[Kartbuilding] Just a quick note on your engines page

Stephen Burke sburke at burkesys.com
Tue Jan 23 20:00:11 GMT 2007

Hi Daniel,

Thanks for emailing me about that. I dont know how I managed to slip up on 
that. I was always of the mindset that with a 4 stroke engine, in a car, 
there are 4 pistons providing power every rev. BUT - as you pointed out - 
its strokes, and not revolutions!

So yes - a two-stroke engine has a power stroke every rev. And in a 
four-stroke engine, there is a power stroke every 2 revs of the 

I will ammend the website and put an acknowledgement.

Thank you for your interest and comments. If you spot any further pieces, 
or whether you would like to add a piece etc. feel free to email it on.

Best Regards,

On Tue, 23 Jan 2007, daniel wrote:
> Dear Stephen Burke,
> I was looking for the HP to Kilowatt conversion and some other bits and pieces on engines and electrical
> motors in particular, torque and whatnot. I found your page useful. However, while perusing your page, I
> noticed something that I am not too sure about. I hope you don't mind the check...
> You note the following:
>       Two-Stroke
>       Two stroke engines are much more power efficient than four stroke. The only problem is that they
>       use more petrol and have bad exhaust emissions, because they burn oil as well as petrol. However
>       if you have a two-stroke engine then you are in luck. These engines are robust, having no valves
>       they can run much faster and have more acceleration. Another problem with these engines is the
>       problem of burning oil to lubricate the piston and crankcase, making these engines prone to
>       seizures. However as long as you have plenty of blue smoke coming from your engine then you are
>       fine. With these engines expect more acceleration and more power coming out of corners. For
>       every 2 turns of the crankshaft, 1 of them is power.
>       Four-Stroke
>       Not all things are bad if you have these engines. They give good gas mileage ( if that is really
>       important for off-road karting). If you happen to have over head valves then your engine can run
>       pretty fast, but not nearly as fast as two-strokes. However with the correct gearing there is no
>       reason for lacking speed. For every 4 turns of the crankshaft, 1 of them is power.
> However, I think, and I might be wrong, that each stroke of the engine is actually only half a revolution of
> the crankshaft. The stroke refers to the stroke of the piston - down with power, then up in a 2 stroke, so
> each revolution is power in two-stroke.
> The four stroke uses one stroke up (1/2 turn) to clear the exhaust, and another stroke down (1/2 turn) to
> suck in the fuel/air mixture, 1 stroke up to compress, and 1 stroke down as the mixture explodes and the
> piston/shaft receives the power. So that for every second full revolution of the crankshaft, there is power
> (although it is only 1/2 a revolution of power).
> Is this understanding right?
> Take care,
> Daniel DeLury

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