Please help electrical n00b with Boost Gauge Install

[WRblueX_Guy]

I do all my own installs, but I don't know anything about electricals

I bought the Defi D series boost gauge, and it came with the vacuum hose, T-fitting, and black & white wires that come out of the back of the gauge.

So if anyone doesn't mind explaining it to me, pretend I don't know anything about electrical stuff

And I have searched on 3 different Impreza boards, and I could not find a clear enough write up that explains the questions I am asking.

1. I've read a little bit about the install, and cutting into the BPV hose for the T-fitting, but I heard some people say you should do it to some intake manifold hose. Either way, how would I go about doing this?

2. And how about getting the hose through the firewall? I read a Subaru write-up where it says to take off the intercooler to get to the grommet. I don't really want to take it off, but I will if I have to. But I heard there's another way down near the pedals.

3. I will be mounting the gauge on my steering column. So how would I get the vacuum hose to the steering column and then to the boost gauge?

4. And I assume the black & white wires are for power. I have no idea where to to hook those up to. I read black is for ground, but where exactly do I put both of them? I read about a couple different spots, but I'm not exactly sure which will be the best/easiest.

I would really appreciate any help.

Thanks,
Brian

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[vinceGC8]

i have no answer for 1 but for 2,3,4. i have something.

2. you dont really need to tkae off the intercooler to get to the grommet. when u put the vacuum hose through the firewall hole, grommet, the hose will show up near the pedals. just keep pushing the hose in till u see the hose at the pedals.

3. to get the hose near the steering column just take off the gauge bezel(easiest way i see) and then run the hose up to the steering column from the bottom.

4. i attached the wires to the clock harness. i forgot what colors corresponds to what colors but, i used the middle 2, black for ground and white goes to the other wire in the middle. u need to remove the clock bezel. you will beable to see an opening from the cluster to the clock area, so u can run the wires that way.

hope i was clear in my write up.

[Mulder]

The BPV hose is a direct manifold connection and is the proper place to tap for the line to your gauge.

[WRblueX_Guy]

Thanks for the replies.

Originally Posted by linkzard

i have no answer for 1 but for 2,3,4. i have something.

2. you dont really need to tkae off the intercooler to get to the grommet. when u put the vacuum hose through the firewall hole, grommet, the hose will show up near the pedals. just keep pushing the hose in till u see the hose at the pedals.

3. to get the hose near the steering column just take off the gauge bezel(easiest way i see) and then run the hose up to the steering column from the bottom.

4. i attached the wires to the clock harness. i forgot what colors corresponds to what colors but, i used the middle 2, black for ground and white goes to the other wire in the middle. u need to remove the clock bezel. you will beable to see an opening from the cluster to the clock area, so u can run the wires that way.

hope i was clear in my write up.

2. So is the grommet behind the intercooler the one that leads to near the pedals? Or is it a different one that's lower on the firewall?

3. Sorry, I don't understand what the gauge bezel has to do with the steering column and why it would need to be removed. Care to explain?

4. Okay, so the black wire (ground) goes to another black wire in the middle? Do I just cut the clock wire in half and tie the gauge wire around it? Or just cut the tubing around the wire? Also, how do I get the black & white gauge wire to the clock without it showing?

Sorry for all the questions

Originally Posted by Mulder

The BPV hose is a direct manifold connection and is the proper place to tap for the line to your gauge.

K. So should i make the cut where the yellow line is? (About 3 inches from the end of the hose)

And insert the T-fitting where the red 'T' is? Would tapping into this hose still be okay if I decided to get a 100% atmospheric blow off valve?

I heard that you should run the boost gauge hose with the AC line to keep it out of the way. Can anyone tell me where to AC line is in this picture?




Thanks guys. I appreciate the help.


Edit: If I ever decided to get rid of the boost gauge, would it even be possible to get rid of it since there is now a cut in the BPV hose?

[WRblueX_Guy]

Bump.

[satrya]

Originally Posted by WRblueX_Guy

2. So is the grommet behind the intercooler the one that leads to near the pedals? Or is it a different one that's lower on the firewall?

The one behind the intercooler leads near to the pedals, but slightly higher. Another one sits much lower, and is less visible when staring at the engine compartment (with the hood propped open of course).

3. Sorry, I don't understand what the gauge bezel has to do with the steering column and why it would need to be removed. Care to explain?

