nice smokey 'tire cleaning').

The answer to your Q is called a torque converter, kind of a hydraulic clutch; keep exploring this new world of burnouts and you'll learn a lot more about these than you ever wanted to (you're on target with that 'snap and seize' part). It lets the $15000 motor spin wildly while the $9000 drivetrain sits there held in place; then you engage it suddenly and hope that it is the tire contact patches that give up and create a burnout. Trans brakes just do the holding in the tranny, instead of with the brakes - what you crave is a line lock (and a '70's Camaro).
Ok nice so that torque converter is the abstraction layer or mediator that allows the input side of the equation to be at 5000rpm and the output side at 0ish rpm?

So its taking the beating / brunt of that force when you release it and you hope the tires break free?

I assume in my automatic car this process is transparent to me, in that the computer controls its engagement based on what I do with the pedals?
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      09-15-2020, 01:11 PM   #5
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The torque converter is the part that allows for engine rotation to be decoupled from drivetrain, and it does buffer the shock somewhat. But it isn't the only part that takes the beating; the whole drivetrain takes a beating from the sudden onset of full power/high revs; everything from the piston to the tires is getting a sudden shock. This is magnified somewhat in our turbo cars, because they make full torque at such low rpm. In the old muscle cars, you were lucky to have even half your torque at the start of a burnout, so the parts weren't hammered on quite as hard (and nobody had thought to try making anything smaller or lighter to save gas, so everything had a little more metal to work with). I'd look online for a 'how it works' video if you are into this, as there is a lot of cool engineering at work. And if you want to really have some hooning fun, code it into a FWD and do the tray trick (or just borrow somebody's Corolla).
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      09-15-2020, 09:58 PM   #6
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Quote:
Originally Posted by Maynard View Post
The torque converter is the part that allows for engine rotation to be decoupled from drivetrain, and it does buffer the shock somewhat. But it isn't the only part that takes the beating; the whole drivetrain takes a beating from the sudden onset of full power/high revs; everything from the piston to the tires is getting a sudden shock. This is magnified somewhat in our turbo cars, because they make full torque at such low rpm. In the old muscle cars, you were lucky to have even half your torque at the start of a burnout, so the parts weren't hammered on quite as hard (and nobody had thought to try making anything smaller or lighter to save gas, so everything had a little more metal to work with). I'd look online for a 'how it works' video if you are into this, as there is a lot of cool engineering at work. And if you want to really have some hooning fun, code it into a FWD and do the tray trick (or just borrow somebody's Corolla).
So when I have the brake pedal at 100, the computer tells the tranny to stay decoupled from the crankshaft?

Then as you back off the brakes it slowly lets it engage?

In my civic Si I could just pick an RPM pre VTEC engagement threshold and dump the clutch right around there. Thing would spin through 4th gear.

Im targeting a C5 Z06 for next car. Going to running nitrous or centrifugal blower. Trying to learn this stuff now before I "step up" lol

Seems like the LS motor, rwd, and godly suspension is the answer to all my problems...
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      09-16-2020, 08:13 AM   #7
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Not really. I think you really need to dig into how these things work before you try motor-killers like nitrous or aftermarket blowers. Here's a fun little Corvette clip to demonstrate how burnouts can sometimes take out the wrong parts; "Bye bye $600" turns out more like $6k: https://www.bing.com/videos/search?q...6&&FORM=VRDGAR
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      09-16-2020, 03:35 PM   #8
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Quote:
Originally Posted by Maynard View Post
Not really. I think you really need to dig into how these things work before you try motor-killers like nitrous or aftermarket blowers. Here's a fun little Corvette clip to demonstrate how burnouts can sometimes take out the wrong parts; "Bye bye $600" turns out more like $6k: https://www.bing.com/videos/search?q...38;FORM=VRDGAR
That's unbelievable he sat there that long thinking the tires were spinning and not the drivetrain internals...

Clutch smells different that rubber lol He didnt lift, thats for sure. Did not lift...

So with the automatic what allows it to go from decoupled to coupled when I start to release the break pedal?

Is there a computerized moment or is it a result of the mechanics as the wheel starts to spin it allows pressure and torque to be transferred?
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