FrontEngineDragsters.Org Forum
Technical => Dan Dishon's Transmission Den => Topic started by: retroboy on October 15, 2015, 03:31:12 PM
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Howdy
Back in the day I ran a Clutch-flight, wind 'er up drop the clutch and change gears - easy. Now some decades later I've built a new FED and fitted a conventional converter driven trans. What a nightmare. Latest thing I have to ask is about converters in hand or foot brake cars. I have a Turbo Action converter that was in an A body Mopar and stalled at 5200. I don't have the vehicle weight so don't expect that sort of number but I can only hold it at 2000 rpm on the brake and it doesn't flash just drives off the line like a slug. WTF.
Cheers
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2000? That's not going to do it. more info needed. is this an 8 inch converter?
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It's a 9" converter
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Torque converter stall speed is a function of:
1. Torque converter design.
2. Engine horsepower spinning it.
If the converter is the same and it was indeed stalling at 5200 rpm with the previous engine, that indicates that the new engine is making less hp.
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Correct on both counts but it was in a Dodge Dart and now is in a 1150 pound slingshot. I can't hold it with my hand operated brake 'coz it wants to drive and I really didn't expect it to flash to high again because of the vehicle weight but this is crazy. I feel as if I should have built a little extra space into the car an stuck with the clutch-auto.
Cheers
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One thing you could check is brake pressure. I had problems with mine, did some math with help from the link and found I needed a smaller master cylinder. http://www.markwilliams.com/braketech.aspx
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Why not just put a trans brake on it?
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Thanks BK I'll look at ratio's. I have a 3/4" master cylinder. And Pipe Dreams I had a guy around today who has been racing consistently since the late 197'0s and he mentioned how good it was last week when his electronic delay stuff was broken and the other guy had a broken trans brake so they had to actually race off the brake off the tree. That's why I don't have a trans brake or any other tricky stuff but I still need help!!
Cheers
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Trans brake was going to be my next suggestion. Unless its a Torque Flite.
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Sorrt so late in reply.
Converters are build to a combination, change anything in that combo and the converter will act different. Converters for door cars and converters for dragsters are built different, dragster converters are usually built with less torque multiplication, and with that torque multiplication coming at a higher rpm. So with that in mind the converter you have will stall less behind less hp, and multiply torque at a higher rate from a lower rpm, than one spec built for your combination. Car weight only comes into effect after launch, the heavier the car the longer it take it "climb" out of the stall range of the converter. Looking at a graph from our car shows .88 seconds from launch we start climbing above stall. From launch till then we are flat at 5800. A heavier car with our same drive line combo would take longer, and a lighter car would take less time. Finding the sweet spot is a matter of testing, too little time and you run into things like tire shake, or spin, for a light front engine car you could wheelie, and unload the tires, making for a very ugly launch. Too much time spent against the stal ends up being a loss of et and creates unwanted heat.
The bottom line is, converters are very important to getting your car to run its best, and using one for a different combo will leave you frustrated and confused. Have one spec built for your combo, or send the one you have in and it set up for your car.
Hope this helps,
Dan
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I agree with Dan you need one built for your combination I would assume not knowing what your engine and RPM's are that a 7" or 8" may be more in line for you but only a good converter shop can tell you what you need
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A purpose built converter is huge, mine went from 8.40s to 7.50s with only a converter change.
Mark
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Mark 7.50's I missed that congratulations!
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Thanks. Finally!
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Yes well deserved!