All I wanna know is.....

[rcavictim]

Regarding reduced speed operation of Chinese horizontal diesels.

I`ve asked this question before and received no helpful chatter, rather more discussion resembling skepticizm.  I would dearly like to know if anyone that possesses a Chinese diesel like a model 1115, in particular the Changfa 1115, has attempted to run it at the lowest possible speeds where it still seems comfortable, at greatly reduced power output of course, , say 2-3 kW from the generator head.  A 20 HP (@2000 RPM) 1115 is almost as large in displacement as a Lister type 6/1 and should be able to make 4-6 HP in the 600-800 RPM regieme without trouble is what I`m thinking.

I have recently purchased a JD 175 (6 HP at 2600 RPM) and have determined that if all one needs is 1 kW, the fuel economy is measurably better at 1200 RPM than at 1800 RPM from an 1800 watt directly coupled head run at reduced speed (lower frequency and voltage not an issue for my application).  My plant can make 2 kW operating at 1800 RPM, 60 Hz and gets normal fuel economy doing so.  At 1 kW it uses more fuel at 1800 than it does at 1200, and at 1200 will last longer.

edit to correct typo

[wiebe]

hi rcavictim.
i think jou have too look at the sweet spot for that engine,
and that depends on the cam if jou are onderspeed joure cam is not controling the valve,s ok.
and then joure economy is not ok.
meaby a 3/4hp engine at 80% rate,t speed is more economic?
just my 2 cents
greetings wiebe

[rcavictim]

Wiebe,

I agree with you that cam profile will have an effect, no doubt about it, but changing cam profile is not an option for 99.999% of purchasers of these Chinese diesel engines.  I have plans to experiment with tuned intake runner to improve my performance even more than it is, but have not gotten there yet.

As a generalization, the larger the diesel engine, the more robustly it is made and the more likely it is to last longer based on improved dimensional stability over the engines operating temperature extremes.  This fact works against one who is trying to optimize fuel economy at micropower generation levels who is also looking for long engine life. For this reason I am not interested in experimenting with any engines smaller than the 175 as they do not have oil circulation pumps. 

On the other side of the coin running a large diesel engine at greatly reduced output is also detrimental to engine life.  Somehow the rather huge Lister 6/1 and `oids of it survive despite cool crankcases.

Your reply does not answer my specific question.

[draganof]

I have purchased a 195 that will be delivered on the 18th. I will be running this engine at 1800 rpm but would also like to operate it at 600 rpm. Your engine and mine are a combination of pressure and splash oil system. What this amounts to is the rocker arms are pressure fed a small amount of oil but all the other parts are splash fed by the rotation of the crankshaft and the dipper tube contacting the oil in the crankcase. Now as long as the engine speed is enough to cause the oil to splash around and lube everything then it should be fine. One other thing to look at is if the engine vibrates excessivly at the rpm you choose. If it does then just raise or lower the speed to find the sweet spot. This is my first Chinese diesel and it's going to be fun! I'll post results on my progress once I get the engine.

[rcavictim]

My 12 horse (7500 watt gen head) is good between 1800 - 2000 with impressive vibration above or below.

I'm looking for better economy... at 1800 RPM a lot of fuel is consumed just to run the engine... this consumption goes up exponentially as RPM increases.. The main reason for the inefficiency at higher RPM is the pumping losses.. at 1200 RPM the pumping losses are minimal... but as you start to get much above this threshold  the engine really starts to get less efficient..  some years ago I did a little experiment with a 2 valve diesel.. Although it wasn't the petter the results should be similar... First run the engine with no load at 450 RPM and measure the fuel consumed over a period of time... let's say an hour... then run it at 900 rpm again measuring the fuel... it should burn a little more than twice as much fuel at double the RPM...  then run the engine at 1800 RPM... If RPM didn't impact efficiency the engine should burn about 4 times the original amount of fuel...  but the reality is the engine will burn about 5-6 times the original amount...  The inefficiency really goes up as you get above 2000.. yes the engine makes more power but you pay a hefty price in fuel consumption.. this is part of the reason that higher RPM diesels use 4 valves... 

IMO slower is better.. less stress on the parts.. and better economy..   

Fatty,

My engine testing coroborates your statement.  I also am after maximum fuel economy, but at the same time I am after minimal total hourly fuel consumption (not the same thing).  I have resigned myself to the reality that is you want maximum power output per gram of fuel you need to load your diesel up and run it around 75-80% max capability, but if you want to keep a genset running lightly loaded, in the interests of using the least amount of fuel you ought to have a means to slow it down below 1800 RPM for reasons you give and use batteries and inverters to get you back to standard 60 Hz line voltage.

I think you really need to have two different displacement diesel generator plants and that is the direction I have gone.  My newly added small one is based on a JD175 engine (353 cc) and will eventually charge my battery bank.  Exhaust heat is being captured in a heat exchanger to drive a fuel processor and the engine liquid coolant is available to make domestic hot water and heat the building (errr, more like move the thermometer upwards a miniscule amount.    ).  This small engine doesn`t make much heat throttled down.

