Pretty Amazing!! Converter Science!!

[cudabob496]

I just read in the March,2010, Popular Hot Rodding, that changing converters in a 700R GM transmission can change hp to rear wheels. In this case they went from a 9.5 inch to a 10.5 inch converter, and increased rear wheel horsepower by about 75!!, and torque around 35 I think. A major factor is the design of the vanes in the converter!! Thats amazing!! 75 more rear wheel hp just by changing converters. Obviously, whether 9.5, or 10.5 inch, they are still both performance converters!

I've got a Hughes 10 converter in my Cuda, designed to give a 3500 stall.
Wonder if I can get 50+ hp more to rear wheels by going to a different converter??

[John Kunkel]

Torque converters multiply torque, horsepower is based on torque. The stall ratio of a converter is the measurement of how much it multiplies torque, for example if a converter has a 2-1 stall ratio it would turn 500 ft. lbs. of crankshaft torque into 1000 ft. lbs. at the transmission input shaft but this ratio only occurs at the instant of stall. Below the stall the ratio is lower.

Many converter manufacturers have advertised stall ratios above 2.5-1

[cudabob496]

Originally Posted by John Kunkel

Torque converters multiply torque, horsepower is based on torque. The stall ratio of a converter is the measurement of how much it multiplies torque, for example if a converter has a 2-1 stall ratio it would turn 500 ft. lbs. of crankshaft torque into 1000 ft. lbs. at the transmission input shaft but this ratio only occurs at the instant of stall. Below the stall the ratio is lower.

Many converter manufacturers have advertised stall ratios above 2.5-1

I agree, there is the torque multimplication effect when you are initially getting on the throttle, but this article is talking peak engine horsepower, measured well beyond the stall rating, if I am not mistaken.

[rampage_82]

Yeah, but this all comes down to the quality of the converter. If you get a cheap converter that they manipulate the fins ect, to get more stall out of it, then it just becomes terribly inefficient, which in turn lowers the power making it to the wheels. So yes going from an inefficient 9" converter to a good 10" would make a difference on the dyno. Technically speaking if you had a lockup converter that would hold up, you would see more power yet on a dyno...

[DartGT66]

Yes, just like rampage 82 said, there can be tremndous differencies in converter efficiency. I once tried "a couple of" 8" converters, found one that gave me 5 mph speed and 0.4 seconds ET, had previously run 10.0/137 and now 9.6/142. After this, I sent the 10.0 converter to be tightened and when I got it back it worked like charm, pulling from about 5000 to 7000, while the previous ones pulled from 6000+. Now, at the track, the tightened converter worked great, and the trap rpm was almost 7500 while previously it hade been just over 7000. However, the ET was now 11.0 and speed 125 mph. So, you can screw up a converter really bad.

[rampage_82]

Yeah, I can spout off all this nonsense I want, but truth be told I've had waayy better luck with a cheap company, than I had with Hughes, TCI, and B&M.. I've run three ACC Boss Hog converters, and they have worked flawlessly. A buddy of mine is running a converter from some outfit in Texas, and it's called Redneck Converters, and it's a 9" that he is running in a C4 Ford, and it works great as well. I know that Dynamic, Coan, and a slew of other converters are way better, but I'm very impressed with these tiny company's converters for the price.. (BTW I have a Dynamic for my real race truck, but I figured in my wifes/sons trucks the cheap ones would be good enough, and I've been pleasantly surprised LOL) ... Although I must admit my brother bought a cheap converter one time it was made my GER, and that was the biggest piece of junk I've ever dealt with...

[cudabob496]

Originally Posted by DartGT66

Yes, just like rampage 82 said, there can be tremndous differencies in converter efficiency. I once tried "a couple of" 8" converters, found one that gave me 5 mph speed and 0.4 seconds ET, had previously run 10.0/137 and now 9.6/142. After this, I sent the 10.0 converter to be tightened and when I got it back it worked like charm, pulling from about 5000 to 7000, while the previous ones pulled from 6000+. Now, at the track, the tightened converter worked great, and the trap rpm was almost 7500 while previously it hade been just over 7000. However, the ET was now 11.0 and speed 125 mph. So, you can screw up a converter really bad.

.4 secs off previous ET represents about 40hp more to the rear wheels! Question is, how do you know you are putting the best converter in your car, for maximum horsepower to the rear wheels. You don't want to try 20 different converters till you find the best one?? I will say, going to a 3500 stall 10 inch converter for my 3300 lb Cuda sure made driving on the street a lot more fun!! I've heard a good converter can multiply by two the initial torque to the rear wheels, for quick getaways!!

