tfs95z28

yeah, im not sure what to do because i cannot launch the car any higher than 1800-2000 rpm. And i know that i should be able to launch it higher than that, and that is one of the main problems why my times have suffered.

What does "leaving off idle" mean?

TQdrivenws6

Just sit there like you are at a stop light, then when you want to go, just release the brake and mash the throttle. It's not necessarily logical, but it helped a guy in the local club (stock head/cc306/vig2800) go from high 1.9 to a 1.70x 60'. The reason for the gain is due to the torque multiplication gained by flashing the converter.

rskrause

While it's true that a given combo may do best launching off idle, the reason is not more torque multiplication but a softer "hit" off the line. Maximum torque multiplication, by definition, occurs when the motor is stalled against the converter, as in a transbrake application. On a car with lots of power and sticky tires, it's feels like someone in a truck going 60mph hit your rear bumper!

Brake stall produces more torue at launch than launching off idle, though of course a lot less than full stall against a transbrake. What it does is delay the point at which max torque to the wheels occurs for a short time. Once the car is rolling, it can often tolerate the torque better than if it's from a dead stop.

When you are buying a converter for racing, a lot depends on the manufacturer. They need to understand different combos and what they need to run best. You may think that you need more torque multiplcation off the line, but actually need less, or need it delayed for a tenth or two. You need to give the manufacturer accurate feedback about how your car launches. It often takes a couple of tries to get a converter "right" for a particular combo. Each time it has to go back, be opened up, modified and re-welded. On a high-end converter, this will be included in the price. But if your combo changes, even relatively minor changes, the converter may no longer be right. That's why high end racers often use the Neil Chance bolt-together. They can make changes, do rebuilds or inspections, etc. themselves. At a high level, this may be done at the track to adjust to changing conditions.

Rich

DarkHorse

Rich - thanks again for taking the time to provide information and help guys out. It's very much appreciated, even if not stated enough for guys such as yourself, Brett, Lloyd, etc.... A lot of guys that do research rely on old posts of yours and others for direction.


I have to mention Shoebox - without his site i'd have been lost a long time ago.

rskrause

You are welcome, thanks for the positive feedback.

Rich

Blownbird355

My car sixty foots better when flashed also. I also had the 1st to 3rd shift problem if i tried brake stalling over 2500 or so. But, I do get the rpms up to about 1k before launch. 1.6 to 1.7 with stock suspension.

Z28Vert19

Im sorry but i dont understand what you mean about flashing? thanks

rskrause

"Flashing the converter" is one way to launch an automatic equipped car. Foot-brake stalling a converter is loading the converter by stomping one foot on the brake pedal and the other on the gas. The RPM at which the converter overpowers the brakes is the "foot-brake" stall. You can use the brakes to launch at any rpm up to that speed.

"Flash speed" is different. Flash occurs by releasing the brakes as you stab the gas. The flash speed may be 500-2500 RPM higher than the foot-brake-stall speed. The flash the converter” launch goes like this: Stage at idle, hold the brakes with one foot and "flash" the converter (flooring the gas pedal with the other foot, and simultaneously releasing the foot-brake) the instant the last yellow on the Christmas Tree comes on.

Some cars work better by flashing the converter. Some combinations work better by outright stalling the converter (which is possible only with a tranny brake). Others work better off the foot-brake.

Rich

ChrisFrez

Congrats, this thread has been chosen as our Thread of the Week in Podcast #55!! http://web.camaross.com/forums/showthread.php?t=474169

rskrause

COOL!!

OneFlyn95z28

I can say with 100% certainty My Yank Pro Thruster stalls to 5,600

Launching it to a dead hook in third gear on juice will let you know fast!

rskrause

I thought I had the franchise on wrong gear launches? Funny thing is, in a car with a good power:weight ratio and a loose converter is makes surprisingly little difference if you stay in it. Heats the living poo out of the tranny though, so don't try it unless you are real curious!

Rich

WS6 TA

Heh, I once threw a 3rd to 2nd instead of a 3rd to 4th shift in my M6 WS6 at the track. My brother actually happened to be in the second lane and was wondering why he suddenly passed me with my rear tires locked up…


That pretty much beats anything stupid I've done with an auto at the track...

TUNDRKYS

May sound stupid, but can someone define stall speed for me?

rskrause

I think if you read the whole thread, you may understand it better. But FWIW I will make it easy for you

If you are talking about "true" stall speed, you can only determine it if the car is trans brake equipped. A trans brake locks the tranny in both first and reverse so that the output shaft cannot rotate. If you apply the trans brake and floor the throttle, the engine speed will increase to a point determined by the torque the motor can generate and the design and construction of the converter. This rpm is the "stall speed" for that combination of engine and converter. The first post in the thread defines how the stall speed changes with changes in engine torque. There is also a foot brake stall speed, which is the rpm you can achieve before the car starts to move forward with the foot brake fully applied. There is also flash stall - how high the engine will rev just after the car starts to move when full throttle is applied just off the line. Obviously the last two, especially the flash stall, are impossible to measure precisely.

In all three cases, a "looser" converter is one which stalls at a higher rpm behind a given engine.

Rich

BTW: many variable will change the foot brake stall and the flash stall. Weight of the car and rear end gear for starters.