One For Lawsy

[IH8TOADS]

Sure does help, cheers. 530 sounds v nice!!!! probably feels even better!

[markxr6t]

I'm not sure, but isn't torque at the rear wheels always much more than torque at the engine (Opposite to power) because the gears and wheels multiply the torque?

Mark

[Lawsy]

  markxr6t said:

I'm not sure, but isn't torque at the rear wheels always much more than torque at the engine (Opposite to power) because the gears and wheels multiply the torque?

Mark

Ahh but heres the trick, though the axils might be spinning 3.73 times per minute less than the engine, my calculation includes the total reduction (1 x 3.73).

So the tractive effort is what the dyno reads directly, you then apply the formula, including the reduction gear, and you get what the actual applied rear wheel torque value is... This is the exact twisting force that the contact patch of your tyres is going to have to cope with. Its much harder to fudge these figures lower in the rev range than it is to fudge top end max power...

The outcome, though some say is the flywheel torque, is not infact flywheel torque. The outcome (and this is provable, get me a dyno and I'll show you, has to be shown, not explained, so I'm not going to ) is always from the measured source of the tractive effort...

If you bolted a wheel directly to the flywheel, you could measure the tractive effort, it would be higher by 3.73+drivetrain losses.

So 530nm at the rear bags is one crap load of grunt and will force your eye balls to the back of your head without much trouble.

[markxr6t]

OK - I think I'm starting to understand. So, if a standard XR6T has 450Nm as measured on an engine dyno:

A) What torque would it show at the rear wheels without the reduction formula?

and

B) With the reduction formula?

Thanks

Mark

[DBOSS]

Im not sure but I think flukey car is a MKI and has a 3.45 diff ratio and the MKII has a 3.73 as this would also have a bearing of the final outcome

CYA JEFF

[Flukey]

  DBOSS said:

Im not sure but I think flukey car is a MKI and has a 3.45 diff ratio and the MKII has a 3.73 as this would also have a bearing of the final outcome

CYA JEFF

Correct Series 1 and Lawsy was right with tyre/wheel size.

[Lawsy]

  markxr6t said:

OK - I think I'm starting to understand. So, if a standard XR6T has 450Nm as measured on an engine dyno:

A) What torque would it show at the rear wheels without the reduction formula?

and

B) With the reduction formula?

Thanks

Mark

Well, look at lukes graph. See how the standard line has a peak of about 4500N? Well that's where there was a peak in torque (its actually a pretty flat curve. This is good because it is meant to be...).

At this peak, the wheels saw 370nm. So if this car made the claimed 450nm at the crank, then it lost 80nm through the driveline and gearing.

that's the answer to C) the torque at the rear wheels.

If you dont apply the formula, the outcome is 1350nm. Yes the units are still in nm ((SI)distance x (SI)force must have units of nm), but it is meaningless.

1350nm relative to what? The reason the formula has the gear in there is because we are measuring at the wheels.

The effect that the gear ratio's have during the dyno run need to be balanced out in order to give a meaningful result.

If you have 4.11 diff gears, your Tractive effort will be higher, but when you apply the formula, you get the same value . This value is the torque relative to the engine after all drivetrain losses have been taken out.

This is why tractive effort is harder to fudge playing with diff ratio calculations and running the car in 2nd gear or whatever... Cause when the formula is applied, it takes those ratio's into account, and gives you the real torque that is being applied to the axils.

[markxr6t]

Thanks - now I get it. that's why we often see ridiculously high torque figures without the application of the formula.

Mark

[Flukey]

  Lawsy said:

  IH8PORK said:

dat alot of twisn powa. Not that I know but that seems like a big increase in torque compared to kws. that's >50% nm increase. I like!!!!

So that's it, you have nearly 530 tooheys news pushing your car allong....

Thanks Lawsy and to everyone else for the input. Rob at HPF said when I picked it up that it was approx 550nm atw, I just never understood how it was worked out.

What would it be at the flywheel?????? Can it be calculated????

Luke.

[Lawsy]

You have 3.46 diff gears? Is it just me or is that odd? Could have sworn that all T's had the 3.73...

Well in that case, I'll have to take 6400N as your max tractive effort (the flat spot) as your true peak torque, as this is roughly where 3500rpm - 3800 would be.

So in that case, with the 3.46 diff gears, you have 555nm... Even better