HP or KW?

[RomanV]

HP, because it's what I learnt first.

A 'horsepower' kind of makes sense in an abstract but an imaginable way, but it's hard to have a reference for how much a 'watt' is.

Unless you've already got an idea of how much KW a car has and how it drives with that much power, etc.

[XERO]

:lol: I like PS as it is just soooo JDM YO!

I agree...

[Dragger_Dan]

Horsepower is great for gloating to old people, cause they say 'wow, 400 hp' rather than 'what the hell is 294kw?'

[Hotgt4]

hp is my prefered unit, or rwkW. Heard one to many blowhard with outrageous power claims when talking in Kilowatts.
Generally it goes something like this:
Got my dyno the other week, only got 250kW from my new turbo and ecu setup.
Is that estimated flywheel kilowatts?
Nah bro that is at the wheels!
Rolling dyno?
Yeah.
How much hp is that?
I think it was 170hp.

Take the larger number and add the high rating(kW) here...

[Snoozin]

Uhmmm kw tend to be the smaller numbers mate.

746w = 1hp, so 1hp is roughly 3 quarters of a kw.

[Mr Revhead]

1 kw = 1.34 hp

PS is german!!

[blackie]

i prefer kW myself..

[Snoozin]

1 kw = 1.34 hp

PS is german!!

That validates my statement then

[RomanV]

1 kw = 1.34 hp

Or multiply or divide by .745

HP = KW / .745

KW = HP * .745

[sergei]

1 PS = 735 W.
1 Hp = 745 W.
I preffer PS becuase they are DIN.
I preffer kW becuase they are METRIC.
Hp - is imperial.
When world will switch to hybrids the kW would start make much more sense.
Horse power is vague value - Watt is not.
1 Watt = 1 J/s
1 Joule = Work done by a force of 1 Newton that moved an object over 1 meter of distance.
1 Newton = force required to accelerate a mass of 1 kilogram by 1 meter / second squared.

As if you use horsepower (any of them) in that calculations they turn into mubo-jumbo with conversions...

[RomanV]

My car gets makes four cubits to the quarter span per hour!

[flygt4]

I work with electric motors often , older ones were rated in hp , but are now rated in kw ,and most electrical appliances and fittings are in kw too , so im pretty comfortable working in both.

to do it quickly i tend to just add or subtract a 1/4 ob the fly depending on which way i want to go


ps and i reckon dyno figures should be quoted atw unless done on and engine dyno , i always laugh when people do guessimations to flywheel figures to give themselves a number that sounds more generous

[sergei]

I was talking to one of the "dyno tuners" guys, and he goes:
"... just add 30% and you will get power at the engine..."
Well it put me straight off going to him for even a dyno run.
And his quote of 30% was just for fwd!
And he said same thing to a workmate of my (he has ~450rwhp drag car), and I quickly done calculation in my head "hold on is there like ~150hp loss through drive train" and I started wandering how bright molten blob of metal which used to be gearbox will glow....

[sergei]

Ok, I quickly done some caclulations on the following figures:
Mass of gear box ~30kg
Gearbox composition - mostly iron
Conditions - no cooling / ambient temp ~20C (not really important as long as ~0 and 100)
Loss through gearbox ~100kW (150 Hp converted to kW and rounded to 1sf)
So here are my results:
it would take ~20MJ to get to melting temperature
and ~10MJ to melt the gearbox (iron, if it was made out of alluminum alloy it would require much less)
so with 100kW (that is 100kJ/s) and with 30MJ energy required it takes 5min to melt the gearbox with 100kW loss through drive train.
If you add cooling effect from air/oil cooler say it would take 15min, still way out from the real world.

[Hotgt4]

Uhmmm kw tend to be the smaller numbers mate.

746w = 1hp, so 1hp is roughly 3 quarters of a kw.

Could you not tell the heavy note of sarcasm. Like I said, blowhards trying there best to make there car sound the business. When they are really just average.
250hp is around 170KW? No? Maybe I just know to many wantabes.

[Snoozin]

No sorry I genuinely thought you'd got it the wrong way round.... all sorted now though

[RS13]

I understand HP more than I do KW.

Seconded. I always mentally convert Kw to HP as well.

[neon_spork]

kW for sure, it's metric, it's SI. Working in kilowatts makes calculations so much simplier.

1 Watt is 1 joule/second. I dont even know what crazy units 1 HP is made up from (Btu/hour ? why would you want to use that?).

[fivebob]

I dont even know what crazy units 1 HP is made up from (Btu/hour ? why would you want to use that?).

It's made up of Horse power, i.e it was derived form the amount of work one mill horse could do in one minute (33,000ft.lb), though they were pretty small horses. A useful measurement in it's day as the engines were being used to replace horses. Interesting enough James Watt devised the measurement

Anyway I find it easier to think in HP for infernal combustion engines, and KW for electrical stuff. Until the US starts adopts the metric system, and the UK fully adopts it, it is much easier to compare results around the world, cause they sure as hell don't know what the KW is

[DexGT]

I understand both , but like a few on here , I tend to convert KW into HP , guess I just like the bigger number