Just had my cooper on the rolling road

[Dom]

Missed out on the peaks run yesterday because my MINI Cooper was booked onto the rolling road at Interpro, Bristol.

Anyone that beleives the official '115' bhp figures are wrong, may well be surprised by my results. I'll scan the graph in when my brother gives me back my scanner, but results are here:

Max BHP (at flywheel): 116.5
Max Torque: 122 lb/ft
BHP @ Wheels: 82
BHP lost through transmission: 34.5

The only engine mod was an induction kit - if you're serious about getting power from any form of modification, the ECU will have to be modified (it doesn't give full throttle). I'm going for a superchip next, and then possible a Unichip...

Dom

[12000rpm]

interesting m8!

so when u say that bhp was lost through the transmission does that mean we're actually only feeling wots left??? im a bit lost on this one...

[ELISEBOY]

yeah a bit more of an explination please!!!

[Dom]

The 116.5 bhp figure (don't forget the .5!) was only what the engine was pushing out. By the time this and gone through the transmission to the wheels, some of it has been lost due to friction and other such factors.

This is about 26% in this case, don't know if this is good or bad. In essence, I guess you only feel what's at the wheels...

Dom

[monsta]

Time to get a straight cut gearbox then... I wonder what the S box would be like on the Cooper

[ELISEBOY]

so reality is bhp of only 80 odd bhp.

Thats a bit dissapointing

Another example of massaging the figures!

[moonshine]

did the fellas at the dyno give you any idea how other cars performed, and is the loss from the crank to the wheels typical?

I guess most manufacturers will quote crank BHP as it is more impressive!

ta

Gerry

[Dom]

In reality, everyone talks about BHP at the fly wheel anyway so no-one really cares what it is at the wheels. I don't think losing 26% through the transmission is all that bad as most cars lose a similar amount.

What everyone seems to have ignored though is the torque...

The Citroen Saxo VTS pushes out 120bhp (more on newer models), yet can only muster 107lb/ft of torque. The MINI has 122 lb/ft, so is excellent in that respect. Just need to up the bhp to match!

Dom

[spanky2k]

Cool! I wonder what it'll be like with a cold air induction kit, new exhaust and a superchip! Any idea what kind of power a unichip can give?

[Dom]

A cold air induction kit and exhaust would all help, but would be best with an aftermarket chip.

The differences between a unichip and a superchip would not really be noticeable on a standard engine. Indeed, the unichip really comes into it's own when mods such as cams have been done, as each chip is set up specifically for the characteristics of your engine.

Cold air induction would help a bit, but the fan on the rollers was blowing air into the engine bay at the time so may have cooled it a little.

Either way, if you're serious about power and not just sound, then a chip of some sort should be done!

Dom

[ADO15]

Dom,

How can theY "read" flywheel BHP on a rolling road?

OH, just for reference;

The original Mini also lost are 26-28% of the power thru the gearbox. A straight-cut 'box would loose a bit less, somewhere between 21-25% depending upon the type of 'box.
I have no sound figurs for 'dog boxes' but I would think they'll be close to SC/CR gears.

[Dom]

Quote:

Originally posted by ADO15
How can the "read" flywheel BHP on a rolling road?

I'm not sure about that, but there's a thread in Performance & Tuning that might answer it at some point

Dom

[Mon]

A rolling road always measures output at the wheels. The flywheel figure is worked out mathematically. True flywheel power can only be measured on an engine Dyno which is usually done with the engine on the bench.

At the end of the day it is the power at the wheels that counts, as this is what is put down onto the road. Also bhp is more about top end speed, whilst torque is about how quickly you get there. A high torque figure is only really useful if the torque curve is relatively flat. That means the engine gives nice progressive power making it more enjoyable to drive.

Hope this helps

Mon

[Paul]

I will add that without other comparisons from a) Other MINI's and b) Other cars with reliable BHP figures (Renault's are usually spot on) a single reading from a single roaling road mean very little.

[bigbaddaboom]

And results of the same car can vary from day to day as well as dyno to dyno.