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  #1  
Old 10-04-2003, 01:23 AM
cumminsnut
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Looking for any performance tips for my 300D

I am currently rebuilding the engine in my 85 300D. I am looking for anyone that can supply me with any tips to this engine. I am interested in suggestions such as removing the EGR system and any tips to squeeze some more power out of this engine. Is it possible to somehow run the exhaust manifold directly into the turbo and discard that big catalyst?
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  #2  
Old 10-04-2003, 01:46 AM
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When I rebuilt an engine for my "79" 240D I bought over sized pistons and had the liners bored out to fit. Shes a real "rocket" now , NOT
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  #3  
Old 10-04-2003, 01:53 AM
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Well if a person where theoritically to take off their EGR for offroad purposes they could either use a thin piece of sheet metal and put it under the valve itself. Or if you're looking to rid of it you can remove the valve, put a thick plate in its place, and then cut out a semi thick piece of circular SS or AL for the exhaust manifold then just use the clamp the current fixture.

If you install boost & EGT gauges you should be able to safely raise the boost pressure up a little higher with a MBC. In case you haven't looked make sure the banjo bolt on the intake manifold and ALDA are clean.
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  #4  
Old 10-04-2003, 10:42 AM
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Sounds like this must be a CA car. The federal (49 state) version of the car doesn't have a catalyst so if you could get the manifold and a few other things (air filter?) from one of them you could do away with the catalyst. Plugging the EGR is easy, I don't think there is any reason to remove it... just more work.
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1985 300D Turbo ~225k
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  #5  
Old 10-05-2003, 03:18 AM
cumminsnut
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I appreciate all of these suggestions. All of my experience on diesels is mainly focused around Cummins engines. I have a lot to learn about this Mercedes engine. If I were to install an exhaust temp and boost pressure gauges what would be the ideal readings to safely shoot for? When I run a Cummins engine such as the dual overhead cam ISX hard on the dyno I read about 950* exhaust temp and 30 psi boost at full load. What does a stock 300d run for boost, and how much can I increase it? Can I just adjust the wastegate to obtain a higher boost pressure? Also, has anyone ever heard about anyone installing a charge air cooler on this engine? My final question as crazy as it may sound to some of you is, I would also seriously consider installing propane injection onto this engine if someone were to direct me in the right direction of doing it. I have seen it done on the Cummins B5.9 in the Dodges. I think people would get a kick when they see a little sleeper diesel Mercedes open it up and smoke their little civic.
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  #6  
Old 10-05-2003, 01:44 PM
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Propane injection and overboosting will kill this engine pretty fast. Remember, it's NOT a huge displacement, and produces considerable horsepower for it size (120 hp, 150 or so ft/lbs torque on 3 L). It's also a pre-chamber engine, so most of the "direct injection mods" won't work as well. Propane in particular can cause detonation if overdone.

Stock boost is 11 psi or so. You can push that up to 13, and get a nice increase in the horsepower and drivability, but if you go any higher engine life will decrease dramatically (read thrown rod).

Engine assembly hints:

Check crank bearings carefully -- oil clearance should be as close to 0.001" as you can get it. Ditto for pistons, they MUST fit very close. IF they "float" on the rings, the cylinder walls will go instantly -- my brother got a short block for his 75 300D in this condition. Nasty.

You could be able to rotate crank with pistons installed with one finger on a wrench after it's together.

Use only new rod bolts, please......

Get a new chain for sure -- old one will be iffy at best. Get a new oil pump chain too.

Make sure you install the spacer on the crank for the oil seal, and use an alignment tool when installing the oil pan upper half -- if the hole for the seal isn't aligned right, the seal will leak on the outside. Don't try to use a seal for this, it's too soft.

leave the full 1 mm crush on the rear main or it will leak, and you CANNOT pull one in, as I'm sure you've noticed.

Make sure you have all the seal washers on the appropriate font cover bolts and seals. Also, use some Permatex on any bolt that goes into the chain case. They leak otherwise.

Measure pre-chamber protrusion before putting head on, fit is critical. Make sure the prechambers and pistons are matched, there are two systems (you should have the later one with a starshaped piston cutout and round-bottomed prechambers, I think). Set with the appropriate shims under the prechamber.

Be very carefull setting the cam timing, other posters have gotten it one tooth off somehow (chain wraps more than half way around the cam). Pry the tensioner rail in against the chain while checking, too, so it won't jump while you turn the engine. Never rotate engine backwards, the slop in the chain accumulates between the crank and the timer and can cause the crank sprocket to jump a tooth when you rotate in the normal direction. This makes cam timing a tooth late, and the valves will contact the pistons.