[cudabob496]

Originally Posted by rampage_82

Yeah, I can spout off all this nonsense I want, but truth be told I've had waayy better luck with a cheap company, than I had with Hughes, TCI, and B&M.. I've run three ACC Boss Hog converters, and they have worked flawlessly. A buddy of mine is running a converter from some outfit in Texas, and it's called Redneck Converters, and it's a 9" that he is running in a C4 Ford, and it works great as well. I know that Dynamic, Coan, and a slew of other converters are way better, but I'm very impressed with these tiny company's converters for the price.. (BTW I have a Dynamic for my real race truck, but I figured in my wifes/sons trucks the cheap ones would be good enough, and I've been pleasantly surprised LOL) ... Although I must admit my brother bought a cheap converter one time it was made my GER, and that was the biggest piece of junk I've ever dealt with...

Another guy bought the same hughes converter I did, at the same time, and it was way out of balance. Mine has lasted 15 years!! So, in some repects its a crap shoot, but in the big picture, you're gonna get what you pay for! You won't see the big time racer boys putting cheap stuff in their cars, when thousands of dollars in sponsorships are on the line!

[cudabob496]

Originally Posted by DartGT66

Yes, just like rampage 82 said, there can be tremndous differencies in converter efficiency. I once tried "a couple of" 8" converters, found one that gave me 5 mph speed and 0.4 seconds ET, had previously run 10.0/137 and now 9.6/142. After this, I sent the 10.0 converter to be tightened and when I got it back it worked like charm, pulling from about 5000 to 7000, while the previous ones pulled from 6000+. Now, at the track, the tightened converter worked great, and the trap rpm was almost 7500 while previously it hade been just over 7000. However, the ET was now 11.0 and speed 125 mph. So, you can screw up a converter really bad.

What does it mean to have a converter tightened?

[cudabob496]

Originally Posted by DartGT66

Yes, just like rampage 82 said, there can be tremndous differencies in converter efficiency. I once tried "a couple of" 8" converters, found one that gave me 5 mph speed and 0.4 seconds ET, had previously run 10.0/137 and now 9.6/142. After this, I sent the 10.0 converter to be tightened and when I got it back it worked like charm, pulling from about 5000 to 7000, while the previous ones pulled from 6000+. Now, at the track, the tightened converter worked great, and the trap rpm was almost 7500 while previously it hade been just over 7000. However, the ET was now 11.0 and speed 125 mph. So, you can screw up a converter really bad.

The 7500 trap rpm must have taken you a little out of the max torque power band/range?

[rampage_82]

Originally Posted by cudabob496

Another guy bought the same hughes converter I did, at the same time, and it was way out of balance. Mine has lasted 15 years!! So, in some repects its a crap shoot, but in the big picture, you're gonna get what you pay for! You won't see the big time racer boys putting cheap stuff in their cars, when thousands of dollars in sponsorships are on the line!

That is very true, however what you will see is us poor boys running the cheap stuff for the fun of racing, plus even when you win you still don't make back you're entry fee and the cost of fuel to haul a big heavy pig truck 200+ miles to run it off in a mud hole... LOL. Everything is relative to what you are doing... Heck I'll be the first to admit my buddies were laughing at the Boss Hogg converter when I bought it (Can't even count the Dukes of Hazard references), but three years later, and now all of them are running the cheap converter.

[cudabob496]

http://www.youtube.com/watch?v=adNW6...eature=related

However, I will buy a Daisy Duke converter!!!

[DartGT66]

Having a converter tightened means lwoering its stall speed by reducing the clearances. The engine was already about out of it's power band with the 6200 stall, it had peak tq at 5000 and peak power at 6600, but that doesnät explain why the speed was over 15 mph less with more rpm. Still, as far as the power band goesm, the situation wasnät as bad as with our current set up that has 6200 stall speed and peak power at 6100.

[cudabob496]

I suppose one way of telling if a converter is inefficient, or degrading, is measuring transmission fluid temp. I installed an electric probe on the return line from my tranny cooler to meausre tranny temp. I don't have the tranny line going through the radiator anymore.

[John Kunkel]

There's a lot more to converter tightness than just clearances, the angle/design of the vanes in the pump, turbine and stator are what controls the stall speed.

If one wants to measure a converter's efficiency with a temp gauge it would be best to install it in the out line, not the return.

[cudabob496]

Originally Posted by John Kunkel

There's a lot more to converter tightness than just clearances, the angle/design of the vanes in the pump, turbine and stator are what controls the stall speed.

If one wants to measure a converter's efficiency with a temp gauge it would be best to install it in the out line, not the return.

Good point. Also, even more accurate is to hit the converter with one of those $50 temp guns! One of the best tools I ever bought!

When you think about it, if you go from one converter to another, and you lose 40 hp to the rear wheels, then that 40 hp has to be lost in the converter, and should show up as additional heat transmitted to the tranny fluid, as a result of converter inefficiencies.