Driveline Loss - a question

[hazy]

So a friend and I were chatting about our cars...he's got an '11 base Corvette with a few mods, and I've got my '11 Camaro, also with a few mods.

We got to talking dyno numbers, and one thing popped into my head that I thought I'd ask the gurus.

If I have a bone stock car and dyno it, I'll get a HP/TQ number that is the Stock rating (425hp for the m6) less any driveline loss. I always see the 15-17% number thrown around, so let's say that a bone stock m6 has 350hp/340tq (~17% loss)

Now let's get all hypothetical on it.

Let's say that I keep the exact same driveline beyond the engine (trans, driveshaft, diff, axles, wheels, etc) And slap in a built 416 with a set of turbos tuned up all crazy. Yes, I know that's not likely to happen (do huge build and no driveline improvements, but bear with me) Pretend that this nasty motor made 1,000hp on the engine dyno. Now, we drag it over to the chassis dyno once it's all installed and tidied up.

Would I still expect a 17% loss? Or could the driveline loss be assumed to be the ~72hp that was seen with the factory setup?

My thoughts are that it is not a direct proportional loss relative to the power you're making. If you have a 1,000 hp motor, or a 425 hp motor, and the same driveline, wouldn't the loss through the drivetrain be the same number regardless of the power that the engine is making?

Or am I completely off base here?

Thoughts?

[DarthZL1]

All of the calculations on driveline loss are estimates, and really bad ones at that. In my personal opinion, the wheel dyno's are pretty good for knowing how much power you're putting to the ground that DAY, TIME, WEATHER, ETC. It's best used as a tool (again in my opinion) to see the Delta between modifications.

I've personally seen different wheel dynos differ drastically (one time about 10%) on the same car. Depends on manufacturer, weather, solar flares, your horoscope, what you had for breakfast, etc etc etc.

Short answer is: There are too many variables to determine a generic formula for drive line loss.

Here's an interesting article about it:
http://www.superstreetonline.com/how...in-power-loss/

[CamaroinCLE]

Very good article that I asked around in the Engineering world and they agree to this.. SAE is king to all of this.

http://www.superstreetonline.com/how...in-power-loss/

[Moto-Mojo]

I think your "driveline" word is more accurately described as, "drivetrain." A driveline is just one more component in the drivetrain. Good article above. The simple act of rotating a single bearing creates more heat and friction (power loss) the faster you try to spin it. Throw in straight gears, right angled, diff gears, friction creating (by design) things like torque converters and you have massive parasitic forces at work.

Quantifying it all gets very subjective. But I suppose crank HP vs. Rear Wheel HP is a good start.

[paul84043]

Originally Posted by Moto-Mojo

I think your "driveline" word is more accurately described as, "drivetrain." A driveline is just one more component in the drivetrain. Good article above. The simple act of rotating a single bearing creates more heat and friction (power loss) the faster you try to spin it. Throw in straight gears, right angled, diff gears, friction creating (by design) things like torque converters and you have massive parasitic forces at work.

Quantifying it all gets very subjective. But I suppose crank HP vs. Rear Wheel HP is a good start.

Exactly where I was going.. Every time your power changes direction and any supporting structure "touches" it, you're going to have loss. Add in the leverage loss created by tire and wheel diameter and there you are..

[hazy]

Thanks for that article - looks like the below quote pretty much answered the exact question I had:
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Nor is it possible to apply a fixed drivetrain loss figure to your car (say 60 whp from my RevUp G35 example), because as you modify the engine and increase its output its ability to generate thrust force and angular acceleration also increases (though not in a linear fashion).
----------

Very interesting stuff. Sometimes I wish that I had gone the engineering route, as opposed to finance, as the applications of it seem much more intriguing to me. Oh well...at least the bills are paid

Appreciate the info; if any others like to chime in, I love learning about this stuff!!

[SS/RS2010]

Originally Posted by hazy

So a friend and I were chatting about our cars...he's got an '11 base Corvette with a few mods, and I've got my '11 Camaro, also with a few mods.

We got to talking dyno numbers, and one thing popped into my head that I thought I'd ask the gurus.

If I have a bone stock car and dyno it, I'll get a HP/TQ number that is the Stock rating (425hp for the m6) less any driveline loss. I always see the 15-17% number thrown around, so let's say that a bone stock m6 has 350hp/340tq (~17% loss)

Now let's get all hypothetical on it.

Let's say that I keep the exact same driveline beyond the engine (trans, driveshaft, diff, axles, wheels, etc) And slap in a built 416 with a set of turbos tuned up all crazy. Yes, I know that's not likely to happen (do huge build and no driveline improvements, but bear with me) Pretend that this nasty motor made 1,000hp on the engine dyno. Now, we drag it over to the chassis dyno once it's all installed and tidied up.

Would I still expect a 17% loss? Or could the driveline loss be assumed to be the ~72hp that was seen with the factory setup?

My thoughts are that it is not a direct proportional loss relative to the power you're making. If you have a 1,000 hp motor, or a 425 hp motor, and the same driveline, wouldn't the loss through the drivetrain be the same number regardless of the power that the engine is making?

Or am I completely off base here?

Thoughts?

Someone correct me if I'm wrong, but if you installed that engine in his hypothetical but left the rest of the drive train stock (tranny on back) wouldn't it be a possibility (however slight) that during a dyno, especially at high revs, something would break badly?

[hazy]

Originally Posted by SS/RS2010

Someone correct me if I'm wrong, but if you installed that engine in his hypothetical but left the rest of the drive train stock (tranny on back) wouldn't it be a possibility (however slight) that during a dyno, especially at high revs, something would break badly?

it absolutely would be a possibility, but think like an economist - "all else equal, what change does _____ have" It may not be the correct way in the real world, but it can help to explain concepts/principles a bit easier when you exclude other factors to isolate one particular concept/principle

I didn't say that it was what would happen in the real world...someone doing that to their motor would HAVE to upgrade drivetrain, I was more speaking in the sense of "all else equal" to get a better grasp on the concept of drivetrain loss, thus the "hypothetical" part of it all, which I also acknowledge is not realistic when I say "Yes, I know that's not likely to happen (do huge build and no driveline improvements, but bear with me)"