Set valve clearance on the bench before installing the head. Re-check after 1000 miles of operation.

Valve guide clearance is VERY tight -- basically, if the oiled valve stem will go into the guide by hand, it's fine. Use ONLY bronze guides for the exhaust, steel ones will be shot in 10k miles or less. If a valve can be moved sideways in the guide at all, the guide is worn out..... I don't know what clearance is common in American diesel engines, but excessive vavle guide clearance is very common in rebuilt MB engines and causes severe oil consumption problems.

Set the injection timing on the engine stand, it's MUCH easier then. Use the drip tube method, it must be very accurate to get max performance. Initially timing is set by placing engine at 24 or 26 degrees BTDC (you will have to check, my engine manual doesn't cover the turbo models), then set the IP to start of delivery. There is a mark on the drive shaft of the pump and a missing spline on the drive hub. These need o be lined up with the mark on the flange held down by four screws -- usually on the upper left, but occasionally on the lower right. Install pump onto block with adjustment slot centered and check timing with the drip tube. If way off, pull pump back off and set initiall timing 180 degrees out (some pumps were manufactured 180 off for some reason) and re-try.

If you are IN California, the calalyst has to stay -- big fine if you get stopped for an emission check and it's missing. In the rest of the country it can be removed. However, it doesn't degrade performance much.

Once you get it rebuilt and running, you need to get the boost up to 13 psi, then adjust the ALDA (or better, re-shim it) to get proper fuel delivery increase with boost increase. You can remove tha anti-tamper device on the top and turn the screw CCW a bit at a time to get just visible smoke at full throttle in 3rd gear at 45 mph -- this is the best performance setting. More smoke will give you LESS power, unlike some DI engines (has to do with flame quench in the prechamber, I think). The better way is to measure the shim under the ALDA and make one thicker or thinner to get correct fuel delivery.

Remember that these are high rev engines -- if you push it hard, you can get almost 6000 rpm out of them for short periods (they will eventually throw a rod), but it's normal for them to turn 4000 revs on the highway for hour after hour.

Oversized pistons with the fuel correctly set will give you more power, too!

Get it back together and report!

Peter
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1972 220D ?? miles
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1985 Volvo 740 GLE Turobodiesel 218,000
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Last edited by psfred; 10-05-2003 at 01:52 PM.
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  #7  
Old 10-05-2003, 11:06 PM
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Stock boost should be about 13.4 if I recall correctly (the spring in the wastegate tends to get weaker and go into the 11s or so). The ALDA can accept upto 17psi but I wouldn't recommend taking it that high. Here is a thread about intercooling. The problem with intercooling is that unless you take the ALDA off and adjust the max fuel flow setting you won't gain that much if anything. Really since the cooler air creates pressure drop and the ALDA senses manifold pressure it could create a power loss unless compensated for. It will however lower the EGTs and your engine aught to enjoy that. If you do decide to do performance mods please do some testing beforehand then again afterwards so we can see what you actually gained from doing what.

