Torque Numbers

[handon]

Cool thanks all.

He was Said should get about 310 but the 296kw is enough for now. I'll no doubt get used to it and want more power down the track. Hopefully it doesn't lose too much during summer. Might use different workshop

Edited 14/08/12 08:59 PM by handon

[Mr_4.0]

Sorry your right ratter.

But the torque "reading" the user gets needs to be altered according to tyre diameter etc to get an accurate reading and it never is.

That's how I understood it.

[Mr_4.0]

Also some runs aren't done in 1:1 gear ratios, diff gears can be changed etc.

So final torque reading can be a little misleading as to what you actually might have at the motor. As ratter mentioned.

[Paulie2256]

Yeh looking at it better is about 19 psi peak fading to about 15psi. Yes did the I/c piping.

Just a bit annoyed at the customer service but it goes well so can't complain

Sounds like you need to mod your turbo as boost cannot be controlled properly if hitting 19psi.

[ratter]

Some of my notes I have, not written by myself though:

The Torque number on a Chassis Dyno can be difficult to understand for an operator, let alone the general public, so I'll try and explain in simple terms.

Most people are aware that Power(HP) = (Torque(ft/lbs) x RPM)/5252, and both an Engine Dyno and a Chassis Dyno use this formula to Calculate Power, the difference is though, an Engine Dyno uses actual RPM(Crank RPM) and Torque measured on a Load Arm attached somewhere to the Engine Dyno Cradle in it's calculation, whereas a Chassis Dyno uses Roller RPM and Torque measured on a Load Arm mounted on the Retarder that is coupled to the Knurled Drive Rollers.

Now the reason why typically you see higher "Torque" numbers on a Chassis Dyno is due to gear multiplication, (remembering that the torque is being measured down in the Dyno Bed),so any gear multiplication between the Engine and Rollers will increase Torque (less any losses).

A typical scenario is (using an LS1 example of 470nm), if we use a 1:1 ratio in the gearbox, we still have 470nm (we won't assume any losses in this example) out the back of the gearbox, the torque then goes thru a ratio of for example 3.46 in the diff, so now we have 1626nm at the AXLE.

The next step is the Tyre to Roller, but in this case it is a gear reduction due to the Tyre being larger that the roller diameter, so we would see a Torque reduction, a typical reduction using a dyno in Australia which normally have rollers in range of 217-218mm Diameter, would be the Tyre Diameter divided by the Roller Diamter, so if we use a figure of 650mm for the tyre and 217mm for the dyno roller we end up with a figure of 1:2.995, so we divide 1626nm by 2.995 giving us 542nm measured at the roller, remember this example is assuming no driveline loss,so the measured Torque would be less than 542nm.

Some people have eluded to that using different gears effects the Torque, this is true, but what evens things (Power) out is, if you are in lower gear on a dyno, yes you will produce more Torque, BUT, the roller will be rotating at a slower speed according to the different gear being used, so the same Power will be produced at a given Engine RPM.

Another difference that no-one realises is that a different Diameter Roller also changes the Torque reading, so a dyno with 217mm rollers that is showing 100RWHP at 100kph would be measuring 215ft/lbs and the ROLLER RPM would be 2443RPM, so those that want to do the maths can verify the 100RWHP.

On a Dyno that uses 270mm Rollers, if one of these dyno's was showing 100RWHP at 100kph, then it would be measuring 267.3ft/lbs and the ROLLER RPM would be 1964RPM.

Rather than looking at Torque on a Chassis Dyno, it is better to look at the Motive Force, which uses the Roller Diameter in it's calculation, so dyno's with different Roller Diameters will show the same Power and Motive Force.

Motive Force is also known as Tractive Effort.

Motive Force is the Linear Force at the Roller Diameter pushing the car forward.

A few things to remember when looking at Dyno Graphs:

1.The Torque Curve (shape) will be the same regardless of gear used or Roller Diameter.

2. The Torque Curve will be the same as the Motive Force (tractive effort), except it will be a higher number.

3. Look closely at the scale on which the Torque/Motive Force/Tractive Effort is displayed, it is very common to see a Tractive Effort plot of around 3000-4000newtons being plotted on a scale of 0-13000newtons, all this does is make the "Torque Curve" look flat, because it is being squashed down on a large scale.

4. If a vehicle has made more power at the same Road Speed with identical gearing after some mods, then it has to of made more Torque, so do we need to see Torque?

A better approach all round is look at the Average Power, or even better, the Integral of the Power, this is the all of the Power added together that is under the curve, and not be too concerned with Torque Numbers.

[handon]

First night I got it was driving pretty hard it was sounding like it was spinning up a lot . I actually thought may be over boosting. Since then I have heard it being limited.

Prob is the bloke won't respond to my emails now. Should prob get some balls and call him I Spose.

Most other tuners recommended 14psi but I went for the one who offered most power!

[Mr_4.0]

Good read mick!

[James xr6fgturboute]

I'm getting 300 on 13psi with the same mods an a cooler

[handon]

So general consesus is query why so much boost and why such average power?

[Mr_4.0]

300rwkw on 13psi? With small fg turbo? You sure?