Hi,
Can anyone with a Cavalier Haynes manual give me the gear ratios and final drive ratio from a 1991 Cavalier 1.4 with 5 speed box. I would also like the tyre size for both 1.4 and 1.6 models.
Cheers
Neil T
SEAT Leon TDi 150
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Gear Ratios
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1st 3.55:1
2nd 1.96:1
3rd 1.30:1
4th 0.89:1
5th 0.71:1
Reverse 3.31:1
Final Drive Ratio 4.29:1
Tyres
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1.4 165R13 T
1.6 Various sizes fitted, dependant on trim level.
Check out www.dunloptyres.co.uk/site/tyres/car/pressureGuide for different sizes fitted.
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As a matter of interest does any know how to convert gear ratio's to
MPH per 1000 rpm
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I think this is how it's done...
say car is in 5th gear the overall gear ratio would be 0.71 x 4.29 = 3.05:1
say the diameter of the wheel is 0.6 metres
so circumference of wheel is 0.6 x 3.1459 = 1.88metres
now engine speed =1000rpm
therefore axle speed is 1000/3.05 = 327 rpm = 5.46 revs/sec
therefore car would travel 5.46 x 1.88= 10.26 metres/sec = 0.01km/sec = 37km/hr per 1000rps
According to my speedometer 30MPH = 50 KMH (approx)
therefore 37km/hr = (30/50) x 37 = 22.2MPH/1000rpm
phew!
steve
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The formula is 60000/(N x R) where :-
N = Number of revs per mile of the tyre.
R = The gearbox ratio times the final drive ratio.
You need a tyre data book to get the revs/mile of the tyre. I have some data on that. Answer to above formula is in mph per 1000 rpm.
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Mmmmm, I guess this is the quicker way....:-)
Oops
Neil T
SEAT Leon TDi 150
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Yes, I have accually writen an Excel document for this, I shall try and explain it, but if it doesn't make sense I can e-mail the Excel sheet to people.
Firstly you need the out tyre diameter....a 195/60 R15 has 615mm diameter.
e.g, 195 x 60% = 117mm (this is the tyre wall depth, 60% being the 2nd number on the tyre)
117 x 2 (there are 2 wall depths in a diamter) = 234mm.
15" wheel = 15 x 25.4 (to convert to mm) = 381mm
381 + 234 = 615mm.
We now need the outer tyre circumference, this is Pi x Dia. Pi is 3.1427, thus 615 x 3.1427 = 1932.8mm
Now you have this you can work out every thing else. For an example lets say that the 5th gear ratio in 0.71:1 and the final drive is 3.76:1.
The complete sum would be:
1000rpm / 0.71 = 1408.45
1408.45 / 3.76 = 374.59 (we now have the number of times the wheels turn in one minute.
1932.8 x 374.59 = 723992.75 (this sum was tyre circumference X number of wheel turns per min = mm travelled per min, now we convert to km/h)
723992.75 / 1000 = 723.99 meters/min
723.99 x 60 = 43439.6 meters/hour
43439.6 / 1000 = 43.44 km/h
43.44 / 1.6093 = 26.99 mph / 1000rpm
If you want to work out maximum speed for a given gear you simply take the mph/1000rpm and times it by the max revs. i,e, red line at 6500rpm:
26.99 x 6.5 = 175.44mph (obviously 5/6th gear and maybe even 4th gear are unlikely to reach max revs)
This works for all gears, although you have to be aware, for instance the VAG 6 speed gear box uses a different final drive ration in 5th and 6th to the fist 4 gears, so you would need to know both depending on what gear you wanted to work out.
Neil T
SEAT Leon TDi 150
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