What is vacuum at idle?
What is vacuum at idle?
Idle Vacuum is the intake manifold vacuum when the engine is idling. The higher the vacuum, the more closed the throttle plates and the lower the amount of air and fuel required to keep the engine running an no load. Idle Vacuum is is a measure of how well the engine can idle.
Why is vacuum high at idle?
If vacuum drops intermittently at idle, one or more valves may be sticking open or dragging. Higher-than-normal vacuum at idle is a common clue to overly advanced ignition timing, while low vacuum can indicate retarded timing. Low vacuum also can be an immediate clue to a plugged exhaust.
What is the idle speed of a vacuum?
In terms of idle quality, this simple move from ported to manifold vacuum increased the idle vacuum in Neutral 2 inches from 13 to 15 inches Hg, and the in-gear idle vacuum is much more stable at nearly 10 inches Hg. Idle speed now is 850 rpm in gear and jumps to 975 in Neutral because of the tight torque converter.
When do you lose the vacuum in a Camaro?
The magic figure is around 230 degrees duration at .050. That is when you start to lose a substancial amount of necessary engine vaccum. Valve lift can play a role too, but cam duration is by far the biggest factor. Power brakes generally require between 14 and 17 inches of vaccum at idle to work properly.
What does it mean when your engine vacuum is low?
Normal Engine: On most engines, accelerate to around 2000 rpm and then quickly release the throttle. The engine should snap right back to a steady 17- 21″hg vacuum. Steady low between 5-10″hg vacuum: This indicates that the engine has a leak in the intake manifold or the intake gasket.
What should the timing be on a vacuum engine?
We know this because the engine idled at 13 inches of manifold vacuum in Park but dropped to barely 8 inches of vacuum in gear, and it tended to surge and misfire at idle in gear. We initially set this combo with 16 degrees of initial timing with 18 degrees of mechanical advance that put the total mechanical at 34 degrees at 2,800 rpm.
