Boost gauge install help **Update** and MBC install

legacy92ej22t · Post by **legacy92ej22t** » Sun Oct 12, 2003 11:08 pm

There was a rubber stopper here, Is this an ok place to run the vac line through the firewall at? Do I need to drill it out because I cant feed the line through. If not a good spot can anyone show me where i should bring it in at? Thanks

LegacyT · Post by **LegacyT** » Mon Oct 13, 2003 12:28 am

Ofcourse, as long as its routable on the other side to where you want to mount your boost guage. What you should do is drill out the grommet, so that there is a small hole in the middle, run the line through the grommet and then insert the grommet back into the hole in the firwall. This will eliminate chafing of the line and keep moisture and sound out of the cabin.

Mark,

legacy92ej22t · Post by **legacy92ej22t** » Mon Oct 13, 2003 5:09 am

I was planning on doing that with the grommet but when I popped it out it disappeared into the engine bay

I'll try and find it again tomorrow, I ran out of daylight today. I think that hole will work good routing wise, I just can't locate it inside the car and I'm nervous to drill in.

LegacyT · Post by **LegacyT** » Mon Oct 13, 2003 10:51 am

If you can't easily find it on the other side try sticking a small maglite infront of the hole and search for it under the dash. Judging by where that hole is on the firewall, it seems it's gonna enter the cabin somwhere behind the dash, which may be a problem to find. If you look under the dash between the gas and clutch pedals right above where the carpet ends you'll find a nice big grommet, about and inch in diameter. This is the one I used, its pretty easy to find in the engine bay as well, And since my guage is mounted down low in front of the shifter in that little compartment the 90-91's had it's was a joke to route.

Hope this helps,
Mark

vrg3 · Post by **vrg3** » Mon Oct 13, 2003 10:57 am

Or you could push some wire through and then look for it coming through from inside.

I use the grommet Mark is talking about for a bunch of stuff. The same one seems to exist on a lot of other cars too.

legacy92ej22t · Post by **legacy92ej22t** » Mon Oct 13, 2003 1:52 pm

Ya I noticed the big grommet you guys are talking about on the inside but didn't see it in the engine bay (didn't look very hard though). Is it under the brake booster? Gonna work on it this afternoon, i'll get it in one way or another.

vrg3 · Post by **vrg3** » Mon Oct 13, 2003 4:36 pm

Yeah, it's kind of under the booster. If you push a wire several inches through from the passenger compartment you'll be able to see it in the engine bay.

legacy92ej22t · Post by **legacy92ej22t** » Tue Oct 14, 2003 5:17 am

Ok what a day. I replaced my fuel filter, got my computer to finally clear, installed my boost gauge and mbc. here's how it went...

Went out this morning to get into my car and the grommet I lost was sitting right next to the driver side door (good start). I used a wire coat hanger to run the nylon line into the car ( after some bending and coaxing)
T'd into the pressure exchange solenoid vac line off the front passenger side intake manifold and ran the inside. Started the car and went for a drive the vac readings were good but I was only getting 5 psi boost in all gears. So I figure my stock boost control solenoid is shot and I go ahead and install my joe-p mbc. First here's pics of gauge install

Nylon line through grommet..

It's there you just can't see it.

Remember, this is just temporary until I get my bulb assembly and can wire the light.

Anyways, then I install my joe-p mbc. Pretty straight forward. Here's a couple bad pics...

So I go for a drive and 1st is still 5-6 psi but when I shift to second and roll onto boost it rockets up to almost 15 psi

I pull over quick and turn it down. Turned it down too much because again I get only 5 psi in all gears. Turn it back up a little and too much again and get a quick burst of detonation at around 13 psi in 4th ( was getting 10-11 psi in 2nd-3rd). So
now I know what detonation sounds like

Turn it down again and finally get it so my max boost in any gear is 10 psi (1st is still only 5-6 psi though) but here is my problem, I think I'm hitting fuel cut! If I boost above 8psi for more then about 3 seconds I completely lose power for about 1 second then boost comes back on for another 3 sec. then off. It actually hurt my neck!

I don't think my gauge is reading off, so what the f#*&K? Looks like I need to reread that cheap fcd thread, huh?

Any suggestions?

