[Staowners] ALPINE engine power

[Richard Atkinson]

Hi Mal,

Brake horse power normally means at the flywheel.  A dynamometer puts  
the engine on a test bed and measures the power at the flywheel, so a  
dyno is giving you BHP, power at the flywheel.  A rolling road does  
the same thing but reading off the driving wheel rather than directly  
off the flywheel.  Strictly, BHP is minus engine ancillaries  
(generator) but these are, excepting A/C, usually fairly small.  I'd  
expect to lose maybe 10-15% between the flywheel and wheels.

The Rootes book BHP figures will be off a dyno, most probably with  
ancillary loads  removed - the point being that this is what the  
combustion system makes available, and how it's divvied it up between  
the wheels, transmission losses, ancilliary loads etc is someone  
else's (i.e. not the engine designer's) problem!  BHP gets used fairly  
loosely to mean 'HP' which is strictly incorrect, since anywhere but  
the flywheel you're just talking plain power (i.e. HP, kW etc) at that  
defined point.

Anyway, 50 seems low to me.  If the engine should produce 80HP at the  
flywheel, and your ancillaries may be taking up to 5HP, then it  
suggests the engine is not making more than about 65HP in total.   
Depends how honest the Rootes figures really were!

Cheers,

Richard


On 5 May 2008, at 13:33, Mal Clark wrote:

> Hi Vic,thanks for email,can you clear up one thing,Dyno man said it  
> produced 50 Horse Power at the wheels is that the same as Brake  
> Horse Power,?? Mal Clark
> ----- Original Message -----
> From: Vic & Rosalie Hughes
> To: Staowners at sunbeamtalbot.info
> Sent: Monday, May 05, 2008 10:09 PM
> Subject: Re: [Staowners] ALPINE engine power
>
> Hi Mal,
>
> Can't claim to be an expert but I reckon that 50 bhp at the rear  
> wheels @ 3000 rpm is probably not too bad.  The 80 BHP claimed in  
> the manual would be at the flywheel, and @ 4200 rpm - more rpm (up  
> to the peak) = more power.  Power loss through the transmission  
> (gearbox and diff) accounts for some of the difference, lower than  
> peak revs accounts for some more.
>
> My Series III Alpine is rated at 82.5 gross, 75 net @ 5000 rpm at  
> the flywheel. It dyno'd 58 bhp @ 4000 (it too was running in)
>
> Cheers, Vic
> ----- Original Message -----
> From: Mal Clark
> To: Staowners at sunbeamtalbot.info
> Sent: Monday, May 05, 2008 9:41 PM
> Subject: [Staowners] ALPINE engine power
>
> Hi everyone,I have been without my computer for a few weeks, now up  
> and running ok, my Alpine is just about finished and driving and  
> running beautiful, highly recommend Jim Wilkinson's Power steering  
> kit,dont think he as yet come up with a left hand drive kit, it  
> makes the Alpine driving a dream so so good,and with the Toyota  
> Celica 5 speed gearbox as well it is superb, Today I had my alpine  
> on the Dyno,I felt is wasn't quite right,being a new engine I didn't  
> want to damage it, as it turned out it was running very rich so  
> different jets in the carb and resetting the timing,etc produced an  
> extra 7 kilowatts of power,the question I have,someone out there  
> must know more than me on these power outputs, the first run up to  
> only 3000rpm (NEW ENGINE REBUILD) on the Dyno it produced 30  
> kilowatts of power after the rejetting etc it produced 36.7  
> kilowatts . if you multiply the kilowatts by 1.34 it gives you the  
> horse power,so it is producing 50 HP at 3000rpm at the back wheels,  
> can someone tell me if that is good or average, as I have worked the  
> motor, quite a bit,as I said it drives great, Manual states 80 BRAKE  
> horse power for the Alpine, regards Mal Clark.
>
>
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