Engine theory - I have a question...
Turbo Mini Forums

Hi!

I've got a question I'm not sure I can awnser myself...

Let'S assume, we have two petrol 4-stroke engines. A 2.0 four cylinder, and a 2.0 six cylinder. Lets further assume, the engines are as identical as possible, resp. can draw the exact same amount of air in a set time. So that the only difference would be, that the six cylinder engine has more ignition strokes per revolutions.

Would the engines produce the same amount power, or would the six cylinder produce more?

Thanks!

Regards,
Jan

PS: this is potentially a realy stupid question, please be gentle with me :)

[X] nail here for new monitor

Same - as near as fuck is to swearing. Too many variables to ever try in practice. Friction, cooling etc etc

Think 1970s F1 engines - all 3 litres but split between 8 and 12 cylinder versions.
The 12s produced more power but less torque, the 8s burnt less fuel.

If your theoretical engines did indeed burn the same amount of air/fuel in the same time, then they would by default have produced the same amount of energy.

Metric is for people who can't do fractions.

Yes, purely theoretical. So power delivery would be just a tad 'smoother' on the six cylinder, probably... And I forgott what I wanted to write as I can't keep my eyes of your avatar

Thanks! :)

[X] nail here for new monitor

Never mind the avatar, just imagine how nasty it was watching four scantily clad young ladies crawl all over my car all day...

Metric is for people who can't do fractions.

In theory- wouldn't the engine with more cylinders have more frictional losses, but with more cylinders firing per revolution it would save a little energy because the crank would be spinning at a more even speed, (with regard to slowing down between firing, which is negligible).

There must be some science there- as all exotics have 12 cylinders, but there are still a lot of cars with big bhp 4 or 6 pots. (Turbo'd albeit).

And yes some bigger pics of your avatar would be appreciated!

www.topcatcustom.co.uk

Also a six sylinder is in perfect natural balance....

Bigger pics of my avatar are available at www.nuts.co.uk - search for Rosie Jones, Holly Peers, India Reynolds and Lacey Banghard.
There is video too...

Metric is for people who can't do fractions.

Edited by Asphalt on 14th Dec, 2012.

[X] nail here for new monitor

I find it funny how BMW's head office in Munich is only four cylinders, when BMW is synonymous with six cylinders Perhaps they fell short on the budget......

The S14 is a peach

I'll never go back to a 4 cyl every day car either....

I've ruined myself by buying an MG ZT-T 260...

After 4.6 litres of Mustang V8, the only way up is to get a Dodge Challenger.

Metric is for people who can't do fractions.

Well, mine is golden and poo brown inside

http://jan-wulf.de/wp-content/uploads/2012/10/alt2.jpg
http://jan-wulf.de/wp-content/uploads/2012/10/alt3.jpg

3l straight six - I use it to commute

[X] nail here for new monitor

I miss my m57. The 6 cyl lumps are much better that the n47 4 pot I have now.

In fact I miss the engine.. Just not the car

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Personally I find 5 the perfect number. Although I have never owned more than 4.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I always had it in my head that more cylinders equaled more power. But I can't remember the maths.

Something to do with surface area

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

On 14th Dec, 2012 t@z said:

On 14th Dec, 2012 Alex said:
Never mind the avatar, just imagine how nasty it was watching four scantily clad young ladies crawl all over my car all day...

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

more cylinders = more possible valve area = more power

for a theoratical 2 liter engine with either 4 or 6 cylinder layout, with stroke corrected to make the engine square, you have 15% more valve area in the 6.
You do lose some power on friction but gain some in rpm potential

Rusty by nature

As most engines with loads of cylinders seem to like to rev, I'm assuming this is because they make them over-square (increasing valve size as well), taking advantage of the possible increase in valve area by utilising high revs that you can get from an over square engine.

Edit: Thinking about it, you wouldn't have to change the bore:stroke ratio to achieve a higher engine speed with more cylinders, as by keeping the same ratio the bore diameter and stroke would both have to decrease to keep volume constant, while increasing valve area. This would create an engine that would favour higher speeds, but would be worse at lower speeds due to lower torque (from shorter stroke) and worse fuel economy (larger surface area to lose heat, lost heat = wasted energy).

Edited by jakejakejake1 on 4th Jan, 2013.