David Carter · Post by **David Carter** » Tue Oct 14, 2003 5:52 am

Off topic...where did you get your down-pipe..how much was it?

I haven't installed my Joe MBC yet.. i got the XP version.. what did you do with the pipe that leads to the bottom of the boost control silinoid.. there are 3 pipes going to the stock one but only 2 connections to the MBC..

David C

vrg3 · Post by **vrg3** » Tue Oct 14, 2003 9:18 am

legacy92ej22t wrote:but here is my problem, I think I'm hitting fuel cut! If I boost above 8psi for more then about 3 seconds I completely lose power for about 1 second then boost comes back on for another 3 sec. then off. It actually hurt my neck! :evil: I don't think my gauge is reading off, so what the f#*&K? Looks like I need to reread that cheap fcd thread, huh? :roll: Any suggestions?

Uh... Stock boost is supposed to be just under 9 psi. Fuel cut comes in around 13 psi.

Maybe your gauge is reading off? Are you getting good seals at all your joints? Did you use teflon tape on the NPT fitting and properly torque the compression fitting?

It does kind of sound like what might happen if your gauge is reading low; if your stock boost system is working and it reads 5 psi instead of 9, and then when you get fuel cut it reads 8 psi instead of 13...

Post by **Legacy777** » Tue Oct 14, 2003 1:59 pm

pics are broked

legacy92ej22t · Post by **legacy92ej22t** » Tue Oct 14, 2003 2:12 pm

David Carter wrote:Off topic...where did you get your down-pipe..how much was it?

I won it at the SCCA STPR last spring from Motor Sport Resources (MSR)! So I actually didn't pay anything. It's a WRX full turbo-back system made to fit. The DP is a ceramic coated twin dump with Boost Enhancement Plate (BEP). Since then I talked C.E.S. and MSR into making a couple bolt on Legacy turbo turbo-back systems! I've been trying to talk them into offering DP's alone and they said if the demand is there they may start so e-mail Jon Miles at msrusa1@optonline.net and tell him you are interested.
For pictures of the whole system go to viewtopic.php?t=1307&start=30
Prices for turbo-back systems www.msr-usa.com . Jon told me he would do a group buy on CES DP's if we could get 4-5 buyers too. The systems sweet.

I haven't installed my Joe MBC yet.. i got the XP version.. what did you do with the pipe that leads to the bottom of the boost control silinoid.. there are 3 pipes going to the stock one but only 2 connections to the MBC..

David C

It goes to the resonator so I just left it hooked up. You don't need it for the MBC.

vrg3 wrote: Uh... Stock boost is supposed to be just under 9 psi. Fuel cut comes in around 13 psi.

Maybe your gauge is reading off? Are you getting good seals at all your joints? Did you use teflon tape on the NPT fitting and properly torque the compression fitting?

It does kind of sound like what might happen if your gauge is reading low; if your stock boost system is working and it reads 5 psi instead of 9, and then when you get fuel cut it reads 8 psi instead of 13...

Thats why I didn't undertsand why I was hitting it. I guess my gauge is probably reading off. I did use teflon tape but maybe somethings loose, I'll check today. Is does seem to make sense if it is reading 4-5 psi low.

legacy92ej22t · Post by **legacy92ej22t** » Wed Oct 15, 2003 4:43 am

Well I think my gauge is reading just over 4 psi low.

I messed around with it today and I consistently hit fuel cut just shy of 9 psi. I tightened and retaped the connection on the gauge and it seemed to make it almost 1 psi more accutare. Right now I have it set at around 6 psi on the gauge so I figure around 10 psi. I think the problem may be the connection on the T by the intake manifold. The little boot adapter on the nylon line I think is leaking under boost but solid under vacuum. What do you think? Possible?
The vac readings seem real consistant. What do you think would be a good way to fix it? Seal it with something?

My car however is running really good and pulling strong

Boost seems to hit harder and faster with the mbc. Cant' wait to get my i/c installed.

vrg3 · Post by **vrg3** » Wed Oct 15, 2003 3:47 pm

legacy92ej22t wrote:I think the problem may be the connection on the T by the intake manifold. The little boot adapter on the nylon line I think is leaking under boost but solid under vacuum. What do you think? Possible? The vac readings seem real consistant.