What linkzard most likely meant was with the gauge bezel removed, you can make use of the grommet behind the IC, pass the hose up, and grab it so that it passes through just above the steering column. Removing the bezel gives you improved visibility on where the vacuum hose will end up during the routing.

K. So should i make the cut where the yellow line is? (About 3 inches from the end of the hose) And insert the T-fitting where the red 'T' is?

Better yet, pull out the hose instead of cutting it; place a short (say, 3 inches long) new hose on the BPV, with a T-fitting on one end. The original hose connects to the second end of the T-fitting, and the hose to the gauge connects to the third end of the T-fitting.

I heard that you should run the boost gauge hose with the AC line to keep it out of the way.

Just zip tie the hose to relatively rigid structures, and make sure it doesn't get in the way of the throttle cable.

Edit: If I ever decided to get rid of the boost gauge, would it even be possible to get rid of it since there is now a cut in the BPV hose?

Hence my suggestion to add a short hose between the BPV and the T-fitting.

[Kean]

Here's a link to a ".pdf" of the installation instructions for the oem boost gauge. I believe page 3 has a drawing that shows you the "BPV tap" location:

https://ssl.autocenter.net/webparts/acatalog/page1.html

....hope this helps.

- Kean

[WRblueX_Guy]

Originally Posted by satrya

The one behind the intercooler leads near to the pedals, but slightly higher. Another one sits much lower, and is less visible when staring at the engine compartment (with the hood propped open of course).

What linkzard most likely meant was with the gauge bezel removed, you can make use of the grommet behind the IC, pass the hose up, and grab it so that it passes through just above the steering column. Removing the bezel gives you improved visibility on where the vacuum hose will end up during the routing.

Better yet, pull out the hose instead of cutting it; place a short (say, 3 inches long) new hose on the BPV, with a T-fitting on one end. The original hose connects to the second end of the T-fitting, and the hose to the gauge connects to the third end of the T-fitting.

Just zip tie the hose to relatively rigid structures, and make sure it doesn't get in the way of the throttle cable.

Hence my suggestion to add a short hose between the BPV and the T-fitting.

Thanks for the reply.

Better yet, pull out the hose instead of cutting it; place a short (say, 3 inches long) new hose on the BPV, with a T-fitting on one end. The original hose connects to the second end of the T-fitting, and the hose to the gauge connects to the third end of the T-fitting.

K. Would it fit if I cut 3 inches off the hose that came with the boost gauge?

Thanks again.

Originally Posted by Kean

Here's a link to a ".pdf" of the installation instructions for the oem boost gauge. I believe page 3 has a drawing that shows you the "BPV tap" location:

https://ssl.autocenter.net/webparts/acatalog/page1.html

....hope this helps.

- Kean

Thanks for the link, Kean.


Does anyone know the answer to my wiring question?

4. Okay, so the black wire (ground) goes to another black wire in the middle? Do I just cut the clock wire in half and tie the gauge wire around it? Or just cut the tubing around the wire? Also, how do I get the black & white gauge wire to the clock without it showing?

[satrya]

Originally Posted by WRblueX_Guy

Would it fit if I cut 3 inches off the hose that came with the boost gauge?

I don't know. I suggest running the hose through the firewall and place one end approximately where the boost gauge would end up, and see if the other end in the engine bay has enough slack for the 3 inch cut. If not, you can always get 5/16" vacuum hose in hardware stores.

Does anyone know the answer to my wiring question?

Not sure. I've never installed a Defi before. You might want to consider tapping the wires that go to the oem stereo. The radio wiring diagram available at www.northursalia.com should be helpful.

As for routing the wiring, you definitely want to route them behind the dash trim, and possibly out just below the speedo/tach bezel, near the steering column.

[WRblueX_Guy]

Originally Posted by satrya

I don't know. I suggest running the hose through the firewall and place one end approximately where the boost gauge would end up, and see if the other end in the engine bay has enough slack for the 3 inch cut. If not, you can always get 5/16" vacuum hose in hardware stores.

Well, it says there's 10 feet of hose, so I'm guessing there will be extra. But I'll check, like you said, to make sure

Not sure. I've never installed a Defi before. You might want to consider tapping the wires that go to the oem stereo. The radio wiring diagram available at www.northursalia.com should be helpful.

But wouldn't it be pretty much the same for most mechanical boost gauges? It's just the two wires, right? I just want the boost gauge light to be on when my head lights are on, and off the rest of the time.

