Dyno Torque figure

[Jesterarts]

Ok,

Something that has been puzzling me for the last few days.

Got the car back from Chevs last weekend and was very pleased with the dyno:
https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-snc6/240836_10151201262461703_22331904_o.jpg

Then I decided to see how much torque increase mods have achieved, so I jumped on redbook and looked up the engine details.

So, stock, the LS2 makes apparently 530Nm @ the fly.

The dyno graph above shows that peak torque was just under 600Nm @ the fly.

Am I correct in my understanding that the cam, heads, full exhaust, OTR and tune is only worth 70Nm?

Thoughts?

[white lie]

IMO Dyno's have never been overly accurate in terms of calculating rear wheel figures, let alone flywheel ones!
It's quite complicated to work out how much the torque is multiplied by the drivetrain, tyre size etc, especially in an auto with a decent converter.

You're saying it makes 530Nm from the factory but the graph has peak torque at 560Nm, so the peak gain is only 35Nm or so, half the 70Nm that you think is still minimal :)
But look at the difference between the two lines, particularly lower in the rev range. There's a gain of 50Nm at around 3300RPM, that's close to 10% right where you use it most. This increase in low down torque will get the car up and moving much quicker and make it much better to drive day in/out. Look at the overall graph, not just the peaks.

[adr8]

I think you will find the LS2 is 550nm at the fly standard, the holden V8(L77) is 530nm and if i remember correctly the AFM V8 is 517nm at the fly.

[boggers007]

Holdens figures would be quoted based on an engine dyno, Until you put yours on one then I wouldnt worry about it. Its probably picked up more then you think but as has been said the dyno can't account for all your losses so it would be a some what educated guess by the dyno.

[QIKMIK]

Similar topic then. I recently got my MY09 Senator tuned (see sig for details) and the graph shows 843NM on 98RON and 895NM on LPG. A stock LS3 is only quoted at 550NM. Surely tune and exhaust isn't worth that much??

Mick

[JezzaB]

Forget calculated flywheel figures. They are calculated. Rear wheel figures are measured BUT diff gears and tire sizes will change the torque at the wheels

Get a run from a stock car and compare it to yours from there.

[Jesterarts]

IMO Dyno's have never been overly accurate in terms of calculating rear wheel figures, let alone flywheel ones!
It's quite complicated to work out how much the torque is multiplied by the drivetrain, tyre size etc, especially in an auto with a decent converter.

You're saying it makes 530Nm from the factory but the graph has peak torque at 560Nm, so the peak gain is only 35Nm or so, half the 70Nm that you think is still minimal :)
But look at the difference between the two lines, particularly lower in the rev range. There's a gain of 50Nm at around 3300RPM, that's close to 10% right where you use it most. This increase in low down torque will get the car up and moving much quicker and make it much better to drive day in/out. Look at the overall graph, not just the peaks.

Green line isn't stock. Green line everything exactly the same mechanically and tuned by another shop, just before is with before Chev got to it. :p

Yeah, I was just curious if I was comparing the right figures to the right figures. I guess the RW torque would have been a bit more accurate but hey.

[fullysikk]

Does it drive better or not?

If you want a dyno graph with more torque...I'll photoshop one up for you :)

[white lie]

Similar topic then. I recently got my MY09 Senator tuned (see sig for details) and the graph shows 843NM on 98RON and 895NM on LPG. A stock LS3 is only quoted at 550NM. Surely tune and exhaust isn't worth that much??

Mick

Tracked down the graph in your "My Ride" thread, is that the right one?
If so, it's rear wheel torque. So its multiplied by the torque converter, final drive ratio and tyre size. If you can calculate all of these, you can divide the 800odd Nm by each of them and arrive at some sort of figure that would be under 600Nm (I presume), which would be engine/flywheel torque.

[Jesterarts]

Tracked down the graph in your "My Ride" thread, is that the right one?
If so, it's rear wheel torque. So its multiplied by the torque converter, final drive ratio and tyre size. If you can calculate all of these, you can divide the 800odd Nm by each of them and arrive at some sort of figure that would be under 600Nm (I presume), which would be engine/flywheel torque.

Argh... now my head hurts. So the torque figure at the wheels is greater than the torque figure @ the fly?

*Thinking, thinking, thinking*

So in the case of my car, given it's a manual, run done in 4th so 1:1 and then through a 4.11:1 diff. Ah yeah, more torque @ the wheels because it goes through a diff with a ratio.

Does that mean that a @ flywheel torque in say my case would be multiplied by 4.11 given I have a 4.11 diff? The figure ending up around 2400Nm @ the wheels?

Does that sound right?

[white lie]

You would also need to multiply by the efficiency/loss of the transmission, which would be around 85% for a manual (0.85), which gives you a figure around 2095Nm.
Seems huge but that's the benefit of gearing. If you compare that to say a 3.08 ratio, you're down around the 1570Nm. Tyre size will also have some effect on this again, not to mention it changing thru different gears!

I'm not sure how the dyno goes about calculating it but I'd imaging it uses the roller diameter and speed like most of its equations. So you'd have to input final gear ratio to work it back?

[JezzaB]

You don't calculate it back. It's measured torque at the rollers. Dyno knows the roller size and load on the load cell. The sheet you have is just a calculation of what it thinks is at the engine based on the torque at the wheels where it is measured.

It drove out with more Nm or Kw or daisys or what ever you wanna measure in so its a good thing and the tuning was successful.

[ittwgn]

this thread has some good info in the second post from awddynotodd from mainline !!!! simple explanation of dyno hp/torque etc!!! cheers
http://www.ls1.com.au/forum/showthread.php?95918-Torque-figure&highlight=todd+mainline

[Jesterarts]

Thanks for the responses guys.

Very interesting read.

I guess at the end of the day, it's how she drives that puts the grin on my face. But a number on a laminated piece of paper is still nice for banter over a few beers.

Cheers.