Standard 1275 Cooper S BHP at the wheels??

[rolesyboy]

Does anybody know the answer? I think it was 75 at the flywheel so would imagine around 60 at the wheels but interested to see what the 'proper' answer is. Cheers. Mark

[foxy52]

Does anybody know the answer? I think it was 75 at the flywheel so would imagine around 60 at the wheels but interested to see what the 'proper' answer is. Cheers. Mark

...mk 2 s was 76bhp...

[rolesyboy]

Thanks Foxy. At the fly or the wheels???

[foxy52]

Thanks Foxy. At the fly or the wheels???

...the 1275 unit produced variable bhp in its mk 1 2 or 3 guise... i thinks the mk2 s in its standard form was the most powerfull in terms of bhp....

[1071 S]

In what terms was it less powerful??

Having heard some first hand stories about RR (who did measure each engines HP) I would be interested to know what the normal variation might have been across ex production S engines (which as far as I know were not measured).

I would guess somewhat south of 60 might be a reasonable ATW hp - but would not be surprised if this was an overestimate.

We have pretty much all the data so someone should be able to do the calcs...

Cheers, Ian

[foxy52]

In what terms was it less powerful??

Having heard some first hand stories about RR (who did measure each engines HP) I would be interested to know what the normal variation might have been across ex production S engines (which as far as I know were not measured).

I would guess somewhat south of 60 might be a reasonable ATW hp - but would not be surprised if this was an overestimate.

We have pretty much all the data so someone should be able to do the calcs...

Cheers, Ian

...be interesting to know..?!

[1071 S]

Many years ago I posted to the calcs to one of the websites. HP an be fairly easily (if you remember/find the formulas calculated using acceleration times. Unfortunately, time, new computers and changed operating systems means that that info is no longer accessible.

However, we have fairly good performance numbers (Autocar 64) weight, we can measure cross section, estimate aero drag index. Using these you can calculate aero drag, roll down numbers will give you mechanical drag.... put all this together and you have your number.

Good luck, Ian

[wil_h]

Power at the wheels is a pretty meaningless figure, why do you want to know it?

Power is measured at the wheels, then losses are measured and the two figures added up to give the flywheel figure. If you ignore the losses and just use the wheel figure you're missing 1/2 the measured figures. Losses can vary so massively that unless you account for them each time you don't know if you're engine is better or worse.

For example losses will be affected by binding brakes, tight wheel bearings, tyre pressures, diff bearings........ Imagine you built a brand new engine and took it to the same RR, but didn't realise that a brake was binding, or a tyre was flatter than last time; you're new spangly engine could well make less power tan your old knacker. Unless you measure the losses, you'll not know why.

[Chalkie]

IIRC the MG metro 1275 and the mk3 cooper S had same BHP

the cylinder heads have same size valves and ports, its basicly the same casting but not at the same time.

[66S]

The tension on the rolling road front tie-downs can have a dramatic effect too.

Al

[Spider]

Unless all the figures for both flywheel and ATW results have standard corrections, then they don't mean much at all. The factory Flywheel figures are corrected.

Without standard corrections being applied, figures can easily vary 30%, even more. The corrections take in to account things such as humidity, air density, altitude, air pressure, fuel temp, air temp at the intake and even tyres, just to list some. Most figures I've seen quoted there days off the dyno are not corrected.

I've not tested them to see for myself, however I've heard of figures in the range of 15 to 25 HP lost through the gearbox.

[LMM76C]

72 bhp was always the figure quoted for the 1275 S, up to the change in standard camshaft to the "510" ( last year or so of Mk1's?). 76 then began to appear as the figure in official specifications/adverts, although it was never mentioned as a change in anything I saw in period.

Losses are usually vastly underestimated on rwd cars in magazine articles etc. A 180bhp at flywheel Escort will often be quoted as 25 bhp losses but reality is 40 bhp. We never used a R/R back in the day so I've no idea what Mini losses were but they would be less than for rwd.