You COULD just strap a JATO bottle underneath for exta acceleration, too....

Seriously, you aren't going to do much besides ruin the engine by horsing around with the injeciton system. This isn't like a typcial US pickup truck engine that is both low compression and seriously overbuilt -- no problem with propane "fumigation" on those since by and large the complression is so low you won't get into trouble if you overdo it. On the Benz you will at LEAST blow the head gasket if you overfuel since the propane will cheerfully ignite long before TDC (21:1 compression ration as opposed to 16:1 or 18:1). More likely you will break the ring lands or pull the head bolts out of the block. You will also over-stress the rods and crank -- they weren't designed with those kinds of loads in mind.

Diesel engine design isn't something someone doodled out on a piece of paper while tripping on acid on night -- there are a large number of interdependent things going on all at the same time, so you cannot just, for instance, swap injector types and expect decent running. Twiddling will leave you with a poorly running fuel hog every time.

You can safely ignore all the "pulling tractor" stuff as well -- the MB engine has only the fact it burns diesel fuel by compression ignition in common, and the vast majority of the "science" involved in that stuff is nonsense. Two stage turbocharging a 5:1 compression ratio engine is simply showmaship, to be polite. Horsepower requirements for all the stuff are minimal -- a WWII fighter plane weighing 30,000 lbs could accelerate to flight speed (60 mph) in 400 ft with 2100 hp, after all.

The 617 engine has a pretty decent power output as is -- 120 hp or so with 150 ft/lbs of torque -- on 184 cubic inches displacement. It's built like a tank, runs 300,000 miles without work if maintained properly, and get 26-28 mpg doing it. What more do you want?

The 603 puts out more hp per cubic inch than a Chevy Vortec, and has MUCH more torque, too!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Guys, Guys, I'm not trying to be controversial here. We have a few of these old engines lying around and can afford to experiment a little bit. I understand mercedes put a lot of time and effort into that engine and car (and thats why I drive another one every day). This is just meant to be fun and see what happens. Hopefully we'll get around to it sometime soon (father and I). Thanks for the input!

Granted there not a mercedes, but there are a good number of people in the semi truck business with some seriously leaned on motors that last a long, long time. There is some excellent general info online. Ditto the Cummins dodge truck guys.

And then there was the VW Rabbit GTD(iesel)
A fellow here in the states went pretty deep into building up a 1.6L TD, plasma coted pistons, cryotreated everyting, head studs, custom head gasket, alternate turbo, recalibrated injection pump and injectors, there was a whole slew of stuff people always talk about but he actually did. If you search around on VWvortex.com's forums you can find him. He was beating import 4 bangers on the street with it, and that's saying something. He was also still getting well over 35mpg and no longevity problems showed up. I believe he just wanted more power and eventualy started looking at a TDI or a 1.9IDI, I don't recall.


I'm reasonably content with the OM617.

The 603, or 604, whatever the SDL had, stuffed into a w123 might be fun..

__________________
One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Calm down Fred...I was talking tongue in cheek. Notice the and the I put after my suggestion.
I won't touch my engine. It works just fine as-is. If I want more power, I'll get a 560SEL

__________________
past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

I repeat, you cannot improve a pre-chamber engine by removing any part of the prechambers. TDI/CDI engines are completely different, so whatever has been done there won't apply.

The difficulty is that the injection system has been designed around the prechamber. To conver to direct ijection, you will have to find a way to get an injector all the way down into the combustion chamber, and find one that sprays only one way (else you will promptly burn a hole in eithe the head or the piston, whichever the flamy hits) AND find a way to point it reliably, etc etc. DI engines normally have the injector more or less dead center, with the fuel spraying out the sides, not straight down. Sometimes they are on the sides, but then the injector is directional and is bolted down instead of screwed in.

Stick with raising the boost and fuel, you are wasting your time with screwing around with the injection system. I'm not being a purist, just passing on information.

The reason the guys with the US pickups get so much more power is that the engine originally only develops about half what the Benz does per displacement, and they tend to run fairly low boost, too, unless user modified. Kick up the power, crack the head.... Compression is also fairly low except on the most recent engines (16:1 or 18:1). Makes it easy to get a lot more power. After all, if a Ford Powerstroke was made like the 603, it would produce 300 hp and 400 ft/lbs of torque right out of the box!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Are they that far from it stock? I figured there torque numbers were up there, and I know there are computer mods to increase things by substantial numbers, and that they do not harm engine longevity.



