Have you ever broken anything during a launch?

Literally 100's of street launches and 60-70 or more track passes between a few different cars and never broke anything but a stock/original clutch. Unless you're making BIG power (600+ wheel) the guys breaking shit left and right need to adjust their launch technique. The only excuse for breaking shit at BPU levels is the driver and/or using an overkill clutch. Granted, sometimes shit happens and something breaks unexpectedly, but generally the drivetrains in these cars are stout; however, they are not tolerant to poor technique.

I ride the clutch until all slack is taken up and I start rolling out then I dump it.

Unsprung hub clutches. 4+ and 5

-Chris

I don't want to think about the answer to this question.

Friggen glass non turbo transmissions. :mad:

Apart from roasting a few clutches I`ve broken nothing while launching my 1st Gen 18 spline tranny.

Solid mounts and Maximal bracket have worked wonders for 200+ launches.

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Originally Posted by steve68

I broke this.
http://img30.imageshack.us/img30/5149/april2009167.jpg

http://img198.imageshack.us/img198/8...ril2009134.jpg


But I make less power than stock.

http://img64.imageshack.us/img64/1593/april2009126.jpg


Steve

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...and you broke that when and how? At how much boost? What do the ring and pinion bearings look like? I bet $100 there's a machined bearing race in that transmission from the a bad bearing or the bearing preloads being out of spec. 99.9% of the time the only reason why teeth bind in a helical gearset is if the end bearings are damaged or poorly maintained. You never put down enough power to excite the gearbox enough to collapse a bearing cage or crush a bearing sleeve or collar in that 0.1%'th tile... so put those pictures away.

That fracture is not from power, it's from poor maint, bad launch technique, possibly stupidity... or any combination of the three, really. Hence, should not be included in discussion.

First post summation... What did you break and at what power level? You broke that on a 12 sec car... please fool :rolleyes3:! Exclude from discussion as to not skew results

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Originally Posted by J. Fast

...and you broke that when and how? At how much boost? What do the ring and pinion bearings look like? I bet $100 there's a machined bearing race in that transmission from the a bad bearing or the bearing preloads being out of spec. 99.9% of the time the only reason why teeth bind in a helical gearset is if the end bearings are damaged or poorly maintained. You never put down enough power to excite the gearbox enough to collapse a bearing cage or crush a bearing sleeve or collar in that 0.1%'th tile... so put those pictures away.

That fracture is not from power, it's from poor maint, bad launch technique, possibly stupidity... or any combination of the three, really. Hence, should not be included in discussion.

First post summation... What did you break and at what power level? You broke that on a 12 sec car... please fool :rolleyes3:! Exclude from discussion as to not skew results

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Originally Posted by steve68

You don't know the facts so you're only guessing, The whole gearbox was trashed (except for the output shaft). Yes it was done on a launch. With a launch, there's bugger all boost unless you've got launch control or similar. I dropped the clutch at 5 or 6 K or whatever. The car didn't even move off the line, was the 3rd launch of the day.
Yes, you're partly right, the gearbox had been rattling for a while. I'll let you work it out.

So how much power does a car make with no load in neutral at 6K?

Steve

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i wasnt going to say anything but since J Fast already brought it up... the point of this thread was to hopefully get a relatively good idea (and hopefully a nice list that i can update in the 1st post) of what is going to break and at what power level. ill take your word that you broke it during a launch, but why post it in a thread discussing what will break at XXX hp when the only reason that trans broke was because of problems unrelated to power. that trans should have held that power + a whole lot more.

For fucks sake this was supposed to be an informative thread that people could use as a reference. A thread where REAL results were shown and discussed. Not where the village idiot comes to take a shit.

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Originally Posted by steve68

There's a difference between breaking something on the startline when the clutch is dropped and breaking something once boost comes up.

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Yes there is, but if your going to break something in these cars its going to be during the launch. Nobody breaks something once there rolling.

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Originally Posted by steve68

The instant the clutch is dropped, there's no boost, the breakages are caused by inertia not power output. Just the same as most broken transfer cases are caused by broken engine mounts rather than high power output.

