Scottie46

I have a tune and I have a dyno chart. I want to know how to convert the bhp to hp at the crank. If someone here can do it I'll give the numbers. Or I can be taught how. It's for a 2013 P31 C63.

Thank!!!
-Scott

HIRO63

I think bhp and hp is same?

Scottie46

I don't know why I wrote bhp. I meant whp conversion to hp. Thanks for catching that!

charliekay

18-20% drivetrain loss on our cars.

~WHP / 0.80 = Crank HP.

mr747

Google bud it does everything

MrBlonde

An engine dyno will tell you hp at the crank. A chassis dyno will give you hp at the wheels. Everything else is a guess.

Autosport7

And asking a simple question here can get results as well.
Never understand it, if you're going to type something into your electronic Internet capable device, why not let it be the answer to the question at hand?
Then this site becomes the wealth of knowledge it should be as a forum... Makes sense eh?

mr747

you are reviving a thread from 6 months ago

cyberorth

Actually, due to the methods of measurement and calculations, every type of dynamometer will give you a different number, so that is not a method of comparison unless you use the same type dyno and are comparing similar types of drivetrains, eg rwd, awd etc.

Also the engine hp measurement methods are different. bhp for example is the hp at the crank and does NOT include losses like the water pump, power steering, transmission, alternator, etc. if you connect a complete engine that drives its own pulleys to a dyno, you're not measuring bhp.

It is not a guess to translate bhp into whp or vise versa. For any given drivetrain, the percentage of total loss can be factored in a simple equation that is pretty accurate for that MY. If it is determined that the loss for 08-11 c63 is 18.xx%, you can use that pretty consistently to calculate one figure from another. That is how we know the power of a p31 m156 engine is underrated by mb.

Note that when you compare significantly different power ratings for a given powertrain, this loss percentage starts to be less meaningful, but that usually means that the powertrain would fail with the power beyond its tolerance anyway.

bhamg

Just for kicks I searched "converting whp to chp." Result - 0 hits. Searching "converting wheel horsepower to crank horsepower" returns three hits, none of them obvious. If I were asking I might not have clicked on any of them.

Moral of the story - it's soooo much easier not to click on a thread you know the answer to and get worked up about. The way the OP asked the question it was obvious to me that he was a "tenderfoot." No harm, no foul...

cyberorth

In all fairness, difference between bhp and hp is a google question, which is the title and possibly why mr747 referred the op to google. Powertrain loss for c63 is a forum question. I wouldn't trust non forum google returns anyway.

cyberorth

What's a tenderfoot?
...no wait! I'll google myself

mr747

the op asked for how to calculate and i simple gave him the answer
Google works pretty well for something simple like that

Autosport7

I didn't revive it, I posted in a revived thread from 6 months ago. Lol

bhamg

Didn't see the date of the original post.

MrBlonde

So what?

MrBlonde

Totally agree. Even the same brand of dyne - heck even the *same* dyno itself will give different numbers.

Ingenieur

here's a link for rototest, a european 3rd party testing agency used by many oem's to rate their engines
it's the C63 test
http://rototest-research.eu/popup/pe...p?ChartsID=795

power loss 11%
torque loss 13%

there is a tab 'downloads' that has the actual certification docs

about rototest
RRI, Rototest Research Institute performs advanced applied research and development aiming to contribute to the international knowledgebase of measurable vehicle performance parameters.

RRI is a non-profit organisation with its principal duty to carry out research and development concerning infrastructure, traffic and transport with priority on individual transport. RRI objective is to conduct its R&D, on commission basis or self-initiated, with highest possible integrity in relation to society, political agenda or commercial special interests.

roadtalontsi

thats an interesting last post and it just goes to show you how amg promises you something and delivers even more. Any real performance shop or dyno operator can tell you there is no way a car is only losing 11% of power through a true torque converter'd automatic transmission.

Ingenieur

http://www.zf.com/corporate/en/produ...nsumption.html

I do some work with dynos
Typical auto eff 90-95%
Manuals 92-97%

The reason the 11% seems low is that it is a hub dyno
No wheel mass or slip, typically 4%+

The numbers are what they are
The source is listed
Details are given on method

'Some guy' in a 'real' dyno shop is not valid

http://www.geartechnology.com/issues...wer-losses.pdf

roadtalontsi

i've never used a hub dyno i liked. They just dont load the car correctly like in the real world. Im sure this place has some high dollar lab equipment that is more accurate than a typical one. I prefer the mustang dyno myself.

jrcart

Lots of things come into play when determining driveline loss. As Ingenieur pointed out a big factor is manual vs auto transmission. Driveline loss is essentially resistance.The transmission and everything behind the tranmission causes that resistance, the weight of the drive shaft, the weight of your brake rotors, the weight of your axles, the weight of your wheels and tires. The heavier all that stuff is the more driveline loss you are going to have. Back when I ran ligtweight carbon fiber Dymag wheels on my CLK the showed an increase of 20 whp on a dyno. The wheels did not technically give the car more hp, the lighter wheels simply freed up hp thus decreasing driveline loss. Lightweight two peice rotors and a cf driveshaft will free up a few more ponies. I am not an engineer and do no know for certain but I would guess that flex in all those components has some effect on driveline loss as well. Any time something flexes it is using energy and that energy that was meant to go to power those back wheels is now be diverted as drive shaft flex ot axle flex I would guess.

Ingenieur

A good hub dyno (eddy current or hydraulic) is much more repeatable than a 'roller'
They have finer resolution and modulation

The only valid power test is steady state
Run the engine up to hp peak rpm +5%
Increase load until the rpm drops to hp peak
Stabilize for 10 sec or so then record for 10 sec minimum

Ramp runs are good for comparison or evaluating changes
Not power rating or magnitude

Diabolis

Hold on a sec... they are arriving at the % loss by measuring what the car puts down at the wheels and then comparing it to the *CLAIMED* engine output by MB, which as we all now is marketing BS. That's complete garbage. Unless they have some kind of evidence other than MB marketing materials about what the engine puts out at the crank, their "calculated" % loss is about as accurate as something you could arrive at by astrology or reading tea leaves. It's bull.