JeffTsai

iTrader: (1)

It has nothing to do with VDIM. Slamming any auto tranny into gear is never a good thing. The clutch plates in an auto are programmed to slip untill a certain speed or load has been achieved. Once the certain condition has been met the tranny will engage a lockup mode, which is where there is no clutch slip by putting full pressure to the plates (same as a manual when you let off the clutch completely).

What happens when you neutral bomb off a launch, the tranny will be slipping like crazy (heats up the clutch plates and tranny fluid very quickly) which is a very very bad thing. Because the plates are slipping, the tranny will then attempt to engage lockup to reduce the slip(more pressure/friction on the plates). The plates will be slipping very baldy already and when the tranny engages lockup mode there will be much more friction and still a ton of spinning and now even more heat. Long story short, neutral bombs are terrible for auto trannies. Lots of heat = very very bad.

Thats just the first part of the problem. Next up is when the tranny does engage lockup and you have a ton of torque going thru the drivetrain. The stock driveshaft may or may not be up to the task of such a high torque load so it may snap in half. I'm sure Toyota builds their stuff pretty tough though. Next up would be the differential gears in the back may or may not be designed to take such a sudden inrush of torque.

Now compare all that to if you brake torque the motor. Once you launch the tranny engages the clutch plates at correct times and slip is reduced. Also the power isn't all of a sudden slammed thru the drivetrain. Yes, it's being built up at a tremendous rate by brake torquing but still nothing compared to the stresses of slamming into gear. It's also very bad to drop the clutch in a manual car but it's not nearly as bad as in an auto because the auto will attempt to slip in the beginnning while a manual applies full pressure at the drop.

Hopefully I've explained it well enough

lobuxracer

iTrader: (2)

The Toyota auto in a Supra? 600 hp? Stayed in one piece? Ummm. No. Definitely not the experience of a large number of MkIV Supra owners. The A340E was not known for tolerating much abuse at all. Either your friend was lucky, or he wasn't making nearly the power you say.

Jeff - I don't know where you got the idea the clutches in an automatic slip, but they don't. All the slipping takes place in the torque converter, and it is the torque converter that locks up, not the clutches. The torque converter does not consist of clutches, it is a fluid filled device and has no parts that directly contact each other from input to output. All the torque is passed through the fluid unless lockup is invoked.

IS350jet

Wow! I can't even break traction in my car. I've tried. S mode, pwr mode, VDIM off, TRC off, brake torque. Nothing will get that car to spin the rear tires. Once, as an experiment, when it was raining out, I put her into S mode, turned off VDIM and TRC, came to a complete stop, brake torqued to about 1,500 and slammed her to the floor. barely spun IN THE RAIN! Doesn't bother me, though. The car has massive amounts of power and massive amounts of traction.

tt061880

you either didn't do it right or something isn't right with your car. All the IS350 spin tires even at the prepped track surface. If I do what you did in the rain my car will fishtail like crazy.

al503

x2. My rears will occasionally break loose in 1st gear at around 5500+ rpm's in good/dry conditions. My buds can't believe it.

Gernby

iTrader: (1)

How many miles do you have on your car and tires, and are they OEM wheels / tires? When my car was brand new, it would rarely ever break traction in a straight line regardless of how hard I tried. Now that it has 10K, I'm starting to get irritated about how I can't even ease into full throttle in 1st without breaking the rears loose.

IS350jet

Yea, you would think so but even in the rain it pulls hard. Maybe it's the surface that i'm on. There's nothing wrong with the car, I smoked a new GS430 already. I didn't mean to imply that I was still brake torquing when I floored it. Of course, I released the brake when I floored it.

Gernby

iTrader: (1)

An IS350 should smoke any other 430.

IS350jet

Good point, Gernby! I have only 1,300 miles on my car. Tires are still like new. Think that would do it?

15951

That will do it. Mine has less than 3k miles, and it still holds like glue - it WILL NOT break free. This is not a negative thing about the car- it has great tires, pulls very hard. Spinning tires might impress 16 year olds, but I'd just as soon have traction and go fast.

The only situation in which I will lose any traction is pulling away from a stop sign and turning while flooring it in the rain.

Gernby

iTrader: (1)

It isn't just the fact that the tires are new, and give better traction. It is also that the engine is new, and isn't delivering as much power as it will when it is fully broken in.

NovaIS350

no way...I was smoking tires at 600 miles. That has nothing to do with it. If he cant even break loose by brake torquing then there is something wrong. THe car has 306hp to the crank. I can get wheelspin with vdim on if I wanted.

tt061880

well said, I took my car to the drag strip when it still had the temp tag on. My 60' was in the 2.2x and you all know 2.2x is because of spinning. That was done with VDIM off in D mode without brake torque the car.

IS350jet

The dealer demo that I drove was the same way. Will not spin for nothin'. the car is extremely fast, however. There is NOTHING wrong with the car. I think it depends on several factors. What kind of tires do you have? What about road surface? Strips are notoriously slick. Temperature? humidity? Elevation? Full/empty tank? Passangers? 91 or 93 octane? So many variables.
So let me ask you this; If I took my car to the strip and ran a 13.5, yet, still could not spin the tires on the street is there something wrong with it?

07Txlex

I have a 350 with 2900 miles on it, dunlop sport maxx 18's around G spyders and I can break it loose any time I feel the need and this has been since day one.. Matter of fact depending on the surface I can break it loose going into second if I'm trying to