Boost Gauge Reading?

[88jspec]

I just installed a swoosh sa58 boost gauge. Connection is at the rear of intake nipple. At idle it reads -10 vac, and when i press the throttle the needle moves up. Really not sure if this is correct, i thought the needle should be at zero (idle) and only move when boost kicked in.
Thanks for all input....

[NewWestSupras]

That sounds right, mine reads a vacuum situation during normal ops as well. Only when it's making positive boost should it go above zero. Ymmv, but I think it's ok. gl.

[tbcmorris]

Your car should always pull vaccum at idle. Your boost gauge should read neg something at idle, then when you hit the gas jump to zer, and from there move into positive numbers as you pressure the intake manifold.

[rayall01]

I just installed a swoosh sa58 boost gauge. Connection is at the rear of intake nipple. At idle it reads -10 vac, and when i press the throttle the needle moves up. Really not sure if this is correct, i thought the needle should be at zero (idle) and only move when boost kicked in.
Thanks for all input....

Seems a little low for vacuum at idle, you sure you don't have a vacuum leak? My boost gauge reads -15 at idle.

[sneakypete]

it depends on the units the gauge reads. it could be in kpa

[rayall01]

it depends on the units the gauge reads. it could be in kpa

True, I overlooked that possibility. I stand chastised.

[RazoE]

I'm at -20 vacuum at idle, -30 when I leave it in gear and let the engine slow the car down...

is there such a thing as too much vacuum..?

[89jdmsupra]

mine is at -20 and doesn't go passed zero and i here turbo spooling soory if i jacked the thread.

[tbcmorris]

I'm at -20 vacuum at idle, -30 when I leave it in gear and let the engine slow the car down...

is there such a thing as too much vacuum..?


no. mine ran 25 at idle 30 during engine braking. you want the make vaccum at idle. think of tuning a carb.

[2jz88mk3]

At idle it reads -10 vac, and when i press the throttle the needle moves up.

How much does it move up?


Your car should always pull vaccum at idle. Your boost gauge should read neg something at idle, then when you hit the gas jump to zero, and from there move into positive numbers as you pressure the intake manifold.

Like morris says, it should be a hair under zero (at WOT) until your turbo makes pressure. Until then you're drawing air in which is always a state of vaccum. A few ram air designs I read about made + 0.1 or something at highway speeds. Doesn't sound like alot, but a non boosted engine never sees 0 afaik.

If you have excessive vaccum at WOT, something maybe restricting your breathing.

As for regular driving, vaccum is a decent gauge of engine load.

[88jspec]

Thanks everyone that is a sigh of relief..... i feel so much better...