Guesses about Gear Ratios and Wheel Torque

[Deslock]

This Subaru video shows 97 km/hr @ 7300 and 61 km/hr @ 3200:

That means redline is approximately at:

2nd 61 MPH
3rd 88 MPH

If we assume typical differences between gear ratios, we can speculate:

1st 40 MPH
4th 116 MPH
5th 144 MPH
6th 181 MPH

For highway cruising, that puts 75 MPH in 6th at 3100 RPM.

Peak wheel torque per gear, rounded to the nearest 10 lbf*ft, assuming 15% drivetrain loss:

1st 1700 lbf*ft
2nd 1110 lbf*ft
3rd 770 lbf*ft
4th 590 lbf*ft
5th 470 lbf*ft
6th 380 lbf*ft

Note that 4th-6th seem a little tall, but that's because 3rd is a bit tall in the video. Before noticing that 3rd was in the video, my guesses were:

3rd 86 MPH
4th 113 MPH
5th 141 MPH
6th 176 MPH

Obviously redline won't be reached in 6th gear, and possibly not in 5th if rumors of a 136 MPH top speed are true. However, some of those rumors claim top speed is due to fuel cutoff (supposedly at 7450 RPM), which raises some questions.

[old greg]

Originally Posted by Deslock

Note that redline won't be reached in 5th and 6th gear

Nah, it'll hit 141 just fine.

[Deslock]

Originally Posted by old greg

Nah, it'll hit 141 just fine.

Maybe. I read a while ago that top speed would be a little less. I don't expect to take it that high anyway.

Edit: Note that I revised 5th to redline at 144 rather than 141

[SUB-FT86]

I wonder why the wheel torque per gear never shows up on a dyno?

[Dimman]

Originally Posted by SUB-FT86

I wonder why the wheel torque per gear never shows up on a dyno?

Because they only dyno in one gear, usually whichever is closest to 1:1 (4th or 5th). So the dyno is getting engine torque multiplied by final drive ratio minus friction losses and converting from that.

[SUB-FT86]

Thanks, Dimman.

[Zaku]

I know this will sound like a very noob question and Im sorry if it does, but do you think the manual will be short throws? like I don't need to mod it with a Short shifter?

[Allch Chcar]

Oh hey Deslock. Nice job on the calculations, I'll run some of mine here if you don't mind. Given the wheel RPM is known, 844 RPM @ 60MPH, I figure this car would need a 3.75 or so Final 5th gear ratio to pull 141MPH. That puts 6th gear around 0.78-0.80 if the 2500RPM at 60mph is true. Not exactly tall but it's not nearly as short as the MX-5/RX-8 gearbox.

Originally Posted by Zaku

I know this will sound like a very noob question and Im sorry if it does, but do you think the manual will be short throws? like I don't need to mod it with a Short shifter?

Yes. It's been mentioned somewhere. I can't remember where though, sorry.

[Deslock]

I happened to re-watch the video and noticed that 3rd gear is also shown, and estimated that it redlines at ~88 MPH (rather than ~86 as I initially guessed). So I added that information and revised my estimates assuming that 4th, 5th, and 6th are all *slightly* taller as well. Again, this is all guesswork.

[carbonBLUE]

Originally Posted by Deslock

Maybe. I read a while ago that top speed would be a little less. I don't expect to take it that high anyway.

Edit: Note that I revised 5th to redline at 144 rather than 141

top speed will be more due to the fact its got a good drag raito

my car has less hp less tq and its drag ratio is .32 and i can hit 150

more tq and hp with a drag ratio of .27 should hit 150 prob topping out after 2-3 miles at 160-165

[ahausheer]

Suppose you can hit 61 at the top of second. This is interesting since they say the car was not designed for spec sheets. If your estimates are true it would make the 0-60 time look good on paper. Perhaps sub 6 sec to 60 mph if you beat the hell out of it and are a very very good driver.

[Allch Chcar]

Originally Posted by ahausheer

Suppose you can hit 61 at the top of second. This is interesting since they say the car was not designed for spec sheets. If your estimates are true it would make the 0-60 time look good on paper. Perhaps sub 6 sec to 60 mph if you beat the hell out of it and are a very very good driver.

All of the gearing is a bit tall IMHO. I like it but I dunno if it's right on. The top speed gearing in 5th is around 3.7 which is on the tall side.

[serialk11r]

Originally Posted by ahausheer

Suppose you can hit 61 at the top of second. This is interesting since they say the car was not designed for spec sheets. If your estimates are true it would make the 0-60 time look good on paper. Perhaps sub 6 sec to 60 mph if you beat the hell out of it and are a very very good driver.

But 100km/h is 62mph, so for European and whatever reviews you'd be a shift short right? :O

Those ratios don't seem very close, about 1.44 between gears :O by contrast an STi transmission is 1.386 (looking at 4th and 5th at least, assuming equal "spacing"). I think first is going to be a little more than 40 since that would put it more in line with the 2nd-3rd ratio.

I think having all 6 gears equally spaced is kinda stupid if 6th gear cannot reach top speed, but that's just me (and Porsche?).

[Allch Chcar]

Originally Posted by serialk11r

But 100km/h is 62mph, so for European and whatever reviews you'd be a shift short right? :O

Those ratios don't seem very close, about 1.44 between gears :O by contrast an STi transmission is 1.386 (looking at 4th and 5th at least, assuming equal "spacing"). I think first is going to be a little more than 40 since that would put it more in line with the 2nd-3rd ratio.

I think having all 6 gears equally spaced is kinda stupid if 6th gear cannot reach top speed, but that's just me (and Porsche?).

It's a street car, Cereal. Top gear is always taller than necessary for MPG, NVH, etc. 5th gear is the top speed gear. If you want to use 6th gear for top speed you need to use a much shorter axle gearing. >