1964 mercedes diesel 4 speed manual optimization.
 

Okay, I'll ask my important question first, then those interested can read the rest of the post for more detail. So I wont bore everyone to tears.

Is adding the correct size turbo to an NA diesel good for mpg increase?
What model turbo should I use to optimise for mpg?
Bonus points if it is a common junkyard turbo, to keep it cheap
Guys are adding turbos to these motors to make crazy horse power, so not worried about blowing up the motor, but what should I set my max boost to to optimize for mpg?
What gauges would be good for tuning for optimum mpg, in addition to basic engine protection gauges like EGT, and Boost?
What additional info do you folks need from me to help you answer my questions? weight of car? horsepower of engine? peak torque rpm? rear end ratio? Let me know if you need any of this stuff and I will get it posted asap. Thanks again.

Well, for all you who are following the drama with my electric truck batteries being stolen on my other thread, I was trying to figure out a way to throw a geo metro motor in it instead since I didn't have a couple of grand for new batteries.

I found a guy, who hangs out on this forum (I'll let him out himself in case he wants to be incognito) through craigslist who wanted to trade his sweet mercedes diesel project and parts car for an electric vehicle project.

A match made in heaven, two happy campers flowering out of a manure pile of theft.

Anyway, on to the project. People on the internets are telling me that these W110 chassis mercedes with the OM621 2.0 diesel are getting between 30-35mpg stock. There have been worse starting points.

First I will baseline the vehicle, change fluids, filters, adjust valves and check compression,(checking compression is like checking the spark plugs for a diesel, it matters that much!) to make sure the basics are covered.

Then mercedes source sells a kit to upgrade the 60's style glow plugs to the 80's style which work a lot better apparently.

I will rebuild the injectors with monarch nozzles, supposedly an upgrade in mpg and power. I found some great plans on the net to build an injector tester out of a bottle jack and some other parts. Tuning the injectors for pattern and opening pressure should help everything else.

The pre-chambers on this engine are removable, so I think I will pull them and scrape all the carbon out that could impede the quality of the fuel squirt.

I could to rear wheel spats and underpan without wrecking the sweet style of the car

The car has a solid rear axle with leaf springs, so swapping to different axles from a different car to get other axle ratios should be doable.

Also, the same body was available with auto transmissions and gas engines, so maybe those came with different ratios and I could swap. The mercedes comes with a parts car that is gas engine manual transmission. I will check to see if it has different axle ratios.

On another thread on turbocharging gas engines for efficiency, it was stated that numerically dropping axle ratios was important for getting the most fuel economy out of adding a turbo.

Factory rear end gear ratio should be 3.92/1 according to the interwebs.

here is some hard numbers to help the physicists help me.
 

Engine 6 Cylinder Diesel OM 621 190Dc:

Capacity: 1988cc 121.27ci
Type: Diesel, watercooled four stroke, reciprocating piston type with 6 cylinders
Configuration: Front mounted, longitudinal, inline
Head: Pushrod and rocker actuated ohv with one valve per cylinder
Fuel System: Bosch injection pump (pre-combustion chamber)
Bore and Stroke: 3.43 x 3.29 inches (87 x 83.6mm)
Power: 55 hp (DIN) @ 4200rpm
Torque: 11.5 mkg @ 2400rpm (87.0 ft/lb)
Compression Ratio: 21.0:1

Manual Transmission (190Dc):

1st: 4.05:1
2nd: 2.28:1
3rd: 1.53:1
4th: 1.00:1

curb weight=2904lb

28.87ft^2 frontal area

Congrats on the new project - glad to hear 2 ecomodders got what they wanted!

Good luck with the car. I know next to nothing about diesels!

I had two Merc 300D cars. drove them over a period of 10 years.

What I found was consistant 24-25 MPG, engines were non-turbo models. I had friends with 300D Turbo models getting close to 30 MPG.

Asked an expert in Mercedes one time about adding a turbo to one of my diesels. He said it would be far cheaper to buy a used Turbo Diesel, since there are vast differences between the Turbo and Non turbo diesels.

One of the issues I had with my 300D was keeping the injectors clean. I used additives like Techron which kept them clean for about 10000 miles per treatment.

Good luck with your project.

I think the newer Mercedes Diesel technology is hard to beat.

Here's a story of a test where they got 40 MPG running over 140 MPH for 30 days!!

World 100,000 mile record: 140 mph for 30 days averaging 40 mpg

I thought it was a 4 cylinder. It morphed into the 240 a few years later. You are right about the glow plugs. Poor injector spray pattern will burn the older glow plugs up in a heartbeat. They were a wire loop and the fuel spray would work like a blowtorch on that wire loop sometimes only taking a couple of days to wipe a brand new glow plug out.

I would not turbo that engine. The turbo versions had considerable modifications to hold up under the added strian, including nozzles that sprayed oil on the bottom of the pistons to keep the pistons from melting, not something you could easily upgrade. Been a long time since I looked t a 190D or a 64 MB car with those fins.

regards
Mech

You are right, it is a 4 cylinder engine.

Granted, it is on forums, but it seems like lots of people are adding turbos with no ill effects. Granted these are people adding turbos with just a couple of psi of boost, just for the fuel economy/noise reduction/bragging rights. As the descenting vote, I would value your opinion on weather you thought a low boost set up would be safe/would have any benefits to FE.