any mods for a diesel - PeachParts Mercedes-Benz Forum

batman1603 · #1 09-29-2003, 09:17 PM

I have a 1983 mercedes 300d turbo
are there any modifications i can make to gain horsepower???

DslBnz · #2 09-29-2003, 09:27 PM

Why did you buy a diesel if you're looking for power?

All you have to do to increase performance in a diesel is to increase the amount of fuel being compressed.

Be careful, though. Boost it too much and you could melt the pistons and basically cook the engine from the inside out.

Turn the ALDA CCW to increase off-the-line power, and make sure your linkage is set at the optimal setting.

Before doing any of this, make sure your car is ready for it. Have an EGT gauge, and a boost pressure gauge. You want to be as careful as possible not to hurt the engine.

lietuviai · #3 09-29-2003, 09:33 PM

Quote:

Originally posted by DslBnz
...and make sure your linkage is set at the optimal setting.

I'm curious as to what you mean by that. There doesn't appear to be any adjustment for the linkage other than making sure the links are greased.

DslBnz · #4 09-29-2003, 09:40 PM

There should be a slider bar. This controls how much the pedal prods the IP.

Here's a picture of what I mean

In the OM617, it should be located to the right of the valve cover.

lietuviai · #5 09-29-2003, 09:53 PM

Quote:

Originally posted by DslBnz
There should be a slider bar. This controls how much the pedal prods the IP.

Here's a picture of what I mean

In the OM617, it should be located to the right of the valve cover.

I'll have to check to see if I have something like that in the photo. I don't remember seeing anything like that but I'm still not 100% familiar with what's under the hood.

DslBnz · #6 09-30-2003, 12:00 AM

I can't explain it, but some linkages are set up differently than others. I hope you have the slider.

I would just advance the fuel, and do nothing else. By doing this, you'll increase pickup, and highway power will be immensely improved.

#7 09-30-2003, 12:24 AM

Some good tips on this link:

http://users.vnet.net/w123d/w123d/repair.htm

dmorrison · #8 09-30-2003, 01:26 AM

lietuviai

Check your engine service manual. There is an adjustment for the linkage on the diesel engine.

Service manual Engine 617.95 Turbo Diesel
Job number 30, Throttle control

Dave

P.E.Haiges · #9 09-30-2003, 10:32 AM

DslBnz,

FYI, Diesel engines do not compress the fuel, only the air. Gasoline engines compress a fuel/air mixture.

P E H

P.E.Haiges · #10 09-30-2003, 10:38 AM

Batman,

If you increase the fuel delivery you will decrease the fuel mileage and spew out black smoke.

I agree that if you want a lot of power, get a gaser or wait for the new common rail injection Diesel MB to be available.

P E H

The Warden · #11 09-30-2003, 02:27 PM

Power increases can be done. Ben Ridge installed an intercooler on his 300D, and was thus able to safely turn up the fuel flow to the point where he was able to get significantly more power.

In addition, there are a few other things that at least theoretically can be done; I don't believe they've been tried on an OM617 (or any other Benz diesel for that matter), but, although longevity may be adversely affected somewhat (ESPECIALLY if you don't install an EGT gauge and monitor it CLOSELY!), I don't see any reason why they won't work.

1) Propane Injection - propane does the same thing for a diesel that nitrous oxide does for a gas engine. The good thing here is, if the injection isn't overdone, you can actually increase your fuel mileage and lower your exhaust gas temperature. THere are companies such as Bullydog that sell kits for truck engines that could probably be adapted to one of our cars, or you could try a home-made setup.

2) Ram-Air Intake - if you can find a way to get more air forced into the intake, that'll make for some "free" power. However, I'm honestly not sure how well this can be improved upon on the 123, although I'll admit that I haven't looked closely. On most diesels, increasing the exhaust pipe size and removing the restrictions (i.e. straight-piping) is also ideal, but the exhaust pipe on a 617-powered car is already big enough that I don't think that any modifications are truly necessary. However, keep in mind that diesels like as few restrictions in the intake adn the exhaust as possible.

3) Lower Compresion Ratio - this requires an engine rebuild and for custom parts to be manufactured. What does lowering the compression ratio do? It'll make cold-starting more difficult, but it'll allow you to safely increase the turbo boost. As the engine sits right now, if the turbo puts out more than 15 or so psi, you're risking damage (blown head gasket, piston damage, etc) simply because there's too much air in the combustion chamber to fit properly; something has to give way. If the compression ratio's lowered, you could safely get the boost up to more in the 25 to 30 psi range. The only way to do this is to get new pistons made that are shorter than what's in there. I believe the current compression ratio os 21:1, and ideally you'd want the "new" compression ratio to be 17:1. The extra turbo boost clearly means there's more air in the combustion chamber, which means that you can again turn up the fuel safely.

Again, if you decide to try any of these (except the ram-air), INSTALL AN EGT GAUGE! With these sorts of modifications done, it's real easy to push the engine harder than it can handle, and how hard the engine's being pushed is best measured by reading the exhaust gas temperature. If you mount the probe in the exhaust before the turbocharger (I would recommend this), you don't ever want to exceed 1250°F, and you wouldn't want to run any hotter than 1100°F for any significant period of time. If you mount the probe after the turbo, those numbers become 1000°F and 900°F.

Hope that helps some! I would actually like to, someday, get a second car with an OM617 and see how far it can be safely pushed, just to see if it can be done.

Also, if yo're really interested in getting the maximum output from the engine, check out this site: http://www.dhraonline.com/ It caters mainly to hot-rod diesel pickup trucks, but might have some additional information that'll help you out.

Good luck!

tonystewart · #12 10-21-2003, 03:09 PM

I installed a K&N Cone Style filter to my 1984 300D over 10 years ago. Improved throttle response and fuel economy. Adjusted ADLA CCW half turn. Installed a 1985 higher stall Torque Converter. Spins right rear tire when the weather is cool in South Florida. I use Red Line RL-3 Diesel Ignition improver and run 12 lbs of boost. EGR removed and ports tapped and plugged. This mods have a made a quick reliable car. 318,000 miles and still going.

DslBnz · #13 10-21-2003, 03:47 PM

Quote:

Originally posted by P.E.Haiges
DslBnz,

FYI, Diesel engines do not compress the fuel, only the air. Gasoline engines compress a fuel/air mixture.

P E H

Well, that's what I meant anyway. Sorry, I guess I got the two ICE's reversed.

I'd rather have a simple manual transmission 240D than a twin turbo VNT S400 CDI electronicly fuel injected common-rail "diesel". Oh yes, and the new 400 is all aluminum, too.

Might as well own an S430 as there is less to go wrong with it.

Stop

R Leo · #14 10-21-2003, 05:28 PM

Crank in the wastegate until you're getting 40psi of boost at full chat and turn the adjustment screw on the ALDA CCW about 3 turns. That should improve things for a minute or two.

Be sure and post on whatever happens. OK?

P.E.Haiges · #15 11-03-2003, 06:47 AM

R Leo,

You are cruel.

P E H