That sounds like a fun CTD.
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Mercedes W123 DIY pages are now located here.
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2005 Avalanche 4x4 ~66k
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  #8  
Old 10-06-2003, 11:10 PM
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Hey Cumminsnut,
All good info so far. You will find there is a "keep it stock" or "MB knows best" mentality around this board, for better or for worse. The MB is similar to Ford 7.3 IDI (pre powerstroke) and the GM 6.2-6.5 diesel engines in head/prechamber design. Any mods that work on them should work on an MB. The MB's have a high 21:1 compression ratio, like the GM's. Since the GM's don't tolerate more than 15psi without intercooling when using stock pistons I would say this is likely the limit with the MB as well. There is a boost switch on MB's that cuts fuel if boost goes beyond 1.1 bar (about 15psi) hooked into the ALDA boost reference line so I would think this is an indication from MB not to go higher. The wastegate is adjustable and there are a few posts on how to perform this so do a search. Regarding EGT's since you mess with modded truck diesels you should be aware the maximum pre-turbo EGT on most engines is 1350-1400* I would shoot for 1250* preturbo or 1000* post turbo as a maximum. Nobody here likes to run egt/boost gauges either. Trusting instead that ultra-accurate "viewing smoke in rearview mirror" method when they tweak the ALDA. I think egt/boost gauges are a better option...... Since you have the engine apart now is the time to do a little pocket porting, gasket matching, etc. A little flow gain here an there could add up to a lot. Everyone here will tell you a free-flowing exhaust isn't worth it. Since nobody has proven it won't work and if you mess with trucks you know thats one of the first mods done, I say go for it. Sure can't hurt. Welcome and enjoy! RT
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  #9  
Old 10-06-2003, 11:56 PM
cumminsnut
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Thanks for all the input to my questions. After seriously contemplating this engine I have decided to just keep it stock. my goal with this engine is to build it tough and build it right. As much money as these parts cost and as much work as it is, I am not planning on doing this again for at least 300,000 miles. Besides from what I have seen, when these engines are blueprinted and freshly built they purr like a sewing machine. I have been doing some parts research on the web and found a couple of what I think are decent sites. The first is http://germanstar.net I can get rod and main bearing, thrust, head gasket set, lower gasket set, valve guide seals, and valve guides for $292.95. The second site is www.sasponline.com so far they have the cheapest oversize piston I can find at $694.00 for a set of five. The last site if I remember right was jem.benzparts, they have wrist pin bushings for $44.60. All this would put me at $1031.55 minus the block machine work cost. Do these prices sound decent? I am able to save costs on the head by rebuilding it myself. After all this is done and running, I pan on resealing both windshields and repainting. The car is currently white with black interior. I was thinking of going with black exterior and try to locate a set 17" chrome mbz rims. Do all Mercedes cars have the same lug pattern, what year and model rims would fit this description? Thanks again for the input, I really enjoy this site.
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  #10  
Old 10-07-2003, 12:06 AM
cumminsnut
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Just to clear up my statment about Cummins engines. I do not build modified high performance Cummins engines. I am employed by Cummins West Inc. I am a full time diesel technician. I work on everything from little B3.9's up to 600 hp twin cam ISX engines. The lastest thing now coming out in the Dodge in either 04 or 05 is the common pressure fuel rail ISB. Instead of running the VP44 pump and seperate high pressure fuel lines, which by the way reach about 22,000-25,000 psi at full load. The common rail system will have one main fuel manifold constantly pressurized at about 20,000 psi. These new engine designs are extremelly quiet and will be available to 300 hp. All turbocharged Cummins engine run between 20 to 30 psi boost, which is why you almost always see some type of aftercooling. The turbo out air temp. at 30 psi can reach about 450*.
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  #11  
Old 10-07-2003, 12:40 AM
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Check out the wheels and tires forum on this site. All Mercedes cars that I know of use a 5x112mm bolt pattern, but offsets vary a LOT from model to model.
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  #12  
Old 10-07-2003, 01:46 AM
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Try here for the best online prices for MB parts: http://www.importedcarparts.com/

Keep us updated on the build and take some dig pics along the way to show us how it's going.
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  #13  
Old 10-07-2003, 01:53 AM
ForcedInduction
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Quote:
Originally posted by rwthomas1
Everyone here will tell you a free-flowing exhaust isn't worth it. Since nobody has proven it won't work and if you mess with trucks you know thats one of the first mods done, I say go for it. Sure can't hurt.
I have run on a straight pipe (i.e. turndown pipe only) for quite awhile. I can't really say it's worth going out and making a custom exhaust unless you can get it cheap. There is a slight reduction in turbo lag and very little power increase except at high rpms (passing on the highway at 50+) where it is there, but is not anything amazing. The real reason I like my straight pipe is the sound. NOTHING sounds (or smells) better than an unrestricted turbocharged diesel exhaust system with just a pinch of black smoke. :p
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  #14  
Old 10-07-2003, 11:41 AM
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cumminsnut,

I beleive the Dodges have the new Cummins (common rail) here already, just not in CA yet. They sure are quiet at idle, I'd love to have one too!
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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k
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  #15  
Old 10-07-2003, 09:44 PM
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Build it stock, turn the boost up to 13 psi, adjust ALDA correctly (either by smoke or by EGT) and set the valve timing and injection timing exactly on (there are offset Woodruff keys for the cam timing) and you will have very decent performance and incredible longevity.

Note that EGT isn't as useful in a pre-chamber diesel as in a DI diesel -- EGT won't rise anywhere near as much with extra fuel, you just get extra smoke. I believe there is considerable quench behavior in the pre-chamber as excess fuel is injected late in the power stroke. Could be wrong, but someon on the forum has measured EGT and it stays pretty low.

Block off the EGR if you want, it won't make any difference in operation (unless it sticks open -- LOTS of smoke, very low power, and strange looks from other motorists!)

Open exhaust, as usual on a diesel, has very little effect on operation except more noise at load -- engine is moving plenty of air at idle anyway, so the exhaust supplied by MB is pretty low backpressure. Turbo adds much more air, and MB has taken that into consideration too.

Peter
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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!
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