Joined: 14 Nov 2008 Posts: 1212 Location: Village life.... Enter the Vale
Posted: Fri Mar 17, 2017 8:23 am Post subject: Petrol engine, subaru gearbox, gear ratios relative to speed
It's been a long time for me, since 2010 I've driven a V12 BMW with a 8 speed ZF auto box. So in 8th gear I'm used to 70mph and roughly 1800RPM or even at 55MPH it's about 1200RPM.
Driving my notch yesterday with the newly calibrated super accurate speedo ( I'm not taking the piss about it's as accurate as my GPS phone speedo) I'm doing 70MPH and the engine is sitting at 3100RPM. So it's half way using half of my available RPM's. I'm thinking for a 5spd 1995 technology this isn't so bad. It's running 205/45/17's and I went unconventional and fitted the 4.4 diff as opposed to the 3.9. I'm sure the 205/45/17 is roughly a standard size subaru tyre size so would expect the RPM's to be lower at 70MPH
Now I had a 1990 MK2 Golf 1.8 GTI 8V, Loved that car. I'm sure this was about the same, 70MPH around 3500RPM.
Reason I'm asking, I've always intended to fit wider wheels on my car, I've got the 19's which are mohoosive, obviously these will gear it down somewhat but I'm now contemplating that 70MPH with 3100RPM isn't a terrible combination. Obviously 70MPH at 2000RPM would be better but isn't realistic with the gearsets available and I'm not changing them. I believe I already have the highest 5th gear available being the UK WRX gesr set.
What RPM are you at at 70MPH and rear tyre sizes please with your petrol conversions. _________________ Think......
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