Rb25det Torque

[JustinP]

I was just wondering, on average, what sort of torque to RB25DET's put out when modifed to around 200 or 250rwkw?

[WPN-O33]

I had my car tuned last week and it made 222rwkw max torque on the dyno sheet was 351.3 Nm so there is a rough idea...

[markimak]

ive seen 500Nm at 210 and one case of 700+Nm on 20*kw this was a black R34 on NS.com forgot the user

[dangerman4]

I was just wondering, on average, what sort of torque to RB25DET's put out when modifed to around 200 or 250rwkw?

tune last week

auto r33 gt3582r-iw

[JustinP]

I had my car tuned last week and it made 222rwkw max torque on the dyno sheet was 351.3 Nm so there is a rough idea...

Sounds a bit low? R34 GTT's put out about 360Nm in stock form, and I though when measuring power at the rear wheels torque figures dont really suffer from drivetrain loss? I would have thought at 222rwkw's it would have been putting out much more than that?

[JustinP]

tune last week

auto r33 gt3582r-iw

Damn, now thats some torque...

[WPN-O33]

Who knows if my torque readout was correct or not but all that matters to me is that my car is hauling arse...

Your right though, when comparing my figure to others out there it does seem to be a bit low, on my dyno sheet though the graph doesnt show th Nm on the side it is just printed under the power figure..

Edited February 4, 2007 by WPN-O33

[JustinP]

Who knows if my torque readout was correct or not but all that matters to me is that my car is hauling arse...

Your right though, when comparing my figure to others out there it does seem to be a bit low, on my dyno sheet though the graph doesnt show th Nm on the side it is just printed under the power figure..

If your cars hauling ass thats all that matter

[Lithium]

At the mid/high 200rwkw area mine makes ~440nm @ hubs when adjusted for final drive at 1bar.

[khunjeng]

At the mid/high 200rwkw area mine makes ~440nm @ hubs when adjusted for final drive at 1bar.

looks like some dodgy figures here.

A few issues to consider, hub or roller etc. 900nm at the wheels is not right mate sorry to say. Toqrue is related to speed and power.

KW = Torque x RPM / 9549

some dynos require you to make some assumptions about the relationship between speed and RPM. If you have a manual transmission it is possible to correlate these pretty well but if you are running an automatic the results will have errors since the convertor slip changes with load and RPM.

Chassis dyno have the issue of tractive effort at the wheels. hub dyno will eliminaites inertia issues and measure torque "at the hub" consistantly (to get Flywheel torque simply divide the figure by the final drive ratio, often a number close to 4.1 for r33s)

The tractive effort is obtained by multiplying the torque by the total ratio of power train and dividing this sum by the rolling radius of the driving tyres.

I'm no guru...but it comes down to the setup..I guess many cbf setting it up properly dunno why. Also remember that peak power is not peak torque so when u calculate it..u get the power at the peak torque rpm.

When 270rwkw my gtst was putting out 440nm

All on a hub dyno.

Guss what...using the above formula...using my dyno sheet....at max torque my power calc. is the same. Amazing.

[salad]

I've been very confused about torque readings as they dont seem to make any sense. 440Nm (which is not much at all) translates to a tractive foce of ~1370N. That's not much to move a ~1370kg car.

Power(W) = Torque(Nm) x Revs (rad/s), so I'm not exactly sure where you got your formula from. And the revolutions here is the speed of the wheels, not the engine (you're calculating torque at wheels, not engine)

Or have I been grossly misinformed about chassis dynos? The numbers that are given seem much more like engine torque figures than wheel torque figures. But for the dyno to work that out, it needs the rolling diameter of your tyre, diff ratio, and gear ratio. Even then it's a bit iffy as it's taken into account drivetrain losses, but there are no drivetrain losses at the flywheel.

Most of the people that I have talked to seem to think it's a lot like power and their one figure means everything. But torque changes depending on which gear you're in, eg. in an R32 1st gear has 3.321 times more torque than 4th gear.

If I am the one that's completely wrong, can someone please explain it to me. I'm going by mostly theory based engineering crap.