The higher powered cars above who've broken parts on the startline didn't do it with power.
They would have done it because of their lower tyre pressures and sticky tyres, totally unrelated to how much power they're making.

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Close but not quite. Assuming you don’t have any sort of launch control or 2 step you will not be building boost with the clutch in at the line. Yes, it will take a fraction of a second for the engine to build boost. But it will also take a fraction of a second for the drivetrain to be under full stress because it will take a fraction of a second for the clutch to 100% engage. The instant the clutch is fully engaged your transmission’s input shaft will be at the same rpm as the motor, irregardless of the angular velocity of the tires or speed at which the car is moving. The stress from a launch does depend greatly on how fast the clutch fully engages. But it is also dependent upon the force turning the input shaft (force coming from the motor) and the resistance caused by traction, weight, friction, ect. So this begs the question, ‘what force is turning the input shaft?’ well the torque of a rotating system with no force opposing it is 0. For sake of argument lets just say that you launch at a constant rpm. Aka the car is at 5500rpm with the clutch in and once the clutch is released the motor is still at 5500rpm. Lets also say that under load on a dyno with resistance opposing the force applied by the motor you produce 500 ftlbs of torque at that rpm. That would mean that the amount of stress on the drivetrain goes from ~0 when the clutch is in and the car is at a stop to potentially ~500 ft lbs in the amount of time it takes for the clutch to fully engage and put the engine under load, provided there is enough traction to provide the ‘counter resistance‘. Thus the peak stress on the drivetrain doesn’t happen in the millisecond before boost, but rather once the car is at its peak power during the launch.
So the peak ‘potential’ stress during the launch is dependent upon the power that the motor makes. A loss of rpm’s during a launch will reduce stress. A loss of traction during a launch will reduce stress. Slipping the clutch for an extra fraction of a second will reduce stress. But nonetheless the peak stress is proportional to the amount of power the motor will make under load at that rpm.

This makes sense because it explains how someone with a 600hp nitrous mustang can launch on a stock drivetrain and not break anything… because there not producing 600 hp until they spray the nitrous. Thus there not asking there drivetrain to hold up to any more stress than a unmodified mustang. Yet if that same person were to launch and spray at the same time there is a higher chance of them breaking a drivetrain component.

Your statement on the other hand does not make sense. Essentially you are saying that all 3000gts on street tires undergo the same ’stress’ during a launch because the inertia caused by the rotating assembly is virtually identical between a bone stock 3000gt and a 1000hp 3000gt. You forget that that rotating assembly has a force causing it to rotate and overpower the drivetrains resistance. You cant really think that the force caused by ‘inertia’ a rotating assembly is enough to get a 3800lb car to move 60’ in 1.8 seconds… But even if it were true (just for sake of argument) that would mean that all the potential energy from the rotating assembly would have to be converted into the cars kinetic energy… which means your rotating assembly now has 0 ‘inertia’ and is not spinning… aka your motor is stalled. If you really think this is true then rev your car up and turn the key off right as you drop the clutch. Tell me what you get for a 60’ time.

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Originally Posted by steve68

Then again , once you get people selling parts which are designed to fix a certain problem, you get people telling lies, making misdiagnoses, in order to sell more parts which aren't needed and don't work.

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A lot of the perceived ‘weakness’ from 3000gt tranny comes from people just like you who have no clue what there talking about. The truth is your setup doesn’t make nearly enough power to come close to being able to do that to a normal trans. I don’t care if you’re on a set of Mickey Thompson wrinkle wall slicks launching with a 2step and dropping the clutch at 7grand. the damage from that pic should not have happened, yet by you saying ‘hey I broke this’ in a thread about the breaking points of drivetrain components just implies that the stock drivetrain is made of butter.

And for any physics majors out there I apologize for the very crude terminology and am well aware that I used some terms out of place. it’s a bit difficult to try to convert everything in layman terms while retaining proper terminology. If someone spots a major error in my explanation, and you actually know what your talking about, just P.M. me and ill fix the mistake.

If I had to guess... Steve broke his bellhousing because he was missing a few bolts holding it to the block. I've seen the same thing happen with turbo eclipses at stock power levels, where they didn't have all the bolts in and tried launching it.