TD42 torque figures vs Kw@ wheels

[UGOTNUFN]

If a car is dynoed to have 220RwKW how many NM's does it take to make this power.

Vehicles specs. TD42T with 4.6 gears and 35" MTZ's.

[Wish I had coils]

depends on what is done if it has been dyno'ed the should be able to tell you the torque figures too, unless some one is just pulling you leg, to make you buy it. 220kw at the wheels on 35's is a lot of power for a td42

[THE-Burger-Ring]

i have 200rwkw.. but i spent major money to get that.. and looking under my bonnet looks nothin like a standard setup. so my point is it will be obvious if the car has power like that. my is 760nm and 200kw with 35's on

[PGS 4WD]

Rear wheel torque means nothing as the gear, diff ratio, tyre size and also torque coverters all multiply torque at the expense of speed. I could show you a 1000Nm from a 4 cyl Corolla running it on dyno it in 1st gear, but it would only make 200Nm in 4th. Power = Speed x Torque. As the gearing makes more torque it also reduces the speed by the same amount.
Our dyno has a unique function that can accuratly calculate engine power and torque it require a little more time for the auto callibration though.

Joel

[UGOTNUFN]

So tell me at 3000 Rpm fully loaded if you saw 220RwKw in a patrol with 4.3 gears and 35" MTZ's how much torque does it take to make that RwKw. I think that we arent seeing the correct torque figure because it is accelerating the rollers too fast and not actually pulling 100% load on the run up.

Thoughts??

[1wilddsl]

I got more!!Lol

[THE-Burger-Ring]

mine was in 4th gear joel,

[UGOTNUFN]

I got more!!Lol

Wateva Man!!!!

[coxy321]

I got more!!Lol

More what?

[uzdnabuzd]

I got more!!Lol

More what?

Nooms!

[Dzltec]

Show up a graph. There is one around here we did that had 200rwkw, I think it peaked at 850nm. What sort of ramp rate? Is it strapped down properly?

Andy

[THE-Burger-Ring]

why show a graph.. you have my graph on your computer haha
Shane

[UGOTNUFN]

Show up a graph. There is one around here we did that had 200rwkw, I think it peaked at 850nm. What sort of ramp rate? Is it strapped down properly?

Andy

Thats the problem,it isnt a loaded power run so it is accelerating the rollers too fast to see full load on the power run.

Unlike mainline dynos this dyno does not do loaded power runs like yours BUT when loaded at different RPM points to measure actual wheel performance we are seeing in excess of 200RwKw.

[Bush65]

Power = force x velocity (in linear form)

In rotational form:-
Power = 2 x Pi x Torque x n (where n is rev/sec)

AFAIK dynos measure Torque and rotational speed of the rollers and calculate Power from those values.

Power would be the same at the tyres (if no slippage between tyre and roller) and if not accelerating. But torque at the wheels is greater than torque at the roller because the tyre rolling radius is greater than the roller radius.

The torque at the wheels is greater than at the engine because engine torque is multiplied by the reduction gearing.

Note also that the torque curve is different to the power curve and peak torque and power of our engines do not occur at the same rpm.

Friction losses etc. account for loss of power and torque between engine and wheels.

If still accelerating when measurements are taken by the dyno, then the power and torque measured will not relate to what was developed by the engine unless the rotational mass is accounted for (force = mass x acceleration). It is not inconceivable for a smart dyno to be able to learn appropriate values for friction and rotational inertia for each particular vehicle if the designers put in the necessary smarts and the operator runs it correctly.

[Dzltec]

Weigh it at, run it down the 1/4 mile. The post up the time, use the moroso calcualtor to give you a close idea.

We have a calc on our dyno, its seems pretty accurate. What type of dyno are you using? What size are the rollers.


Andy

[UGOTNUFN]

Weigh it at, run it down the 1/4 mile. The post up the time, use the moroso calcualtor to give you a close idea.

We have a calc on our dyno, its seems pretty accurate. What type of dyno are you using? What size are the rollers.


Andy

1/4 mile times for a winch challenge truck dont interest me, what im trying to work out is why we arent seeing the 780 Nm that we would need to make 220RwKw with 35" tyres and 4.6 gears at 3000 rpm working with approx 25 RwKw power losses. Also another figure that we have mapped is 151RwKw at 2000Rpm which eqautes to needing 860Nm to achieve.