[khunjeng]

I've been very confused about torque readings as they dont seem to make any sense. 440Nm (which is not much at all) translates to a tractive foce of ~1370N. That's not much to move a ~1370kg car.

Power(W) = Torque(Nm) x Revs (rad/s), so I'm not exactly sure where you got your formula from. And the revolutions here is the speed of the wheels, not the engine (you're calculating torque at wheels, not engine)

Or have I been grossly misinformed about chassis dynos? The numbers that are given seem much more like engine torque figures than wheel torque figures. But for the dyno to work that out, it needs the rolling diameter of your tyre, diff ratio, and gear ratio. Even then it's a bit iffy as it's taken into account drivetrain losses, but there are no drivetrain losses at the flywheel.

Most of the people that I have talked to seem to think it's a lot like power and their one figure means everything. But torque changes depending on which gear you're in, eg. in an R32 1st gear has 3.321 times more torque than 4th gear.

If I am the one that's completely wrong, can someone please explain it to me. I'm going by mostly theory based engineering crap.

speed...RPM...blah its all maths and can easily be derived. RPM makes much more sense for ppl who are used to SI units...speed means not much to me on a dyno, but again its just calulated.

Horsepower is a measure of force in newtons/pounds against a distance in meters/feet for a time period of one second. The distance per second of a rotating object would be the circumference of an arbitrary arm connected to the object (=2.p.r) multiplied by the number of revolutions in one minute divided by 60 (seconds in a minute). And thus horsepower equals to: F.r.2.p.RPM/60 = T.2.p.RPM/60 = 550 lb.ft/s or 745.7 Nm/s

Hence the formula in English units for power is:

Power [HP] = T [ft.lb] . RPM / 5252

In SI units power is expressed in Watt = (T [Nm] . 2p . RPM/60) (1kW= Watt/1000)

Power [kW] = T [Nm] . RPM / 9549

Power [HP] = T [Nm] . RPM / 7121

kW x 1.341 = HP

This formula IS NOT MINE...use it and see for urself on ur dyno sheet.

As for the wheels and engine stuff?? lol where do u think RPM comes from? the engine on a chasis or hub dyno? lol Speed in KMPH can easily be calulated mate...its all maths. Dynos with KMPH confuse me personally.

As for the gear etc...your right. Will make a difference and needs to be factored in accodingly.

Btw 440nm on the hubs is a lot IMO stock r33 gtst is about 200 or something...what car are u driving a XR8 ute? Seems to move my car pretty fast...

[salad]

Speed is more easily calculated than RPM of engine as you need to know diff ratio, gear ratio and rolling diameter to calculate RPM. All variables from car to car, where as speed is just measured off the speed of the rollers.

I'm still not seeing where you're getting the equation from. Power = torque x revs, with everything in SI units, i.e. Watts, Nm, and radians/sec.

Anyway, enough of that, lets look at an R32 (just cos I have the specs around). We'll assume the factory power and torque specs of 158kW and 245Nm.

Drive train losses in 4th are about 50-60kW, so we'll take 55kW. That equates to 103rwkW. i.e. 65% of the stock power.

Power is proportional to torque, so we will assume that at the wheels, 65% of the torque has made it there ignoring gear ratios. But 4th gear is 1:1 and diff ratio is 4.3:1 so we have to multiply these in.

Engine torque x percentage of power that makes it to wheels x 4th gear ratio x final gear ratio = Wheel torque.

So, 245 x 0.65 x 1 x 4.3 = 686.8

Therefore we have 686.8Nm at the wheels in dead stock form, much more than what you have in modified form.

I have an old dyno sheet where it shows the tractive effort. I had 169rwkW and 3900N. 3900N translates to 1250Nm. 440Nm translates to a tractive force of around 1370N, not much at all. If you look at other peoples dyno sheets that have tractive effort on them, they will be quite high. From that you can work backwards and get the wheels torque

I have confirmed my numbers with both this method and using the equation I stated at the start to get the same wheel torque figures.

