I just ordered the Autometer Boost-Vacuum Gauge today from Summit Racing.

What kind of readings should I expect on
1)idle
2)cruising
3)acceleration
4)full throttle.

Please educate me.

 

I have a 17% pulley and am getting the following readings..

1) idle= 20 Hg
2) cruising= 10-14 Hg
3) light throttle= 2 Hg
4) WOT @ redline= 15 psi boost

 

Ditto Big Daddy

 

I have the stock pulley.

1. idle = 11-12 in Hg <--- Big Daddy, we're way off on this one
2. cruising = 10-14 in Hg in lower gears. 6th gear usually 8-10 in Hg.
3. light acceleration = usually in low vacuum
4. full throttle = I can make 4-5 lbs of boost at full throttle, 2k rpm. 7 lbs before 4k rpm. 9 lbs at 5k-5500. Haven't really checked above that (too much going on to look down).

I'd like to add a 5th... deceleration in gear. I make 18 in Hg when off throttle no matter what rpm.

 

Just went out and started the car to check this. I was a little off...it sits at about 18 Hg at idle.

 

Thanks. I'll post mine once installed.

 

I just installed the stewart warner gauge set from MINI. I haven't got a chance to really open him up, but here is what I managed to get today driving back through town from the parts store.

1. Idle ~20 in Hg
2. Cruising 15-18 in Hg
3. Light Acceleration ~0

Like I said. I never got a chance to hit WOT. Accelerating in town I usually hit ~5 psi before I had to lift the throttle.

I will say that I was slightly suprised that the voltage gauge sits at 12.5 - 13 volts after I start the engine, but before I start moving. Even if I play with the throttle first, but once I put it in gear and start moving it goes up to 14 (where I expected it to be) and stays there.

I also noticed that the whistle I hear now that I have a CAI seems to be linked to the bypass valve. When I am cruising on part throttle I will get a high pitched whistle. More throttle, or less throttle causes the whistle to go away. Less throttle and I get 5-10 in Hg. During the whistle it wavers from 5-0 in Hg. More throttle and I get 0-2 psi. Guess I need to look at VGS or fixing my bypass valve to close completely.

 

I took the MINI out for a little spin to stretch his legs. I managed to hit 12 psi under heavy throttle. Of course, I don't have a pulley. I really need to look into optimizing my bypass valve.

 

My Scangauge reads MAP, which doesn't consider existing (nominal) air pressure. Adding in that factor (approx 16 where I live) gives me very close to these measurements.

 

Why am I the only one who's only getting 12 in Hg at idle? I never hit 20 inches even under high rpm in-gear deceleration. Everything else matches pretty close so it can't be a leak.

 

kink in the line esp if you have a lower max. Also where are you drawing the reading from?

I'm 18-20vac at idle 12press WOT 20-23 vac when shifting from WOT Stock pulley, so we'll see how that changes down the road/

 

Hmm. I'm tee'd into the stock vacuum line between the FPR and manifold. The gauge is connected with a 1/4" hard line into the tee. I'm not really seeing a lower max boost though. As I said in my previous post, I haven't redlined it but at 5k+ rpm I'm seeing over 9 lbs of boost. I'm also not getting any hiss or erratic idle that are usually associated with vacuum leaks.

 

I'm seeing a full 10 psi of boost long before redline, and 12 if I really hit the gas just before the computer forces a shift.

 

Interesting. At low revs, my boost increases pretty quickly but after 4k rpm or so, it goes up much slower. The other thing is that I didn't really feel a difference in performance after my boost gauge install so Im not sure that even has anything to do with it. I guess I should take the intercooler back off and secure those vacuum lines better. Could a leaky BPV cause this as well?

 

I did notice that my guage is much smoother, and the boost builds faster after I did the VGS. I posted my experience and changes on this thread:

https://www.northamericanmotoring.co...=38268&page=16

 

Well I took it all apart and made sure the connections were tight. I even added some spring loaded clamps. It's still the same 12 in Hg at idle. I also just finished installing my Webb Sportbox RAF today. With the new intake, boost seems to rise much faster than before. It seems to go very linearly/quickly to 9 lbs at 4500 or 5k rpm and then the speed at which it climbs drops off after that. I still haven't had the chance to get a reading at 6k or above as I normally don't rev that high.

edit... I just got back from another run. It was dark and my gauges aren't as bright as the factory one's so getting a reading was a little tough. I took it up to around 6500 rpm and boost seems to taper at around 5k rpm. I get to 9 lbs and then sit there for the next 1500 rpm or so. I almost suspect the bypass valve as part of the problem. One more thing to note, my car is a very early '02. I wonder if they changed things. I never see 20 in Hg even when decelerating. It's weird to see that you guys are getting nearly the same vacuum readings when decelerating in gear (at high rpm's) and at idle.

 

Is it possible you have a bad gauge and it bottoms out at 12 in/Hg? If you have a friend with a boost gauge, just swap them out for a minute to rule out the gauge as the issue.

 

Nope, it's not a bad gauge. I see 18-19 in Hg when decelerating in gear.

 

Hmmmm <scratches head in puzzlement>

 

I did another run in daylight this time . A 2nd gear pull to redline ended in 10 psi boost. I was over 9 psi near 5k rpm. Looks like whatever is causing my different vacuum readings is not affecting boost. This run was in 90+ degree Florida heat. I also did a vacuum test where I decelerated in gear from 4k rpm. I had around 19 in Hg from 4k down to about 1200 rpm. At 1200, I began loosing vacuum. At 1k rpm, I was around 14 or 15 in Hg, and pushing the clutch in to bring it down to idle went up to 12 in Hg. I never saw more than 19 in Hg. What does all this mean? I haven't the faintest idea .