Heres the calc results from the first setup we ran which is a little different from what we are using now

:For sure as you say, and the calcs sound correct. I did tell you over the phone or by email or both that I thought the Torque was much higher. If you remember, when loading up the VNT (I recorded everything in my notes) the power was (Blue is @ wheels, I added in red what my spreadsheet says the corrected flywheel kW the flywheel torque must be to do that allowing for some theorectical drivetrain and inertia loss):



2000rpm: 151kW 173.6kW 829nm

2500rpm: 178kW 208.9kW 798nm

3000rpm: 201kW 243.1kW 773nm

3500rpm: 216kW 270.7kW 738nm



We are using a Bosch FLA 206 which has a roller circumference of 1 metre. The calcs are worked using the fixed division number of 9549 which most dynos use,but we believe as it is not loaded on the power run it is over accelerating the rollers anything above 600NM,so we will do it in 4WD when it gets back on the dyno.

Remember that you are using a load figure (ramp rate) in you power runs which shows boost rates and how things perform very diifferent to a non loaded power run.

[Jimbo]

working with approx 25 RwKw power losses

I would think that driveline losses through a patrol would be a lot higher than that!

Maybe your torque figures don't add up because the engine may not be making the quoted power.

[coxy321]

Isn't driveline power loss supposed to be around 25 percent?

[KiwiBacon]

As well as calculating torque from power and engine rpm, you can also back calculate from boost pressure to make sure it fits.

Most diesels do 70-75 Nm/litre unboosted. To double the torque you need double the inlet air density etc.
It's a good way to shoot down or confirm ridiculous claims.

[UGOTNUFN]

Isn't driveline power loss supposed to be around 25 percent?

That is the most stupid statement that anyone has ever come up with!

No im not saying that you came up with it. That statement can only ever be attributed to STD production vehicles of which losses are always the same and not normally as high as 25%,

EG: TD42 putting out 85Kw at the engine, we see about 63RwKw on 33 inch highway tyres.Which is about 25% SO now if you make 220RwKw on the same tyres and driveline does the power loss still equal 25%??

Dont think so tim.

Anyway the calc to work out Nm

rwkw x 9549 divided by rpm x diff ratio.

EG 225 x 9549 divided by 3000 x 1, the last number is for 4th gear which is 1 to 1 which equals 716.175 Nm at the wheels in 4th gear!!!

Nm in 4th gear at the wheels 1 to 1 is the same as at the engine except for power loss,,, if you have 30 kw power loss at 3000 rpm that is 95Nm also lost ,so you add that to the 716.175Nm for engine Nm.

[UGOTNUFN]

working with approx 25 RwKw power losses

I would think that driveline losses through a patrol would be a lot higher than that!

Maybe your torque figures don't add up because the engine may not be making the quoted power.

Driveline losses depend on a lot of variables but around 3000 on 35" tyres it IS approx 25Kw.

Basic maths tells us that to make 220 RwKw then the torque figure must be in excess of 700Nm by a long shot. 150CC of fuel and 32 Psi of boost with 40 degree charge air temps will easily make more than 700Nm.

[KiwiBacon]

Anyway the calc to work out Nm

rwkw x 9549 divided by rpm x diff ratio.

EG 225 x 9549 divided by 3000 x 1, the last number is for 4th gear which is 1 to 1 which equals 716.175 Nm at the wheels in 4th gear!!!

Nm in 4th gear at the wheels 1 to 1 is the same as at the engine except for power loss,,, if you have 30 kw power loss at 3000 rpm that is 95Nm also lost ,so you add that to the 716.175Nm for engine Nm.

Where is your correction for tyre size?

Simply stick a tacho lead on the vehicle, torque can be calculated from power and rotational speed. Nothing else matters.

[UGOTNUFN]

Anyway the calc to work out Nm

rwkw x 9549 divided by rpm x diff ratio.

EG 225 x 9549 divided by 3000 x 1, the last number is for 4th gear which is 1 to 1 which equals 716.175 Nm at the wheels in 4th gear!!!

Nm in 4th gear at the wheels 1 to 1 is the same as at the engine except for power loss,,, if you have 30 kw power loss at 3000 rpm that is 95Nm also lost ,so you add that to the 716.175Nm for engine Nm.

Where is your correction for tyre size?

Simply stick a tacho lead on the vehicle, torque can be calculated from power and rotational speed. Nothing else matters.

Tyre size correction is takin into account by the measured power loss of 30Kw at 3000. Dyno measures powerlosses on the run down.

Ive got the rotational speeds which i posted before,normally working at 3000RPM

[coxy321]

Isn't driveline power loss supposed to be around 25 percent?

That is the most stupid statement that anyone has ever come up with!

No im not saying that you came up with it. That statement can only ever be attributed to STD production vehicles of which losses are always the same and not normally as high as 25%,

Point taken. When you're talking about putting out double/triple the factory power/torque, the 25% theory is sort of blown out the window.

