Crank to wheels HP loss?
11-15-2015, 02:12 PM
#1
Burning Brakes
Thread Starter
Crank to wheels HP loss?
What is the typical % of HP loss from the crank to the wheels? My dyno sheet for my '02 Z w/Maggie shows 498 RWHP, just curious what it makes at the crank. Thanks.
Last edited by switchplanner; 11-15-2015 at 02:12 PM.
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SBCGENII (11-18-2015)
11-15-2015, 03:25 PM
#3
Team Owner
The difference can be anywhere between 10 to 15 per cent. But the dyno reading can be different based on the specific dyno being used. I have heard that some dyno's can be programmed to show a higher reading than what is actually being delivered to the wheels. Not sure if that is really true, but I have seen different RWHP/Torque values for my Vortec supercharged '02 coupe.
11-15-2015, 11:29 PM
#5
Team Owner
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Close to 20% diffs from crank to wheel.
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switchplanner (11-16-2015)
11-17-2015, 11:59 PM
#6
Platinum Supporting Vendor
I think the "generally" accepted answer is 15% for manuals and 20% for autos.
But don't do this: 498 X 1.15 = 572.7
It's actually : 498/.85 = 585.88
Obviously it's the same for autos. 498/.8 = 622.5
But don't do this: 498 X 1.15 = 572.7
It's actually : 498/.85 = 585.88
Obviously it's the same for autos. 498/.8 = 622.5
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switchplanner (11-18-2015)
11-18-2015, 05:36 PM
#7
I have to say I disagree with the whole percentage theory for the sake of discussion. Unless your willing to consider that the percentage drops proportionate to hp being made....roughly.
Autos don't consume 20% across the board...the same as a manual don't consume 15% across the board. As power increases the percentage value should drop, even though the actual parasitic number may increase.
Example;
500hp manual car = 15% drivetrain loss = 75hp
1000hp manual car = 15% drivetrain loss = 150hp
Not happening...lol. Or if you believe this example is true, please explain.
I believe it's more like this....
500hp manual car = 15% drivetrain loss = 75hp
1000hp manual car = 10% drivetrain loss = 100hp
And honestly, this example maybe to much also...more like 9%. Or even less !!
We all understand that as power increases so does some of the parasitic loss via, heat, friction pressure...etc. But it's all relative, it's only going to take X power to turn that trans & diff....regardless of overall power.
Flame on.....
.
Autos don't consume 20% across the board...the same as a manual don't consume 15% across the board. As power increases the percentage value should drop, even though the actual parasitic number may increase.
Example;
500hp manual car = 15% drivetrain loss = 75hp
1000hp manual car = 15% drivetrain loss = 150hp
Not happening...lol. Or if you believe this example is true, please explain.
I believe it's more like this....
500hp manual car = 15% drivetrain loss = 75hp
1000hp manual car = 10% drivetrain loss = 100hp
And honestly, this example maybe to much also...more like 9%. Or even less !!
We all understand that as power increases so does some of the parasitic loss via, heat, friction pressure...etc. But it's all relative, it's only going to take X power to turn that trans & diff....regardless of overall power.
Flame on.....
.
Last edited by LSOHOLIC; 11-18-2015 at 05:56 PM.
11-18-2015, 07:53 PM
#9
Melting Slicks
I have to use something for reference, so here it is:
A stock 04 C5Z was rated at 405hp. They routinely dyno'd 350 to 355 rw if I recall.
That's about 50hp worth of loss or ~ 12%.
Take the same car with the same transmission and rear diff plus an upgraded clutch and let it make 1000hp at the engine. Is it now making 880rwhp due to a 12% loss through the driveline? I don't see how the trans and diff are now causing a loss of 120hp. I would make some allowances and say with the added power, the car is now experiencing a ~60-65hp loss and is making 935rwhp.
Yes there is a greater load being transferred causing more load on the faces of the gear teeth, a little more deflection, a little more friction and heat. An additional 70hp worth? It doesn't seem believable.
This has to be balanced somehow. Nothing has really changed from a mechanical aspect that would cause the type of loss suggested by using a flat 12, 15, or 20% drivetrain loss across the board for every vehicle.
A stock 04 C5Z was rated at 405hp. They routinely dyno'd 350 to 355 rw if I recall.
That's about 50hp worth of loss or ~ 12%.
Take the same car with the same transmission and rear diff plus an upgraded clutch and let it make 1000hp at the engine. Is it now making 880rwhp due to a 12% loss through the driveline? I don't see how the trans and diff are now causing a loss of 120hp. I would make some allowances and say with the added power, the car is now experiencing a ~60-65hp loss and is making 935rwhp.
Yes there is a greater load being transferred causing more load on the faces of the gear teeth, a little more deflection, a little more friction and heat. An additional 70hp worth? It doesn't seem believable.
This has to be balanced somehow. Nothing has really changed from a mechanical aspect that would cause the type of loss suggested by using a flat 12, 15, or 20% drivetrain loss across the board for every vehicle.