Yeah, it's certainly possible. I've never had a problem getting my gauge to read right even with really shoddy connections, though; it would usually just hurt response.

So you're reading about -19inHg at idle?

What do you think would be a good way to fix it? Seal it with something?

Maybe you could first just try a ziptie around the nylon side of that little rubber union fitting.

Nylon tube inside a rubber boot is supposed to seal pretty well up to a bar or two of differential pressure, though... Are you certain that little rubber union is the correct inner diameter?

To get a very good seal (stronger than the tubing itself) with nylon tubing the best thing to do is probably to get another compression fitting that mates with a male NPT-to-barb fitting. That'd be huge and really unwieldy though.

legacy92ej22t · Post by **legacy92ej22t** » Wed Oct 15, 2003 5:07 pm

vrg3 wrote:
So you're reading about -19inHg at idle?

Hmm.. no. I read about -13 inHg at idle. I get about -19 inHg when I down shift and coast though.

Maybe a zip tie will work. I will try it. So I definitely want -19 inHg at idle though huh? I wasn't sure what I was supposed to be reading.

vrg3 · Post by **vrg3** » Wed Oct 15, 2003 5:13 pm

-13inHg is not enough vacuum. If you only get -13inHg but your idle is not extremely rough, your gauge is probably reading wrong. I got around that when my intake manifold gasket was leaking and the idle was really bad.

The difference between -13 and -19 inHg is about 3 psi, since two inches of mercury is about the same as a pound per square inch.

Properly running you should get between -17 and -19 inHg at idle and around -21 inHg when coasting from high engine speeds.

If there is a vacuum leak, you should be able to hear it hissing at idle if you listen very closely. A piece of nylon vacuum line (the hard kind, not the soft rubber kind) can work well as a stethoscope to help you listen.

It's possible your gauge is miscalibrated. If the spring is too stiff you'd get low vacuum and low boost readings.

legacy92ej22t · Post by **legacy92ej22t** » Wed Oct 15, 2003 5:23 pm

vrg3 wrote: If there is a vacuum leak, you should be able to hear it hissing at idle if you listen very closely. A piece of nylon vacuum line (the hard kind, not the soft rubber kind) can work well as a stethoscope to help you listen.

I will check for that.

It's possible your gauge is miscalibrated. If the spring is too stiff you'd get low vacuum and low boost readings.

I really hope that isn't the case

I will be extremely upset if it is. First the bulb assembly is missing, then if it's miscalibrated that will really
upset me. Is there anyway to recalibrate it?

vrg3 · Post by **vrg3** » Wed Oct 15, 2003 5:41 pm

I don't know if you can recalibrate it yourself. If you're daring enough to pop the case open you may find some kind of calibration screw(s) if you're lucky...

mikec · Post by **mikec** » Wed Oct 15, 2003 6:01 pm

Argh, I was hoping this was what was wrong with mine (miscalibrated). But I'm reading the correct 17 - 18 inHg at idle.

legacy92ej22t · Post by **legacy92ej22t** » Fri Oct 17, 2003 6:41 am

Ok, I retaped and tightened my connection on the gauge again and now it's
much more responsive. Before there was a lag between throttle and the gauge. I now have about-15 inHg at idle but boost still seems 4 psi off. Now though at max boost the gauge needle flutters.

It only does it at WOT, if I go full boost at partial throttle it doesn't seem to do it. By flutter I mean it bounces back and forth across about a 2 psi range so quick it is a blurr. It also makes a rattle noise when it does it. Do you think this has something to do with the car or is it the gauge?

vrg3 · Post by **vrg3** » Fri Oct 17, 2003 2:35 pm

15 inches is not enough vacuum for a good idle, so I'd guess there's a problem with the gauge.

If you make a gauge responsive enough, you can get flutter -- that's one reason most gauges ship with that thin nylon tubing -- but flutter could also be due to an oscillating leak.

