Hi Olin, sorry I didn't give detail info. it's 4 cylinder engine standard old 40 yea= rs=20 old vw bug car. I have been told measuring from sensor side I should get 133hz @ 8000 rpm but the way I see it 8000rpm/60 thats 133hz for each cylinder that means I = need=20 to x 4 to get sensor side value am I right? AA ________________________________ From: Olin Lathrop To: Microcontroller discussion list - Public. Sent: Mon, March 7, 2011 9:56:25 AM Subject: Re: VW engine RPM question Andre Abelian wrote: > There is some thing I do not clearly understand about VW battle > engine. What equipment does this enging go in? > the rotor has 4 magnets on it and the board has > 1 hall effect sensor with none latch version so each magnet will > control each cylinder. How many cylinders? Rember that only half fire in any one revolution, at least if this is a two stroke gasoline engine. > lets say 8000 engine RPM OK. > I divide by 60 to get the frequency 8000/60=3D133.33 Where to begin. First 8000 RPM is a frequency. Second, 133.33 is clearly not a frequency since frequency has units of 1/time. What you apparently mean is 133Hz. Pay attention to details. They matter. If the engine speed is 133Hz and it is a two-stroke engine, then each cylinder fires at a rate of 67Hz. > my question is witch one is correct 133.33 or 533.33 > my understanding is it should be 533.33 Again, none of these are correct as should be obvious since they aren't in units of 1/time. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .