high lifted cam / presure

[Ä‘uro]

I just want to ask, when y. put high lifted cam in y. car, pressure on boost gauge will drop down.

So does this mean car won't hv so much power as would get in the atmospheric engine when changing the cam shaft, or engine power will rise (for certain amount), even pressure gauge show less presure?

Tks
Damjan

[hayesey]

I've already answered this once in your other thread!  The reading on the boost gauge is only measuring the back pressure inside the inlet manifold not the pressure inside the actual engine.

There could be two reasons for what you are seeing, one is that the engine is flowing more air so less back pressure is seen in in the inlet manifold - this is good it means the engine is consuming more air which is the whole point of engine tuning.

The other reason is that you have an unsuitable camshaft fitted and the air pressure is simply escaping through the exhaust because of too much overlap (where both inlet and exhaust valves are open at once).  A bit of overlap is good for exhaust gas scavenging (getting rid of all the exhaust gas in the cylinder so there's as much room as possible for fresh air and fuel mixture).  But too much overlap on a forced induction engine means you are just losing boost through the exhaust.

The only way to know if you are making more power or not is to go on a rolling road.

Are you using a 268/268 cam with a G-Lader?  If so then it's not really suitable, you need something like a 252/276 (the schrick cam for a g40).

[Ä‘uro]

Hi Paul,

No, not any more the car was totaly "dead" only in middle section was raning good. so for now I decide to put standard cam.

bt my Q was when (let say 252/276) high lift cam will be in, will I hv more power even pressure will be lower?

[hayesey]

you should yes