DIY Exhaust backpressure gauge

gmcman

Original poster
Member
Dec 12, 2011
4,656
Looking at the gauges available, I figured I could build a decent one at a price close to the cheaper ones. I understand now why the expensive ones command their high price and that was after I priced the stainless braided hoses. :crazy: $30-40 per foot and since this won't be used in a commercial environment the hose I used should be more than sufficient.

Could you save about $15 and use a rubber hose for short term use? Probably.

I wanted to build it to withstand moderate temps without causing me any trouble. I went with some high-temp vacuum rated hose 6' in length so I could view the gauge from the drivers seat.

Gauge is a Winters Instruments purchased from Fastenal.

Gauge price $40

Gauge specs:

0-5 Psi Gauge

Hose specs:

Temperature Range: -65° to +350° F
Hose: Silicone rubber
Cover: Silicone rubber
Reinforcement: Polyester
Bend Radius: 1 3/8"

1/4" ID, 9/16" OD, 60 PSI, Blue $3.39 per foot, 6 feet = $20.34 from Mcmaster-Carr

O2 plug was a M18x1.5 drain plug that I tapped for a 1/8 NPT hose barb, sealed with high temp thread sealant rated @ 400 deg F.

Hose barb on gauge end was 1/4"

Total price for everything was about $70

I can always upgrade it later with a stainless braided hose but for now it should serve it's purpose well enough.



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Not quite sure how I punched it in the center and ended up way off but needless to say the bit walked.


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:crazy: :redface:

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I drilled in steps, first was 1/8 all the way through, then 1/4" half way down, 9/32" then finishing with 11/32 which is the correct drill bit for the 1/8 NPT fitting.

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This M18 plug is rather soft so even the black oxide bits chewed right through it.

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Using the high-temp sealant I don't need to worry about any rubber gaskets or teflon tape being exposed to the high exhaust temps.


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At some point I will find or build a 5 PSI safety valve I can incorporate in this setup to save the gauge if I encounter an over-pressure.
 

Chickenhawk

Member
Dec 6, 2011
782
Nice job!

When you get around to testing it, post your pressures at idle and at 2500 RPM. It would be great to amass a database of good and bad pressures over the years because the cat converters come in at least two different sizes in our platforms.

As our platform ages, cat converters will degrade more and more. They are very sensitive on modern vehicles and with our history of bad thermostats, this will be an increasing problem in the coming years.
 

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