Greetings with another boost gauge question...

[boost addict]

First off, i'd like to say how amazing this community is, i've been able to put off posting my first thread for quite some time now using the search. I've already checked the codes my engine was throwing, identified them, cleaned my EGR valve, ordered and changed my shifter bushings, as well as a handful of other miscellaneous things. The amount of knowledge you members bring and make available on this website is nothing short of amazing.

I recently bought a 89 MX-6 GT for $500, 300k on it. I'm so pleased with the car, but it definitely has it's issues. I'm randomly getting boost cut at 4k +, usually in 3rd gear or higher.

Today i had planned on installing a boost gauge i bought off a buddy at work, I've never installed one before. This is what the fitting at the back looks like. (My apologies for my pictures, can't find the cord for my digital camera so the cell phone is all i can use.) I went and bought a plastic 1/8" T, and 4 feet of 1/8" vacuum line from the local parts supplier.

I have 3 basic questions. The first is relating to the spot in the firewall to run the vacuum line through. I have searched and searched, and from what i understand, underneath the clutch master cylinder there should be a rubber grommet that is easily seen and should pop right out with a screwdriver. I see no such grommet near the cylinder, and I can't feel one underneath. The only thing i can find is a hole in the heat insulation about 3/4" wide, but it is solid metal and i would have to drill. Can anybody help me out with locating this hole, either inside the cabin or the engine bay?

Second, I'm wondering if the vacuum line i bought will be sufficient to hold boost and vacuum without collapsing. It is the solid rubber kind, also used for windshield washer fluid i believe, not the kind with polyester cords running through it.

And Third, I've heard all this talk about nylon hose that runs directly from the back of the boost gauge to the vacuum line. I'm really clueless about this, and had planned to just clamp the vacuum hose directly to the back of the boost gauge. Can somebody fill me in as to why this isn't a good idea?

Thanks in advance guys, this forum's amazing.

[Zach]

Welcome to MX6.com, enjoy your stay.

[maffatato15]

Originally Posted by boost addict

I have 3 basic questions. The first is relating to the spot in the firewall to run the vacuum line through. I have searched and searched, and from what i understand, underneath the clutch master cylinder there should be a rubber grommet that is easily seen and should pop right out with a screwdriver. I see no such grommet near the cylinder, and I can't feel one underneath. The only thing i can find is a hole in the heat insulation about 3/4" wide, but it is solid metal and i would have to drill. Can anybody help me out with locating this hole, either inside the cabin or the engine bay?

If you see that metal hole, then you arent looking high enough from inside the cabin. The grommet is way up, near the fuses and relays that are under the dash. Im not sure if anyone has taken any pictures of the exact location but i have a free min so ill run out and take a quick pic for you.


As for the boost cut its most likely because there is either a boost controller installed, an upgraded exhaust or a leak someone where in the intercooler piping.

[maffatato15]

alright here you go. I hope this helps.

This is to the left of the clutch pedal inside and way up next to the relays.


Just follow my red amp wire and the white vacuum line.



Here is the location in the engine bay.

[mx_masta]

Or if you have Air Conditioning the drain hose grommet is perfect.

Look on the underside of the dash on the passenger side. It's the little hose coming out of the A/C box and going through the firewall.

[boost addict]

Maffatatto, the hole that you went through I also noticed, but it's completely solid on my car. You didn't have to drill through it at all? I've been trying to drill through the hole underneath, as it's *slightly* easier to work a drill at. If you're looking at the master cylinder from inside the cabin, it's to the bottom left of it, directly down from the hole you went through (It's that black rubber circle between the red and white wires on your first pic). I'm afraid I'm actually going to have to tear apart the dash just to be able to get a drill up in there.

mx_masta, my gt does have A/C, but is the reading on the gauge going to suffer by running such a long hose from one side of the car to the other and back?

[maffatato15]

thats weird. I have had a 91 mx6 and now an 89 and both have had rubber grommets there.

[mx_masta]

mx_masta, my gt does have A/C, but is the reading on the gauge going to suffer by running such a long hose from one side of the car to the other and back?

I wouldn't think so with such small tubing the difference in the response of the gauge would be hard to pick.

Even if you had to add another half a metre the difference in tube volume would only be about 16cc.

[defiler]

Ive owned 8 MX6/PRobes and thats the same hole Ive gone thru on all of them. They all had a gasket there (Or had a hole where the gasket used to be)



I dont like using the AC hole because its too far away. Thats a lot more line considering the source is right next to the hole near the brake booster/

[Mazda Carnage]

Originally Posted by defiler

Ive owned 8 MX6/PRobes and thats the same hole Ive gone thru on all of them. They all had a gasket there (Or had a hole where the gasket used to be)



I dont like using the AC hole because its too far away. Thats a lot more line considering the source is right next to the hole near the brake booster/

Believe it or not the holes around the clutch slave that have the rubber grommets in them are NOT on every MX6, all the 626's have them and the MX6's with vin# starting with J have them, but my US built 89 mx-6 gt, nor does the white 89 GT I sold to Rob (use to be GTboi's) also US built So some US built MX6's dont have the holes.
I figure these holes are for right hand drive set-up so only cars built in plants that put out both left and right hand drives have the hole.

My 89 GT also came with AC which eliminates two other useful grommets on the passenger side.

For the SDS EIC and Boost gauge I passed them through the main engine harness grommet.
For the Wide-band I removed the block off plate for the Automatic shifter cables just behind the ECU, 2 10mm nuts hold it in place, you undo it under the dash, there is a plastic cover that pops off to expose the nut's, then you have a metal plate with a piece of rubber on it, remove the rubber from the metal, drill a hole in the metal plate and plastic cover large enough to pass what you want to through, then cut a small x in that spot in the rubber so you can slide things through. To protect what ever you run through the plate from chaffing just put a short piece of rubber hose (gas line, coolant line, vacuum hose... what ever is close to the right size) over the wires or boost gauge hose where it passes through the fire wall

Then finally for the boost controller (After a confusing search for the non existing rubber grommet net to the clutch slave that I used on many other F2/F2T's) I had to brake down and drill a hole in the fire wall.

Myself I T the boost gauge into the vacuum line going to the Fuel Pressure Regulator that way I see the how many pounds of boost the FPR is reacting to .

[Zach]

My GT's VIN starts with a "1" and I have the rubber grommet as well...so who in the hell knows why some have it and some don't...lol

[maffatato15]

yeah i have an 89 GT and a 91 lx and both have the grommets there. Both also start the vin with "1"