Bhp and whp

[Cambaines]

Proper car question!

My car has been on the dyno at unicorn and is putting out 285whp, the dyno is top notch and is pretty new so I'm trusting the figures! I've just used a whp-bhp calculator and I'm confused it's come out at 328bhp... I understand this is at the crank and not usable! When Audi quote 200bhp, am I right in saying this is wheel horsepower?

 

[Shane-Ireland]

Car manufacturers always use the BHP figure.

 

[Cambaines]

So power at the crank? This has proper blagged my head to be honest with you, is the RR figure converted to bhp then? Well confused

 

[Cambaines]

Is my car 285bhp or whp!

 

[Cambaines]

It just says Hp but that's obviously at the wheels

 

[Sayam]

Car manufacturers always quote power at the crank, or what you're calling BHP.

Your car has gone from 220BHP standard to 280BHP. That's BHP not WHP.

A K03 won't make 328BHP unless it's had the K04 swap.

So say my car is 170BHP, I'm probably getting 130/140 at the wheels, the rest being lost through transmission losses etc.

I'm no expert but that's my understanding.

 

[Cambaines]

That's cleared it for me, It through me about the through the wheels part, and then I thought well a RR measures bhp through the wheels... It's crank measurement that is tested never really come across this in my time!

 

[S3Alex]

That's cleared it for me, It through me about the through the wheels part, and then I thought well a RR measures bhp through the wheels... It's crank measurement that is tested never really come across this in my time!

The only truly accurate way of determining bhp at the crank is on an engine dyno,which most of us are unlikely ever to use.
RRs measure at the wheels and infer crank horsepower,but will not be as accurate as a properly calibrated engine dyno.

 

[Cambaines]

Love it, I was confused at how a RR would measure crank power, didn't realise there was some maths to it! cheers guys

 

[-Ju-]

As has been said, the only true way to measure engine horsepower is with the engine out on a engine dyno.
On a RR the calculation from wheel horsepower to engine horsepower is taken from the coast down after the power run. This works out the transmission losses and adds them to the whp figure

 

[desertstorm]

@Rick @ Unicorn Motor Dev. Dyno is pretty good when it comes to it's accuracy. When he runs standard new cars on there the readings are pretty accurate against what the manufacturer claims. A good dyno operator along with a decent dyno can produce accurate repeatable measurements . In America they quote a lot of figures in whp but in this country pretty much all you ever see is figures quoted at the crank, bhp.
The interesting thing for me is the before and after difference. The car picks up much better and the there is a significant continuous improvement across the rev range and all the way to the red line.
I bet it's a lot quicker and nicer car to drive.

 

[S.]

It's all about the delta.

 

[Rick @ Unicorn Motor Dev.]

look at the bottom of the graph - you will see the wheel figure

 

[Cambaines]

look at the bottom of the graph - you will see the wheel figure

I see, cheers Rick, 254 through the wheels, something I've never actually thought about

 

[Sayam]

@Rick @ Unicorn Motor Dev. Dyno is pretty good when it comes to it's accuracy. When he runs standard new cars on there the readings are pretty accurate against what the manufacturer claims. A good dyno operator along with a decent dyno can produce accurate repeatable measurements . In America they quote a lot of figures in whp but in this country pretty much all you ever see is figures quoted at the crank, bhp.
The interesting thing for me is the before and after difference. The car picks up much better and the there is a significant continuous improvement across the rev range and all the way to the red line.
I bet it's a lot quicker and nicer car to drive.

Agreed, it's more about the before/after and how it drives rather than absolute figures - although it can be nice to know what your car is making in the region of in terms of bhp.

 

[Cambaines]

Yes I'm not about chasing figures at all, it's about the drivability and mid range pull that I love, hit nice to know the facts of how it works like!