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Low vaccuum reading

Joined
16 January 2008
Messages
675
Location
tx
I have 91 with 73xxx miles with apx turbo kit running 7 psi. The car runs perfectly normal, smooth idle and everything, no burn oil, no smoke, check catch can don't see any sign neither. Two days ago I noticed the car only pull -10 at idle it seems too low for nsx motor, highest is -13 then goes back to -10. I'm gonna do leak down test when I have time. Any idea what wrong with it? Burn valve? Worn piston ring? Vaccuum leak? Thanks
 
I have 91 with 73xxx miles with apx turbo kit running 7 psi. The car runs perfectly normal, smooth idle and everything, no burn oil, no smoke, check catch can don't see any sign neither. Two days ago I noticed the car only pull -10 at idle it seems too low for nsx motor, highest is -13 then goes back to -10. I'm gonna do leak down test when I have time. Any idea what wrong with it? Burn valve? Worn piston ring? Vaccuum leak? Thanks



Not sure what technical reference you are suing to state that -10 is too low. Care to share? Mine with CTSC/Auorotor runs "around" that -10 too at idle.
 
Mine is between -19 and -20 at idle.
 
Low vaccuum at idle means something wrong with the motor like timing off, stick valves, worn piston rings, vaccuum leaks or u run very aggressive cams with a lot over lap. Late last night i can't sleep ( keep thinking what wrong with the motor cause the car doesn't drive any different, losing power or smoke). So I hook up the old dual blitz turbo time I had and it shows -48 cmHg at idle which is -20 inhg so I need to check my aem serial gauge. But I'm glad that the motor still healthy
 
Can also be a boost leak somewhere. Need to verify all possible sources of vacuum/boost leaks are sealed fully. In another words, do a boost leak test. If that checks out, then start looking at your motor, not the other way around.

Oh, and in general, most cars sit around -20 +/- in full vacuum.
 
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Not sure what technical reference you are suing to state that -10 is too low. Care to share? Mine with CTSC/Auorotor runs "around" that -10 too at idle.

Might depend on the frame of reference of the gauge, e.g. absolute or gauge? A vacuum has an absolute pressure of 0 inHg, and ambient at sea level is about 30 inHg. But gauges are often scaled to read 0 at ambient and -30 at complete vacuum (or sometimes +30). A 10 inHg gauge reading is the same as a -20 inHg absolute reading.
 
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