Author Topic: DES 8/1 Propane Conversion project  (Read 104081 times)

BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #45 on: January 26, 2015, 12:17:23 AM »
I'm looking for a thermostat mod/housing for the DES 8/1.  Anyone have any suggestions? 

BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #46 on: January 31, 2015, 10:55:46 PM »
I'm grinding the head for the thermostat, but am still looking for a flange spacer or gasket to space out the stock flange.  Cork gasket material looks like it could do it, but I don't have experience with it.
Any suggestions?


mike90045

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Re: DES 8/1 Propane Conversion project
« Reply #47 on: February 01, 2015, 02:01:41 AM »
Quote
I'm grinding the head for the thermostat, but am still looking for a flange spacer or gasket to space out the stock flange.  Cork gasket material looks like it could do it, but I don't have experience with it.
I found a thickish gasket at NAPA parts and stuck several togther with gasket shellack and made a spacer, it's held for a year so far .  I can look up the part # tomorrow f you need it,

BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #48 on: February 01, 2015, 05:27:04 PM »
If you get a chance, Mike, I would like to have that NAPA part number.

BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #49 on: February 02, 2015, 04:51:33 AM »
My friend Mark put in 4 hours with a needle scaler and die grinder inside the stripped down crankcase yesterday.  He's just got a bit more work to do in the lower sump, which he needs an angle die grinder for.   This crankcase interior was very rough with sharp bits protruding and badly needed grinding. It did finish up nicely.  It will get a coat of glyptol type red electrical varnish (thanks 38ac).   The machined parts of the case look quite good and the casting looks sound.

It's quite a change from my Metro Listeroid; this is a true CS clone with the oil pump, upper and lower sump, 7 bolt head, one piece cylinder (no sleeve) and bushed mains.  I'm ambivalent on the clone vs listeroid choice, but I am glad to not have to deal with the inevitable liner protrusion.

The head is flat overall though somewhat wavy, and I think I'll put it on my sandpaper/plate glass and see how it looks.

I'll be uncrating Jeff's new ST-3 from Central Georgia Generator tomorrow.  Tom at CGG has upgraded the bearings and bridge diode on these, so I'll only have to add 4 EMI suppression capacitors on the bridge.

« Last Edit: February 02, 2015, 05:07:14 AM by BruceM »

mike90045

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Re: DES 8/1 Propane Conversion project
« Reply #50 on: February 02, 2015, 08:42:59 PM »
Quote
I'm grinding the head for the thermostat, but am still looking for a flange spacer or gasket to space out the stock flange.  Cork gasket material looks like it could do it, but I don't have experience with it.
I found a thickish gasket at NAPA parts and stuck several togther with gasket shellack and made a spacer, it's held for a year so far .  I can look up the part # tomorrow f you need it,

NAPA 1038-ST
  is a gasket that fit my metro water outlet.  I stacked several of them to make a spacer, which I needed even after grinding the head outlet & the housing cover.

BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #51 on: February 03, 2015, 01:42:25 AM »
Thanks, Mike!

buickanddeere

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Re: DES 8/1 Propane Conversion project
« Reply #52 on: February 03, 2015, 03:24:23 AM »
  I was just thinking. If operating a diesel engine on just diesel for pilot ignition and only LP for the primary fuel. If the cam was retarded a tooth or two, the intake valve would close late and allow some of the AF mixture to be pushed back into the intake manifold. This would lower the effective compression ratio and reduce the tendency for detonation.
  It would be worth tinkering with on a slow afternoon.

BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #53 on: February 03, 2015, 04:17:38 PM »
What timing changes would be best for propane is an interesting idea.  I'm hoping that due to the slow speed, it won't be critical.

dieselgman

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Re: DES 8/1 Propane Conversion project
« Reply #54 on: February 03, 2015, 04:48:03 PM »
For spark ignition N.G. Listers, in the variable speed range of 1200 to 2200rpm, ignition timing is quite critical. I suspect that if you were using diesel as the pilot fuel, and using compression ignition rather than spark, that it would substantially change the combustion dynamics. It will be quite interesting to see what kind of results are obtained from this project/experiment.

dieselgman
« Last Edit: February 03, 2015, 04:51:57 PM by dieselgman »
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38ac

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Re: DES 8/1 Propane Conversion project
« Reply #55 on: February 06, 2015, 01:37:16 PM »
Have you any idea how  much "a tooth or two" actually changes ignition timing?  I can see problems with mixture and fuel consumption here.
 Of course then there is the question of how that is going to effect the exhaust valve timing in the cycle and what that is going to do.
It would be a surprise if the engine ran at all 2 teeth out.

