Low Vac at idle
 

99 Eclipse Turbo FWD
- walbro 255
- 14b turbo
- 3" turboback
- pacesetter header
- vr speed FMIC
- Greddy RS BOV

Hey guys i just got my motor back in my car finally, and am trying to figure out some minor issues. When the car sits at idle or at cruise, the boost gauge reads that its at 10vac, i dont have trouble boosting or anything, so i wouldnt think its a boost leak, but im not sure yet, because im still breaking in the brand new clutch and turbo, so i don't want to over spool on the turbo. I'm going to Boost leak test it 2mrro. Just wondering if anybody had any ideas of something it could be off the top of their head?

Re: Low Vac at idle
 

My car pulls about ~12 in/hg (Give or take 1 or 2 in/hg) at ~700-800rpms when it's at operating temperature, and anywhere from 16-20+ in/hg at cruising speeds. I think about 70mph in 5th gear I pull close to 18 in/hg. I do have 272 cams though, I'm not sure if how much of a difference 272's make when it comes to pulling vac at idle when compared to stock cams, but if you're at cruising speeds on the highway you should definitely be pulling more than 10 in/hg.

Does it stumble or sound rough when it's at idle?

Re: Low Vac at idle
 

no, thats the funny thing, it idles fine. I'm starting to wonder if the line is kinked or the gauge is fd. I guess when I leak test it in the morning I'll check that out too.

Re: Low Vac at idle
 

FYI: I edited my post a minute ago, and not sure if you saw it before you responded.

Re: Low Vac at idle
 

What was the gauge reading before? The lower the engine idles the less vacuum it will pull. The only leaks you would have would be in the intake manifold to see a vacuum drop at idle.

~John

Re: Low Vac at idle
 

I was getting about 18-21 in vac at idle before @ about 750rpm. And while the motor was out, I didnt do anything with the intake manifold at all, so it must be the gauge or the line is kinked somewhere.

Re: Low Vac at idle
 

You probably have a vacuum leak somewhere.

Re: Low Vac at idle
 

Big cams will also pull less vacuum at idle. What cams are you running? If they're stock then 10 is way too little.

Re: Low Vac at idle
 

Yeah, DSMs should idle between 22 and 15 depending on the idle speed.

Re: Low Vac at idle
 

If your cams are stock, check the cam timing.

Re: Low Vac at idle
 

havent thoroughly checked cam timing yet, but the marks line up dead on. Also, dsmlink reads 20-25 at idle, where the boost gauge reads 11 in vac. Is dsmlinks boost source reliable? I cant remember where it gets the data from

Re: Low Vac at idle
 

2g's have a map sensor on top of the intake manifold.

Re: Low Vac at idle
 

So is the MAP sensor (dsmlinks vacuum/boost readout) just as reliable of a source for boost and vac as the boost gauge?

Re: Low Vac at idle
 

No

Re: Low Vac at idle
 

I have the FP intake pipe with BOV return, so i just routed the charcoal canister hose down behind the firewall, would that cause loss of vacuum? I would think not considering it is blowing out fumes, but im not 100% sure, so i figured id ask.