Haha!
The second boost gauge is for exhaust pressure-so he can keep on eye on the state of his VNT setup. I have one also.

My shot flex pipe gives me a nice wheeeeee noise too Gotta love turbodiesels

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

What's wrong with gauges that is dash mounted??? I like to keep an eye on my boost pressure, it better than placing it at the kick panle because you can't see road when your looking at your boost gauge unless you have 3rd eye on your forehead ...

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Current Garage
2008 Mercedes GL320 CDI 188k mi Repair/Work in progress
1994 S350 160k mi Garage Queen & prepping for repairs
2005 E320 CDI 203k mi Healthy & Daily Driver
1994 S350 357k mi Retried as parts car
1984 300TD 214k mi Blown OM617 Poss OM603 Swap??

Sold
1987 300SDL 200K+
1994 S320 181K mi
2008 E320 Bluetec 127k mi
1999 S420 130K mi
1980 240D 360k mi
15+ Others that has come, stay and gone

GONE, BUT NOT FORGOTTEN
1995 E320 SE 220k mi
1984 300SD 350k mi

Thats it. Vanes are able to control boost by directly altering the velocity of the exhaust gasses (which changes the backpressure), a wastegate just limits boost by bleeding off existing exhaust pressure. Monitoring exhaust pressure is important to make sure it isn't too high when accelerating.

Its also helpful in trying to get the desirable 1:1 exhaust:boost pressure ratio.

Kinda sounds like my skidsteer.
Makes me glad I replaced the resonator and mufflers on mine.
Guess all you need now is one of those enormous cans that all the little tuner cars have. That and putting the row of gauges on the A-pillar, and maybe lowering the car, and maybe spending 5k on a set of wheels and low profile tires, and the dingle balls around the windows.

Have you seen an increase in performance?

Thanks for the turbo lesson. What kind of additional power do you see with the VNT?

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1974 450SL White/Navy Blue

1983 300SD White/Parchment, VDO Boost Guage, 215/60R15 Bridgestone Potenza RE960AS Pole Positions on 15X7 15 Hole Wheels, Straight Piped, 298K?

2004 Ford Excursion XLT 4X4, 5.4L V8, 285/65R16 BFG AT KO

Sorry but how do you mount the guage so as not to melt the tubing?

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1974 450SL White/Navy Blue

1983 300SD White/Parchment, VDO Boost Guage, 215/60R15 Bridgestone Potenza RE960AS Pole Positions on 15X7 15 Hole Wheels, Straight Piped, 298K?

2004 Ford Excursion XLT 4X4, 5.4L V8, 285/65R16 BFG AT KO

This dyno chart is a comparison between the stock KKK K26 and the Garrett GT2256V. There were no fueling changes between the two, just the turbo swap.


Copper tube is used for the first 2 feet then normal plastic tube to the gauge.

very interesting graph. Is the KKK K26 standard on 603 and 617s? While it looks like the Garrett falls off pretty quickly past 4250...it looks MUCH more friendly on typical everyday driving scenarios.

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1983 300SD ~250k

I have a down-turn on mine





It's now painted black for a more stealth look.

I also have a muffler, so I guess it's not really a straight pipe either.

Attached Thumbnails

 

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Is this idea different in turbo diesels (vs. turbo gassers)? In the gas world, that is an absolutely impossible idea. NEVER will you have the exhaust pressure come anywhere CLOSE to intake pressure. In my 944 Turbo, with the stock K26/6 turbo, you are likely to see 45+psi in the exhaust for about 18psi in the intake. But of course that is with the stock turbo (running slightly higher than stock boost). This is the whole game of turbo efficiency for a given application...and why 1psi DOES NOT EQUAL 10hp - and all these other crazy theories. It all has to do with efficiency of the turbo. I guess people don't realize that at a given psi, different turbos can run as much as TWICE the cfm as others.

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1983 300SD ~250k

No. It was used at the same time, depending on what Mercedes had available, from 83-87.

The VGT really helps, I can just about hit 1:1 at cruise with mine. To get that kind of ratio with a conventional turbo it would have to be extremely large for the engine. Relatively small turbos and higher than stock boost levels probably aren’t helping things on your Porsche.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

A K26 is small for our 3.0L diesel. Its REALLY small for a 6400rpm 2.4L Porsche.

Also, at 18psi a K26 is just a heat pump. Its efficiency drops off dramatically above 14psi, Audi owners have known this for years.

Yes, yes, and more yes. The ratios I was talking about are at full boost, not cruising. Stock boost for the 2.5L 944T is around 14psi, which arguably is pushing the max efficiency to begin with. the 944 Turbo S of 1988, and then standard on the '89 Turbo went with a bigger hotside (K26/8), which helped things quite a bit.

I found that dumping the exhaust just after the downpipe, along with a MAF on the intake side (and all the engine mods to support) let the K26/6 stay efficient up to about 18psi (I monitored EGT's, knock, air/fuel with wideband, manifold intake temps, etc). By the data I saw...it was doing just fine at 18psi...but I'll be the first to admit that was COMPLETELY due to my mods. A stock 944T engine with a K26/6 at 18psi is a headgasket job waiting to happen.

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1983 300SD ~250k