4000 In 5th - What mph should my 94 WRX be doing?
04 March 2001, 01:31 PM
#1
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Hey folks,
Got my scoob recently and I could have sworn that the standard gearing for 5th was higher than my one. Think I read a thread about it a while ago..... I have compared the speedo and revs and they seem to be spot on. My car is doing literraly 80Mph at 4000 in 5th. What do your guy's jap imports do? I have found all sorts of top-end goodies added onto this car, so maybe the gearbox has been altered?
Any info would be most appreciated.
Cheers,
Nick
Got my scoob recently and I could have sworn that the standard gearing for 5th was higher than my one. Think I read a thread about it a while ago..... I have compared the speedo and revs and they seem to be spot on. My car is doing literraly 80Mph at 4000 in 5th. What do your guy's jap imports do? I have found all sorts of top-end goodies added onto this car, so maybe the gearbox has been altered?
Any info would be most appreciated.
Cheers,
Nick
04 March 2001, 09:14 PM
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Hi Mr. Footlong!
I'm a little confused myself, I thought that 5th gear was an overdrive, about 0.89:1 and that the final drive was 4.111:1, which would make 4000RPM 79.9MPH assuming that the rolling diameter of your tyres is about 1.96 metres (based on 215/40/17). I should really get out the GPS receiver and double check....
But then there are people who dispute that the final drive on these cars is 4.111:1.... guess that I should really jack the car up, mark the prop shaft, and rotate the rear wheels until the shaft has completed one revolution, then see how far the rear wheels have turned...
Cheers,
Pat.
I'm a little confused myself, I thought that 5th gear was an overdrive, about 0.89:1 and that the final drive was 4.111:1, which would make 4000RPM 79.9MPH assuming that the rolling diameter of your tyres is about 1.96 metres (based on 215/40/17). I should really get out the GPS receiver and double check....
But then there are people who dispute that the final drive on these cars is 4.111:1.... guess that I should really jack the car up, mark the prop shaft, and rotate the rear wheels until the shaft has completed one revolution, then see how far the rear wheels have turned...
Cheers,
Pat.
04 March 2001, 09:18 PM
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OH MY GOD 
. Pat, are you for real or mocking me? If you are for real, then cut down on the coffee!!! Thanks for the above,
Nick
. Pat, are you for real or mocking me? If you are for real, then cut down on the coffee!!! Thanks for the above,Nick
04 March 2001, 11:29 PM
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Hello all,
According to some old sales literature from David Hendry Cars a WRX and a WRX STi III both run a 5th gear ratio of 0.738:1 (not 0.89:1) and run a 4.444 diff.
With 215/40/17 tyres that would equate to 21.52 MPH/1000rpm or 86.08 MPH at 4000rpm,
With 205/50/16 tyres it would be 21.82 MPH/1000rpm and 87.31 MPH at 4000rpm.
All figures are approximate.
It should be noted however that different tyre manufactures may produce tyres of varying diameters for the same width and aspect ratio sizes as another manufacturer (by a small margin I would hope), which would render all this calculator bashing a touch innacurate.
Like Pat says you need to establish what diff ratio your own car is running, then do the maths, or get one of these dam fangled GPS thingys.
For interest the ratios are listed as follows,
1=3.166
2=1.882
3=1.296
4=0.972
5=0.738
All relate to :1, and are listed as the same for WRX and STi models at that time.
Cheers MTR
[This message has been edited by MTR (edited 04 March 2001).]
According to some old sales literature from David Hendry Cars a WRX and a WRX STi III both run a 5th gear ratio of 0.738:1 (not 0.89:1) and run a 4.444 diff.
With 215/40/17 tyres that would equate to 21.52 MPH/1000rpm or 86.08 MPH at 4000rpm,
With 205/50/16 tyres it would be 21.82 MPH/1000rpm and 87.31 MPH at 4000rpm.
All figures are approximate.
It should be noted however that different tyre manufactures may produce tyres of varying diameters for the same width and aspect ratio sizes as another manufacturer (by a small margin I would hope), which would render all this calculator bashing a touch innacurate.
Like Pat says you need to establish what diff ratio your own car is running, then do the maths, or get one of these dam fangled GPS thingys.
For interest the ratios are listed as follows,
1=3.166
2=1.882
3=1.296
4=0.972
5=0.738
All relate to :1, and are listed as the same for WRX and STi models at that time.
Cheers MTR
[This message has been edited by MTR (edited 04 March 2001).]
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05 March 2001, 01:27 PM
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MTR,
I think you're spot on for the STi III, there were some changes to the engine and gearbox which meant that they moved to a 4.444:1 final drive, but IIRC, the MY94-MY96 jap cars ran 4.111:1, I've seen specs to that effect but this was a while back when I broke my first gearbox, and I cannot find them anymore :-(
Mr. Footlong,
No I'm not mocking you, but perhaps I would be wise to reduce my caffeine intake. LOL
Cheers,
Pat.
I think you're spot on for the STi III, there were some changes to the engine and gearbox which meant that they moved to a 4.444:1 final drive, but IIRC, the MY94-MY96 jap cars ran 4.111:1, I've seen specs to that effect but this was a while back when I broke my first gearbox, and I cannot find them anymore :-(
Mr. Footlong,
No I'm not mocking you, but perhaps I would be wise to reduce my caffeine intake. LOL
Cheers,
Pat.
