Minor Project: Adding a boost gauge to my gauge cluster ('88 626)

Mazda never put a boost gauge into their turbo 626es, and there really isn't any good place to mount one on the dash. I am not a fan of pillar mounted gauges either. So I decided I'd try to add one into my factory gauge cluster.

The factory 88-92 MX6 and 626 cluster has a removable rectangular thingy on each side. One of them is used for the PRNDL indicator in the automatics, but I can't remember what the other one is for...Anyways, here's where I intend to put my gauge:

And you can see that there's some nice empty space behind these rectangular openings:

On the left side there's even a hole in the housing, as if they planned to put a boost gauge there but never got around to it.

Here's the innards of an autometer gauge I'll be using:

It fits into the space, but it is very long and sticks up way too high:

I happen to have this other compression fitting for my signal line, so I am making the gauge shorter by combining the two:

Here I have cut off the long protrusion from the back side of the autometer gauge, and I've turnt down my compression fitting in my lathe:

My "turnt down" fitting just fits into the hole, as intended. And now I have a shorter gauge that fits where I want it:

I'll glue the parts together with red loctite. I would braze them but I don't want to disturb the brazing that is already on the gauge. I would have tapped the hole on the gauge, and threaded the fitting, but I didn't have the right die. I don't have the gears I need to cut threads on my lathe either. There's a lot of surface area and it's a tight fit, so I think red loctite will be fine.

Next up I'll be making a rectangular gauge face, attempting to make it as factory-looking as possible.

That's pretty slick. I like discreet and well executed modifications.

Here's my early attempt at drawing up the gauge face. I'm using Inkscape which I am not very familiar with, so it's not quite there yet. I tried to find the closest match to the factory gauge font, which turned out to be "Square 721," though I had to squish it vertically.

I'm debating on making the boost half a different color, or doing a yellow-orange-red progression of some kind. The vacuum side needs to be adjusted in its span of increments.

Bumboclaat wrote: That's pretty slick. I like discreet and well executed modifications.

I love the look of this!

The Autometer gauge you're using looks to have about 270 degrees of needle travel, but the scale of the dial you created shows about 180 degrees of travel... How are you planning to address the discrepancy in travel? A healthy engine will easily pull 30Hg of vacuum as I'm sure you know. Are you just going to let the needle overrun the meter of the gauge?

His motor won't pull 30hg.

Mezzanine wrote: I love the look of this! The Autometer gauge you're using looks to have about 270 degrees of needle travel, but the scale of the dial you created shows about 180 degrees of travel... How are you planning to address the discrepancy in travel? A healthy engine will easily pull 30Hg of vacuum as I'm sure you know. Are you just going to let the needle overrun the meter of the gauge?

The scale of increments on the vacuum side needs adjustment. You can see on the Autometer face that the vacuum side has smaller increments than the boost side.

Swank Force One wrote: His motor won't pull 30hg.

This, too.

Interesting data point, btw: I noticed minimal vacuum level change when putting in the big 272 cam last time around. This may have been from cleaning up other things as well, but it still idles around 18hg and pulls about 24 under decel.

Just something that came to mind.

Now back to your badass regularly scheduled programming.

So you're going with the expectation that it won't pull more than 25Hg or ~18PSI? That looks about right. Why won't your engine pull more vacuum? Old/tired, or big cam overlap? I can't wait to see it in action!

OK, here's another stab at the gauge face. It's still not quite there. I need to unsquash the font a bit to match the rest of the cluster. The vacuum side has been re-scaled so I think it matches the Autometer face now.

And I put it in place in my cluster to get an idea of what it will look like:

BTW, I'll be using a proper Mazda needle on this so it will look correct.

Looks good! Can you put small hashes between the ones you have?

In reply to Mezzanine:

Motor designed in the 60s with relatively big stock cam.

Swank Force One wrote: Looks good! Can you put small hashes between the ones you have?

The dashes on the vacuum side count by fives, the dashes on the boost side by ones. I did this because the vacuum dashes would get too squashed together if I tried to put a tick on every increment.

This is really neat. I'm looking forward to watching it all come together. Do you plan on posting the wiring process?

Tmc22 wrote: This is really neat. I'm looking forward to watching it all come together. Do you plan on posting the wiring process?

Hooking it up will be pretty much like any other boost/vac gauge, but my goal is to build the gauge face so that it lights up from the back side like the other gauges.

Well here's how it turned out:

Cool! Nice work.

Tremendous.

Nicely done!

Great work!

Wow, thats pretty dang cool.

Great work!

When do we get to see a video of it in action!?

Thanks guys!

klodkrawler05 wrote: When do we get to see a video of it in action!?

I've gotta put the car that this cluster belongs to back together first.