My main plant at the moment is a 1.5 litre, 4 cylinder VW Rabbit diesel engine directly driving a 1800 RPM, 3-phase head. It is used to power my machine shop and heat the building from the radiator and radiated engine/exhaust system heat.  When not using my machines I often put a wooden spacer in the throttle linkage to close the rack to 1200 RPM.  This consumes far less diesel fuel per hour than light/no load operation at 1800 RPM, (due to the phenomenon you speak of) but the shop lighting on it and the reduced but still present heat output is still very useful.

[rcavictim]

I have purchased a 195 that will be delivered on the 18th. I will be running this engine at 1800 rpm but would also like to operate it at 600 rpm. Your engine and mine are a combination of pressure and splash oil system. What this amounts to is the rocker arms are pressure fed a small amount of oil but all the other parts are splash fed by the rotation of the crankshaft and the dipper tube contacting the oil in the crankcase. Now as long as the engine speed is enough to cause the oil to splash around and lube everything then it should be fine. One other thing to look at is if the engine vibrates excessivly at the rpm you choose. If it does then just raise or lower the speed to find the sweet spot. This is my first Chinese diesel and it's going to be fun! I'll post results on my progress once I get the engine.

I look forward to hearing about your experiences with your engine. BTW, my 175 had no dipper tube as manufactured.  The engine has an oil pump which sucks from a small hole in the sidewall bottom of the sump (no screen) then pushes the pressurized oil through a mesh rock filter (I have upgraded mine to brass mesh with 50% hole size compared to the original for better protection), then to the pressure gallery.  The pressure gallery feeds the top end as you say which returns to the sump via return in the pushrod tunnels.  The gallery also feeds the oil pressure indicator-plunger module and a spray port in the block that is aligned with a catch hole/cavity (1/2 inch diameter and about an inch deep) in the side of the crankshaft throw.  Once per revolution, for a microsecond or two this catch cavity is in the path of the pressurized oil stream.  Centrifugal force of the crankshaft causes the oil that has been captured by this `drive-by shootin lube system` gets delivered to the lower rod bearing by the pressure created by the crankshaft centrifugal force through an internal oil passage inside the crankshaft.  When the crank is in other positions of rotation the pressure stream is splashed around in the crankcase to deliver oil to the camshaft, cam bearing and bushing (the amazing steel cam in a cast iron hole without a bushing), and the two main bearings (open ball bearing units).  IMO the splash system was completely inadequate and I designed my own lower rod end dipper which I installed and which does a superb job getting oil on the cam and lifters, the poorly oiled far end of cam bushing woithout a bushing, and especially the far and largest main bearing next to the output end of the crank and flywheel. My engine will not die from inadequate bearing oiling now!

I plan to install an outboard flow through filter from a custom plate and hoses that will replace the stock oil filter (rock catcher) module.

[okiezeke]

I'm looking at a similsr problem with my listeriod 20-2.  Day in and out 6-7kw will run the house fine.  I'm going to try the engine at 600-700 rpm and see if I can find a sweet spot down there.  If it works, I'll have better fuel efficiency, less wear on the engine, reduced coking by running more loaded, and I get that 650rmp music that everyone loves so much.  Nobody is sure if it can be done, so I figure I'll just try it and see what happens.
Zeke

[dkwflight]

Hi
I am running my 28/2 at 650 rpm.
What I think I am seeing is the stock governor spring was way too strong. I replaced it with a much lighter spring. The rest of the engine is more critical. The rack adjustment is more critical as well.
Everything must work together.

I may end up adding weight to the flywheel somehow.
Dennis

[okiezeke]

Thats great,
I figured Id have to fiddle  to get it slowed down.  Mabe get another pair of flywheels, and just put em next to the ones already on there??
Zeke

[dkwflight]

Hi I was thinking more along the lines of plate steel bolted to the flywheel. I would have the plates turned to fit the shaft and then the outside to a constant radius. maybe 1.5" or 2" thick
Dennis

[rcavictim]

Hi I was thinking more along the lines of plate steel bolted to the flywheel. I would have the plates turned to fit the shaft and then the outside to a constant radius. maybe 1.5" or 2" thick
Dennis

Dennis,

The plate is a good idea IMO but the extra weight will not be your bearing`s friend.  For this reason I`d suggest going with the thinner 1.5 inch plate perhaps and go larger on the diameter to 24-26 inch overall.  Steel can safely handle a higher rim speed than cast iron. You can thin it in the inner area as well if you have the lathe time.  Metal in there does nothing for centrifugal force but adds unwanted weight.

edit addition

On further thouight.  If you intend to hog out the center then go with a 2 inch thick plate.  What the heck. As the flywheel mass increases presumably the useable RPM gets lower and lower.  In theory then at some flywheel mass (probably infinite) you can get the RPM reduced to zero and that will save a LOT of fuel!!!  An infinite amount in fact!

[okiezeke]

Dennis,
was your 28-2 originally rated for 1000rmp?
Zeke