Negative Boost Number @ Idle

[StevoHemi 113]

My boost gauge has been not working since last year. My fault.... when installing my Trans Temp gauge in the triple pod A pillar last year , the nylon hose to the Boost gauge got pinched. I admit it..... been lazy and not shown much interest in the RT this year. I have the Magnuson Supercharger.

So, I put down my Big Boob Monthly Magazine, got off my fat ass and got to work on the car. Pulled the A pillar pod and installed a new nylon hose with fittings to the gauge.

Started the car and the gauge went to -14 on the dial. WTF? I have vacuum at the gauge? Car idles fine as it always has. With the engine idling I pulled the hose off the port that feeds the boost gauge. Sure enough, I can feel vacuum on my thumb. Checked the dashpot for the flapper door. Looks good. Moves freely when I put my hand lever.

Took the car for a spin and it pulls/goes into boost no problem. Gauge goes to 7 lbs of boost at WOT.

Searched the web but have found not much. Maybe something going on inside the case like a bad gasket?

Anyone seen this before?

Thanks for your help.

Stevo

[OsO 34]

Sounds like the gauge wasn't working before you installed the trans temp gauge if a vacuum at idle is new to you. No boost at idle is a good thing.

[StevoHemi 113]

Boost Gauge working fine before I pulled the triple pod to do the Trans Temp gauge.

Stevo

[OsO 34]

Boost Gauge working fine before I pulled the triple pod to do the Trans Temp gauge.

Stevo

I reworded it.

[StevoHemi 113]

I reworded it.

Drove the car since last year with a non working boost gauge (pinched tube). This problem could have happened anytime after that and I was not aware of it because the gauge was not working.

I am guilty. Should have fixed the pinched tube right away last year. Me... a.... dumbass....

Stevo

[OsO 34]

There is no problem i would expect there to be a vacuum at idle.

[StevoHemi 113]

So....you are thinking a bum gauge?

Stevo

[sharkcohen 60]

Should show vacuum at idle

[Cam 157]

Nothing wrong bud. You're supposed to have vacuum at idle.

[rdrdr90 35]

Stevo- same gauges. I have about -18 at warm idle and -14 at cold start. Driving around varies. As all have said, no issue bud.

Sent from my StarTac using Tapatalk

[StevoHemi 113]

Ok...must be getting old. As far as I can recall.... since Arrington installed the Maggie and when I installed the warranty Maggie a year later..... this gauge has always read "0" at idle. I have never seen this gauge produce a negative number.

So, what I am hearing is that nothing is wrong?

Scratching my head.....

Stevo

[us1champ 22]

Correct. If U have zero then u are headed into boost. Negative is vacuum. Everything is fine

Sent from my iPhone using Tapatalk

[Cam 157]

Think of it this way stevo. the engines nothing more then a pump right. So as its trying to draw air and fuel into the cylinder at idle, it can't since the throttle blade is closed so the intake manifold is under vacuum. Like sucking on a cocktail straw but it's the olive is stuck on the end. As you give it throttle the blade opens up relieving the negative pressure and after you reach enough RPM for the blower to make boost it then goes to positive pressure.

[StevoHemi 113]

Ok... I believe you guys but....

Maggie been on my car since Oct 2011 and this is the first time I have seen the gauge give me a negative number.

So, for the last five years of operation, there was a faulty install of my Boost Gauge by me and now it is correct? Ooops!

Ok... I got it. Thanks everyone. I will give it a whirl.

Stevo

[Cam 157]

Ya something's been wrong for that time.

[Speedy 247]

Mine reads exactly the same SteveO. Notice on the gauge itself the side below zero even says "VAC in/hg" standing for vacuum inches of mercury (unit of measurement).

It's perfect. If it wasn't doing this before, then it wasn't working proper.

[StevoHemi 113]

Thanks a bunch guys....

I appreciate!

A good weekend to all!

Stevo

[sharkcohen 60]

[StevoHemi 113]

Ok.... I think I know what happend here.

The original hose installed at the tub was being pushed down almost level. Car goes into boost and the pressure pushes the hose up slightly and I see positive numbers in the gauge. Boost is off and the hose goes back down level sealing the hose so I cannot see the negative numbers/vacuum at the gauge.

Dang.... 5 effing years I drove around thinking "0" at idle on the gauge was normal.

Shit.... embarrassed.....

Stevo

[OsO 34]

Ok.... I think I know what happend here.

The original hose installed at the tub was being pushed down almost level. Car goes into boost and the pressure pushes the hose up slightly and I see positive numbers in the gauge. Boost is off and the hose goes back down level sealing the hose so I cannot see the negative numbers/vacuum at the gauge.

Dang.... 5 effing years I drove around thinking "0" at idle on the gauge was normal.

Shit.... embarrassed.....

Stevo

Dont worry you may not of known how it works but I still cant keep any of my personnel engines together for 5 months much less 5 years.

[BJB 40]

Think of it this way stevo. the engines nothing more then a pump right. So as its trying to draw air and fuel into the cylinder at idle, it can't since the throttle blade is closed so the intake manifold is under vacuum. Like sucking on a cocktail straw but it's the olive is stuck on the end. As you give it throttle the blade opens up relieving the negative pressure and after you reach enough RPM for the blower to make boost it then goes to positive pressure.

"Like sucking on a cocktail straw but it's the olive is stuck on the end." Hahahahahahaha!!!!!!