I have zero experience with all of this but wondered along those lines myself.  What is the difference between the pressure needed to ignite the diesel fuel and the pressure which causes LP to detonate?  40 years ago there were kits sold for farm tractors that injected propane into the intake as a power adder for heavy work. There was no real regulation of the LP, just a constant stream that was on or off  but the primary fuel was diesel and the percentage pf propane was small.
Collector and horder of about anything diesel

dieselgman

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Re: DES 8/1 Propane Conversion project
« Reply #56 on: February 06, 2015, 02:10:17 PM »
Pre-ignition is the enemy and can hammer a good engine to pieces pretty quickly - or at least make a nasty hole in your piston and ruin your day. With spark ignition, the adjustment can be easily made for varying conditions of speed and loading to avoid getting into an engine destroying condition.

Compression ignition in the diesel relies on the timing of the fuel pulse... not simply reaching the flash-point temperature in the chamber.

Both of the above are very precise and fussy adjustments and have quite large influences on the power output, longevity, and efficiency of your engine.

We know from previous experience that propane will operate fine as supplemental fuel in a diesel engine - where the diesel fuel (compression ignition) is providing the primary timing pulse because it is providing the entire ignition source.

Now, if you are going to switch over to propane (or natural gas - methane) fuel and run without the diesel, you will need to add a spark ignition and also drop the compression ratio at least to a point where the fuel does not pre-ignite in the cylinder (before the spark is applied). Engine manufacturers (including Lister/Petter) have already performed many of these experiments and given us some base-lines to refer to.

I think we are primarily lacking good experimental data for a slow-speed situation such as what the CS presents...
Some things to think about.

dieselgman
« Last Edit: February 06, 2015, 02:12:20 PM by dieselgman »
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BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #57 on: February 07, 2015, 12:09:02 AM »
Hopefully the low, fixed rpm will make valve timing issues non-critical.  I can do whatever is needed re: dynamic spark timing adjustment if I have to go spark.  I'm hoping the Smartplug (smartplugs.com)  I made in a spare COV plug will work as well with propane as the last conversion (alcohol fuel) I did with it. It was a 4 cycle outboard, and it worked well at any speed and had decent acceleration.

The crankcase is done and painted, and Mark says he'll bring it out for me to start on it Monday.  We've both got several other projects going in building my new neighbor's home and off grid power system.




buickanddeere

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Re: DES 8/1 Propane Conversion project
« Reply #58 on: February 07, 2015, 06:48:29 PM »
  I was just thinking. If operating a diesel engine on just diesel for pilot ignition and only LP for the primary fuel. If the cam was retarded a tooth or two, the intake valve would close late and allow some of the AF mixture to be pushed back into the intake manifold. This would lower the effective compression ratio and reduce the tendency for detonation.
  It would be worth tinkering with on a slow afternoon.

Have you any idea how  much "a tooth or two" actually changes ignition timing?  I can see problems with mixture and fuel consumption here.
 Of course then there is the question of how that is going to effect the exhaust valve timing in the cycle and what that is going to do.
It would be a surprise if the engine ran at all 2 teeth out.

The idea is to limit combustion chamber fill and the effective compression ratio to prevent pre-ignition with the "low" octane LP fuel. Rather than restricting inlet airflow with an orifice which only works at a single rpm and load.
   There should be enough adjustment on the injection pump lobe to keep the injection event occurring at 15 or so degree BTC ? 
   Considering the care and accuracy how the cam lobes are hammered onto the cam shaft in India.  Intake and exhaust timing is already all over the map.

BruceM

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Re: DES 8/1 Propane Conversion project
« Reply #59 on: February 16, 2015, 12:58:47 AM »
Some photos of the COV plug converted into a primative smartplug using an RC glow plug (see smartplugs.com).  Think of hot tube ignition only with a platinum element glowing instead of heating the pipe.  Timing is adjusted by the length of the chamber after the glow plug.  In my version the timing is controlled by the length of a bolt threaded into the post plug cavity.  I've used this method before successfully in a Honda 2HP 4 cycle outboard.

https://drive.google.com/open?id=0B-wQ0EwBmioQYUF6cVk3bEtVaWc&authuser=0

https://drive.google.com/open?id=0B-wQ0EwBmioQQ2paalBmaFJQOGs&authuser=0

And a photo of my spark plug adapter. It's just 1/2" black pipe with a threaded bushing to fit the injector hold down.  I don't know how it will hold up over time but the fit is pretty good. The spark plug boot had to be sanded down a bit and then silicone grease is a must.  

https://drive.google.com/open?id=0B-wQ0EwBmioQVkpLTjZ4cXNQWlU&authuser=0

I also checked the connecting rod and wrist pin today. 0.0025 clearance, nice quality machining on the wrist pin.  Piston is also very nicely made.
The big end is 2.005" with  shims still in place from the factory, which is right in the ballpark. Same on each side, also encouraging.  I haven't gotten the case and crank back from Mark as he's been busy on the building project.  I want to get the camshaft in my hands next.

Bruce





« Last Edit: February 16, 2015, 01:01:59 AM by BruceM »