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-   -   Is it possible to lauch an AT? (https://www.rx8club.com/rx-8-discussion-3/possible-lauch-54635/)

RX8rider 03-06-2005 10:03 AM

Is it possible to lauch an AT?
 
This may be a very dumb question, but is there any way to lauch the AT without killing the transmission?

V_for_velocity 03-06-2005 10:41 AM

Maybe a catapult in the style of The Lord of the Rings.

markd 03-06-2005 11:48 AM

I tried that once but the wheels didn't spin. Maybe I was holding down the brake too hard...?

RX8rider 03-06-2005 12:16 PM


Originally Posted by Ryan13b
You want to find the point where the car is just about to be moving. Full throttle and just enough brake to keep the car still.

Does this damage the brake at all?

BlueEyes 03-06-2005 12:20 PM

I cannot imagine it would hurt the brakes, but, the I don't think it's good for the torque converter.

RX8rider 03-06-2005 12:30 PM


Originally Posted by Ryan13b
It's real bad for the brakes.

The brakes convert kinnetic energy into heat via friction. They work well, but they're not designed to hold back a force. They're designed knowing that the energy of the car will lessen as they work.
So if you're going 100mph the brakes have a lot of energy to dump, but that energy goes away as they slow you down.

When you're not moving and you're trying to accelerate the brakes have to convert all the energy that the engine is making, which they're capable of doing up to a point. Now, since the car isn't moving or slowing down and the engine just keeps making power the brakes have to get rid of the energy at a constent level, it doesn't drop off until you let go of the gas.

I'm not going to bother with the formulas, but I would guess the brakes are stopping the equivalent to about 70mph, except you're holding that energy level. Instead of them getting that energy for just a split second and then it begins to lessen, they're seeing it until you let up.

Thanks for the in depth explanation. So what you're basically saying is that if I want to keep my 8 in top shape and not put excessive wear on the components, I shouldn't try to launch it...

BlueEyes 03-06-2005 01:03 PM

I don't really understand Ryan. What do you mean "the brakes have to convert all the energy that the engine is making"? convert it too what? via what?

BlueEyes 03-06-2005 01:24 PM

I understand the way they dissapate energy when they are moving, but you mentioned they convert the energy when the car is not in motion, i.e doing a power brake. This is why I reasoned that the torque converter would be the weakest link in the chain while doing this, because I could not see the brakes dissapainting any energy.

therm8 03-06-2005 02:42 PM

And the lack of wheelspin is due to low torque. Power brake an AT F-body or Mustang and you get crazy wheelspin.

RX8rider 03-06-2005 02:50 PM


Originally Posted by therm8
And the lack of wheelspin is due to low torque. Power brake an AT F-body or Mustang and you get crazy wheelspin.

I wonder if that might change once TCS/DSC is disabled?

therm8 03-06-2005 03:15 PM

not in my experience.

crossbow 03-06-2005 04:25 PM

Doing this is rather hell on an automatic transmission. I don't know how strong the 8's 4 spd is, but I'd seriously invest in an automatic transmission cooler (like a B&M) to run in line with the car's stock cooler if I was going to consider doing a powerbrake more then once. Technically you should put in a cooler anyway, but since most people think its unnecessary till their ATX explodes out of warranty, I'll just try to stick in a recommendation in a transmission abuse thread.

JeRKy 8 Owner 03-06-2005 04:40 PM

Even ifyou ignored all the potential problems youwere causing by doing this type of launch w/the automatic - the rewards are pathetic anyway. What doyou gain by this? Ill tellyou - you get to 60 by as low as 7.8 seconds instead of the typical 8.1 - 8.2 seconds. Is thatreally worth it to you? Bythe way I havespun out the tires once before by usingthis method butthat was back when my replaced transmission was slipping. Ifyou really want to maximize thelaunch from an automatic you do a neutral slam.

scottmhr1 03-06-2005 04:41 PM

Brakes convvert the friction of the rotors into heat. Power braking will do nothing to the brakes unless you are letting them slip a bit. It will tear up your tranmission in a heart beat. Brakes, nothing at all. No friction involved.

GeTcRuNk 03-06-2005 05:15 PM

What I did with my 2000 celica gt-s is put it in reverse...reverse back about 5 mph...then drop it in neutral and rev it up...and then drop it into drive and bingo...fwd burnout in a celica :-D good times on the day before i gave her away...

markd 03-06-2005 07:38 PM


Originally Posted by JeRKy 8 Owner
Even ifyou ignored all the potential problems youwere causing by doing this type of launch w/the automatic - the rewards are pathetic anyway. What doyou gain by this? Ill tellyou - you get to 60 by as low as 7.8 seconds instead of the typical 8.1 - 8.2 seconds. Is thatreally worth it to you? Bythe way I havespun out the tires once before by usingthis method butthat was back when my replaced transmission was slipping. Ifyou really want to maximize thelaunch from an automatic you do a neutral slam.

A "neutral slam," I am assuming, is when you rev the engine high in neutral and then shove it into drive? I have tried that before as well but didn't realize any added benefit from doing it. Once the tranny locked into first gear, the car progressed at normal speed. It would seem that power braking would produce better acceleration than a neutral slam, although it would also seem to be more damaging in the process.

Can you tell I don't street race often? :)

markd 03-06-2005 07:44 PM

Oops, just read GetCrunk's post--guess that would be a neutral slam.

BlueEyes 03-06-2005 07:46 PM

I kinda agree with Jerky here. I mean, although I don't own an 8 I have driven both the mt and at offerings now. I thought the mt was a little on the slowish side when I first drove it, but still a wee bit faster than my current car. The at felt a lot slower than the mt, slower than my car I think. On the otherhand, both were a lot more fun to drive than my solara. It's just not worth the damage to the drivtrain to try to make the car a little less slow.

JeRKy 8 Owner 03-06-2005 10:56 PM

The onlyway to make the 6spd manual reach 60 in the low 6s is by launching from high up in the5000+ RPM range. For a regular street start (like from 5mph - 60mph) forgetabout it - not enough torque. Thats theproblem w/the automatic. You cant get away w/that typeof abuse on the transmission theway you can w/a clutch. Imsure that ifwe could safely rev the automatic Rx8s to 5000 RPM andnot worry about destroying the tranny youcould probably makeit to 60 down in the mid to slightly low 7s. Im surethats about the time the low power 5spd manual Rx8s make in Europe

Shoafb 03-07-2005 01:14 PM

If you are asking how to launch an RX-8 you bought the wrong car. What are you going to race? Civic? Mini Van? F150 would most likely take you out. The car is just not going to cut it drag racing....it's for the curves. Enjoy what it is.

Ike 03-07-2005 05:07 PM

If all else fails find a ramp and a cliff ;) :p


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