high rpm at 75 mph normal ?
08-17-2011, 05:00 PM
#16
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I have an 89 S4 (Canadian car). Based on the tire circumference of 79.5" (265/35 x18), it should take 797 wheel revs to go 1 mile. Using this figure, I should get the following kind of mph @2000rpm.
2.20 final drive = 68mph
2.36 final drive = 63mph
My speedo reads 100kph(62mph) @ 2000 rpm, so I assume I have a 2.36 final drive. I thought 89 S4 used 2.20???
2.20 final drive = 68mph
2.36 final drive = 63mph
My speedo reads 100kph(62mph) @ 2000 rpm, so I assume I have a 2.36 final drive. I thought 89 S4 used 2.20???
08-17-2011, 05:19 PM
#17
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08-17-2011, 06:04 PM
#18
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for those who are unsure research the Moorehouse CDs or 928Specialists site for all gbox type, ratios and final drives.
Theres a 'few' variations between the models and years
08-17-2011, 08:10 PM
#19
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The torque peak on a S3 is at 2700 rpm. My '85 5-speed got better mileage at a constant 84 mph/2700 rpm vs. 69/2100 on the way to/from SF10. (2.20 diff. Best MPG was ~25.5!)
08-17-2011, 11:29 PM
#20
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From my notes of a Tx-Ca-Tx trip years ago in a 1983 US 928S five-speed. Stock wheels, tires and trans. Not all my observed numbers matched perfectly, so I'll give all the speeds I noted at a given RPM. Maybe I did the math once.
1700 - 60, 60
1800 - 62, 62
2000 - 70
2100 - 72, 72, 72, 75, 76
2250 - 78
2300 - 80
2400 - 80
2600 - 90, 90
3000 - 100, 105, 105 - My comment on one of these was "Car's at a fast amble." Gotta love 'em.
3600 - 4th gear - 80
3100 - 4th gear - 70
1700 - 60, 60
1800 - 62, 62
2000 - 70
2100 - 72, 72, 72, 75, 76
2250 - 78
2300 - 80
2400 - 80
2600 - 90, 90
3000 - 100, 105, 105 - My comment on one of these was "Car's at a fast amble." Gotta love 'em.
3600 - 4th gear - 80
3100 - 4th gear - 70
08-18-2011, 03:34 PM
#21
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Will, that is exactly what I got on my 1984 euro 5 spd with a 1987 gearbox. Thanks for sharing you information. I always thought revs were really low in 5th gear, but now know your car is the same.
I love the fact that it cruises at 100mph at only 3000 rpm. And then shift down and floor it... Haha.
One question: do you get top speed at about 4500rpm? Or did the lack of autobahn limit that measurement?
Leo
I love the fact that it cruises at 100mph at only 3000 rpm. And then shift down and floor it... Haha.
One question: do you get top speed at about 4500rpm? Or did the lack of autobahn limit that measurement?
Leo
08-19-2011, 12:36 AM
#22
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I've never had the car above about 130. There was more car left but I was running out of road. And thinking about revenooers.
http://928gt.com/t-928trans.aspx tells me my '83 has a 2.36 rear end, though my owner's manual and the "Models, Dimensions, Tolerances" book tell me 2.2666. I thought it was 2.20, but appear to have confused it with the '83 auto.
http://www.jekylhyderacing.com/HeightofTires.htm
225/50/16 + 24.86" height. Pi x D = 78.06"/rev = 6.5'/rev. Now I'll have to do the rest of the math.
