737 Jock

During a brake torque launch the turbine side of the torque converter (which powers the driveline) is locked, because the brakes are preventing the wheels from turning.

Torque converter stall occurs at the rpm where the engine "stalls" ie, will not accelerate further because it can't overcome the hydraulic drag of the TC. Some vehicles will overpower the brakes first and turn the wheels (brake stall) but apparently the RDX brakes hold all the way to TC stall.

This puts the engine in it's max power range when the brakes are released -- AND the TC is operating at about it's max torque multiplication (x 2.5 or more).

Four wheels drive the RDX to 60 in six-point-something and embarrass the kid in the slammed Civic so bad he misses second.

TC stall is factory set in the RDX at 1950 rpm and the service limits are 1800 to 2100 rpm. So on a brake torque launch you should not be able to exceed 2100 rpm. At 2000 rpm the engine should be generating about 230 ft/lbs, or 88% of available torque.

Inside the TC the fluid is shearing violently between the impeller -- which is turning at engine rpm -- and the locked turbine. Tremendous heat is quickly generated that is destructive to seals and to the ATF itself.

At brake release the TC absorbes most of the driveline shock which can break off the vanes on the impeller, turbine or stator and damage the stator clutch.

Honda's shop procedure for TC stall speed testing is 1800 to 2100 rpm for 6 to 8 seconds and not more than ten.

Heat is the enemy and a 20F rise in steady temp can cut the ATF life in half.

Here is the inside of a Civic TC; the impeller is on top, the turbine on bottom and the stator is the small wheel inside the turbine.

F.Rizzo

I do this quite frequently with the RDX. Nice to know that 1950 is the point to shoot for to take up the driveline loss.

You can launch hard enough to engage the traction control.

porsherules911

I try to avoid doing this as much as possible, don't want my TC to be shot.

weeeerd

That's okay, that's why there is a warranty on the vehicle.. for negligence such as this.

mau108

what you brake torque launch ? thats brutal. And you wonder why people complain about failing components (such as drive train) and blame it on the manufacturer.

Drive like a normal human being, not an animal. If you want to drive like an animal, get a ferrari.

737 Jock

The transmission Power Control Module monitors the status of hundreds of trans parameters such as each solenoid and each clutch, but here are some of the pertinent ones:

Engine RPM

Accelerator pedal position

Brake pedal position

Throttle position

ATF temp

Wheel speed

When the PCM throws a Diagnostic Trouble Code for a trans abnormality, it takes a snapshot of all data input to the PCM as well as all fuel and emissions data. This snapshot is called the freeze data, and it would be recorded if a DTC is thrown during brake torquing.

During service the Acura tech first downloads and records all DTCs and freeze data. The next step is interesting from a warranty perspective, so I'll quote directly: "Drive the vehicle for several minutes under the same conditions as those indicated by the freeze data...."

This would be fun to watch if it wasn't your car, but you'll more likely see the Service Manager flipping to the "abuse" clause in the Warranty contract.

Additionally, a trans PCM DTC will not neccessarily light the CEL, as that is an emissions light. Trans abnormalities only cause the "D" in the gear selection display to blink. Might not notice that, but the DTC is recorded.

F.Rizzo

Since this thread gets the holier-than-thou types all riled up, I went out and tried a couple of 2500 RPM, "VSA off" launches. You can get all 4 wheels to scratch.


Shame that some of you have the equipment and are afraid to use it. I'm sure you make extenisive use of the AWD also
Consider a Camry Hybrid next time

porsherules911

Have equipment? I've heard from plenty of people who brake torqued from time to time and then hear how they had to replace their tc. Personally, I'll brake torque when I have to but not to just mess around. I see better things to spend money on besides replacing a TC. just my

VeNeNo

iTrader: (1)

you can really get all 4 tires to squeal with the VSA off and a torque launch!?

cwepruk

I've never really heard of people blowing torque converters except for maybe 1980's turbo ford probes.

As long as you aren't constantly doing it, it shouldnt be an issue, much like if you have a manual trans.