05 March 2001, 01:43 PM
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Hi All!
After a bit of digging I have found the specs for the MY96 jap gearbox
OK, MY96 WRX ratios are :
1st 3.454
2nd 2.062
3rd 1.448
4th 1.088
5th 0.825
Rev 3.416
Final drive is 4.111:1 as suspected, but this gives 86 MPH at 4000RPM, but apparently there is a very rare set of ratios, which may be the 0.89:1 fifth set.... will have to get out the GPS and work it out methinks...
Cheers,
Pat.
After a bit of digging I have found the specs for the MY96 jap gearbox
OK, MY96 WRX ratios are :
1st 3.454
2nd 2.062
3rd 1.448
4th 1.088
5th 0.825
Rev 3.416
Final drive is 4.111:1 as suspected, but this gives 86 MPH at 4000RPM, but apparently there is a very rare set of ratios, which may be the 0.89:1 fifth set.... will have to get out the GPS and work it out methinks...
Cheers,
Pat.
05 March 2001, 04:26 PM
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Wheel/tyre size will not make any difference to what your speedo says. Most imports have the odometer chnges and calibrated for mph on a rolling road and very accurate. Some cars have the cheap option which is simply to stick a new printed facia over the kph speedo. The only way to check if your speedo is correct is to get it on a rolling road, or drive next to someone else at the same speed and see what they register.
05 March 2001, 05:13 PM
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I'm running just over 4,400 revs at 80mph in 5th.
I think my speedo reads faster than the car, as at SPOD my speedo read 100ish over the line, and the chitty said 99 on the dot.
MY94 TypeRA 17" rims with 215 40's on.
I think my speedo reads faster than the car, as at SPOD my speedo read 100ish over the line, and the chitty said 99 on the dot.
MY94 TypeRA 17" rims with 215 40's on.
05 March 2001, 09:20 PM
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Ok I have a 94MY and I get an indicated 82 mph, however my limiter comes in at an indicated 106mph so I would say my speedo was inaccurate. (tyres-205/50/16) My car is standard but with blitz exhuast and air filter.
05 March 2001, 11:09 PM
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Yup.
I have an MY93 WRX and hit around 81mph @ 4000rpm in top, and 100mph in 4th @ 7000rpm.
As stated previously, the speedo reads from the axle, and will read the same speed per rpm regardless of the size of wheel/tyre.
I have an MY93 WRX and hit around 81mph @ 4000rpm in top, and 100mph in 4th @ 7000rpm.
As stated previously, the speedo reads from the axle, and will read the same speed per rpm regardless of the size of wheel/tyre.
05 March 2001, 11:36 PM
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Hello all,
The speedo drive is taken from the gearbox, not the axle
And if you could fit 10" Mini wheels to your car the speedo and tacho would still show the same figures, but you would be travelling considerably slower than the speed indicated.(I can't be bothered to work it out).
HOWEVER,
The initial question was what speed will I be doing at 4000rpm, not what speed should my speedometer be reading.
Differing wheel and tyre sizes WILL alter the actual speed of the car, but not the speedometer reading.
The answer to the question lies in gearbox and diff ratios, and WHEEL & TYRE SIZE.
With that then established, a check can then be made on the accuracy of the speedo, and presuming alternative speedo drive gears (a small plastic gear on Fords) are available, the speedo recalibrated to suit the ACTUAL SPEED.
Cheers MTR
[This message has been edited by MTR (edited 05 March 2001).]
The speedo drive is taken from the gearbox, not the axle
And if you could fit 10" Mini wheels to your car the speedo and tacho would still show the same figures, but you would be travelling considerably slower than the speed indicated.(I can't be bothered to work it out).
HOWEVER,
The initial question was what speed will I be doing at 4000rpm, not what speed should my speedometer be reading.
Differing wheel and tyre sizes WILL alter the actual speed of the car, but not the speedometer reading.
The answer to the question lies in gearbox and diff ratios, and WHEEL & TYRE SIZE.
With that then established, a check can then be made on the accuracy of the speedo, and presuming alternative speedo drive gears (a small plastic gear on Fords) are available, the speedo recalibrated to suit the ACTUAL SPEED.
Cheers MTR
[This message has been edited by MTR (edited 05 March 2001).]
05 March 2001, 11:58 PM
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DaveD,
Just for interest, I believe the Porsche 924's have the speedo drive taken from one of the undriven front wheels, NOT the transaxle (they don't have a gearbox as such).
So if you were to put huge back wheels and tyres on those cars, the speedo would still read correctly, the revs would show a lower reading for any given speed.
But if the front wheel and tyre size was increased the speedo would then underead, smaller wheels it would overead, but the ACTUAL speed at any given RPM wouldn't change.
Cheers MTR
Just for interest, I believe the Porsche 924's have the speedo drive taken from one of the undriven front wheels, NOT the transaxle (they don't have a gearbox as such).
So if you were to put huge back wheels and tyres on those cars, the speedo would still read correctly, the revs would show a lower reading for any given speed.
But if the front wheel and tyre size was increased the speedo would then underead, smaller wheels it would overead, but the ACTUAL speed at any given RPM wouldn't change.
Cheers MTR
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