Edited February 4, 2007 by salad

[Adriano]

When i used to do dyno tuning, i did wonder about this, especially as there is two settings in the menu for it, (N)newtons and (Nm). Now i can understand how it can figure out the force(N) as tractive effort, as it is simply the torque to the retarder x radius roller. as for Nm, where is this torque at? because torque is measured about an axis, so are we talking axle torque, in which you would have to enter the wheel diameter, which you dont. I think tractive effort in newtons is more important, as the acceleration can be calculated from it. Anyway its the shape of the curve that is the most important thing.

[salad]

Either way, the curves will be the same as you're multiplying by a constant, so I guess it's not important, but it's the numbers I've never understood.

I would love to know where the torque is measured, it's been confusing me for ages

[Adriano]

True, i just dont see where DD get that constant from?

[Lithium]

A few issues to consider, hub or roller etc. 900nm at the wheels is not right mate sorry to say. Toqrue is related to speed and power.

I'm no guru...but it comes down to the setup..I guess many cbf setting it up properly dunno why. Also remember that peak power is not peak torque so when u calculate it..u get the power at the peak torque rpm.

When 270rwkw my gtst was putting out 440nm

What the f**k? I never said 900nm, I said 440nm - my car is ALSO making 274rwkw @ hubs.... and I know all about the torque thing. There is nothing wrong with my dyno reading, to me it sounds very similar to yours to be honest.

[khunjeng]

Speed is more easily calculated than RPM of engine as you need to know diff ratio, gear ratio and rolling diameter to calculate RPM. All variables from car to car, where as speed is just measured off the speed of the rollers.

I'm still not seeing where you're getting the equation from. Power = torque x revs, with everything in SI units, i.e. Watts, Nm, and radians/sec.

Anyway, enough of that, lets look at an R32 (just cos I have the specs around). We'll assume the factory power and torque specs of 158kW and 245Nm.

Drive train losses in 4th are about 50-60kW, so we'll take 55kW. That equates to 103rwkW. i.e. 65% of the stock power.

Power is proportional to torque, so we will assume that at the wheels, 65% of the torque has made it there ignoring gear ratios. But 4th gear is 1:1 and diff ratio is 4.3:1 so we have to multiply these in.

Engine torque x percentage of power that makes it to wheels x 4th gear ratio x final gear ratio = Wheel torque.

So, 245 x 0.65 x 1 x 4.3 = 686.8

Therefore we have 686.8Nm at the wheels in dead stock form, much more than what you have in modified form.

I have an old dyno sheet where it shows the tractive effort. I had 169rwkW and 3900N. 3900N translates to 1250Nm. 440Nm translates to a tractive force of around 1370N, not much at all. If you look at other peoples dyno sheets that have tractive effort on them, they will be quite high. From that you can work backwards and get the wheels torque

I have confirmed my numbers with both this method and using the equation I stated at the start to get the same wheel torque figures.

LOL - I worked out what the deal is...I'm calulating Fly torque...as is calculated by thr power...I think u might have said this before, soz mate.

My formula holds...but to get Torque at the wheels multi by the final drive...in my case I think its 4.1 in 4th so lets say 440*4.1=1800Nm I wont include losses as the KW atw has already factored this in which was used to get the torque...seems a roudabout way to get there...but if u do need to, u can do as u did and use 30% as a guess.

I guess with a roller dyno u need to factor in the rolling radius of the tyres...I think u need to divided by 2.

[khunjeng]

What the f**k? I never said 900nm, I said 440nm - my car is ALSO making 274rwkw @ hubs.... and I know all about the torque thing. There is nothing wrong with my dyno reading, to me it sounds very similar to yours to be honest.

mate it wasnt about urs. Read all the posts and u will see its the dyno posted.

Either way...I think urs (and mine) is Calculated fly wheel torque as the long winded posts above explain...lol.

was fun, i learned something. so chill out.

[SiR_RB]

there is no exact way to get a deadly accurate engine torque reading on a chassis dyno.

there is heaps of torque multiplication happening on the chassis dyno, which is why many owners get excited when their midly tuned rb25 shows over 800nm at the bak wheels. this is coz the crankshaft torque is been multiplied by the gearbox ratio, diff ratio and tyre size.