Vacuum at idle
01-21-2013, 01:15 AM
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Vacuum at idle What is the standard vacuum at idle. Mine is 30Kpa or around 9 inhg. Anyone know whats normal and why some people claim 60kpa at idle? My car is almost stock.
01-21-2013, 01:45 AM
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So what is normal vacuum then? I don't think I have a leak because I seem to have an increase in vacuum not a decrease. A leak puts it closer to atmospheric which is 14.7psi which is 101kpa...so anything below that is vacuum. I have heard 60kpa but mine is 30kpa... thats twice as much.
01-21-2013, 10:48 AM
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18-22" is usually the norm for a stock cam in a properly tuned/proper running stock engine. 9" is far too low for a stock cam, and would suggest a cam with considerable overlap, or a vacuum leak or leak and tuning issue combined.
Even with a small cam I was able to get 14" out of an LS1 at idle. Stock should be considerably higher, but I don't recall the exact figure that I've seen before. 18-22" is a standard normal stock reading though.
Even with a small cam I was able to get 14" out of an LS1 at idle. Stock should be considerably higher, but I don't recall the exact figure that I've seen before. 18-22" is a standard normal stock reading though.
01-22-2013, 04:31 AM
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That is map pressure which is a representation of vacuum because it is less then atmospheric pressure which is 101kpa. So when I turn on my car my map reads around 29-30kpa.
01-22-2013, 12:59 PM
#7
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VAC = BARO - MAP
so you see 30 kPa MAP (71 kPa VAC) when engine runs at idle...
if you see 30 kPa at idle on the stock cam, then you have very good compression/sealing.
so you see 30 kPa MAP (71 kPa VAC) when engine runs at idle...
if you see 30 kPa at idle on the stock cam, then you have very good compression/sealing.
