Busta wrote: 31 inch tyres increase the gearing by 17% so would have the same rev drop as you propose in 5th. Just search this forum for what affect they have on 5th gear and cruising speed with standard gearing!
Even modest 215/75 R15s have a noticeable affect on 5th gear cruising- that's only 5% change.
With your background you'll have a better idea than me, but I reckon the engine is making, at best, 45hp at 3000rpm. Drop down to 2500 and you are going to be in the mid 30s. Not a lot to play with!
The Vitara 1.6 in any guise is a very different engine to the Jimny 1.3! Even the 8v has more torque, and peak torque is at 3000rpm, compared to 4000rpm in the Jimny.
thanks Busta,
although 31" tyres would produce the necessary "ratio" modifications, it is not a true like for like change compared to altering gear ratios, because 31" tyres produce significant additional driveline mass, requiring further hp still to rotate.
the vitara reference was not related to the Jimny, just in vitrara terms, the higher ratios were beneficial.
with a naturally aspirated Petrol engine, the power curve (which admittedly i have not looked at for this engine) is going to be fairly steady all the way up, with a slight step at around 4250 when the vvt switches over, so i would guesstimate closer to 60hp at the flywheel at 3000rpm, perhaps 50hp at 2500rpm. the most recent engine through the dyno produced maximum power at 4750rpm, and it was a petrol engine with 6500rpm redline. a good percentage of the power was available at 2500rpm upwards, which is the "driveability zone".
for the timebeing this is just a healthy debate on the matter, as the car is still in warranty.
cheers, Paul.
