I'm gonna buy a boost guage but have come across some that have a range I'm not familiar with.

Some of these offer a range where the needle goes from X in Hg to 0 to X PSI.

Would having this 'dual' range type guage be of ANY benefit to me?

I figured on just getting a 0-15 PSI guage and being done with it.

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Chris
1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)

The part of the range labeled inches of Hg is the vacuum part of the gauge. It could be used with a switching valve to check vacuum points. Probably intended for a gasser originally.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

I'd go with the cheapest 0-30psi pressure gage you can find. If you know of anyone who works with pneumatic controls they would have plenty. All you need is a 1/4" barbed fitting and some 1/4" poly tubing. Standard stuff in the world of pneumatic controls. I'd say 0-15 psi is ok also. You probably won't see any boost pressures on your benz over 10psi or so if its original. The combination gage of Inches of Mercury and Pressure in psi is perfectly fine also. We're not building a watch, just checking turbo boost pressures here.

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Orland Park, IL
1985 300SD 215,000 miles

Actually, I think the vacuum reading can be used to determine how clean the air filter is...like, if you're seeing very much of a vacuum at idle, that means the engine's working harder to pull air in. Just a thought...

Also, where are you planning to mount this? I would like to put in a boost gauge along with a pyrometer, but I don't knwo where to locate the gauges where they would fit in with the rest of the interior...?

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2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999

I'm *wanting* to mount it in the ashtray. Anywhere where it would be seen, it would look out of place I think.

The idea of seeing vacuum levels while the turbo is not producing boost is an interesting thought.

__________________
Chris
1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)

I wouls suggest that you try and get a scale that would allow you to see it in a glance. If the range is to high you would need to focus on it to know the boost level.

I wonder if anyone make a digital unit (3/4" by 1 1/2") , that way it would be clean no matter where you put it.

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1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it

Hey, how does this gauge look? That's from Isspro...I can't rememebr exactly what the max boost is on these engines...

Here's what I installed:
16.99 boost gauge!
Also, why T? There are additional ports in the intake manifold into which the boost gauge line can be tapped.

I would buy a gauge without the vacuum section and the smallest psi range possible, a 0-15psi would be perfect as these engines shouldn't be over 14psi anyway. A 0-30+psi gauge or one that has a vacuum scale on it reduces its readability and adds nothing for our application. Check this gauge out: http://www.dieselpage.com/iss14.htm
or this: http://www.dieselpage.com/issev2.htm
For digital, check out: http://www.speedshop.org/store/Scripts/prodView.asp?idproduct=20

Have fun! RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

Somewhere in a textbook "Handbook of Instrumentation and Controls" by Kallen......there is a reference to what I'm getting ready to type.....will do my best to look it up if necessary.....

Basically, most mechanical pressure and vacuum gages that we are likely to find at a reasonable price will be of the "Bourdon Tube" type...Bourdon Tube manufactured from Phosphor Bronze.....I'm not gonna go into how and why it works.....but as the tube tends to straighten out under pressure, or contract under vacuum....the end of the tube is connected to a gear train that ends up operating a pointer.....to prevent the tube from operating at it's designed limits (the max pressure on the gage face).....one should select a gage that will operate somewhere near it's midrange....(if you wanna measure 15psi, buy a gage that reads 30psi).......prolonged operation at or near the gage's maximum range will eventually damage the gage, the Bourdon Tube will take on a set.......

Digital gages are a totally different subject......but basically the same rules apply regarding range selection, of the sensor or transmitter element...no matter how the digital onformation is sensed.....

Trust me.....I have replaced many pressure gages in my lifetime ......

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

I have been thinking about using the Gasser Economy Gage for/as a Vacuum Gage.....it will be operating in a range that it was designed for......Economy=Manifold Vacuum.....I have wondered why MB did not do this, instead of manufacturing a different instrument cluster for Diesels??

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

I finally got the needle off the shaft. I ended up using a fork and pulling it straight up with my thumb on the pointer head.

Attached Thumbnails

 

A diesel doesn't operate at the same manifold pressures. With a diesel more Manifold vacuum = blocked air filter = poor economy.

Higher manifold pressures, to a point, give BETTER economy with a diesel.

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Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY

Check out egauges.com, they have a pretty impressive selection of VDO gauges that are suprisilngly inexpensive. I will be adding a 15 psi boost gauge to my 123 as soon as I get time. Haven't decided on a mounting place yet. I will post pics as soon as it is completed.

jhal: Jep...already been looking at egauges.
Let me know if you think of any good places to put the gauge. I plan on *trying* to fit it into the ash tray.

__________________
Chris
1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)