are these cars supposed to not spool when there is no load? my gauge doesnt go up unless its under a load. maybe its spooling just the guage cant read unless theres a load...i have no idea...just curious.


-Matt

 

The stock boost gauge is BS. The turbo is always spinning, but its going to be in vaccuum until you give it enough load. The gauge is useless.

 

I have found the same thing... when my clutch was slipping like a bitch, I got no boost... now I have the new clutch, it was quite a wake up call...

I just figured it was something to do with pushing a larger quantity of exhaust gases thru the turbo when the motor was under load, as opposed to the amount of exhaust the motor produces when not under load... (you hardly want your turbo spooling in idle...)

perhaps the waste gate stays open until a certain injector duty cycle or something...?

guru's?

 

yeah i know how the turbo works i was just wondering about the guage...thats kinda what i figured though

 

That's perfectly normal. The stock boost gauge only reads down to 200mmHg vacuum, but in normal driving it's much lower than that unless you're accelerating or climbing a hill. Cruising vac will be 250-300mmHg, so the gauge will stay at the bottom of the scale until you open the trottle a bit more.

If you have any plans to modify your engine the first thing you should buy is a decent aftermarket boost gauge. Not only will it give you a proper scale that you can read boost pressures off, it will also have a full vacuum scale so you'll know manifold pressure under all conditions.

 

you shouldnt really be revving your motor while not under load anyway, but my car makes about 3-4 psi it i give it a good rev in neutral

 

Technically, the turbo doesn't make "boost" with no load or a pressure differential over the turbo wheels.

Yes, you can get some boost just by revving it, but we're talking about revving it close up to redline.


-Ted

 

All you need to make boost is airflow though the engine and turbo, and that comes from revs and an open throttle. "Load" is simply any resistance that slows the rate that revs rise and hence allows you to control engine speed. The pressure difference Ted speaks of is just a result of that airflow. The problem with revving in neutral is that if you floor it the engine reaches redline before the turbo gets up to full speed, so depending on mods and the health of your turbo, only a small amount of boost is generated, or none. This is why engines tend to make more boost in higher gears. The turbo has more time between gearchances to speed up.