On Thu, 30 Nov 1995, U. Goettsch wrote:
> On Thu, 30 Nov 1995, Frank van Dalen wrote:
>
> > I think you got it wrong John...
> >
> > Each piston has combustion once every 4 strokes of 180 degrees, ie once
>every
> > two crankshaft revolutions. If there was a knock from one piston/rod, you
>would
> > hear it 500 times per minute at 1000 RPM, ie 500/60 = 8.33 times per second.
> > The camshaft goes round at half the speed of the crankshaft, 4.17 a second,
> > which is the frequency of the knock in question. Or have I gone mad?
>
> Mad, no, but read your post again - you contradicted yourself.
> cam = crank / 2, yes, but crank is 1000, not 500!
> => both rod knock and cam knock are 8 times per sec!
>
I'll grant you that I screwed up and ignition should occur in a cylinder
once every 2 crank cycles.
I'll even grant you that cam RPM is half of crank RPM. This makes sense
since the distributor fires a spark off for each cylinder as the rotor
goes around. If cam shaft RPM is 1/2 crank RPM this would correspond
with the previous paragraph.
I'll finally grant to you that I shouldn't have tried to answer this
question this week.
I still think it's a rod knock on one cylinder. The sound of a rod knock
can range from 'tick' up to YEEECATS!!!
Oh, now that I understand how RPM works in a 4/4 piston car, can you tell
me how it works in my RX7? <grin>
John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire E Stock | '88 RX-7 C Stock
Home Page: http://www.widomaker.com/~trindle
"Remember, no matter where you go.... there you are. - Buckaroo Banzai"
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