vacuum gauge, what line to tap into?

[RadeOn]

I'm finally installing gauges I got a while ago, so I'm wondering what vacuum line to tap into? I tried a line coming right from the top of intake manifold, and that sucked, since this was an EGR line and readings after few minutes of driving were starting to jump up and down within 10 inHg, useless and very annoying.
And I don't line the idea of tapping into brake booster line. What are my other good options?
PCV system?
Thanks guys.

[Wiscon_Mark]

PCV would be easy enough to tap into.

[RadeOn]

Yeah, but that's pretty far from manifold. Either through pcv valve which is not always open, or through intake duct, where the pressure is probably higher.

[Wiscon_Mark]

Yeah, but that's pretty far from manifold. Either through pcv valve which is not always open, or through intake duct, where the pressure is probably higher.

huh? PCV line goes directly into the manifold! And it's open anytime there's vacuum (provided it's working properly). You'd be surprised how much air gets sucked through the PCV line, I certainly was when I ran seafoam through it.

For reference, so we're on the same page:
https://sl-i.net/FORUM/images/imported/2005/11/PCVValvePic-1.jpg

[RadeOn]

I know where pcv valve is. I am not 100% sure the valve is open all the time when the engine is running.
PCV valv at least restricts the air flow at idle, and possibly when the vacuum is high.

[Wiscon_Mark]

The valve simply opens when there is vacuum. I'd assume it's on whenever the engine is on. Somebody that knows more about this system want to confirm/deny that?

[RadeOn]

Valve restricts flow at idle to let the IAC valve do its work. Since its mechanical it also restricts flow at high vaccum. At least that's what my Haynes manual says.
Anyway, I did not find any suitable place other than brake booster line, so I'll just have to live with that :)

[Wiscon_Mark]

So you've got it hooked up?

I really didn't think the PCV was very complicated...just seems like a simple valve that opens up when vacuum is present.

[backpack09]

...Brake booster is proabably a bad place to be introduceing a possible leak.

Is the fuel pressure regulator vacuum controlled? That is where I tap for boost gauges on turbo cars.

[RadeOn]

...Brake booster is proabably a bad place to be introduceing a possible leak.

Yeah, that's why I don't like it.
Is the fuel pressure regulator vacuum controlled? That is where I tap for boost gauges on turbo cars.[/quote]
Yeah, it is vacuum controlled, forgot about that option, thanks

I though that on turbo cars people usually use BOV line?

[RadeOn]

...Brake booster is proabably a bad place to be introduceing a possible leak.

Yeah, that's why I don't like it.

Is the fuel pressure regulator vacuum controlled? That is where I tap for boost gauges on turbo cars.
Yeah, it is vacuum controlled, forgot about that option, thanks

I though that on turbo cars people usually use BOV line?

[backpack09]

Actually the vacuum line to the FPR is a good place to tap. On most turbo cars the FPR adjusts fuel pressure based on engine vacuum or boost.

BOV line on a turbo car is generally bad, because it tends to be farther from the manifold, giving a different pressure reading.

[RadeOn]

So this is the FPR, right?
http://daniil.manaenkov.googlepages.com/IMAGE_00001.jpg
It sits on the fuel rail on the passenger side. And there are two rubber lines coming off it - not clamped one (#1) and clamped one (#2). (#1) attaches to a metal line and both then go somewhere under the manifold.
I take it the vacuum line is the one that is not clamped, right?

[TRUBLU]

make your tee connection right the first time and it won't be an issue. Every vacumn gauge I've used has been through the brake line and never once have I ran into trouble with it.

[jlk2.5gt]

i agree with the brake booster option,any dealer that performs a "intake cleaning" service uses the vacume line at the brake booster because it is true unrestricted vacume pressure.

[RadeOn]

Do not go to that dealer any more :)
BB line is not a good choice for intake cleaners. PCV valve or EGR line are much better.

On the subj - I ended up T-ing into line going to stock manifold pressure sensor. It seems to have a restrictor along the line, so the gauge does not rattle as it did at all other locations (FPR, BB line, EGR line), but moves smoothly.

[jlk2.5gt]

I have performed many an intake cleaning service using the "i.v." bag style intake cleaner and using the brake booster line is a good place to introduce cleaner because its before the egr valve in the vacume circuit and will therefore clean the inlet side of the egr valve. And i am referring to cleaning, those spots you mentioined are probally better for gauge sensor placement.

[backpack09]

Yes, but the cleaner can also eat through the diaphram inside of your Booster.

[RadeOn]

BB line is bad for cleaning because it is off center, that's all.

[TRUBLU]

off centre? they are all off centre. The only place you could use those cleaners and get it on centre is giong in throigh the plastic air intake. The PCV is way off centre. In Reality, it really doesn't matter. It's called vacumm for a reason. It sucks the shit EVERYWHERE.

[jlk2.5gt]

True. true.

[jlk2.5gt]

True. true.