A number of people have asked to ride in my W116 (1978 300 SD) lately and everyone comments on the smooth, seamless power of my 617.950 engine.

At the request of one local 617 enthusiast, we hooked up a boost pressure gauge so he could observe the boost pressure curve over the rpm range, as opposed to just the maximum boost pressure output.

I found the results interesting and decided to post them here in the forum.

Keep in mind I have modified this engine with increased fuel delivery pressure, '05' cmashaft, advanced camshaft/injektion timing, fully polished turbo/intake tract, 6 angle valve and seat faces, port matched cylinder head and a modified T3 Airesearch turbocharger.

The turbine housing was machined to accept the larger Buick Grand National V6 Turbine which allows faster spool-up at lower exhaust gas velocities. The housing was fully polished and 'Jet-Hot' Thermal barrier Coated.

The intake turbine is also special. It has twin vanes (blades) instead of one and they have a unique pitch. This was provided by Advanced Diesel Systems in Fresno, CA.

We used a Snap-On Vacuum/Pressure Gauge for this test. We attached a fitting into the plug at the front of the intake manifold. This allowed us to retain the Overboost Protection Circuit. The air filter was left in place.

At an idle speed of 875 rpm, the needle fluctuates slightly, which gives you an idea of how sensitive this instrument is.

Snapping the throttle wide open (and quickly releasing it) indicated 7-8 psi on the gauge. Rpm peaked at about 3200 during this portion of the test.

As we took the car out for a drive, we noticed the boost gauge imitated the movement of the tachometer. We were registering about 3-4 psi by 1200 rpm and it continued to climb in relation to engine rpm very rapidly.

At a 65 mph cruise, we were developing 6.5 psi at an indicated engine rpm of 3000. Opening the throttle fully, instantly swings the needle past 10 psi of boost.

We then conducted the WOT test, holding the engine against the brakes at 4000 rpm in the second speed range. We recorded 14.5 psi of boost pressure.

I blocked the wastegate hose to test the overboost circuit. I connected a test light to verify the circuit was operating. The boost pressure would 'flash' to 15.5-16.0 psi followed by a noticeable decrease in acceleration and a subsequent reduction in boost pressure to about 10-12 psi.

The interesting part of the test was how quickly I could produce 10 psi of boost pressure. In the second speed range, at a vehicle speed of about 20 mph, I can sweep the throttle open (without downshifting) and swing the needle instantly to 10 psi.

At 70 mph, I can sweep open the throttle quickly and swing the needle up to 14 psi as quickly as the throttle is opened.

Most people who ride in the car comment on the fact it doesn't feel like a turbo diesel because there is no acceleration surge. The power is immediate and constant. I am sure adjustement to the Aneroid Cell (ALDA) on the injektion pump is associated with this sensation.

It is night-and-day compared to my Dad's stock 1982 300 SD. We are planning a similar modification to his car in the near future.

Fuel economy is fantastic and visible exhaust smoke is present only during high boost operation. The car doesn't 'chalk' the back bumper with soot either.

One of the reasons I think my fuel economy is so good (over 30 mpg so far) is due to the increased boost pressure. I have to open my throttle very little to get big performance from the engine.

I wanted to post this in hopes you might find it an interesting read. Best of luck on your projects...Bert

30 mpg? that great I get about 25 in my daily driving on my W116 which is better than my W123 gets........but I don't have long flat stretchs of highway either..............I would love to duplicate that engine but I know thats likely never going to happen.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

pics to share? tia

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

I have some photos of the W116 in this forum under the post "W116 Goes Home." I will snap some photos of the engine this weekend...Bert

Bonehead: This engine would be surprisingly easy to duplicate. I think many of my modifications are overkill...Bert

I have a good running spare engine that starts in 3 revolutions in 18 degree farenheit weather (without using a block heater) to piddle with.

OPh and about the ACC manual...I should be able to copy it next week.....too busy this week to camp in front of the copier for half the day.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

sounds like i t drives like my 03 dodge with cummins and six speed. the power is like having niagara under your foot. mind saying how much you have invested in this powerful device?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Thanks Bone....

Well, Walgamuth.....Since I do all my own work, I don't have much invested. I buy parts from a couple of sources and still get an employee discount (from when I worked for them) so parts are very reasonable.

The turbo coast me about $250.00 for the used Buick Turbine and the basic Overhaul Kit. I machined the housing myself.

Anyone who had an engine apart could do the porting and polishing with a 3/8 drill and some abrasive cartridge rolls. However, you can get really good performance from just the turbo upgrades.

In fact, I used the improved input turbine on my Dad's 1982 300SD with the stock MBZ exhaust turbine, adjusted the ALDA, advanced his camshaft timing 4° with an MBZ Wooddruff Key and adavnced the Injektion Pump Timing to 28° BTDC.

I then took the injektors to a local shop and had them tested, with the results (in psi) written on a tag. I then added the special shims (again an MBZ dealer item) to increase and equalize the deivery pressure of each injektor.

These changes were like bolting in a V8. No cylinder head porting, 6 angle valve job, polished intake tract and turbine housing, just a basically stock motor with 176,000 miles on it.

I paid about $200.00 - $225.00 for the new Intake Turbine Wheel and the Overhaul Kit for the T-3 Turbocharger.

