If there was anyone interested enough to try the worksheet? My post âFor the weekendâ this attachment may help; Iâve rewritten it for MS Works, a more common Spreadsheet. Itâs quite safe to RUN.
Those of us with twin cylinder engines could also carry out a rough CAM timing check using it. We realise of course! When we check the ignition timing, theothercylinder is on the exhaust stroke, if the inlet valve is checked, it will have started to open, remember valve overlap. At this point we are too far ahead of most cam-timing checkpoints. Find the point where the inlet valve just starts to open, now this is much easier said than done, this method is notoriously difficult, especially on cams with QRâs. Now measure the position of piston (as ignition). Enter this into the âActual measurementâ cell, the âTiming set atâ cell, will then give the cam point in degrees. A 99 cam would give at 50 Deg BTDC 16.2mm. A 650 should be 17.8mm. below the TDC measurement. On single cylinder machines I think the open exhaust valve will be in the way. Ron C.
Hi Ron. I have opened up y…
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Hello Les, Your assumption…
Hello Les, Your assumption are correct, It was aimed at owners that use a plughole gauge for ignition timing, 1st post, to give an idea of error in their final setting. Finding TDC is simplicity itself with this type of gauge and the cam degree check should be with in the range of their gauge. Time and others will decide on the merits or otherwise of this rough checking idea.
Ron.
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Hi Ron.
I have opened up your calculator.
As far as I can make out from what you are saying is that your calculator can provideone withthe engine's VALVE/CAM TIMING by measuring the piston position in the borerelative to TDC...am I right?
If this is the correct assumption, I cannot see how this method is anymore simpler than doing it conventionally with a degree disc as the difficult part is, as you stress,actually knowing the point at which the valve starts to open or close. You say yourself thisis always "notoriously difficult" but with this method,you still has to find this position and then you ALSO have to add another difficult to do measurement, requiring amethod of measuring the EXACT position of the piston down from TDC...not as easy as you might first imagine if real accuracy is required.
Using the conventional timing disc method, at this same point that you have ascertained the exact point of valve opening, you will mearly have to read off the angle from the disc....job done.
Setting the discEXACTLY to TDC is a VERY simple exercise if one uses the piston stop method either side of TDC and halving the angle.
The only advantage with your calculator method is that you will not have to fit the timing disc onto the engine shaft, but I would imagine the only time you would be wanting to find the valve timing is when you have the engine in an assembly state anyway.
Perhaps I have missed the point with it Ron? If so I look forward to more explanations of it's use.
Best regards.
Les H