Fabr's Car-VW/busa crossbreed

[Engineer]

busa                       VW
2.615--1st----------1st-3.80
1.93---2nd----------2nd-2.06
1.285-4th-----------3rd-1.26
1.043-6th-----------4th-0.82   

A busa @10.5K after the 1.596 is 6579 RPM at the countershaft. Same type of rpm the VW runs at redline. Also similar rpms under all drive conditions as the VW. The VW seems like it has a nicer spread of ratios also. Actually lower by a lot that I think would improve all around drivability.
So the question I REALLY need an answer to is this-What is the real world torque at the busa countershaft if the dyno shows REAR WHEEL TORQUE of say 200 lb Ft.?  Is it an actual 200 at the countershaft?  I'm a bit confused on that point.       

Hold on fabr, I am not following your math, and where are you getting the 1.596?

Just for reference the primary reduction on the busa is 1.596, and the gear ratios are as follows:

          1 - 2.615    total reduction (1.596 X 2.615) = 4.17
          2 - 1.937    total reduction = 3.09
          3 - 1.526    TR = 2.44
          4 - 1.285    TR = 2.05
          5 - 1.136    TR = 1.81
          6 - 1.043    TR = 1.66

So with the Busa at 10,500 RPM the output shaft speed would be:

         1 - 10,500/4.17 = 2,518 RPM
         2 - 3,398 RPM
         3 - 4,303 RPM
         4 - 5,122 RPM
         5 - 5,801 RPM
         6 - 6,325 RPM

Lets just say your Turbo busa makes 300Hp @ 10,500, and it also peaks torque there.  Its torque will be (torque = (horsepower x 5252)/engine speed) 150 ft/lbs at the crank.  If we look at it in 6th gear at the countershaft it will be 150ft/lbs x 1.66 = 249 ft/lbs.  That is why busas tear the crap out of things.....

If we look at a stocker 178Hp = 89ft/lbs at the countershaft = 148 ft/lbs, at 6,325 RPM.

It looks like if you buy aftermarket gears for the 091 you can get anything but lets run the numbers so see what we will have in 4th with your ratio of .82, and a 4.57 ring and pinion.

6,325 RPM / (.82 x 4.57) = 1688 RPM at the CV flange

Add a 31" tall 1300 plus.....

31in x 3.141519 = 97" rollout x 1688 = 163736 inches/minute divide by 12 for feet, divide by 5280 for miles, multiply x 60 for hours instead of minutes = 155 miles per hour.

Looks about right.  When will it be done?  I want to see how it works. 

[Engineer]

busa                       VW
2.615--1st----------1st-3.80
1.93---2nd----------2nd-2.06
1.285-4th-----------3rd-1.26
1.043-6th-----------4th-0.82   

A busa @10.5K after the 1.596 is 6579 RPM at the countershaft. Same type of rpm the VW runs at redline. Also similar rpms under all drive conditions as the VW. The VW seems like it has a nicer spread of ratios also. Actually lower by a lot that I think would improve all around drivability.
So the question I REALLY need an answer to is this-What is the real world torque at the busa countershaft if the dyno shows REAR WHEEL TORQUE of say 200 lb Ft.?  Is it an actual 200 at the countershaft?  I'm a bit confused on that point.       

I re-read your question..... Remember there is no Rear Wheel Torque number.  They measure it at the rear wheel, then calculate it back to the crankshaft.  Not the countershaft, the crankshaft.

If everyone was bragging about there rear wheel torque numbers, I would run mine in 1st gear, because you would have much more torque.  Everyone is correcting the numbers back to the crankshaft.  The Rpm number is always at the crank, 10,500RPM.  If they were correcting to the countershaft they should tell you the RPM was 4,286......   

[Nutz4sand]

http://www.europeancarweb.com/projectcars/0310ec_1986_porsche_944_turbo_specifcations/index.html

These trannys already have the nosecone built for you. Just flip the Hayabusa sideways and get a driveshaft adaptor. Get a lil driveshaft made up. It would be a tad longer though.   

You can see all the specs above at the link but the car weighs 3040 pounds and the motor stock makes:
 Power (SAE net): 217 bhp @ 5800 rpm
Torque (SAE net): 244 lb-ft @ 3500 rpm

Plus HUGE tires on pavement.

Just some food for thought. You be your own judge on it but share opinions with us!

Even if you had a Hayabusa cranking out 367.5 ft/lbs of torque the reduced weight would make these trannies survive fine. If you go looking these numbers are stock HP and torque and many people have built these cars up. Plus these trannies would not need aftermarket gears as much.  Chances are you can find these trannies near you as well. The little extra you pay for the name on the fender would offset the cost of beefing it up after you got it.  Bill

[fabr]

Hold on fabr, I am not following your math, and where are you getting the 1.596?