Boost has always been the best way to more power on a diesel, you just have to make it hold up to it. It's not cheap or quick for more than a small improvement with older motors.

What exactly did MB do to the 617 in the C111 or whatever it was? Does anyone know?

__________________
One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Mostly manufacture VERY close tolerances and boost the hell out of it. Might have had a different head with larger valves, etc, too, but I don't know that for sure.

I believe the bottom end was stock.

I also don't know how long it would run -- probably not 250,000 miles at that horsepower output!

Don't remember the numbers on the powerstroke right off my head, but it's not 300 hp or 400 ft/lbs of torque, and the rpm limit is something like 3000, not 5000. If you can get more power out of it with a computer chip, it's detuned as shipped.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

All computer controled motors are that way, de-tuned if you will. The issue is, least in the recent past, they have to function as well at one temp/altitude extreme as another, and on crapy fuel, and overloaded, etc, etc. Almost anything with a computer can have the fuel and spark curves turned for more power. From z28's to hondas to TDI VW's. And in the VW's case, it even gets better MPG too..



That's interisting about the C111. Sure would be fun to build one strong if one had really deep pockets.

And looking online, the powerstrokes had over 400ft/lbs since the late 90's. HP around 235 or so. I can tell you from personal experience, they will move a 2001 F250 4x4, which is a boat anchor, pretty well. I'd bet faster than a w123 300D in a lot of cases.

"For the 1994-1998 Powerstrokes, the truck responded amazingly. In the mid-range, we achieved an extra 50 horsepower at 2000 RPM and a 100-ft/lb torque increase. Also notice that by extending the power band in the RPMs we gained an extra 25 peak horsepower. For the intercooled 1999 and up Powerstrokes, we gained even more horsepower and torque. With the Performance Chip, the Powerstroke gained up to 125 HP and 140 ft/lb torque over stock figures. "

Must be nice to be able to plug in that kind of power increase..

__________________
One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Let's just drive our diesels, and not worry about such petty things. I'd rather have a diesel that could barely do 70 mph, then one that could do 200. At least on a 200D or 220D, you could max the car out on the highway, foot to the floor. That's awesome! THAT'S REAL fun!

A new performance perspective; the slower it is, the more challenge it will be to drive. I love a good challenge. I should get away from these cars of mine and get at least an automatic 240D. Seriously, it sounds intrigueing.

You guys who are always complaining about the autobahn having no speed limits, blah blah blah. Well most of us are in the good 'ole US of A where speed limits rarely go above 65 mph. Wouldn't it be nice to have a car where you didn't have to worry about Staties all the time in? I think so....

Open your eyes and you will find that the Powerstroke/Cummins/Duramax are all around or exceeding 300hp/500ft/lbs torque and have been for quite a few years. While US truck diesels are different from MB diesels they are not inferior designs. Consider what they are used for: Pulling things! They don't just loaf down the highway with a few passengers at 75+mph. They can do it with 10K hanging on the hook. Mile after mile year after year. Most US truck diesels will pull their max payload and beyond for 200+K, many without the lavish maintainence that our beloved MB's get. I just can't stand the snobbish crap I hear here sometimes. Most US diesel worktrucks spend a hellish life getting the crap beaten out of them. That they survive at all is amazing. Thats the reason they are overbuilt. Getting back to the original post, I wouldn't mess with removing the precups but it is interesting to note that when GM modified the 6.2NA motor to the 6.5TD the combustion holes in the precups was increased by about 20%. It has been noted that when 6.2's are run with the larger precups they make more power. That may be a place to start, slightly increasing the holes by grinding them out adn polishing smooth. Sorry about the rant. RT

__________________
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

Been there done that, for about six years. The diesel VW is by all acounts slower than a 240D. But it will outhandle and out brake it, judging by my 300's performance. It does reaquire a lot more forethought and attention be paid driving something that mistakes cannot be covered up by punching the throttle.
Good training.

