Run a 4 cylinder on just 2?

[ST Dog]

Any one have thoughs on running an MEP-003A on only 2 cylinders?
Trying to get a MEP-002A, but I've seen 003As going for the same or less recently.


I'm new to diesels, but wondered if it might be possible to block/disable the injectors/pump so only 2 cylinders were running to reduce fuel consumption/power output. The 002a injector pump looks to have 4 output ports, with 2 of them capped off.

 

[maddawg308]

You can, but then the problem is you are using 2 cylinders to move the inner workings of 4 cylinders. The other "dead" pistons and valves are still moving. This is called "reciprocating weight", and it is impossible to remove this from the equation without a LOT more work. So, your 2 cylinders are moving 4 cylinders of parts, which ends up in decreased power efficiency and more fuel usage than you think. Not to mention it would probably run a lot more vibration as well.

Cadillac did this in the early 1980s with the 8-6-4 engine concept. The less the engine worked, the more cylinders the engine would "shut off". I doubt any of those engines are still in use, most were junk not long out of the factory.

Bottom line answer is "yes, you can, but it's not that great an idea."

 

[ST Dog]

I own a '70 Coupe deVille and have been active on Cadillac forums for 10 years, particularly ones devoted to performance mods to the '68-76 472 and 500 cid engines.

I'm well acquainted with the V864 engines. It's a de-bored 472 with solenoids that prevent the intake valve from opening on the cylinders that are deactivated. No intake stroke, so no fuel drawn in to the cylinder.

It actually works quite well. The problems was the electronics to control the solenoids just weren't ready for prime time. The algorithm cause it to change the number of cylinder too often and at bad times (several early electronic transmissions have/had similar problems). The electronics would also fail and the engine would be stuck in 4 cylinder mode, which did not produce enough power to get the car moving.

I know people that have modified the 472 and 500 heads to use the V864 rockers and solenoids, and use manual control to deactivate 4 cylinders when cruising. It works great and improves fuel efficiency a lot (only feeding 250cid and lower throttling losses).

The diesel wouldn't have the throttling issues (no throttle) so just some pumping losses.
While I don't expect fuel consumption to drop to 50%, i would expect 35-40% less fuel usage.

Depending on the valve train on the 003A engine, I might be able to prevent the valves form opening and reduce the pumping losses, for a lower fuel consumption still.


I was just wondering if anyone had tried it and had results to share.

Any one see a problem with capping the pump ports? Is my assumption about the same pump being used correct?

 

[RichardR]

ST Dog,

<<<Any one see a problem with capping the pump ports? Is my assumption about the same pump being used correct? >>>

I have both 003A and 002A generators and they use the same IP except for the two ports capped off on the 002A. I would have thought that the IP would be unhappy with two ports capped... maybe build up enough pressure to hurt something internal. But it is apparently designed to work that way.

Upon further reflection, maybe I'm missing something about the cam drive for the IP. Do the 002A and 003A engines have the same number of lobes on the cam that drives the IP plunger? Maybe the 002A is missing the lobes that drive the plunger when it would pump into the capped ports. Need the opinion of a real expert here, and that's not me.
Richard

 

[Bill W]

Heck a 003A burns the same amount of fuel at half load ( 5kw) that a 002a burns at full load (5kw) so the 003A is just as efficient as the 002A and its not going to be working as hard

 

[steelypip]

The old school way to do this (as was done back during WWII when men were Real men, gasoline was rationed, and cars were flatheads with < 6:1 compression and crappy fuel economy) is to take an opposing pair of pistons and rods out of the engine. With an OHV engine you also take the valve linkage (but not the valvesprings and valves) off the dead cylinders. This was commonly done on straight eights to make them sixes or even fours.

Removing the unused pistons and rods gets the frictional and pumping losses very close to what they would be on an MEP-002A. There would be a slight difference because of extra crank main bearings, a little more windage in the crankcase, and the slightly lower efficiency of a 10 KW genhead delivering 5KW versus a 5 KW genhead doing the same.

Now whether or not it's worth doing this for the marginal difference in efficiency on such a small genset is a really good question...

V8-6-4 came back around again in the '90s briefly under another name, but didn't stay. If gasoline goes above $5/gal, expect to see it in a pickup truck near you soon.

 

[ST Dog]

Did those old L8s and L6s have pressurized oiling to the crank throws?

If so, you's need something to control the oil pressure., not to mention the crank imbalance from the missing rod and piston.

I don't see removing the pistons being worth while on a 4 cylinder. I wouldn't expect the losses being too bad with them there as long as the valves stayed closed.

If I could get the fuel usage at half load down I think it's be a good deal.
Still more than the MEP-002A, but better than with all 4 cylinders at half load.

