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Posted by bnpimpn, Nov 17, 2005
Automatic Tranny - 4G63 automatic tranny discussions. Sponsored by Import Performance Transmissions
www.howstuffworks.com for a good read on torque converters and that will give you an idea of how it works.
Pro's = Everything I listed above!
Con's = You'll need a better trans cooler to dissapate the heat generated while brake boosting. PS. Don't brake boost all the time you'll just shorten the life of your trans. Also my story above is not "street racing" I call it "Spirited Driving" HAHAHAA
I hope this clears things up for you better.
Torque Converters Explained
They can be set for all kinds of applications, the lowest is the stocker (2600-2800rpm) and the highest ive heard of is IPT's billet 9 incher (5000rpm)
In an automatic, you put the car in drive and keep your foot on the brake. It doesn't move. If you keep pressing the gas pedal, the rpm will go up until it reaches a point in which the torque converter is grabbing too hard for the brakes to hold. This is the stall speed.
A higher stall speed means you can put the car in drive, keep your foot firmly pressed on the brake, and bring the engine rpm up higher before the car begins to move. Stall speed has nothing to do with how quickly or slowly it engages.
This is good for better launches by putting the engine up higher in an rpm range that is providing more horsepower. So if you have an engine and turbo that doesn't build good boost until 3,500 rpm, then a 3,500 rpm stall torque converter would be good for getting strong launches. On the flipside, if you have a fwd car that spins its tires off the line as it is, then a higher stall torque converter would be useless.
And also, for example, a 3,500 stall speed torque converter does not mean that the car won't move until the rpm reaches 3,500 rpm. It will just provide more "slippage" until it reaches 3,500 rpm.
Hope this helps and I addressed all your questions.
I would report this as misinformation, however you're close enough that I'll just correct it such that no one is mislead by your statement.
The stall speed is a complex thing. Its derived using the Mue of the torque converter and the engine torque curve. Basically what it tells you is how fast the engine "input" side of the torque converter can spin while the transmission side does not. It is at what time the non moving side of the TC exerts enough force such that the engine is under full load, and cannot rotate the engine side of teh torque converter any faster. It has NOTHING to do with your cars braking ability, or ability to "stay put".
An overly simplified way to think about a torque converter is to think of 2 fans in a liquid. the engine is connected to one, and the trans/drivetrain is connected to the other. By spinning the first (engine) fan, you push the fluid in a circle. you put the second (trans) fan facing the opposite direction right next to the first fan. (as if lining up the axis they spin on) This then is pushed by the fluid to rotate in the same direction. There is also a lockup clutch that when activated "locks" the fans together.
Any time you make make one side spin faster than the other, you're creating heat in the transfluid. This heat must be dissapated somehow, and thats why you need a better transmission cooler.
The way a "looser" (higher stall) converter effects daily driving is the time in which it takes to load the engine. Everyone knows the non linear way an automatic transmission loads. It revs up quick (to say not quite 3000 rpm), the RPMs rate of increase slows a bit, then the engine revs quickly up to redline. The higher stall TC will allow that "pause" (the RPM in which the converter locks up) to be higher. On a car with a larger turbo, this can allow more time in boost.
If anyone wants me to go into more detail about this, I will be happy to do so.
I just got an IPT trans and I am very confident in their work and there customer service is great. Havent really had a chance to drive arond yet ... bt i'll let you guys know..
As of now I have a 50 trim seeing full boost at about
ThI have a high stall 4000k tq
Still have to feel everything out and have john test drive since the car wasnt tuned at the time of tranny install
i have a precision industries torque converter with a 3500 stall but i bought the car with it in the trans and with a shift kit and b&m tranny cooler and im just wondering how can i really tell it has a 3500 stall converter in there? just have it in drive hold the break down and rev it and see if it locks up in 3500 rpms?
A good example of the theory above is the dyno testing of my Talon with the IPT billet TC with a 4300 RPM stall. When the run started the engine went to over 4000 RPM immediately and all four wheels just tried to catch up. The engine spent so little time in the low and mid PRM range that the cam gears could not be adjusted. In normal driving with the high stall TC behind the stroker there is zero turbo lag.
well i tried holding the brake down and give it gas but the car wouldnt stay still so how can i tell the stall is 3500?
The results may not exactly match the specified stall speed because of your car's weight and torque curve but it should be close.
i have a b&m tranny cooler and pi 3500 stall torque converter so is it ok to do launches? you think that was bad for the turbo since i had the car reving up and then it died and had to start it back up? i was reving up to like 2800 rpms....i just wanted to see if it would stall at 3500.
all i have is a pi 3500 stall torque converter,b&m tranny cooler,performance trans parts, and black spring shift kit.
yea that sounds right. but is it ok to do the launching thing since i have a tranny cooler?
This may also be helpful:
For what it's worth the IPT high stall torque converter is a pleasure to drive with a 4G63 stroked and cammed for more low end torque.
What's your setup TunaTalon ? How long does it take you to build boost on the line ?
The car does not go the drag strip and brake boost. Going to WOT from a stop takes the engine to about 4000RPM in a few feet after a good hard bang at launch.
The engine reves up so fast on the dyno that the tuner could not set the cam gears because there was not enough time at mid range.
Now that I know what affects what torque converter is needed (engine torque at specific rpm's, gear ratio, car's weight, cams...etc) I was wondering how they specifically affect it...like what does having stock cam's do to a torque converter compared to a pair of 280's or F4R's?
The auto I have right now is a 97 stock GSX which I have been collecting parts for. I have an hx35 that I am going to put in the .55 bep housing, since I have a track car already I don't feel the need to go T3 since this will be on a stock bottom end. I am trying to do a budget build to have a fun car to drive around town so I am hoping I can get away from buying/re-stalling my torque converter. If I leave the stock cams in the car will it help me or hurt me? I have a set of FP2's laying around that I could throw in but if that will cause me to need a higher stall I will just stick with stock. What other things can I do to keep from needing a higher stall?
If this doesn't make sense I'm sorry but I really am new at this . I'm just trying to save $500.
(Saving money is necessary since I am building the car without my wife's knowledge )