Relationship between engine CC and KW output

Our man in Havana · 27-03-2011 02:41PM #1

Is there a direct relationship between the CC of an engine and the KW output?
So if you had 2 different 1 litre engines would the KW be the same?

Mycroft H · 27-03-2011 02:47PM

Our man in Havana wrote: »

Is there a direct relationship between the CC of an engine and the KW output?
So if you had 2 different 1 litre engines would the KW be the same?

No.

KW is essentially power output. 1BHP=0.745KW

You could have an old 8v OHV 1 liter engine with 45hp (34kw) and a then a modern 16v VVTI ect engine with a power output of around 65-70bhp (48-52Kw)

No real correlation at all

Max_Damage · 27-03-2011 02:48PM

The only people who measure a car's power in Kilowatts are the French! :pac:

But back to the question, depends on alot of things (fuel injection or carb, turbo or not, number of valves, among other things). So no, a 1 litre car from one manufacturer will not have the EXACT same power output as a 1 litre from another manufacturer.

Idleater · 27-03-2011 02:50PM

Short answer is no. Longer answer is yes, at least once most likely at least twice (at 0 rpm and again at some x rpm).
For even longer answer, consider the output of a single 1000cc cylinder, two 500cc ones, and a 4 cylinder engine.

challengemaster · 27-03-2011 02:54PM

Quick example

Ford focus 1.6 (Zetec-SE) has 100bhp
Nissan pulsar VZR n1 1.6 (SR16VE n1) has 197bhp
Civic Si-RII (EK4) 1.6 (B16A4) has 174bhp

Nissan doctor · 27-03-2011 03:19PM

Its all to do with the design and purpose of the engine. Different designs will create more high or low end toque, high or low end power etc. The reason that the majority of 1L cars(as the example above) have similar outputs is down to torque. There is a certain amount of torque required to make a car move at an acceptable rate. The RPM of the engine is kept relitavly low so as to keep torque figures usable.

All N/A 1.0 engines fitted to your average car will rev to 6500 approx max, allowing them to create good torque for the engine size.

Alot of the old Japanese k cars had less then 700cc engines and reved to 10k plus rpm, but were fitted with turbo's which created the torque lost to the increased engine RPM.

And in motorbikes a 1.0 engine will likely rev to 16k in some cases, creating a high HP figure, 150hp+ is possible, but a very low torque figure. But as bikes are very light compared to cars, they don't need torque to accelerate quickly.

Nissan doctor · 27-03-2011 03:27PM

challengemaster wrote: »

Quick example

Ford focus 1.6 (Zetec-SE) has 100bhp
Nissan pulsar VZR n1 1.6 (SR16VE n1) has 197bhp
Civic Si-RII (EK4) 1.6 (B16A4) has 174bhp

To compare to my above point,

Focus 1.6 : Max power, 100hp @ 6000rpm and 107lb/ft of torque
VZR n1 1.6 : Max power, 197hp @ 7800rpm and 133lb/ft of torque
Civic sir 1.6 : Max power, 170hp @ 7800rpm and 116lb/ft of torque.

The civic and pulsar have vastly more power then the focus, but only slightly more torque due to the higher rpm ceiling required to create the power.

Our man in Havana · 27-03-2011 03:31PM

The reason I asked is that in some countries the road tax is assessed on the KW and not the CC.

_Conrad_ · 27-03-2011 03:35PM

Our man in Havana wrote: »

The reason I asked is that in some countries the road tax is assessed on the KW and not the CC.

well it's kind of going by a general idea that the bigger the engine, the more kw you might have i susspose.

Anan1 · 27-03-2011 04:17PM

Max_Damage wrote: »

The only people who measure a car's power in Kilowatts are the French! :pac:

And the Germans..

Matt Simis · 27-03-2011 04:18PM

Anan1 wrote: »

And the Germans..

And the Australians and Canadians. I think all EU is meant to be using KW now.

Break all ties · 27-03-2011 04:27PM

So do the Bulgarians. They don't recognise CC at all, they only want to know the KW for taxing purposes. So if the Irish logbook does not have the KW on it you have to go and get the KW verified so you can register the car. The Irish log book has KW on them but they are not used.

Eric Cartman · 27-03-2011 04:34PM

Our man in Havana wrote: »

The reason I asked is that in some countries the road tax is assessed on the KW and not the CC.

the horror, and not a singe EVO was seen there

shamwari · 27-03-2011 04:39PM

Our man in Havana wrote: »

The reason I asked is that in some countries the road tax is assessed on the KW and not the CC.

That's the same as here years ago when road tax was assessed on horse power rather than capacity.

Anan1 · 27-03-2011 04:52PM

shamwari wrote: »

That's the same as here years ago when road tax was assessed on horse power rather than capacity.

To further complicate matters, 'horsepower' here for tax purposes was based on cc rather than bhp - 8hp was 1000cc, 16hp was 2000cc etc.

