Theoretical Engine Modification OM616 - PeachParts Mercedes-Benz Forum

Miklas · #1 05-23-2010, 03:00 AM

After doing some reading, I had a mad scientist idea, but no clue as to the feasibility, and probably no skill or money to carry it out right now. Wondering if anyone knew if you could put spark plugs and a distributor on an OM616 from 1980 240D. It's to make a "Homogenous Charge Compression Ignition Engine" that is, possibly a more efficient than diesel ethanol engine. Totally pie in the sky, as I only have auto mechanics 101, I was just interested in the possibility, as I saw a few nice holes near the cylinder head with nice threads on them and everything. Thanks!

rummur · #2 05-23-2010, 04:10 AM

Im sure you could but why?

They are fine with just compression ignition?

Alastair · #3 05-23-2010, 05:59 AM

Quote:

Originally Posted by Miklas

After doing some reading, I had a mad scientist idea, but no clue as to the feasibility, and probably no skill or money to carry it out right now. Wondering if anyone knew if you could put spark plugs and a distributor on an OM616 from 1980 240D. It's to make a "Homogenous Charge Compression Ignition Engine" that is, possibly a more efficient than diesel ethanol engine. Totally pie in the sky, as I only have auto mechanics 101, I was just interested in the possibility, as I saw a few nice holes near the cylinder head with nice threads on them and everything. Thanks!

Hmm, But if you fit plugs and distributor etc, it would no longer be a Compression Ignition engine...

It would be a spark-Ign engine!

De-compress, fit plugs etc, and you got a Gasser!
--Fit a carb and Not de-compress, and it'll not run....(without destroying itself that is!)

t walgamuth · #4 05-23-2010, 06:07 AM

A piston engine is an air pump. Perhaps you could take a well worn one that is worn eveny and add spark plugs and a carburator. I don't know how you would mount the distributor though. In the end you would be cheaper to just buy a good used engine even if it were a gasser.

The old 5.7 olds diesels were so similar to the gas engines you could bolt on gasser heads pull the injection pump and install a distributor there and run them as gassers using the stock diesel cams. I hear they put out a lot of power too.

Miklas · #5 05-23-2010, 06:59 AM

Quote:

Originally Posted by t walgamuth

The old 5.7 olds diesels were so similar to the gas engines you could bolt on gasser heads pull the injection pump and install a distributor there and run them as gassers using the stock diesel cams. I hear they put out a lot of power too.

That's interesting. The reason why you'd want to do this is because dedicated 96% ethanol 4% water engines in Brazil have high compression at 19:1 or so, which a diesel has. I think these engines are more efficient than gas or diesel. I was reading about some researchers that did a study for the EPA that converted a jetta TDI in this way, adding spark plugs and a distributor for idle and low speeds but it would diesel at higher speeds. So I guess it would be a spark and compression ignition engine. They got 22% better fuel efficiency than diesel from alcohol, more power, and the thermal efficiency was 43% with half of the exhaust gas recirculating into the manifold. Also very low emissions. Not sure if you'd need a carb, it says they used a lower pressure fuel pump from a gasser and had the fuel go into the heated manifold. Also they lowered the compression to 18:1. I think the idea is to de-compress but not by as much as a standard gasser which is less efficient on alcohol than gas. I bet it'd sound super smooth, should be much cooler and less vibration.

layback40 · #6 05-23-2010, 09:45 AM

If you were not using the injectors you could replace the IP with a distributor & maybe put spark plugs in the GP holes. The injectors could be replaced with DI ones if they were needed for fuel delivery. I think you would be better off with a more modern motor though.

JHZR2 · #7 05-23-2010, 01:04 PM

arent small diesel gensets actually spark assisted?

babymog · #8 05-23-2010, 02:15 PM

Quote:

Originally Posted by JHZR2

arent small diesel gensets actually spark assisted?

How small? We get 12.5kw-20kw in daily, never have I seen one with a spark-ignition system though just glow-plugs and/or heated intakes for cold-start.

junqueyardjim · #9 05-23-2010, 04:31 PM

On something that cool you wouldn't want to mess with AC. So in place of the compressor you could mount an HEI distributor, mounted toward the back and under the IP, and then drive it with the "unused AC compressor drive belts. You could even "Hot Rod" the timing and kind of set your own time. Instead of firing a plug every other revolution, choose a slower number like every 3rd or 5th revolution. That way the points won't burn up so fast.

Miklas · #10 05-23-2010, 06:08 PM

Quote:

Originally Posted by junqueyardjim

On something that cool you wouldn't want to mess with AC. So in place of the compressor you could mount an HEI distributor, mounted toward the back and under the IP, and then drive it with the "unused AC compressor drive belts. You could even "Hot Rod" the timing and kind of set your own time. Instead of firing a plug every other revolution, choose a slower number like every 3rd or 5th revolution. That way the points won't burn up so fast.

Quote:

If you were not using the injectors you could replace the IP with a distributor & maybe put spark plugs in the GP holes.

Haha cool idea. I'm an amateur, so how would the HEI be driven, by putting a wheel on the little gear that usually drives it and attaching the AC belt? Wouldn't firing the plugs every other time waste fuel?

The only thing I thought of with putting spark plugs in the GP holes was that there is a prechamber in the engine, and I was unsure if igniting the cylinder through that was wise.

nickofoxford · #11 05-23-2010, 07:18 PM

prechambers can be pulled AFAIK. i've always wanted to convert a 617 to direct injection, port and polish the pee out of the head, and see what it can do.

unfortunately that's all a big dream right now.

DieselPaul · #12 05-23-2010, 07:18 PM

I would run megasquirt or similar with GM coil-on-plug. That way you can time the engine for the fuel much better. You'd need an intake with injector bungs and a throttle body. Both very do-able.

On my 1.6 jetta diesel the motor is nearly identical to the 1.8 gas. The vacuum pump on the 1.6 is where the distributor is on the 1.8. Same hold down and everything.

Miklas · #13 05-25-2010, 01:34 AM

The only thing I can't understand is how you would get the spark plugs to switch off at the point when the engine starts to diesel. Thanks for the help guys, it doesn't seem that far fetched.

DeliveryValve · #14 05-25-2010, 03:30 AM

The classic International Harvester tractors from the '30s, '40s, '50s & '60s had engines that started cold on Gas and switched over to diesel once warmed up.

The combustion chamber had an additional valve that opened up to a pocket which decompressed the chamber to allow for gas operation. There is a mechanical lever that a person would shift to switch over to diesel operation after the engine warmed up. This lever cut off fuel to the carburetor, the magnito for spark and closed the valve for the pocket. It also allowed the Injection Pump to operate to provide diesel fuel.

Here an excerpt from an old IH TD-6 crawler ad.

.