hello all, Ive a question thats been bugging me for about a month. What is high vacuum a indicator of, if anything? what would cause vacuum to be high, and is it something to worry about? Im new to boosted engines and dont really have a grasp on the vacuum side of the turbo. Ive a catch can installed if that matters. I need to take the car in for a CEL(broken 02 sensor), would these two things be related? I want to make sure car is in top form before I bring it in. From what I gathered in posts on vacuum normal pressure for my altitude is 18-20 HG, I idle at 50. I really have no idea what that means and even if its a problem. The car seems to run fine, it pulls hard and holds boost ok. APparently I am a worry wort, but its just been bugging me that I dont know, Im curious as to know why its so high. If its not a problem just slap me for being a newb hehe thx guys

 

An idle vaccuum of 50? There is something definitely wrong! A catch can will not affect the idle. An O2 sensor could be messed up because of a weird idle. I do not know how it could be that high, almost all gauges bottom out at 30hg? Possibly you have a really weird hookup or even a faulty gauge?

I would check on those few things first. If your car's compression is good, and there are no boost leaks, the car should be running fine. My first impression is that there is something wrong with the hookup or gauge.

 

Vac is anything below 14.7 psi (amount of pressure per square inch a air column produces) which is zero on most gauges. Vac is totally dependant on what cams you have, what rpm the idle is at, many things. If the car idles well them don't worry about it. Vac has no effect on the car as soon as it makes .x gauge pressure. It idles at 50hg?

 

haha, ya, IX mr has the gauge marked 30 and 75 with 10 increments, it lays right on or over the second mark after 30. I just snapped a pic. *edit - idles around 700 rpm IIRC. Idle seems fine, little rough after the set of motor mounts but not vibrating like some...

thx for the help

 

From the picture it looks like "cm/HG" (I don't have the factory gauges but I assume it is metric). The 18-20 HG that you are referring to as normal is "in/HG". So when you convert 50 "cm/HG" to "in/HG" you get about 19.7 in/HG (50 / 2.54). So you seem normal to me.

Here is me at idle in "in/HG".

 

^ you think your so smart eh... er wait its the other way around? ok im giong in my corner now. Thx chuck I need to relax a little, one thing goes wrong with my car and I think the world is ending. ugh <duncecap> *I swear it wasn't idleing that low(high) before my CEL came on. Thx again man I really wasnt too worried as the car ran ok, but enough to ask.

 

No worries.

When I installed my boost gauge I freaked out because the needle was going below zero. After a quick search on "what the hell is going on my needle is below zero??" I realized I was normal too.

 

Go Brewers!

 

Ya i missed the game tonight, I watched the cards lose lol i know we are a sad sad crew. We are right on track for a HUNDRED LOSSES YA! its getting to the point of funny bad. back the f'in truck up. Get rid of dusty, mcFAIL. Hire stoney as GM and brenley as coach. Man it hurts watching the sox, they are good :\ Brewers? meh hehehe, did you guys finish ahead of us last year too? iirc you did, thats when you know you are REALLY bad (jk)(notreally). Milwaukee is cool, the summer fest you guys have is a good time. Been many times. I was actually just in wisconsin and you reminded me of something I forgot to post about. I talked with the short throw shifter guy known in the srt community about a six-speed MR short throw. Ill make another post about that tho. Anyways GO BREWERS fck the cubs

*edit bolsen your pictures in your sig are switched, new and old. Typical brewers fan clueless

 

Normally if you get slightly higher like 22 - 25 hg, your pistons rings are probably sealing hella good.