What do our trannies run for efficiency? Does this differ from your monster boxes? I noticed you dyno them....

So I guess you adapt a known power to the input shaft, and measure the output hp?

Thanks!

 

Hey said about 11% loss through our trannys. I don't know the specific hp/torq he put through the tranny for that number. I do know that the loss is not a set value, it increases for the amount of power you run through th tranny. Same with a 5/6 speed tranny, more stress on bearings means more friction/heat, lost of power.

Brandon

 

Not right, it decreases with output torque up to the peak torque, as measured in 3rd gear with the converter locked. It's just very bloody complicated, I get exhausted trying to explain it. Most of the loss is in the converter, which is why 1) most people believe the "typical" loss is 20-25%, which was true before lockup converters, and 2)..senior moment, I forgot 2, well, maybe I'll remember.
Oh, 2 is why it's best when the converter is locked, at that point your more or less on equal terms with a manual transmission, you have a direct mechanical link from the flywheel to the input shaft, on through the clutches to the output. With the converter locked and in third gear, you have direct mechancal link to the rear wheels at 1:1 ratio. It can't be accurately measured in OD because you can't lock the tranny in 4th gear.

It's late....



G

 

my understanding it that the loss is not linear. It takes X amount of HP to run the tranny. The more HP you have the more efficient it becomes.

someone correct me if i am wrong.

 

You're more or less right, it's more complicated than just that, but the tranny does take X amount of torque to turn. It's more like a sliding scale, but in general yes.

Is that sentence as confusing as it looks?

G

 

I guess my relation to numbers relates more so to manual transmissions, but the automatic also becomes a power eater on high hp cars. Heat builds up quickly (obviosuly quick blasts can be made up for with teh use of tranny coolers and such, but on long duration pulls the auto tranny starts to decrease its effieciency depending on fluid temps. Now PLEASE correct me if I am wrong on that, thats how it has been explained to me 100 times by many folks in the biz.

During lockup sure the tranny becomes more effiencient, because its most like having a direct drive from motor to tranny. What was left out of that statement is that during a dyno session you can see where the torq convertor locks up, soo the effiency changes quit a bit during that transition. During non lockup times the torq convertor eats quite a bit of power as its slips, now this isn't evident during most dyno runs but at part throttle they use quite a bit more than the 11% I would guess.

I do think no matter manual or auto, the power to run the tranny is not a set value its linear and does rise dependant on power inputed. Bearings distorting, clutches slipping, longer engaugement during shifts it all has to add up somewhere.


Greg how did you get the magical 11% anyways, i see and tell peopel all the time, but a little background info would be awesome!
Brandon