Last edited by Turbo-Geist; 11-18-2015 at 07:55 PM.
11-18-2015, 08:12 PM
#10
I have to use something for reference, so here it is:
A stock 04 C5Z was rated at 405hp. They routinely dyno'd 350 to 355 rw if I recall.
That's about 50hp worth of loss or ~ 12%.
Take the same car with the same transmission and rear diff plus an upgraded clutch and let it make 1000hp at the engine. Is it now making 880rwhp due to a 12% loss through the driveline? I don't see how the trans and diff are now causing a loss of 120hp. I would make some allowances and say with the added power, the car is now experiencing a ~60-65hp loss and is making 935rwhp.
Yes there is a greater load being transferred causing more load on the faces of the gear teeth, a little more deflection, a little more friction and heat. An additional 70hp worth? It doesn't seem believable.
This has to be balanced somehow. Nothing has really changed from a mechanical aspect that would cause the type of loss suggested by using a flat 12, 15, or 20% drivetrain loss across the board for every vehicle.
A stock 04 C5Z was rated at 405hp. They routinely dyno'd 350 to 355 rw if I recall.
That's about 50hp worth of loss or ~ 12%.
Take the same car with the same transmission and rear diff plus an upgraded clutch and let it make 1000hp at the engine. Is it now making 880rwhp due to a 12% loss through the driveline? I don't see how the trans and diff are now causing a loss of 120hp. I would make some allowances and say with the added power, the car is now experiencing a ~60-65hp loss and is making 935rwhp.
Yes there is a greater load being transferred causing more load on the faces of the gear teeth, a little more deflection, a little more friction and heat. An additional 70hp worth? It doesn't seem believable.
This has to be balanced somehow. Nothing has really changed from a mechanical aspect that would cause the type of loss suggested by using a flat 12, 15, or 20% drivetrain loss across the board for every vehicle.
.
11-18-2015, 08:41 PM
#11
Melting Slicks
, I'm right there with you. Just trying to provide more info.
11-18-2015, 11:01 PM
#12
Le Mans Master
I have to use something for reference, so here it is:
A stock 04 C5Z was rated at 405hp. They routinely dyno'd 350 to 355 rw if I recall.
That's about 50hp worth of loss or ~ 12%.
Take the same car with the same transmission and rear diff plus an upgraded clutch and let it make 1000hp at the engine. Is it now making 880rwhp due to a 12% loss through the driveline? I don't see how the trans and diff are now causing a loss of 120hp. I would make some allowances and say with the added power, the car is now experiencing a ~60-65hp loss and is making 935rwhp.
Yes there is a greater load being transferred causing more load on the faces of the gear teeth, a little more deflection, a little more friction and heat. An additional 70hp worth? It doesn't seem believable.
This has to be balanced somehow. Nothing has really changed from a mechanical aspect that would cause the type of loss suggested by using a flat 12, 15, or 20% drivetrain loss across the board for every vehicle.
A stock 04 C5Z was rated at 405hp. They routinely dyno'd 350 to 355 rw if I recall.
That's about 50hp worth of loss or ~ 12%.
Take the same car with the same transmission and rear diff plus an upgraded clutch and let it make 1000hp at the engine. Is it now making 880rwhp due to a 12% loss through the driveline? I don't see how the trans and diff are now causing a loss of 120hp. I would make some allowances and say with the added power, the car is now experiencing a ~60-65hp loss and is making 935rwhp.
Yes there is a greater load being transferred causing more load on the faces of the gear teeth, a little more deflection, a little more friction and heat. An additional 70hp worth? It doesn't seem believable.
This has to be balanced somehow. Nothing has really changed from a mechanical aspect that would cause the type of loss suggested by using a flat 12, 15, or 20% drivetrain loss across the board for every vehicle.
11-23-2015, 04:47 AM
#14
Drifting
i dont understand these discussions. if you put a car on the dyno you get the drivetrain loss measured with rwhp, no? all dynos over here are calibrated to be within 2% according to EN-80-1269 i believe. my cars dyno the same on all dynos i put them on, bosh usually.
am i missing something?
am i missing something?
11-23-2015, 02:08 PM
#15
Le Mans Master
over here, most dynos don't read the same - especially going from one manufacturer to another. a Mustang historically reads a bit lower than a Dynojet, for example. there's a correction factor than can be applied to compensate for atmosphere differences and nuances of the dyno & should give you what your SAE power is, but even those correction factors ain't always spot-on either.
Last edited by _zebra; 11-23-2015 at 02:08 PM.
11-23-2015, 03:11 PM
#16
Melting Slicks
Everything matters, after the crank but it would all depend(especially manual guys) on the weight of everything. A 47lb triple plate textralia clutch will rob more power than a 14lb carbon tilton clutch.....metallic rotors,....will rob more power than carbon ceramic rotors(ZR1 cars)....light weight wheels, vs some heavy china replica wheels....etc would, should also effect power to the ground.
lsholic/Turbo-Geist got it right though in my opinion.
lsholic/Turbo-Geist got it right though in my opinion.
