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Q: Backfire

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Hello i have a serious backfire issue and here are the points. Checked timing Checked carburator cleaning and synchronisation. New sparkplugs New fresh petrol Good petrol pump Very high compression of 11.

Good stationary running but when i increase around 2500 rpm the engine backfires and doesn't come trough to higher rev's. Driving is nearly impossible.

1/ is the very high compression a possible cause 2/ cdi ignition is not working but on stroboscope measuring it seems working well 3/ a petronic is installed to replace the points

I'm scared the high pressure is the cause and means I have to rebuild the engine.

Would be great to hear an experts opinion

My car has 9999999 miles.
My car has a manual transmission.

Hi there;

In most cases a backfire issue occurs because the air to fuel ratio is too rich, the timing is off (which you’ve checked) or the spark plug tips have excess carbon build-up (which you’ve also replaced). Typically when compression is high, ignition timing is retarded or advanced to ensure optimal engine performance. Without being there to examine your engine with the stroboscope, it’s hard to tell you exactly where timing should be set. I’d reach out to a local mechanic with experience with smaller, high performance engines or with Porsche certified technician for those timing recommendations. Cheers and good luck.

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