Horsepower

[girlpower]

whats the difference between wheel hp and crank hp ?

[paulr33]

for my gtst it is 74% difference from engine power to rear wheels, 187kw becomes 140kw at the rear wheels

i would assume the same relationship for horsepower, however gtr has 4wd as well so maybe %1/2% variance ?

[ARTZ]

for my gtst it is 74% difference from engine power to rear wheels, 187kw becomes 140kw at the rear wheels

i would assume the same relationship for horsepower, however gtr has 4wd as well so maybe %1/2% variance ?

see now thats what i was saying a while back that driveline loss was around 20-25% , but the Nismoid reckons my theory was flawed and that on average the loss was 50-60kw.. He was maybe going to get some test results to prove it..

I wonder what happened to that

[paulr33]

well that's for bog stock GTST with std everything. i would expect as power goes up, so does wear and tear, friction, losses etc

but its probably very linear in relation to power you make. like the loss might double at say 950kw who knows?

[Trozzle]

I'd say it'd be more of a set figure than a percentage...

Let's say in theory, you're putting out 2000hp at the flywheel - a 500hp loss through the transmission is a MASSIVE amount of drag and friction - just think of the heat and wear that kind of resistance would be causing...

[paulr33]

yep could be fixed, but there would be a lot of complexities behind it

a simplistic rule 25% is a good number

[zebra]

From what I have seen and have heard its around 17-18% for a GTST skyline, different cars have different percentages, eg the 300kw VT2 HSV GTS made around 220-230rwks due to the big T56 gearbox, with has massive gears internally etc, so if you put the same motor infront of say an RB20 box you might see around 240rwkws, same goes with Diffs.

Eg going from a Borgwarner diff in an older Ford V8 to a 9" diff means you instantly lose 25rwhp due to the way the gears mesh (its what gives the 9" its strength)

Troy - the more power you have the more heat everything gets, think of it as: the more power you have the harder the gears in the gearbox/diff mesh together, the harder they mesh the more friction therefore heat is produced so the rear wheel power figure will be lower.

[ARTZ]

Allthough i guess it would also make sense that a low powered car will lose power through the driveline more easily as it would have a reduced ability to overcome the drain..

A higher powered car would simply overcome these friction loses no matter how great..

But still Id think a 2000hp would quite easily lose 3-400 through driveline which is still close to 20% but once again the style of driveline would make a huge difference ,for instance a regular sedan with tailshafts compared to a car that has the engine/gearbox bolted directly to the diff..

Edited December 18, 2010 by Arthur T3

[STATUS]

From what I have seen and have heard its around 17-18% for a GTST skyline, different cars have different percentages, eg the 300kw VT2 HSV GTS made around 220-230rwks due to the big T56 gearbox, with has massive gears internally etc, so if you put the same motor infront of say an RB20 box you might see around 240rwkws, same goes with Diffs.

Eg going from a Borgwarner diff in an older Ford V8 to a 9" diff means you instantly lose 25rwhp due to the way the gears mesh (its what gives the 9" its strength)

Troy - the more power you have the more heat everything gets, think of it as: the more power you have the harder the gears in the gearbox/diff mesh together, the harder they mesh the more friction therefore heat is produced so the rear wheel power figure will be lower.

yeah i always thought so but it is less than we think.

STD VE is listed @ 270rwkw (this figure is derived without accessories so is high)

untouched on the dyno it reads 201rwkw

both auto and manuals tuned make the same RWKW to just about the dot so in this case auto vs manual is moot.

But generally the skyline stuff has a drive line loss of around ~40rwkw from engine dyno (full accessories) to chassis dyno.

[JonnoHR31]

general rule, 70-80hp. you'll never get exact figures for every skyline but who cares, arguing over 5-10hp is like sticking a dildo up your own ass, gay.

[KiwiRS4T]

As above . Its mainly a number not a percentage. For example for my Stagea driveline losses are estimated at 70kw for auto and awd which is a big proportion from stock (say 40% but when i was making 245awkw it would be only about 22%

[wolverine]

I think the power loss will be relatively fixed.

I'm sure we went over this a few times before & I thought it was settled by the suggestion that adding a 100 shot of nitrous would increase wheel hp by 100hp.

Does that sound about right Trent?

[Brandon]

I think this has been covered a lot of times and after reading, I find % doesnt make sense as your power increases, your loss will only be that high and should peak at a certain value (meaning any increase is negligible). From memory the difference is around 70hp?

[GTScotT]

I am on the figure side of the fence, more than the percentage.

I also think a car with 150rwkw would be losing more than a car with 400rwkw. Simply that the drag becomes negligible against the power at a certain level. But hey that could also work in opposite.. The higher the power the more load on components and the more mechanical drag... Who honestly knows, yet a "rule of thumb" for a power figure in loss is probably the most reasonable way to look at it.

[scotty nm35]

So how much does a 50hp 65 mini put to the wheels? Loss will increase as power/torque rises imo due to extra friction on the gears.

[R31Nismoid]

see now thats what i was saying a while back that driveline loss was around 20-25% , but the Nismoid reckons my theory was flawed and that on average the loss was 50-60kw.. He was maybe going to get some test results to prove it..

I wonder what happened to that

I don't have enough money is what happened

But there is no way its 25% dude. just d

600hp, 440kw, loss would be 111kw. 330rwkw is not equal to 600hp

[rob82]

It really depends on if you talking about manual or automatic transmission losses.

In a manual transmission the side loading on the bearing will increasing linearly with increasing torque. So the more torque produced the higher the transmission loss. However I would have thought that the axial bearing loads would stay realtively consistant with torque. Which brings me to the point that sraightcut transmission gears will most likely consume the same amount of power whether your making 100hp or 1000hp.

Automatic losses are a completely different ball game.

[R31Nismoid]

Ye i aint talking Auto's, just manual

[WHITER33GTS-T]

So who has a engine dyno to try this and work out a average...?

[tridentt150v]

I disagree with the set figure idea........laws of physics - the harder you work something the greater the friction involved to do it and the greater the losses due to friction = heat.

I can live with a baseline loss that you can never alter, but then your losses will increase in proportion to your friction area vs power output. You can alter or improve this in degree's by things like using a betetr oil, new bearings, teflon coating, reducing the mesh or friction area etc but you will never ever eliminate it.

In cars/motors, heat is a byproduct of friction, it is an inefficiency, heat is power lost to the rear wheels. Things like diffs and gearboxes get hot via friction ]the motor does as well, but it also has combustion as a heat source], and the more power you put through, the harder you work it, the greater the heat loss.