Horsepower measurement: BHP versus PS

[MINIAC]

In looking at horsepower ratings from Superchips and John Cooper Works, I notice that the former expresses it as BHP (braking horse power) and the later as PS. What does PS stand for and how are the two different?

[Dom]

I think they are exactly the same, dunno what PS stands for though... Pony something?!?

What confuses me is convering Nm into lb/ft torque... can never be bothered to work it out!

Dom

[Silverstone]

Actually an SAE hp is slightly bigger than a DIN PS.

You get 1.0139 PS per hp.

DIN is German and SAE is the US standard.

The ISO measure of Power is the kW and there are 1.36 PS per kW.

Here endeth the lesson. Amen.

[MINIAC]

Quote:

Originally posted by Silverstone
Actually an SAE hp is slightly bigger than a DIN PS.

You get 1.0139 PS per hp.

DIN is German and SAE is the US standard.

The ISO measure of Power is the kW and there are 1.36 PS per kW.

Here endeth the lesson. Amen.

Assuming that bhp is SAE hp, then the John Cooper Works rating of 132 PS equates to just over 130 bhp, which is slightly less than the Superchips rating of 131 bhp.

[Dom]

but you have to remember that the cooper works was tested at BMW, and so takes from those wierd high-altitude german figures. On a rolling road, I'd expect the works conversion to put out the most. On a track, I'd expect the works conversion to p*ss all over a superchip. On a bank balance, well, it's hardly a works conversion is it

It comes down to whatever floats your boat...

anyway, this is slightly off the beaten track!!

Dom

[BruceK]

Quote:

Originally posted by Dom
but you have to remember that the cooper works was tested at BMW, and so takes from those wierd high-altitude german figures. ....

Perhaps I've missed it, but where does it say the Cooper Works was test at high altitude in Germany? Unlike the production version of the Cooper, BMW didn't supply the horsepower figures for the Cooper Works, JCW did. It's my understanding the Cooper Works was developed and tested near sea level at JCW in Sussex. But please correct me if I'm mistaken.

[Dom]

I read it somewhere on this forum... but if superchips say standard cars are around 124bhp, I'd expect more than 7bhp from the modifications that come with the works conversion. I also expect BMW gave it a thorough going over at some point if it was to be fitted by BMW dealers. Although I'll readily admit, I'm not an expert on this!

Dom

[MINIAC]

Quote:

Originally posted by Dom
I read it somewhere on this forum... but if superchips say standard cars are around 124bhp, I'd expect more than 7bhp from the modifications that come with the works conversion. I also expect BMW gave it a thorough going over at some point if it was to be fitted by BMW dealers. Although I'll readily admit, I'm not an expert on this!

Dom

A FAQ is under construction which has a comparison of performance gains realized by Superchips and Works modifications.

[Silverstone]

There is no way on earth that Superchips have magically extracted more power from a MINI with just a new ECU "chip" than JCW have extracted with:
1. Low back-pressure exhaust
2. Gas Flowed head
3. ECU "chip"
4. Low loss intake

I would lay money on a back-to-back test showing the JCW had more power.

Unfortunately we know nothing about how JCW or Superchips test their engines, so comparing hp/PS claims is next to impossible. So many factors affect the end result (especially on a rolling road)

What we need is a couple of cars and a Drag Strip - anyone game??

[MINIAC]

For the difference in price I would hope so. Regardless, you get some cool cosmetic goodies with the Works kit.

The FAQ merely compares the horsepower and torque figures stated on the respective vendor's websites. They are just numbers and, hopefully, someone will soon answer the question with a head-to-head on the track.

[danielcraig]

I believe that we nned to see the head to head between the two cars, as someone else suggested, we can talk figures until we are all out of breath, the proof as they say is in the pudding, or in this case in the engine.

I still think that the works car is not good value for money, you may get fancy badges, and nice car mats, but you can get those from Halfords, I have changed cylinder heads, and other bits on many cars, and have never gained such a low increase in power as they have managed to achieve. It is possible of course that BMW have given them directives as to what they can and cannot do.

This would make sense as why would BMW spend millions on fitting the Supercharged engine in the S just to have a small british performance company upstage them by introducing a 150BHP kit for the cooper for £2,500??!!??

The superchips car may invalidate the BMW warranty, but at the moment the works car could well do the same thing, and at the end of the day if you spend £250.00 on the chip and gain the same performance then you can save the other money for other goodies like exhaust and air filter from auto fashion, who are also cheaper than john cooper works, double savings to be had!!!!!!!!!!!

If you want to put the car back to standard, isnt it also easier to get the chip changed? As they do give you the original chip back. Where as do you get your original cylinder head back in the works deal?? I doubt it, in fact does it not got to be machined and upgraded to make another head to be re-sold as, oh no it cant be, a John cooper works kit well now wouldnt that be a suprise.......

[JV]

PS is a German abbreviation for HP (PS in German is Pferde Stärke - literally horse power), but I believe a German horse extracts slightly less or is measured differently as PS and BHP claims vary slightly in my experience. I understand BHP to be HP measured at the crank after a brake has been applied to it (hence Brake Horse Power), but is it the crank, or is it at the wheels? Surely a rolling road will only measure power at the wheels (which will be marginally less than at the crank due to the energy wasted in the gearbox and axle etc.)?
Does that sound right to the techies out there????

[Silverstone]

"Official" power measurements are made on an engine dynamometer (brake) with a direct link from the flywheel to the dyno. The measurement is corrected for atmospheric conditions (temp and pressure) to give a standardised number. The SAE, DIN and ISO standards are all slightly different!

A rolling road (chassis dyno) can only give an approximate measure of flywheel power, since the losses in the transmission and tyres are rarely known exactly. They give an accurate measure of power at the wheels.

Since power at the wheels is what actually matters in the real world, a rolling road is a useful piece of kit. Nobody is quoting power at the wheels yet, so we can't compare.

[Mini Magnum]

The US standard for SAE HP means the manufacturer must now have all accessories hooked up to the engine, ie alternator,power steering,fan, air cleaner, exhaust etc. The old standard was misleading due to the fact that the engine was run on a stand with NO power robbing accessories attached. In the US advertised horse power must be correct or the lawyers (barristers) take over. Mazda had to buy back or offer other incentives to Miata owners when they found out the new ones didn't have the advertised HP, The same thing happened to Ford when the Mustang Cobra was found out to be short also. Most German manufactures underrate their cars a bit so they don't get into this in the US (Porsche & BMW).