Nordicflame

What does your boost gauge read at 3500 rpm cruise?
Boost or Vacuum?
This is assuming your gauge is in the manifold.
Thanks

Mrgoodwrench

I can play with the throttle right around this rpm range and get 0 to 3 psi.

Turbojack

In the manifold pressure is about 0, in box before carbs is about 4psi. I think I have to be about 4k before motor starts to be in boost. This last summer I ran it up & recorded all the reading but by the time I got home I had lost the sheet we recorded the info on.

Kanookstr

at 3500 rpm cruise, I am reading 2-3 inches Vacuum. I am at "0" around 4000rpm cruise

PIERFECT

At 4000 RPM about zero boost. Other variables probably come in to play though. Like what size pulley, which determines turbo charger RPM, and therefor affects boost or vacuuuuuuum relative to engine RPM. Why do you ask?

P29 SCARAB

AT 3500 I READ -2 TO 0 ON EFI 383 TWINS.
STEVE

HPJunkie

I read about 0 at 3000 then it climbs up .

Pure Energy

3500 RPM reads 0 from the manifold. I do not get boost till 4000 RPM,

Nordicflame

Thanks Guys,
it appears then that even though the blower is making boost at cruise, the intake is not seeing it unless you are hammering the throttle blades wide open.
Reason I asked is I'm working on a timing curve for my F.A.S.T. ECU and am trying to confirm what's happening there. I'm thinking I can run 35 degress at 3500 at easy cruise and no boost in the manifold but when the manifold (MAP sensor) reads boost/heavy load at 3500 I can run 30 degrees.
Just doing a little preliminary studying
Later,
Dave

Turbojack

Is your system going to have a knock sensor? If so I would say you could run that much timing. You have to remember that just because your motor is not in boost it is still under heavy load. The way I compare it is just think of the motor as a N/A motor. When it goes to "0" vacuum motor is under heavy load. When I had my turbo setup I had the timing set so it would retard when ever motor would see boost.