Trouble understanding dyno run data

[Andy_Mac]

Can anyone explain the torque portion of this dyno run and what its actually reading to get so high.

Have been shown some rough calcs to try account for gear ratio and final drive ratio torque multiplication but still doesn't quite seem to add up as it should to the power figure

Logs done with Romraider and Virtual Dyno running the Dynojet option give roughly 175kw and 335nm.

So the power figure is resonable but has a very different torque interpretation.

Engines essentially stock apart from a decatted downpipe and 3-port EBC

Base run data is with the new tuners base rom running 12psi

Edited October 26, 2015 by Andy_Mac

[Guest]

Did you ask him about running more boost? No help on the torque thing seems to be reading double what i would expect.

[Andy_Mac]

Thats what it was turned up to. Was at 16 after the last tune. They're apparently start to get off the comp map after about 20

[Guest]

 Andy_Mac said:

Thats what it was turned up to. Was at 16 after the last tune. They're apparently start to get off the comp map after about 20

That boost graph is correct? Seems to be tanking from 3.5k. Surely it can hold more boost thro mid and even a little more in high.

[Andy_Mac]

Think so. Been told both times they struggle to maintain that kind of pressure and are slowly dropped back from about 4k

[Guest]

 Andy_Mac said:

Think so. Been told both times they struggle to maintain that kind of pressure and are slowly dropped back from about 4k

EGBP

[Koom]

[h=5]HP = Torque x RPM ÷ 5252[/h]

In hp and ft-lbs of torque.

Dyno plots showing torque at the wheels will vary wildly depending on what gear was used, tyre size or hub dyno.

To calculate the correct torque output figure, use the equation above but rearranged to find torque.

Torque = (HP x 5252)/rpm.

So for the max. torque figure, pick the highest point on the torque curve and use the hp and rpm at that point.

e.g. Torque (ft-lbs) = (170hp x 5252)/3500 [bit of guessing around 100 kph]

= 255 ft-lbs (346Nm).

There's metric versions of this calculation but it's too late on a holiday weekend for that sort of carry on.

[Andy_Mac]

 evowrx said:

EGBP

Exactly why i'm so interested in testing it.

[Andy_Mac]

 Koom said:

[h=5]HP = Torque x RPM ÷ 5252[/h]

In hp and ft-lbs of torque.

Dyno plots showing torque at the wheels will vary wildly depending on what gear was used, tyre size or hub dyno.

To calculate the correct torque output figure, use the equation above but rearranged to find torque.

Torque = (HP x 5252)/rpm.

So for the max. torque figure, pick the highest point on the torque curve and use the hp and rpm at that point.

e.g. Torque (ft-lbs) = (170hp x 5252)/3500 [bit of guessing around 100 kph]

= 255 ft-lbs (346Nm).

There's metric versions of this calculation but it's too late on a holiday weekend for that sort of carry on.

Yea I've roughly been through the calcs too, get that side of it but aren't dyno's reading torque values rather than power so shouldn't torque always be a reliable figure? Or do they just get a raw figure thats then manipulated by gear ratio's and wheel diameters to allow a power calc to be made and then for some dyno's they show the calculated value rather than the unadjusted one? Just intrigued why some dyno's show huge torque values and others have expected ones whilst still giving relatively consistant power values

So when people say they have Xnm atw is that actually correct saying it that way? Or since you've had to include wheel diameters, gear ratio's and final drive ratio's is that not then considered flywheel values again. Why else would you go to the effort to calculate out any gains created. Torques the turning force at the centre of the axis so shouldn't wheel diameter be the only factor that needs to be considered.

There's obviously different methods of collecting this data that different brands use but say this one measures the turning force the car creates against its rollers. Could that then be the figure they show rather than the torque at the centre axis of the wheels?

Think I might just spend a few days doing a lot more reading.

Can't seem to find any real info for dynotorque dyno's though, don't suppose they go by another name anyone knows of?

There's the metric one

Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488

So then Torque = power x 9.5488 / speed

Edited October 26, 2015 by Andy_Mac

[Guest]

 Andy_Mac said:

Exactly why i'm so interested in testing it.

Yea seems crazy to drop boost that much.

[McDoof]

Dynotorque is custom made by Torque performance right here in Auckland so there won't be much info on it. If you need more information I would get hold of Robin at Torque performance or just speak with Geoffrey directly at MCR. They will both be able to answer the questions you have with some accuracy rather than speculation and guessing :-)

Also, is that bottom portion your boost? On mine (I know it's NA) the aux channels were hooked up to the wideband on the exhaust so that was Exhaust AFR.

If you want the actual boost numbers I would do a fresh log with your Tactrix or check if Matt has the matching data for you.

Edited October 26, 2015 by McDoof

[Andy_Mac]

Ahh that'd be why. Alright I might actually get hold of one of them, interested to know how its getting these values.

[McDoof]

Were you really only getting 124kw before this tune. WOW. It must feel like a new car.

[Andy_Mac]

Na based on virtual dyno it was previously about 150-155kw

Since he had to completely rewrite the def file the base run there is just the initial map using his first revision not the previous tuners final revision.

But actually getting usable boost in first gear makes it a completely different drive

[McDoof]

That dyno was showing about 11kw less than Virtual dyno on mine. Geoffrey recons that his dyno reads a bit low, so you may actually get higher numbers on a different machine. Every dyno is different.

[Koom]

 Andy_Mac said:

Yea I've roughly been through the calcs too, get that side of it but aren't dyno's reading torque values rather than power so shouldn't torque always be a reliable figure? Or do they just get a raw figure thats then manipulated by gear ratio's and wheel diameters to allow a power calc to be made and then for some dyno's they show the calculated value rather than the unadjusted one? Just intrigued why some dyno's show huge torque values and others have expected ones whilst still giving relatively consistant power values

So when people say they have Xnm atw is that actually correct saying it that way? Or since you've had to include wheel diameters, gear ratio's and final drive ratio's is that not then considered flywheel values again. Why else would you go to the effort to calculate out any gains created. Torques the turning force at the centre of the axis so shouldn't wheel diameter be the only factor that needs to be considered.

There's obviously different methods of collecting this data that different brands use but say this one measures the turning force the car creates against its rollers. Could that then be the figure they show rather than the torque at the centre axis of the wheels?

Think I might just spend a few days doing a lot more reading.

Can't seem to find any real info for dynotorque dyno's though, don't suppose they go by another name anyone knows of?

There's the metric one

Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488

So then Torque = power x 9.5488 / speed

The dyno is reading the torque at the wheels. Which is multiplied from the crank by the gearbox, diff ratio and wheel diameter.

So you can get a massive torque reading by doing the run in 3rd gear (or 1st...).

The calculation is for estimating torque output of the engine as torque at the wheels is not a useful figure for any sort of comparison.