Stupid question time....

[BO55 VXR]

Will a change of Diff Ratio affect RWBHP/Torque?

[Paul-C]

BO55 VXR said:

Will a change of Diff Ratio affect RWBHP/Torque?

No.

[splatspeed]

a longer ratio will improve top end and make the gears longer

a shorter ratio will reduce top end and make the gears closer together

first is very long and there is a lot of overlap on the gears with the large torque range in the monaro so changing it will only have the realy effect of increasing top speed or moving the gears nearer if shortening

you only need the gears nearer if you are changin the engine charecteristics to a narrower power range ie serious modding and the top speed should not really be a problem as mine does 40 mph at 1000 rpm

which equates to 200 at 5000 rpm roughly so long enough

only real reason for elongating the gears is better fuel econemy

ie 6 becomes a real overdrive

shortening the gears will give a slight increase in performance butnot enough to justify the cost

prefer engine mods

Sean

[V8HSV]

Totally agree Sean, engine mods are best & box is fine with more power, my 6th pulls hard at m/way speeds, when standard 6th was a 'no progress' gear, now it sometimes feels better than 5th for max out runs...

[Paul-C]

BO55 VXR said:

Will a change of Diff Ratio affect RWBHP/Torque?

Erm............did I misread the question BO55 VXR? Confused now looking at the other replies. The question and answer as I read it was 'will diff ratio affect rear wheel BHP and torque?', if that was it the answer is still no. No difference at all.

[GreenV8S]

BO55 VXR said:

Will a change of Diff Ratio affect RWBHP/Torque?

Depending what you mean by RWBHP/Torque, the answer might be yes.

If you change the gearing this will have some effect on the power measurement you get from a rolling road. It will also affect the rear wheel torque i.e. the torque actually delivered to the rear wheels, not prop shaft torque.

[Paul-C]

GreenV8S said:

BO55 VXR said: Will a change of Diff Ratio affect RWBHP/Torque? Depending what you mean by RWBHP/Torque, the answer might be yes. If you change the gearing this will have some effect on the power measurement you get from a rolling road. It will also affect the rear wheel torque i.e. the torque actually delivered to the rear wheels, not prop shaft torque.

Please dont take this as a flame but it needs killing If you remove an engine from a car and measure its BHP and Torque output, nothing except engine modifications will affect those figures. Gearbox / diff ratios will affect its performance in terms of acceleration and speed only.

[Paul-C]

Have a look at these sites. Hope it helps.

www.pumaracing.co.uk/power3.htm

www.pumaracing.co.uk/power2.htm

Edited by Paul-C on Friday 2nd June 11:14

[splatspeed]

bhp is torque times speeed

therfore diffrent gearing will change the torque at diffrent speeds in 1 gear

of corse gears change and there fore this changes

torque changes with gearing so a 2 to 1 ratio of speed ie 1/2 of speed doubles torque

torque directly relates to force on the car

Force = Mass X Acceleration

force / Mass = Acceleration

so the greater the torque at the rear wheels the greater the acceleration

but there is a limit

tyres have a static friction and a dynamic friction

static friction is higher than dynamic friction

so the force up to the static friction will give you max acceleration.

when you go over the static friction force wheels spin and you enter dynamic friction

the shorter the diff the quicker you run out of gears

Sean

PS i have drag racing sim if you want to see the effects of diffrent ratios and see the 1/4 mile times change without spending a penny

>> Edited by splatspeed on Friday 2nd June 11:30

[V8HSV]

"so the greater the torque at the rear wheels the greater the acceleration" - yum, I have 590 ft lbs over 570 bhp


"the shorter the diff the quicker you run out of gears" - I will stick with standard box as I hate loosing time changing gears