 

[Killer_Junior]

Current Dodge Ram pickups with the 5.7 Hemi have a setup called MDS (Multi Displacement System) that uses electronically-controlled lifters and an active fuel management system to shut down four of eight cylinders at lower loads and cruising speeds. The engine computer also turns off fuel flow to the whole engine for short bursts when you lift your foot from the throttle or coast down a hill. Chrysler calls this IdFSO (Interactive deceleration Fuel Shut-Off).

All of this sounds cool but it takes a bunch of special electronics and other stuff to work. I'm not sure if shutting off cylinders is a viable thing for a little genset. You could maybe try trading for a set that matches your power needs/ fuel consumption desires...just my $.02.

 

[ST Dog]

All of this sounds cool but it takes a bunch of special electronics and other stuff to work.

Like I said, that was the bane of the Cadillac system, the control electronics.
Just compare the home computers of the early 80s to today's cell phones, and you get why it didn't work then but can now.

I'm not sure if shutting off cylinders is a viable thing for a little genset.

Just to be clear I'm talking about disabling the semi-permanently, not turning them on and off at will.

I've been watching the 5kW and 10kW auctions and seen them sell for about the same most of the time. I' prefer the 5kW as it's smaller and a better fit with my needs. Just looking at options.

One of the reason for looking at diesel engines is the more linear fuel curve.
Anyone got numbers on the fuel usage of the 5kW at 75% and 100% load?
How about the 10kW at the same output (37.5% and 50%)?

It's all just speculation at this point.
If they are already within 10% then it's probably not worth the effort.

This sort of came up a few weeks ago with a guy at work who has a 30kW industrial genset powered by a 6cyl gasoline engine. That unit dislikes running with a light load (7-10kW) for long, and still has rather high fuel consumption.

Tornado damage in April has the local grid really unstable. They anticipate problems as the demand increase in the summer, as the grid won't be repaired until September. So I started seriously looking at a genset. I know I want a military diesel, so I'm exploring options.

 

[Bill W]

ST
The info I posted was from the TMs that a member had posted earlier this year ( I think it was from one of the Kipman clan )

A 002a burns like .56gals per hr at full load
A 003A burns 1.02gals per hr at full load and around .58gph at half load.
If the TM section is up you can go confirm the info there

 

[ST Dog]

If that's correct, the that's only 3% more for the 003A at 5kW.

And the 003A is using 57% of the full load fuel at half load.
I doubt I'd get that much lower (55% would be the same as the 002A).

I'd need a 5% improvement to get from 0.58gph to 0.56gph, and I don't think that's possible.

But, if I get a 003A I'll probably play with it and see
The difference is only a few fl. oz., so I'd have to figure out a way to accurately measure fuel consumption first.

 

[steelypip]

The engine computer also turns off fuel flow to the whole engine for short bursts when you lift your foot from the throttle or coast down a hill. Chrysler calls this IdFSO (Interactive deceleration Fuel Shut-Off).

It's funny that they're advertising deceleration fuel shutoff. Every EFI vehicle I've ever driven turns off the injectors if engine RPM is above some value and load is zero. On manual trans vehicles it's pretty easy to spot, especially with a cold engine - just coast down a hill (not applicable in Florida) using engine braking to slow the vehicle. When the engine winds up to some magic number (1500 RPM cold on my Toyota), the engine braking gets noticeably better as fuel flow is cut off.

On the Grand Marquis I can't feel it, but I can see it thanks to the MPG indicator on the ScanGauge. Downhill miles/gallon goes up to a maximum of about 150 as the car coasts, then if your foot is off the pedal long enough and speed is not going down fast enough, mileage goes to 9999 MPG indicating that the injectors have been turned off. If I switch to the fuel rate display it goes to zero at that point. 4400 lbs of American behemoth in the mountains does it pretty often.

The ScanGauge rocks, btw. Definitely the first thing I'll get for any OBDII vehicle I buy from now on. I got it for monitoring trans fluid temperature while towing, but it is a great driving aid all the time.

The air cooled gen sets are going to have a pretty high minimum fuel consumption because the cooling blower is always eating power and is (for some unknown reason) throttled at the outlet instead of the inlet. Water pumpers with electric fans win on this point, because the fan only runs as much as necessary to maintain operating temperature.

If you want to improve small load fuel economy, consider restricting cooling fan intake. You'll have to fit temperature gauges, of course.

 

[3dAngus]

The -003 burns 3/4 gallon per hour at half load, which is probably where most people would run it at anyway. Rare to pump out full load unless you have multiple air conditioners in this 100 degree heat we're experiencing right now, and run the entire house.

The weight difference between the two gen sets is only about 200 pounds. It pretty much makes the -003 a much better value for me.

If running the -002, with it's much lower fuel consumption, I would not mess with it. I'm not sure the risk of relibility problems you create in cylinder reduction for fuel savings would be worth the effort, nor the financials if something goes wrong, or something starts overheating. If you plan on using it 24/7, disregard the above comments. You could always just buy another one if problems arise, and with that kind of usage, it would probably be well worth the effort.