You should probably try a known-good gauge and compare. Do you know anyone who can lend you a gauge locally?

legacy92ej22t · Post by **legacy92ej22t** » Sat Oct 18, 2003 3:45 am

I recently changed my fuel filter which seemed to smooth out my idle just recently but I had been experiencing pretty rough idle. Even though it is smoother since the filter, it is still not very even. My rpm's at idle don't hold steady they kinda fluctuate (spelling?) a couple 100 rpm. If i have a vacuum leak would it effect my boost readings though? I tried that starting fluid check before and came up empty. I have noticed though at WOT the past few months that I feel a very slight, uneven kinda bogged down surge in the accelaration. I only really notice it at full boost, WOT in 4th and 5th. What do you think?

I don't know if I can get a gauge to try or not, I have a couple of friends running them but both complained about the install so I don't know how willing they will be to unhook them and let me check.

What actually causes the gauge to flutter if everythings ok and what is an oscillating leak? Thanks

vrg3 · Post by **vrg3** » Sat Oct 18, 2003 4:33 am

If your idle is rough then it's possible you actually have low vacuum. Does it hold steady at -15inHg?

A vacuum leak can become a boost leak when you get on boost. That can make you run overly rich, which can cause the bogging feeling.

It's really hard to say... If you were thorough with your starting fluid check (sprayed all over the intake tubing, all around the intake manifold, all around the brake booster, etc) and came up empty then it's pretty certain there's no vacuum leak though.

The gauge can flutter if actual manifold pressure flutters at the point where it is sampled. Since the intake valves open and close, there is some lumpiness to it. That's one reason some cars with really lumpy cams can't fuel based on a MAP sensor.

By "oscillating leak" I just meant a leak that opened and closed rapidly, as if a piece of rubber were fluttering in the airflow or something.

I may be able to help you out with respect to borrowing a gauge. No promises, but I may be driving through Williamsport next weekend so maybe I could visit and swap my gauge in for yours? Even if not, I might have a spare that I could mail you. Let me just find it and verify that it works right.

legacy92ej22t · Post by **legacy92ej22t** » Sat Oct 18, 2003 5:00 am

vrg3 wrote: If your idle is rough then it's possible you actually have low vacuum. Does it hold steady at -15inHg?

Yes it holds steady. If in neutral I gas it to 2k rpm and let off the gas
I get -18-19 inHg with no load.

A vacuum leak can become a boost leak when you get on boost. That can make you run overly rich, which can cause the bogging feeling.

I do run pretty rich

It's really hard to say... If you were thorough with your starting fluid check (sprayed all over the intake tubing, all around the intake manifold, all around the brake booster, etc) and came up empty then it's pretty certain there's no vacuum leak though.

I didn't really do the intake manifold or brake booster.

I'll try that tomorrow.

I may be able to help you out with respect to borrowing a gauge. No promises, but I may be driving through Williamsport next weekend so maybe I could visit and swap my gauge in for yours? Even if not, I might have a spare that I could mail you. Let me just find it and verify that it works right.

That would be really cool! It'd be great to meet you. You could stop by for a respite and check out each others cars.

vrg3 · Post by **vrg3** » Sat Oct 18, 2003 5:53 am

legacy92ej22t wrote:Yes it holds steady. If in neutral I gas it to 2k rpm and let off the gas I get -18-19 inHg with no load.

Weird. It's, like, just slightly less vacuum than it should be.

Do you have access to any mercury? =) It'd be neat to build a pressure tester. Just get about about 35 inches of thin clear tubing, mark it off in inches, hold it vertically with one end down into a container of mercury and hook the other end up via vacuum hose to a nipple on the manifold.

I do run pretty rich

Then again, most Subaru ECUs like to run rich...

I didn't really do the intake manifold or brake booster. :oops: I'll try that tomorrow.

Yeah, it's easy to forget... I had been looking for my vacuum leak for months before I realized that I hadn't checked at the interface between the manifold and the heads. I felt really dumb, especially since I had bought new manifold gaskets a long time ago and they'd been sitting on my desk.

That would be really cool! It'd be great to meet you. You could stop by for a respite and check out each others cars. :D

Like I said, no promises. :) My girlfriend and I are driving down to DC to pick up a car (her sister's giving her her old Saturn something-or-other) and we may or may not have time to stop. Are you gonna be around on Saturday or Sunday, though? If you are, PM me your phone number or something.

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Boost gauge install help Update and MBC install

Boost gauge install help Update and MBC install