Just for reference the primary reduction on the busa is 2.352, and the gear ratios are as follows:

          1 - 2.615    total reduction (2.352 X 2.615) = 6.15
          2 - 1.937    total reduction = 4.56
          3 - 1.526    TR = 3.59
          4 - 1.285    TR = 3.02
          5 - 1.136    TR = 2.67
          6 - 1.043    TR = 2.45

So with the Busa at 10,500 RPM the output shaft speed would be:

         1 - 10,500/6.15 = 1,707 RPM
         2 - 2,302 RPM
         3 - 2,925 RPM
         4 - 3,477 RPM
         5 - 3,933 RPM
         6 - 4,286 RPM

Lets just say your Turbo busa makes 300Hp @ 10,500, and it also peaks torque there.  Its torque will be (torque = (horsepower x 5252)/engine speed) 150 ft/lbs at the crank.  If we look at it in 6th gear at the countershaft it will be 150ft/lbs x 2.45 = 367.5 ft/lbs.  That is why busas tear the crap out of things.....

If we look at a stocker 178Hp = 89ft/lbs at the countershaft = 218 ft/lbs, at 4,286 RPM.

If looks like if you buy aftermarket gears for the 091 you can get anything but lets run the numbers so see what we will have in 4th with your ratio of .82, and a 4.57 ring and pinion.

4,286 RPM / (.82 x 4.57) = 1144 RPM at the CV flange

Add a 31" tall 1300 plus.....

31in x 3.141519 = 97" rollout x 1144= 110968inches/minute divide by 12 for feet, divide by 5280 for miles, multiply x 60 for hours instead of minutes = 105 miles per hour.

Looks about right.  When will it be done?  I want to see how it works. 

Sorry,engineer, but you need to redo your math.The busa PRIMARY INTERNAL reduction from the crank to the tranny is 1.596:1. You are quoting the FINAL reduction from countershaft to rear wheel .That is not relevant to this. Your thinking is correct but you've used the wrong numbers.
Herein lies my question also.The "crank" torque that is quoted on dyno sheets is that actually at the crank or is it at the countershaft? In other words many t'bo busas can make 200 lb.ft. numbers so is this "at the crank" actually 125 lb.ft. x 1.596=200 or is it actually 200 lb.ft. at the crank and therefore 319 at the countershaft? I think its at the countershaft that the 200 is measured at. I'm trying to find that out for sure.

[Admin]

you would have to reduce the rear wheel torque number by the sprocket gearing to get counter shaft torque..

[fabr]

[Engineer]

Why would they quote the RPM at the crank, and the torque at the countershaft?

I could be wrong about the primary reduction.  Where did you find your numbers?  If you are correct then is the 1.043 6th gear, the total reduction from the crankshaft?  That would mean that it is overdriven in the tranny to almost eliminate the primary reduction?

[plkracer]

No, primary is 1:1.59 and the 6th alone is 1.043. Together they are 1:1.665 at the countershaft.

[plkracer]

That's 6300 rpm at the CS when the engine is turning 10,500.

[fabr]

Why would they quote the RPM at the crank, and the torque at the countershaft?

I could be wrong about the primary reduction.  Where did you find your numbers?  If you are correct then is the 1.043 6th gear, the total reduction from the crankshaft?  That would mean that it is overdriven in the tranny to almost eliminate the primary reduction?

Many sources give the primary reduction.  1.596 is correct for all busas.

busa                       VW
2.615--1st----------1st-3.80
1.93---2nd----------2nd-2.06
1.285-4th-----------3rd-1.26
1.043-6th-----------4th-0.82   

The ratios in the above chart are actual tranny gear ratios.The busa will multiply those ratios by 1.596 for the actual gear ratios.

So what I think is correct is this for 6th gear. 10.5K rpm/1.596=6331/1.043=6307 rpm@the countershaft.
 Or 150 Lb.ft.@ the crank x 1.596 primary reduction=239 lb.ft. x 1.043 =250 lb.ft.@the countershaft.
 

[plkracer]

Check your math on the rpm fabr.  :P

[Admin]

math looks right to me...

[fabr]

I fat fingered a key.It's correct now.

[Admin]

are you figuring ring and pinion in your math as well...for final ratio to tires?

[fabr]

No reason to .All I'm trying to determine is if 091 can take the input torque that a busa makes at the countershaft.It looks like a stocker won't hurt it and a built 091 I think can handle a built busa to maybe 400 HP.