The engine looks stock, except for the Jet-Hot Coating on the turbocharger. Just a clean overhaul. Nice paint on the engine, but not a show car. I drive this one.

I hope the information is helpful...Bert

Can you give us any details on the mods you did to the intake turbine housing? I need to rebuild the turbo on my 300SD and would consider some additional investment/work if it made a substatial difference in performance.

Thanks,
Ray

__________________
1985 300SD, 203,000 miles, dark blue

Lil Sarah says: "Poor old Grandma Blue Car...She's sad."

Ray,

Basically, I just polish the inlet side of the turbo with a Dremel Tool. I wrap a piece of 'Scotch-Brite' abrasive pad around a round wire brush (in a 3/8" drill) and polish the adapter tube (between turbo and intake) and the turbo inlet itself.

Very basic polishing technique....

My 617 had a lot of slag in the intake tract, which I knocked loose with a sharp chisel. I then polished the entire intake manifold to a smooth finish. You can't cover every square inch, but you do what you can reach.

I do the same thing to all the oil passages. I enlarge and blend the openings in a brand new pump and match that to the adapter tube entering the block. I also polish all the oil passages with a 3 foot mandrel and a series of abrasive cartridge rolls.

This may be overkill, but with a stock oil pump and Shell Rotella T 15 w 40 oil, I am getting 28 psi at 875 rpm hot and pegging the 45 psi gauge at 1800 rpm. I believe this is simply a reflection of more volume through less restriction. My crank is standard and bearing clearances were all in the .002" range.

The biggest issue is ensuring you have correct camshaft timing, valve adjustment, injektion start of delivery and boost pressure.

Even without the polishing, which probably is overkill on a street engine, you can get fantastic performance from these engines...Bert

One more thing....intake turbines wear out from abrasives in the air intake system. No matter what kind of filter you enploy, some dirt will get through and over many thousands of miles, the blades wear to the point they produce less airflow per revolution.

Replacing the intake turbine when you rebuild the turbo makes a vast improvement in spool-up because you get more air volume per revolution of the turbine shaft.

The bushings (not bearings) in the T-3 Turbocharger 'float' in the housing exactly like the connecting rod bearings in a Flathead Ford V8. The bushings rotate in the housing and are drilled for oiling 360° around the OD of the bushing. In other words, the bushings not only wear on the Inside Diameter (ID) but they also wear on the outside diameter.

When wear reaches a certain point, the turbine will contact the housing and start sending aluminum shavings into the intake tract. Not a big deal, since they are soft, but still not a good thing. In addition, when the turbine contacts the housing, it drags down the turbine speed and results in less boost, slower spool-up and increased heat.

One very important factor people disregard is allowing a turbo to cool down at idle for 2 minutes after driving. When you don't allow the turbo to cool, some of the oil 'cokes' (or burns) in the turbo and carbon is formed. The carbon is hard and will immediately start attacking the bushings.

Another modification I perform is enlarging and polishing the oil inlet opening in the turbo to improve flow and volume through the unit. This makes a huge difference.

Another thing I saw a lot of when I was rebuilding turbos for the dealer was people leaving things off during a budget overhaul. The most common item is the heat shield under the exhaust turbine. This must be in place to deflect heat from the sealing rings and bushing on the exhaust side of the turbine.

If built correctly, these T-3 units are suprisingly trouble-free and yield a long service life. It usually takes me about (8) hours to polish and overhaul a turbo, not including R&R. This allows me the time to do it the way I like. At the dealer, I had much, much less time because I was working flat-rate and they don't offer us much time for polishing.

What are you paying for a rebuild kit and new inlet turbine these days???...Bert

Do you attribute more low speed power due to the advanced cam timing with proper IP timing first? Then adding the turbo next?

Also - you basically install the exhaust wheel from an OE Buick GN turbo in the T3 that's on the 617 currently correct? Used OE GN turbos are pretty cheap last I looked about (if all I need is the exhaust wheel, I'd just get a soild core). I have access to a T3 that needs a full rebuild for $40 locally, shaft is stuck so I'm not sure if it's a good core or not...



Lastly, was full load fuel from the IP turned up at all or is it still on spec with OE? I'm curious if I need to investigate further on that if this can get me the type of torque I'm looking for.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Hit Man X,

I think it is more a matter of having 4-6 psi of boost at 1200-1400 rpm than anything else. Again, the turbo modifications simply allow faster spin-up at lower exhaust gas velocities. This is why GM increased the size of the exhaust turbine on the Buick V6...Bert

Do you have any 0-60 times? Without that we really have no idea what you have gained. I'd love to see a 10 second 0-60.

I don't think my stopwatch would be accurate. But, I will be going to Famosos Raceway in bakersfield CA. soon just for fun.

I can tell you the car is capable of a stopwatch-timed 27 second 60 to 100mph in high gear without pressing the throttle far enough to induce a 3rd speed range downshift.

There is even a video of the speedo during the test on this forum...Bert

Interesting stuff! I may get that bum turbo that's out here and have it rebuilt, a local place called Forced Induction Systems ports exhaust housings for about $90. They were big in the Subaru WRX world when I had mine.

Any idea how many pounds of boost is made stock at 1200-1400rpm?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]