bhp to whp conversion

Canadian370Z

I was just wondering what the bhp on the 370z would be when the car is 332 bhp and you are adding a Stillen CBE which adds 18 whp.

CBRich

Well, it seems some guys are getting around 280 whp stock from the 332 hp engine. That would be a drivetrain loss of 16%. If that holds true then 18 whp should convert back to about 21 hp at the crank. So say about 353.

Disclaimer: This is all just simple math and conversions and there are many other factors but it should be ballpark.

eXo5

I like math!!!!

I cant wait to see this cars full potential.

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dad

what does whp stand for?

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eXo5

Wheel horse power

from what I understand vehicles are usually rated from the crank. 332 is rated at the crank the amount of HP you would get from a dyno is probably going to be around 280. HP is lost from a number of things. WHP is the HP being put down at the wheels. I am sure someone cant explain it better than I.

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dad

Approx--14.74hp increase for manual. 14.04hp increase for automatics..(but don't quote me this whp is new to me.)

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eXo5

Effective (true, wheel) hp
Effective horsepower (EHP), True horsepower (thp) or wheel horsepower (whp) is the power converted to useful work. In the case of a road vehicle this is the power actually turned into forward motion as measured on a chassis dynamometer. Power available at the road is generally 10% to 20% less than the engine's bhp rating due to "coastdown" losses, most of which are due to the vehicle's rubber tires rather than true transmission losses. Front-wheel drive cars (provided a transverse engine layout is used) suffer slightly lower coastdown losses due to the absence of the bevelled crown and pinion gears used to change the drive direction in the back axle of a RWD car [14].

For railway locomotives the terms Drawbar Horsepower or Equivalent Drawbar Horsepower (EDHP) refer to the power available to haul a train. This is synonymous with the Effective horsepower.[15] This figure takes into account the horsepower needed to move the locomotive, which is not available for hauling the train. The Rail Horsepower is the power at the wheels of a locomotive, directly comparable to the wheel horsepower of a road vehicle

Source: http://en.wikipedia.org/wiki/Horsepo...ower_.28whp.29

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Canadian370Z

Thanks guys.

MightyBobo

Correct - wheel horsepower is the power that actually makes it to the wheels.

Power can be lost in many things, because power is really just another form of energy. Its all lost in the drive train in one way, shape or form. The transmission is the first place its going to lose it, particularly in the clutch and gears. In an automatic, a stall converter will make your power at the wheels look HORRIBLE, but yet you will run amazing times at the track. Then it has to make it to the rear end, and even things such as the weight of the drive shaft will cause lost power. The rear end will be even more power lost, converting the power sent through the drive shaft and sending it to the wheels. Even the weight of the wheels alone will be lost power, due to unsprung weight needing to be spun.

Its not fair to simply say, "Well, the average power loss from crank to wheels is XX%". Look at RCZ - he "only" put down mid 250's in stock form at the wheels, but that is because the dyno he chose puts a load on the wheels, versus the OTHER dynos that say we're putting down 280's to the wheels. Those are simply drums that you spin up, that don't put a load on the wheels, and are considered to be less accurate.

There is a lot more science to this than a lot of people on here understand. You need to understand that wheel horsepower ratings can fluctuate on 2 of the exact same type of dyno's side by side - each one is different. Never mind even factoring in varying weather and altitudes...

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theDreamer

Question about HP loss for a rear wheel drive car.
~Is there a way to limit this loss with part upgrades, I know adding a new exhaust, intake, etc. will increase your WHP but can you decrease the overall loss in general on a rear wheel drive car?

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eXo5

Counter Act it with weight reduction? Get a good tune? Forced induction? Improve the transmission somehow?

Im kinda throwing ideas out there not sure if any of these things would really "help".

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theDreamer

A good tune might be helpful, but adding FI I think is like adding a new intake or exhaust. You are just adding to the base line and not increaing the base line number.

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MightyBobo

When you're thinking of improving performance, a motor is simple - its a lung. Help it breathe faster (or breathe more air in), and it'll perform better. Whats the point of being able to exhale very well if you cant inhale as efficiently, and vice versa? A well-built car will be able to do both, in the proper proportions. Dont always assume that slapping any intake on a car will increase performance, though - manufacturers claims can differ from real life, greatly.

Now that you understand how to actually improve your base performance, we'll go into recovering lost power.

Lowering unsprung weight is one way to recover "lost' horsepower. Replacing a steel driveshaft with a carbon fiber one, for instance. Replacing ridiculously heavy, shitty wheels with lightweight, performance wheels (hence why many of the performance-minded guys laugh at people wanting to get 20's or bigger that weigh more than stock wheels - you're LOSING performance, really!) will recover some power. Aside from that, you're probably talking upgrades that many simply wont do, like a locker rear differential that allows no slip.

BTW, its worthy to note that, after unsprung weight, recovering horsepower due to parasitic losses becomes very difficult.

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MightyBobo

Wrong concept - he's talking about making the most of the power he already has - not making more.

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Diversion

We're looking at about 18% loss to the ground on a 6MT Z. It's about 1% higher than a simple RWD manual car usually sees (about 17%). I can only assume it's the additional hardware/technology adding the 1% extra loss to the ground.