piston blow-by flow rates

srtames · Oct 14th, 2002, 15:40

My 340 has a lot of crancase pressure when idling ,noticed by removing oil filler cap . I have measured it with a rotameter flow meter at 7 litres per minute but do not know what it should be.
The only figure I can find is for diesel engines which they quote 27 litres per minute . Any body got any rough figure for petrol engines in general.
The cylinder pessures are all in spec at 160 psi but blow-by rates is a better test for worn rings.

Thanks, Steve

pettaw · Oct 15th, 2002, 09:19

I'm sorry I don't have any figures for that, but IMO you should be getting air drawn IN through the filler cap if all is in order with the PCV system. Maybe there is a block somewhere. Check and clean.

Sorry I can't be more help.

Andy

sheerwater · Oct 29th, 2002, 23:39

I agree with the above. 27 litres per minute for a diesel though?? Thats a litre every 2 seconds which is one hell of a volume of gas for any ventilation system to deal with on the tiny orifice on a manifold. Cheers Nige

Oct 14th, 2002, 15:40	#1
srtames Member Last Online: Jun 16th, 2020 17:21 Join Date: Jan 1970 Location: reading	piston blow-by flow rates My 340 has a lot of crancase pressure when idling ,noticed by removing oil filler cap . I have measured it with a rotameter flow meter at 7 litres per minute but do not know what it should be. The only figure I can find is for diesel engines which they quote 27 litres per minute . Any body got any rough figure for petrol engines in general. The cylinder pessures are all in spec at 160 psi but blow-by rates is a better test for worn rings. Thanks, Steve

Oct 15th, 2002, 09:19	#2
pettaw Forum Support Team Last Online: Jul 23rd, 2023 15:29 Join Date: Jan 1970 Location: Glasgow, London	RE: piston blow-by flow rates I'm sorry I don't have any figures for that, but IMO you should be getting air drawn IN through the filler cap if all is in order with the PCV system. Maybe there is a block somewhere. Check and clean. Sorry I can't be more help. Andy

Oct 29th, 2002, 23:39	#3
sheerwater Master Member Last Online: Feb 24th, 2019 17:59 Join Date: Dec 2001 Location: Northampton	RE: piston blow-by flow rates I agree with the above. 27 litres per minute for a diesel though?? Thats a litre every 2 seconds which is one hell of a volume of gas for any ventilation system to deal with on the tiny orifice on a manifold. Cheers Nige

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