So i'm new to the tuning scene and would like to know which area of the map is the 'vacuum' part? I'm doing research on street tuning ignition and would like to know. Also how do you tune this part on a turbo car on the street? I know dyno is the best place to tune ignition but for knowledge i would like to know. Thanks in advance.

 

Anywhere on the map where manifold pressure is less than atmospheric is vacuum to some degree.

 

Vac is less than 1000mbar. Over that is pressure.

Ignition is influenced by crank/rod/piston to valve/camshaft timing. Have you modified any of these?

If not, stock timing is fine.

 

1000mbar is 1bar, which is atmosphere. if you're new to tuning, read the manual in my signature.

 

suppose for a turbo car at high speed cruising say you're at 5000 rpm at low load. Wouldn't the turbo be somewhat spooling? And wouldn't i have to reduce stock timing to some extent?

 

yea thanks i read some of it. Will print it out to read over again. Great manual it is thanks.

 

No.

I have a small turbo. Unless you are into the throttle for accel, it won't ride pressure while cruise. No worries.

Timing won't change, just air-fuel ratio.

Within pressure, yes, drop timing, but any tuning program that sets up boost will recommend a retardation policy such as 1degree per psi.

Turbo makes cruise like riding a bike down a slight slope, timing when to push down in the crank rotation won't change, it just won't be trying as hard to pull air into the chambers as it gets stuffed.

 

Think about what you're asking... If you were making boost, you wouldn't be in the vacuum range of the tables, would you?

There is the issue of increased backpressure and reversion at low loads, but that's another discussion.

 

Thanks for the replies. That clears out some of my confusion.