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Discussion Starter · #1 · (Edited)
With the helpful posts of our members I was able to install a boost gauge. The install was very straight forward and MUCH easer then I had anticipated and the best thing is no permanent modifications was needed.
The most PITA part of the install was pulling the vents. The clips do their job well.

Im sure most of this DIY can be performed on a CLA250 but Im not sure where to tap into the intake manifold, however.

Helpful links:
Pete's air vent removal.

Pete's underpanel removal.

Weistec's surge valve PDF to access boost pressure on the manifold.

The adaptor that I bought Its a 1/2" adaptor with a 1/4" NPT tapped hole . Cheap, discreet and effective and a great seller too. Speedy shipping as well, it only took a week to arrive from China.
1 2 Black Billet Aluminum Fuel Pressure Gauge Inline Barb Adapter with 1 8" Port | eBay

I chose the Autometer over the Speedhut because I am more familiar with the brand and it costs about 1/3 less. To be honest, Ive never heard of Speedhut before seeing a few of the other CLA45 guys installing them.
You will need 2 5/8" or about a 66mm gauge.

I will begin in the engine compartment.
Note: if you choose a different gauge, the fittings might be different. Autometer supplies 1/8" NPT fittings and PVC piping with their boost gauges.
The PVC hose needed to be tapped into a 1/2" OEM hose on the intake manifold. There is a chance you can find a plastic "T" connector for the connections but I was worried the boost might pop off the fitting.

This is the original adaptor I built from buying adaptors and fittings from a plumbing supply store. I only used it for testing because it was too large and heavy and might stress out the other end of the OEM hose that I tapped into.

Once I verified that it worked I bought the purpose built adaptor.

The parts needed for tapping into the manifold. I used teflon tape for the threads and 1/2" fuel line. I suppose you can use oil lines if you like.

A little 1/8" Techflex sleeving for the PVC hose so it'll blend into the engine compartment better.

Tools needed. The socket is a 1/4" for the hose clamps.

This is what it looks like with the fittings installed on the adaptor. I eventually trimmed about 1" off the hose pictured below. Overall, the hose was about 1.5"

This is the way the sleeve and hose connects to the adaptor.

Remove the engine cover, it will free up some extra room.

The hose needed to get tapped. Its in back of the intake manifold, near the oil filter and throttle body

The position of the hose made it a bit difficult to remove the clamp push it back. So I opened the clamp with the pliers and pulled the hose out. I removed the OEM clamp and installed my own.

Install the hose before installing the adaptor. It makes it a lot easer.


The tubbing was zip tied to the OEM tube. Be sure to give it some slack for engine movement. Use a little common sense and route the tube cleanly and out of the way. Avoid moving parts and high hear areas such as the coolant lines.

Running the hose thru the firewall. There is a grommet on the firewall where a clutch pedal would be if this car were a manual transmission. Please excuse the power wire and radar wire. Just poke a small hole and run the tune through. Its 100 times easer to run the tube from inside the car. The battery is on the other side of the rubber plug. Run the hose up and to the right and you'll eventually see it poke up into the engine compartment.

After removing the driver side under panel trim, you can run the tube up and around the steering column. You can see a bit of mine. The tube runs up the side of the radio and through the center vent. If you peek through the center vent and to the drivers side floor you'll see an open area of where the tube can run.

I didn't take any pictures of how the gauge attaches to the air vent trim. But I can assure you, it was very easy because the shape of the trim and gauge mates up to each other perfectly. All you need is high quality double sided tape. Apply a thin strip on the outer ring of the gauge bezel and attach it to the air vent trim. You might have to try it a few times to get it perfectly centered though. The convex shape of the ring bezel makes up perfectly with the concave part behind the air vent.
You'll have to disconnect the air locking mechanism by prying open some clips, they should separate easily.
Again, sorry I didn't take any pics.

Fixing the air vent trim on the dash with out the air locking mechanism. I used 1/8" and 1/16" neoprene foam and taped a trip around the trim so it acts a pressure fit on the dash. You can find the tape at McMaster. The tape is also great at eliminating squeaks on other parts around the car.

The air tube behind the dash was plugged with a microfiber towel lol. Funny but works.

You'll have to extend the light bulb (I used an LED bulb) wire with about 3ft of wire and run it through the passenger side footwell. Its basically the same way you run the tube from the driver side footwell.

Remove the floormat and pull back the carpet to access the fuses.

I could not find a wire that is switched with the headlamps so I did the next best thing by using a switched power wire - always on when the power is on. This is where its beneficial to use an LED bulb - not only because it produces a more pleasing white glow, it runs cooler and very unlikely to melt your bulb housing and draw less current.

I taped into the orange 5a fuse in the past for my audio system. I didnt have a fuse tap you I spliced into the wire behind it - black with a white line. I ran the wire to a Bosh type relay so it doesn't overload the OEM circuit. My test light is poking at the wire I tapped. You wouldn't have to worry about it if you buy a fuse tapper.

Here is a random Bosch relay diagram. #85 goes to the 5A fuse wire. #87 goes to the light bulb. Don't forget to fuse! I fused my LED bulb with a 3a fuse and thats probably over doing it.

And there you have it.

Heres a quick video.
I didn't mash down on the pedal, just a light progression to wide open throttle. There was a slight stall at 15PSI when I was pushed back to the seat and my foot let off the pedal a bit. :)
Sorry, not the best video...hard and a little dangerous to accelerate with one hand on the steering wheel.

In the end, it was a fun little project and much easer than I had thought. The overall cost was about $75.

529 Posts
Great DIY
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626 Posts
Discussion Starter · #7 ·
A quick update.

A few members contacted me requesting more detailed pics and the procedure of securing the gauge to the vent.

The center vent

The vent is made of 3 pieces that you can separate. The top, middle and back. The back piece is the part you no longer use.

The top trim screws off. But you have to wedge down the little lever.

Once the lever is pushed down with a small screwdriver, hold it the same way I am holding it and spin off with the same hand. It takes very little effort to remove. Sorry, not the best picture.

Once the top piece is off, you can wedge off the middle trim. There are 4 clips and all you need to do is stick in a small flat head screwdriver and wedge it out.


All 3 pieces taken apart. Put away the actual vent and keep the 2 trim pieces for the gauge install.

Its hard to see but the inside of the middle trim is shaped like a bowl

The trim of the gauge is shaped like a dome

And they both fit together like a glove.

At this point, you can use silicone to attach the two together but I used double sided tape for the ease of putting the vent back to stock form.
I used 3M double sided tape (the gray stuff) and cut it down to 1/4' x 3/4" strips. There isn't any rocket science used here, I just used 4, somewhat evenly spaced pieces. I didn't cover the entire rim of the gauge because it might be a major pain to remove if needed. This tape is very strong.

Don't forget to clean off the mating points with alcohol first.

I didn't take a picture of me pressing in the gauge but all you have to do is align the gauge and trim a closely as you can. If you mess up, just start over.

Completed pod.

A couple things to note with this install. I know, very obvious but just to be sure.

-Use teflon tape for all the tube fittings
-Clean off parts with alcohol before attaching double sided tape
-Make sure none of the tube is kinked and run it with as little sharp bends as possible
-Dont forget to fuse the light bulb

1,843 Posts
Anyone have a picture of where to tap the line for an after market boost gauge ?? There is many line on the engine, i don't know which line to use..

I have a P0299 (Low Boost) and i want to know what is the actual boost.

I don't want a pretty installation inside the car.
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