what is the usual IN-Hg VAC at idle?

[Mikael Mikkelsen]

I've actually had a problem finding this online?? Odd as I'd expect it to be a manual sort of question... Oh well,


What is everyone reading for IN-Hg Vac at idle?

I have a boost gauge that doesn't light up (bad light or something, its an "AC" gauge...) It sits at about 10in-hg when not connected to anything.

When powered up it looks to operate ok but I'd like to make sure. So what's the number at idle? What are you guys boosting FROM FACTORY? Like no mods?

[Remi Raymond]

A not-factory new engine should be 18ish at idle (No lower than 16) and cam'd will be anyones guess but typically moving from 12-18.

On decell you should see 24 or so rising to 20 as the rpm steadies.

[Mikael Mikkelsen]

Ok so it is showing me right around 16-20 which is good. But its saying I'm only getting a max of 7-8 psi...

It does suck, like its not much boost feeling, would this be a real reading? Or is it just too low for a stock dsm? I have not removed the solenoid btw

[Remi Raymond]

The solenoid will go into low boost mode as a safety if one of many things are tripped. It's a bit to much to go into detail here, but i'm sure you can find further information on it. 8ish psi is the stock wastegate spring pressure.

The other possibility is just a boost leak and even though the car is trying to run at stock boost, it can't keep the intake system pressurized. Where did you plump your boost gauge?

[Mikael Mikkelsen]

I'm really not worried about leaks, I'm certain I have that under control. Its ran through the steering boot, zam strapped in, no kinks, tied to the intake right near the drivers side on the motor near the window.

So 8 is about right eh... Laaaame


I'm just about to install a controller for it. I think I'm going to run it at 12 for the next week or so, then try to push it to 14 and leave it there



Only one more question...

I have a manual controller, should I start it screwed all the way in first I assume and back it out slowly. Not the other way around.


**edit**

Duh, all the way out. I'm boosting at 10 peaking at 12. No error codes present.

[Shane Sawatzki]

wait stock boost on a dsm? isnt that like 12 psi? 

[Mikael Mikkelsen]

only the 1g's

[Zach Holt]

I tossed arm in my stock 1ga with 14b blah blah blah. And it was 12.4psi pushing hard on the dyno.

212 hp at 12.4 psi. anyways ya that's stock boost


Ps watch your self. Wideband is now your best friend.

[Mikael Mikkelsen]

Oh, I hope I don't throw an arm. I don't run the car very hard, but its seriously batting 1000 rite now (ya a dsm)

Wideband will be the next one. I plan on 5. 3 on the a-pillar and 2 in that awesome dash pack.

So far I have water temp - oil press - boost

Plan on wideband + ext temp for the front.

Eventually I've always wanted to replace an entire cluster with real and good gauges. One thing I hate about our cars is the dash, I've driven 94 tempo's with a nicer looking cluster

[Brett Haviland]

and zach... that 12psi of boost... you had full exhuast correct?

adding full exhuast from turbo back will cause it to creep a bit. 

i know 100% stock including the exhuast and  stock boost controller hooked up properly it will boost around 10-11 psi

If you run a vac line strait to the wastegate, bypassing the stock boost controller then it will run more like 8-9 psi.  this is on a 14b im talking about... you have a T25...  not sure what they boost like stock on a 2G.  Im a 1G guy

[Remi Raymond]

Yeah the stock 1g wastegate is set for 8psi. Pretty sure the T25 is the same.
The stock car will run higher than that because it has a boost control solenoid, as I said above it goes to 8psi if it's in fail safe mode which is caused by about 50 different possible triggers. You will also run higher than that with some modifications like a free flowing exhaust.

[Mikael Mikkelsen]

I'm getting a solid -22 in-hg now at idle

is that too low? good/bad? fix? any ideas?

[Remi Raymond]

On a stock engine?

[Mikael Mikkelsen]

Stock internals and turbo
Yea...

[John Hartman]

if its warm and at 750rpm, thats totally excellent idle vacuum.