__________________
One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

RT:

My main complaint with US diesels is that they still resemble stationary constant speed engines too much.

This appears to be a design philosophy on the part of the manufacturers, and since they were exempt from emissions regulations until the late 80s (or there abouts), US diesel truck engine design was somewhat lethargic. The emissions requirements changed that, you must have an efficient engine to run clean.

Unless the latest models have improved considerably (later than last year, anyway), they are still fairly low hp output, low speed, very noisy engines that get poor milage even at light load (driving an empty truck). The over the road engines are vastly better, but they had a very long way to go.

Cummins is the best as far as my limited experience goes (my friends who drive diesel pickups prefer Cummins engines) and they seem to have fewer problems, but they could be much more efficient.

The MB 603 (developed in the early 80's -- twenty years ago --) produces 145 hp/195 ft/lbs torque on 3.0 L. The 606 (DOHC, center injectors) produces about 160 hp and 210 ft/lbs. Converted to 6.9 L, it would be 334 hp and 449 ft/lbs torque, so only the later powerstrokes produce what Benz sold in 1985. Benz makes truck engines, too, that last just as long and make just as much power.

US automotive engineering tends to lag considerably behind Europe and Asia, mostly because there is very little pressure from customers to increase efficiency and lower costs -- in the US great leverage is used to subsidize the trucking indutry to cut costs, no one really pushed hard to get better engines until about 1990.

Low efficiency and waste bother me.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

psfred,
I agree that low efficiency and waste are a bad thing. I also think that MB builds great diesel engines. I can't agree however that US light truck diesels are inferior or low power as you suggest. The US diesels are all multivalve, direct injected, common rail, intercooled, computer controlled, etc. I don't see how they are in any way lacking in technology. They may still be long stroke but I think that is by design. The work truck/towing/RV crowd is not going to be happy with an engine buzzing away at 3500rpm on the highway no matter how much power it makes. My truck, an admittedly questionable motor, the torque peak occurs at 1900rpm. It makes towing/hauling much easier. Regarding the inefficiency I don't see how you can say this. They all deliver about 20mpg running empty and 14-15mpg towing moderate loads. Obviously they can't compete with a new MB CDI at 40mpg but thats not a fair comparison given they weigh 2-3times more, are about as aerodynamic as a barn and have much higher rolling resistance due to the nature of the tires, running gear etc. Regarding the supposed low power, again I believe it is the manufacturers policy not the technology. Some of the Dodge crowd was making enough power to twist the frame enough to pop the windshields out of the cabs. Ford and Dodge have had problems with auto transmissions not withstanding the power. I think they are afraid of the warranty problems if they turn up the power. How else can you explain the easy 100hp/150ft/lb gains with just a simple chip change on these engines? If they were so low tech and at their limit why is it so easy to get more power out of them? Why is it that even when chipped, etc. the mpg's stay the same or improve? Why is it also that chipping or other moderate modifications that increase powers so drastically not seem to affect longevity? Hmmm, could it be they ARE actually pretty good engines? RT

__________________
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

Actually, For those who like challenges modernizing one of the old mercedes would be outstanding. I think Tymbrymi is on to something. As a college engineering senior design project converting from a fixed timing mechanical indirect injection system to a computer driven commonrail direct injection system would expose you to a ton of engineering issues.