CiniO · 28-03-2011 12:35AM

Matt Simis wrote: »

And the Australians and Canadians. I think all EU is meant to be using KW now.

kW (kilowatt) is the SI unit, and obviously it's a standard all over EU.
But when it comes to engine power, BHP is pretty much used over most of EU.

Conor_M1990 · 28-03-2011 04:07AM

KW is aload bollix wouldnt mind it

pajo1981 · 28-03-2011 09:52AM

Conor_M1990 wrote: »

KW is aload bollix wouldnt mind it

Care to elaborate?

coylemj · 28-03-2011 10:30PM

shamwari wrote: »

That's the same as here years ago when road tax was assessed on horse power rather than capacity.

For tax disc purposes 125 c.c. was assumed to be one horsepower regardless of the actual power of the engine so it was based on c.c.

Normally the horsepower number was rounded up e.g. 8.2 horsepower was rated as 9 horsepower for tax purposes but a fraction of less than one tenth of a horsepower was disregarded so at one stage Ford had a 2012 c.c. engine which at 16.096 (2012/125) was rated at 16 hp as the fraction was less than 0.1 hp. Another 1 c.c. would have pushed it up to 17 hp which in the days of accelerating rates per hp would have had a serious effect on the cost of the disc.

coylemj · 28-03-2011 10:37PM

Max_Damage wrote: »

The only people who measure a car's power in Kilowatts are the French! :pac:

Look at your Vehicle Registration Certificate - code P.2 Engine Max. Net Power (kW)

keithclancy · 29-03-2011 07:04AM

Anan1 wrote: »

And the Germans..

The Germans Measure it in PS

The Pferdestärke PS (German translation of horsepower) is a name for a group of similar power measurements used in Germany around the end of the 19th century, all of about one metric horsepower in size

The French are mental, didn't the want a metric clock and calender at one stage

Anan1 · 29-03-2011 09:00AM

keithclancy wrote: »

The Germans Measure it in PS

They do also use ps, but (from memory) the Fahrzeugbrief quotes power in kW. Look at the internal boot sticker of any VAG car and power will be in kW.

pajo1981 · 29-03-2011 09:11AM

keithclancy wrote: »

The Germans Measure it in PS

The French are mental, didn't the want a metric clock and calender at one stage

No keith, mental is using two different units.

Our man in Havana · 29-03-2011 10:16AM

coylemj wrote: »

Look at your Vehicle Registration Certificate - code P.2 Engine Max. Net Power (kW)

That is usually blank. Well it is on mine.

Joe 90 · 29-03-2011 11:03AM

Just to add to the confusion you also had RAC horsepower, related to the size of the engine, but not directly in proportion to the capacity.
The RAC (British) formula for calculating tax horsepower:
$ed52e0dd9d4af62d4b20f230c743d943.png$ where D is the diameter (or bore) of the cylinder in inchesn is the number of cylinders [2]I can rememebr, not all that long ago, when I mentioned to someone that such and such a car had so many bhp that he asked me what was that in normal horsepower.

keithclancy · 29-03-2011 12:41PM

pajo1981 wrote: »

No keith, mental is using two different units.

You've obviously never used a cooking book

Break all ties · 29-03-2011 01:12PM

The problem is that some countries just don't understand CC at all. When I went to tax my car they asked for the engine power. I said it was 1043 cc, they shrugged their shoulders and said "no". So I had to go to a garage and get a certified specification for the engine in KW.

KamiKazi · 29-03-2011 01:34PM

Nissan doctor wrote: »

And in motorbikes a 1.0 engine will likely rev to 16k in some cases, creating a high HP figure, 150hp+ is possible, but a very low torque figure. But as bikes are very light compared to cars, they don't need torque to accelerate quickly.

Not true of Vtwin engines, they don't rev quite as high as the I4 engines but produce ridiculous amounts of torque.

keithclancy · 29-03-2011 01:44PM

Break all ties wrote: »

The problem is that some countries just don't understand CC at all. When I went to tax my car they asked for the engine power. I said it was 1043 cc, they shrugged their shoulders and said "no". So I had to go to a garage and get a certified specification for the engine in KW.

Its written on a sticket in the boot, or on a plate in the engine bay.

Yer man was yanking your chain anyway, could have just looked it up for you from the Plate or chassis number

Nissan doctor · 29-03-2011 02:38PM

KamiKazi wrote: »

Not true of Vtwin engines, they don't rev quite as high as the I4 engines but produce ridiculous amounts of torque.

But there are no v-twin cars so I wouldn't have used that example..

KamiKazi · 29-03-2011 02:58PM

Nissan doctor wrote: »

But there are no v-twin cars so I wouldn't have used that example..

You specifically said in motorbikes, hence my post

Relationship between engine CC and KW output

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