Poll : How much you know about diesels??? - Page 4 - PeachParts Mercedes-Benz Forum

Lycoming-8 · #46 08-31-2002, 06:34 PM

The picture in the post by 'dabenz' looks very much like the OP engines supplied by Fairbanks Morse for use in WWII US submarines. These were also applied to railroad diesel electric locomotives marketed by FM up thru the early 60's. They marketed the first 2400 hp locos called the Trainmaster, but they were relatively unsuccessful due to the need to pull everything out the top to get to the lower set of pistons for maint. The latest issue of Trains magazine has a good picture of this, their largest offering in demo paint scheme. Hope this somewhat off MB posting is not out of place. Do have a strong interest in MB diesels though, as have driven a '61 and '68 from 1965 with only a gap from 1990 to August of 2002. Some 300,000 + miles altogether. Expect to put quite a few more on the latest acquisition, an '83 300D Turbo.

kweimer · #47 08-31-2002, 08:52 PM

On diesel engines running backwards, I understand that this is not a good thing on Mercedes diesels because thare is no governor control when the engine is running backwards and the engine will run to maximum rpm and destroy itself if not stopped. I once accidentally got a 200D engine running backwards by letting it roll forward to get it started while accidentially in reverse---it started and immediately ran up towards max rpm but I was able to get to the stop knob and shut it off before any damage was done. Very scary. Lots of oil and smoke blown out the air filter.

dabenz · #48 09-01-2002, 01:33 PM

I retract my previous award and give the virtual cold one to Lycoming-8!

The pic is a F-M engine developed for naval amphib ships and is still in production. F-M is alive and well, building these engines primarily in generator sets for ships, municipalities, and hospitals. Latest and greatest are dual fuel (natural gas or diesel). Visit your local hospital's emergency generator to see one near you.

I'll now shut up and listen.

Stevo · #49 09-01-2002, 10:35 PM

dabenz

Two years ago I delivered a surplus 110 foot, navy YTB, tug around from Norfolk Va to Seattle, fun trip,

anyway it had a 2000 Hp fairbanks Morris OP (opposed piston) engine, 10 cylinders and 20 pistons. It was 2 cycle and ran about 800 RPM if I remember right. It had a crank on the top and one on the bottom with the injectors in the middle. The navy had a bunch of these and are still running them for docking ships. thats my 'sea story' anyway, have a good evening all and I'm gona get my 240d running tomorrow or else. (I'm gona be pissed)

william rogers · #50 09-03-2002, 03:29 AM

old timer told me that if you ran diesel backwards that they would start burning the oil in crankcase and run away till they blew ?????
William Rogers.......

psfred · #51 09-03-2002, 10:11 PM

When an MB diesel runs backwards, so does the oil pump. Need I say more?

Peter

kweimer · #52 09-03-2002, 10:21 PM

With no governor control when running backwards, it won't run long enough for the oil pump to make a difference.

patterson · #53 09-04-2002, 11:23 PM

I hate to bring it up again. I have attached a picture of a VW TDI piston cutaway and what you see in the crown of the piston is not a prechamber. In direct injection diesels turbulence is created in the incoming air by the angle of valves and how the head runners are set up. There is mush research in fluid flow analysis to determine the optimum set up to create a swirl in the incoming air. Anyway the piston is made this way to group all the air in the cylinder together (this is called squish). As fuel gets farther away from the injector the chances of it igniting become less and less because it becomes less atomized. Direct injection diesel injectors don't inject out of the bottom as prechamber injectors do. There are holes in the side of the injector to make the fuel inject more parallel to the crown of the piston. The design of the piston crown prevents the fuel from hitting the cylinder wall and washing oil off the cylinder wall. The direct injection design helps efficiency by reducing pumping losses. In prechamber diesels you lose energy by pumping the air in and out of the prechamber. Also direct injection increases efficiency because less head surface is exposed to compression heat. This helps very much in cold starts because less of the compression heat is soaked up into the cylinder head and the piston.

Peter I have enjoyed your posts very much since I have been lurking around the forum, but I am curious about where you got the information about the new Cummins diesels being prechamber diesels. I only know of one Cummins with a prechamber and that was the A-series which wasn't even a cummins design it was an Onan design. Cummins advertises they are able to meet the new emmission standards without significantly altering their engines with EGR and the engines will be similar to the older engines. So I am curious about the Cummins prechamber issue. I agree that the older Mack and other american direct injection diesels were smoky monsters, but this was not the fault of the direct injection design but the engines were crude in every respect to current standards. New injection technologies and much higher injection pressures have made the direct injection diesel clean and efficient.

The VW TDI loses so little heat to the coolant that there are supplemental heaters to help with passenger compartment heating. As a owner of a Ford/International prechamber diesel and a former owner of a Chevrolet prechamber diesels I know well about one of the largest trouble with prechamber engines. They overheat when you pull them hard. Ford IDI diesels have a 4 core radiator and I still have trouble when pulling heavy load with overheating, and the Chevrolet was horrible about it you hit a hill and watched the temp gauge climb. This can be explained by the amount of cylinder head surface exposed to the combustion heat. This is much less of a problem with the Ford "Powerstroke" Direct injection diesel eventhough they have the same radiator. All direct injection diesels will have a bowl looking thing in the piston similar to the TDI even though there are variations.

The prechamber is a thing of the past, used to smooth combustion before the advent of extremely sophisticated diesel injection systems.

Matthew