As for routing the wiring, you definitely want to route them behind the dash trim, and possibly out just below the speedo/tach bezel, near the steering column.

That sounds like a good idea, thanks.

[WRblueX_Guy]

Okay...

I hooked up just the electrical wires to the two middle clock wires, and it works just like the stock gauge cluster. So now I'm okay with the electrical part.

But I think I might have a problem. I took the by pass valve hose off to see if the T-fitting would fit...and it seemed a little loose. It'll stay in fine when just sitting there, but I think it might slide off while I'm driving or something. Do you think a zip tie would work in this case? If not, does anyone know where I can buy a new T-fitting and what kind/size?

I also tried satrya's idea about putting some new hose on the BPV nipple. I tried it with the vaccum hose that came with the boost gauge, and it kind of fits if I push it on really hard...but the vaccum hose hole is a little smaller than the BPV hose, so do you think it would be bad for flow or something?

[satrya]

Originally Posted by WRblueX_Guy

I took the by pass valve hose off to see if the T-fitting would fit...and it seemed a little loose. It'll stay in fine when just sitting there, but I think it might slide off while I'm driving or something. Do you think a zip tie would work in this case? If not, does anyone know where I can buy a new T-fitting and what kind/size?

Perhaps I don't quite understand what you mean here about replacing the t-fitting. If the hose's inner diameter is slightly too large, then it will indeed feel a bit loose. As long as the difference is minor, a zip tie should be a reasonable temporary solution. You can get these hose clamps in hardware stores that are small enough for the rubber vacuum hose. They usually look like a metal belt with one screw to tighten the hose. Home Depot & Ace Hardware (if they are available nearby) should have them.

I also tried satrya's idea about putting some new hose on the BPV nipple. I tried it with the vaccum hose that came with the boost gauge, and it kind of fits if I push it on really hard...but the vaccum hose hole is a little smaller than the BPV hose, so do you think it would be bad for flow or something?

As long as the hose can fit snugly, I don't think the inner diameter is too small that it will adversely affect the flow out of the BPV.

[WRblueX_Guy]

Originally Posted by satrya

Perhaps I don't quite understand what you mean here about replacing the t-fitting. If the hose's inner diameter is slightly too large, then it will indeed feel a bit loose. As long as the difference is minor, a zip tie should be a reasonable temporary solution. You can get these hose clamps in hardware stores that are small enough for the rubber vacuum hose. They usually look like a metal belt with one screw to tighten the hose. Home Depot & Ace Hardware (if they are available nearby) should have them.
As long as the hose can fit snugly, I don't think the inner diameter is too small that it will adversely affect the flow out of the BPV.

I have read about some people having to get a new T-fitting because sometimes the ones that come with the boost gauge are too small. But it's not that much of a difference. I'll definately pick up some of those clamps before the install.

Thanks a lot satrya. You've been more than helpful.


I think I pretty much know everything I need to know now.

One quick question. If I were to use the grommet behind the intercooler, where exactly would the hose come out in the interior?

The grommet near the pedals is easy to access from the interior, but kind of hard to reach from the engine compartment. So if I stuck the hose through the grommet behind the intercooler, where would I be able to reach it from the interior?

[vinceGC8]

oh man its taking u forever to install a boost gauge. i was and i guess still am a car noob, but this was an easy install.

as for the interior Q, you can probably see it come down from the top right corner in the driver-side footwell.

[WRblueX_Guy]

Originally Posted by linkzard

oh man its taking u forever to install a boost gauge. i was and i guess still am a car noob, but this was an easy install.

as for the interior Q, you can probably see it come down from the top right corner in the driver-side footwell.

Thanks.

Well, I don't have my mounting cup yet. So I can't really install in until then. And I want to get as much information as possible before the install.

[satrya]

Originally Posted by WRblueX_Guy

One quick question. If I were to use the grommet behind the intercooler, where exactly would the hose come out in the interior?

As linkzard mentioned, it shows up on the upper end of the footwell. If you look at the pedals from foot-eye-level (if there is such a term), you will see a bar that serves as a part of the pedal hinges. The hose should come out at least 2 inches above that, closer to the gas pedal. Be sure you don't have too much slack on the hose; I imagine having the hose get in the way of your brake pedal, or any other pedals for that matter, isn't a pleasant thing. Not too safe either.