It would take deep pockets though. You would need:
A 4 or 5 injector common rail system. You might find a 4 cyl setup off of one bank of a V8 Duramax or similar. I dont know of a 5 cyl CR available in the US and have no idea of whats available in europe but you might cap off one port on a 6-cyl rail to make it work. You do not want to be trying to gin up a 2000 bar (29,000 psi) accumulator rail down at Bubba's Welding.
A new head. The current head with the precombustion chambers is not going to work in a direct injection setup. Whatever CR setup you find, I would try imitate the combustion chamber design of its usual application in a couple of areas such as intake air swirl, Piston shape, the shape of the combustion chamber in the head and injector depth and angle. There's been 100's of millions of dollars spent on combustion chamber design in the last ten years and the guys who do this for their lunch money make a big deal out of whether an injector has 6 holes or 7. Find a good race engine builder to build your head to your specs (and use hydraulic lifters!). Don't worry to much if the compression ratio is lower than the original 21 or 22:1, especially if you live somewhere warm. Compression ignition works down as low as 12:1 and is more efficient lower. The higher compression is just for cold starting.
A differential with the tallest ratio you can find. The indirect injection of the 616 and 617 is done to expand the power band and rpm range. While this makes these engines more drivable it is at the expense of a 15 to 20 loss of efficiency (bsfc). With the direct injection CR expect stunning mileage and excellent torque over the low end but I expect peak RPM would fall from the 5200 to 5400's to about 3000. The slower flame propagation speed of lean combustion diesel allows the piston face to out run it above a certain rpm. The precombustion in the indirect injection diesel is a method of dealing with this.
While you're changing the differential get rid of the vacuum control on your transmission and set it up for computer control by the ECU. Shift points would be wrong anyhow because of the new power band. Mercedes design is a schizophrenic blend of anally excellent mechanical engineering with mediocre electronics all covered with a cobweb of vacuum lines. If you don't know what I mean then you don't change your own oil. Other problem areas that could be cleaned up by the ECU would be cruise control, tach.

If I had the money, this would be great fun. Until I hit the lottery I'll just stick with trying to get rid of that silly U-shaped air inlet into the turbo

Thanks to rwthomas. That reply finally gave the original poster some useful information. One note: extrapolting HP and torque numbers between direct and indirect injection give skewed results due to the higher rpms (T x RPM = HP) of indirect injection, at the expense of mileage. In spite of the reduced RPM's, I'm hearing mileage numbers from the new Duramaxes as good or better than my 300D in vehicles twice as heavy and much worse aerodynamically.

RT:

What's wrong with running 3500 rpm? I do it all the time in the 220D. The notion that high rpm and diesel power are incompatible is a result of US manufacture engines that wouldn't pull themselves below 1800 rpm and tossed a rod at 2400. Long gone now, but the mythology lingers -- 2000 rpm is the only speed that works. Never true for Benz (most Benz diesels have a redline between 4600 and 5500 rpm). Longer stroke may give more torque, but at the cost of flexibility, and believe it or not, most automotive engines don't drive gensets at fixed rpm.....!

I agree about lowering power output for warrenty purposes. As far as I know, no one has come up with an automatic that holds up under the torque load of a diesel, and many of the manual trannies are somewhat inadequate as well. Most heavy applications really need a split ratio rear end, too.

Another part of the problem is people, IMHO, using pickups for jobs that really require more truck -- I have a story about someone dragging a Sundowner horse trailer with a "fake dually" diesel pickup and tires -- that big Sundowner puts the combo over the GVW when you drop it, empty, on the fifth wheel hitch! Ain't a job for a pickup, not enough truck, not enough tires, and not enough brakes. Add that to a ladder frame with nowhere near enough rigidity and you got trouble!

I would imagine that chipped engines will also fail NOx and particulate tests, too. Power don't come free.

New engines certainly have much better technology, but ten years ago when I moved home, the norm was long stroke, low (16 or 18:1) compression ratio, fixed injection timing engines. Most of them even now are horribly noisy at idle, which can only mean poor combustion. CDI/TDI engines are better, but again, all new in the last few years.

I've also heard one should avoid whatever GM is using -- short IP life (ditto for some Fords), and cracked blocks and heads. Shades of the 603?

NC:

High compression is more efficient, period -- elemetary physics. The more expansion, the more heat is converted to work. Low compression diesels produce tons of soot, will blow unburned fuel out the exhaust cold, and use considerably more fuel. "Normal" compression for high output diesels is 21:1 or 23:1 in European practice (Benz, Volvo) and usually results in higher output per volume, with considerably less specific fuel consumption. My Volvo TD (late 70's early 80's vintage design) puts out 105 hp on 2.4L. Engines as built often exceed 26:1. MACK makes at least one engine with a 35:1 compression ratio (don't know the application). US manufacturers seem to have ring land problems at high compression, I have no idea why.

US built "low compression" engines all have much larger turbocharger systems (many multiple) running at considerably higher boost -- you get the same effective compression ratio under full boost either way, but complicated turbo systems aren't the way I would do it.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!