[sswaffie]

working with approx 25 RwKw power losses

I would think that driveline losses through a patrol would be a lot higher than that!

Maybe your torque figures don't add up because the engine may not be making the quoted power.

Driveline losses depend on a lot of variables but around 3000 on 35" tyres it IS approx 25Kw.

Basic maths tells us that to make 220 RwKw then the torque figure must be in excess of 700Nm by a long shot. 150CC of fuel and 32 Psi of boost with 40 degree charge air temps will easily make more than 700Nm.

I Would be highly supprised if you would be making 220rwkw with 150mm 3/1000 st , i would be comparing your run to another dyno ,are you using tempreture correction? is it in shootout mode?

[KiwiBacon]

Tyre size correction is takin into account by the measured power loss of 30Kw at 3000. Dyno measures powerlosses on the run down.

Ive got the rotational speeds which i posted before,normally working at 3000RPM

The coast down can only measure tyre rolling resistance. Not tyre diameter.
The diameter is as important as your gear and diff ratios and influences the reading in exactly the same way, get it wrong and your torque reading is wrong. The shape of the curve will still be correct but the numbers will all be out.

Of course if you have a tacho lead, then it's easy to check the readings are right.

Basic maths tells us that to make 220 RwKw then the torque figure must be in excess of 700Nm by a long shot. 150CC of fuel and 32 Psi of boost with 40 degree charge air temps will easily make more than 700Nm.

To burn 150cc of fuel cleanly requires a lot more than that.
Yes it will deliver over 700Nm if you can burn it cleanly, but if you don't burn it cleanly then you're not making power, just sooting up the engine and burning pistons.

At 15:1 A/F ratio (i.e. extremely smokey and dangerous EGT's) you still need 40psi. To burn remotely cleanly you need over 50psi.

[B.D.R]

I only know about Dyno's from what i read in some Car mags, so take this with a grain of Salt

It is relativly easy to make a Dyno read what ever power figure you want, within reason of course, some people do this to brag or when there trying to sell something, they say look at this it has a 500rwkw

Dyno's from what i've read are a good Tuning tool, and that's about it, as no two are the same, as ramp rates can make a massive differance even different Weather can play a role in what they read.

If it is a concern about the Torque, then i'd take it else where to get a camparison run done.

As long as the motor's not going to blow up, i personaly don't see the point in how much Torque\Kw a motor has, as long as it drives well

[UGOTNUFN]

working with approx 25 RwKw power losses

I would think that driveline losses through a patrol would be a lot higher than that!

Maybe your torque figures don't add up because the engine may not be making the quoted power.

Driveline losses depend on a lot of variables but around 3000 on 35" tyres it IS approx 25Kw.

Basic maths tells us that to make 220 RwKw then the torque figure must be in excess of 700Nm by a long shot. 150CC of fuel and 32 Psi of boost with 40 degree charge air temps will easily make more than 700Nm.

I Would be highly supprised if you would be making 220rwkw with 150mm 3/1000 st , i would be comparing your run to another dyno ,are you using tempreture correction? is it in shootout mode?

Yes it is making that power,that is not in dispute and the pump is pumping 150cc of fuel at max,now i haven't taken the pump off to measure exactly what amount we are using but it is almost maxed out at the moment. Temp correction is fine and shootout mode is only for DD dynos mate.

[Dzltec]

I think your calcs are up the fritz. You have a diff ratio of 1:1 instead of 4.6:1. Then have to think of the radius from the centre of axle to outside of tyre.

Anyway, the 200rwkw car we had made 868nm @ 90kmh 4th gear, max torque was 889 for 195rwkw @ 87kmh. Sorry did not do a derived rev setting on this. It had 35" tyres, 4.6 diffs.

The idea of a 1/4 mile is to confirm power figures, not to prove what it does.


Andy

[UGOTNUFN]

I think your calcs are up the fritz. You have a diff ratio of 1:1 instead of 4.6:1. Then have to think of the radius from the centre of axle to outside of tyre.

Anyway, the 200rwkw car we had made 868nm @ 90kmh 4th gear, max torque was 889 for 195rwkw @ 87kmh. Sorry did not do a derived rev setting on this. It had 35" tyres, 4.6 diffs.

The idea of a 1/4 mile is to confirm power figures, not to prove what it does.


Andy

Yeah i understand the reason for the whole 1/4 mile thing but not really interested in that at the moment.

Would have been handy to have an ACTUAL rpm setting instead of a derived one, really doenst help using derived figures.