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Finding TDC of Rotary without marks on Pulley

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Trying to find out if there is any clever way of finding TDC on a rotor. I know there should be timing marks on the pulleys, but these are not on the installed pulleys. So, I have used a TDC finder with reasonable success, also used the keyway behind the pulley for extra comfort.

Problem is both mechanism are not dead accurate, they have got me in the ballpark, so I was wondering if there was anything I can use from ECU to determine if by retarding or advancing during during calibration if I am moving away/towards TDC, and if there are any tell tale signs of going past TDC at idle.

ECU I am using is Link Extreme, car runs and idles.

Also, if this is a stupid question, then by all means say so!

Thanks - James

There's no such thing as a stupid question James!

Finding TDC on any engine is a mechanical aspect of the engine and you can't do this with the ECU. Unfortunately I don't build rotary engines so I can't give you a technique to find true TDC. I'd always be suspicious however of any aftermarket pulley and always confirm then markings based of a factory pulley.

Hi James

Attached photo shows TDC in a rotary.

Not sure what series engine you have but the accuracy of the timing marks on the factory pulleys can vary quite a bit.

Best solution is to have your pulley checked on a disassembled engine (of the same series as yours) that is set to TDC as per the photo and have it remarked if necessary.

Rotary engines are very intollerent of excess timing. In my opinion the varience in timing marks on rotary engines along with timing drift from the factory CAS (I recommend switching to a crank trigger if you have a CAS) are a big factor in many engine failures.

Attached Files

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