Excessive Vacume..

[TSIsean]

I've got a 1990 TSI AWD with 2.5" I/C pipeing with spearco fmic and rfl bov....

my vacume gauge reads 21, and sometimes when im breaking its all the way up to 25-26 then when i stop completely its back to 21 or even a little higher,,, i heard for 1G's its suposed to be around 18..

any ideas why it does this? and it only goes up to 25-26 SOMETIMES and only when im brakeing....

my boost is set to 16psi...

 

[Enigma_Man]

It's normal. Those numbers aren't outside the range of normal, and the gauges aren't that accurate anyway.

The reason why your vacuum is less when idling than engine braking is because when idling, the throttle is open slightly (the Idle Controller is open, not the throttle plate, but I'm calling that all "throttle") so it's letting some air in, reducing the vacuum so the engine doesn't stall out.

When you're engine braking, the ISC and throttle are both shut tight. This is because if you're engine braking, you don't want any throttle, because you're trying to slow down. It saves on gas, and makes you slow quicker.

-Jesse

 

[my95tsi]

Thats not excessive vacuum. I thought you would say 30 or more.

 

[TSIsean]

Thanks for the help...
at least i know whats going on now...

aslo my ISC is busted... if that had anything to do with it...