DES 8/1 Propane Conversion project

[dieselgman]

I see that the J type Impco regulator is commonly used on forklift engines... we have a couple of them in service at our shops.  There are plenty of forklift servicing agencies and lots of parts around for them, so it should not be that hard to scare one up for your project.

dieselgman

[BruceM]

Yes, the Impco model J and clones are readily availble and cheap.  The Cobra model regulator is it's less troublesome upgrade.   They need at least 30 psi input, up to 300 psi, they are designed to connect direct direct to the propane tank.  I've not been able to find something for 10-15 psi input, the more commonly used propane intermediate pressure.

For low pressure models, the Garretson KN types take 13" or less in, and have -0.5" out.  Ditto for the Beam 202ANL.

Centuryfuelproducts.com carries quite a selection at very competitive prices.

Update: looks like the Garretson KN type is the way to go after talking with my propane supplier, as distribution above 10 psi is not encouraged, and the tank is 50 feet from the engine shed.  So we'll use the standard 10 psi distribution in the yellow propane Pex-type pipe (buried) and down regulate to 11" at the generator shed wall, then at least 1/2" hose for the sort run to the KN type regulator.

The Model 100 may be the best carb for the Lister CS:

"The Model 110 carburetor/mixer is designed primarily for one and two cylinder engines where severe
intake manifold pressure pulsations are present. However, its use is not limited to these applications. Improved
mixture control and air-gas valve durability can also benefit other applications in intake systems where
pressure pulsations could adversely affect a standard 100/125 model assembly."
 
SPECIFICATIONS
Fuel Type .......................................... LPG Vapor
or Natural Gas
Inlet Pressure .................................... -1.5”w.c. (-0.37 kPa)"

So either way (CA55 or CA110) I need to get my pressure way down.

[BruceM]

I highly recommend centuryfuelproducts.com.  They actually have helpful technical support.  They suggested the IMP52 regulator, which takes 4-12" WC in and has the -1.5" output that the CA55 or CA110 need.  $59.   Shipping to me today.  Their technical guy thought I should start first with the CA55 carburetor.

[32 coupe]

I would like to add that this experiment has kept me "on the edge of my seat" !!
Anxious to see.the final result.

Gary

[BruceM]

There will be more issues to work out but that's just the way it goes when you're doing something new.

I had to flatten the head and cylinder the other day; I was waiting on that until it went to the machine shop for the hardened valve seats.  It developed a fire ring leak into IP side 6th bolt.  Head was concave, cylinder top also, so not enough pressure in the fire ring on one side, only 1/4 from bolt hole.  Took a few hours even with help on 100 grit sandpaper on glass by the farmer method. 

I suppose the Rajkot Listeroid mod to eliminate the ring-side bolts and raise the liner protrusion where attempts to solve this QC/tolerance problem.  Alas, the latter just created new problems. 

[BruceM]

I got the new -1.5" water column regulator plumbed up and did another test run yesterday.  Alas, no change, still missing; carb rich/lean adjustment seems to have little effect now.  I lowered the compression ratio to 13.3 before this run, which increases the problem as it did before, when I raised it to 13.9.  I also replaced the breadboard spark circuit with a soldered board. 

The engine will not start or run cold on spark, only on the smartplug. Once it warms up a little, it runs on spark with less missing but still intermittent missing, then running, then missing, worse as it reaches full temperature.  Adjustments to the carb main rich-lean mix, idle bleed screw and hand choking have no effect. 

Today I'll be removing the CA55 and disassembling for inspection, and mounting the new adapter plate for the CA110 and CA125 carbs to the intake via JB weld. 

[Tom]

Bruce, Perhaps if you put an induction timeing light on the spark plug wire you'll be able to see if the plug does not fire when it misses. It could be that there is just not enough umph (technical term) to make a spark at speed.

[BruceM]

Good theory, Tom.  I don't think the spark is intermittent, since the smartplug has the same trouble,  but I'm wondering if the spark is adequate to get ignition.  From what I've read, propane demands a high power spark system, even more so for a lean mix.  I also wonder about sparking in the indirect ignition chamber...where it could be even leaner.  I know the woodgas guys got it to go but woodgas is very different than propane. 

I might try the CDI ignition hardware I have.

I've got the CA110 mounting plate secured to the intake manifold, fiddling with the plumbing now. 

I did take apart the CA55; there is no rubber diaphram, instead, the diaphram is a roughly 2" diameter plastic and aluminum piece with a single plastic ring that rides in a cylinder.  It has a metal projection that is the main metering element, and a big 2 diameter spring pushes it closed, acted against by the intake vacuum. The internals were clean, new, unworn, smooth.  I saw nothing that led me to believe it was damaged or defective.

I hope to have the CA110 going this weekend.  It's so huge, an intake restriction will surely be needed!

[Tom]

My thought is that there just might not be enough voltage to jump the gap at the high compression ratio with propane. It would only take 5 min to setup and test, although I don't really claim to understand the smart plug.

I had a '71 Triumph Spitfire once with a GT6 engine swapped in. The thing ran great cold, but once warmed up it would start to miss around 4k rpm's. What I eventually found was that the GT6 engine came with an internal resistance coil and the Spitfire had a resistor on the firewall. Running both left the ignition system with just not enough voltage to work at high RPM's. Removed the balast resistor on the firewall and joy of joy's the thing ran great!

[dieselgman]

Bruce, 

Even on the HRG twins and triples, an intake restrictor is used. I would have to go measure one to be completely accurate, but I believe it closes the inlet down to about 1" diameter.

dieselgman

[BruceM]

Tom, after thinking about your good suggestion some more I ordered a couple types of spark testers, just in case.  One will let me test the spark strength, the other let's me see if it's sparking when it's missing.  I'm looking at high output coils as well, but the CA110 will give me some good data before I order one.  I am using resistance ignition wire, the carbon fiber type. 

The CA110 has a big diaphram, some sort of paper or fabric type stuff, coated with brown goo (some sort of oil). Much more diaphram area, a bit less mass to move.  Many thanks for the loaner, Gary! (dieselgman).  I've just got to cut a gasket, and bolt it on my new adapter plate which is JB welded  to the intake manifold.  I'll plan on less than an inch of inlet opening...thanks!

[dieselgman]

Bruce,

That is a used 110 carb and apparently had been run on a dirty fuel supply at some point. The diaphragm should be clean and is normally a slightly glossy flexible material. We have repair kits for them that include the diaphragms.

dieselgman

[BruceM]

Good news-  the engine starts and runs pretty well on the CA110 carburetor!

It struggles a bit at no load- carb gets closed down all the way and it then misses a beat but continues in a stable manner and at the set rpm.    I have to fiddle with the idle screw still, and also with the governor for load/no load.  I hooked up the compressor for a load and pumped up a tank to 150 psi.  No problems at all. The main mixture doesn't seem to affect running at idle or at load.  No signs of knocking at 13.25 compression, I'll consider raising it after a max load test.

The one adjustment that is critical is the intake restriction.  I used a PVC ball valve that was a close friction fit into the intake.  Too much restriction and it starts to miss, too little and it also starts to miss.  It likes about one square inch of opening area.

No EGT yet, which needs to be done, as well as fine tuning spark timing. etc.

Many thanks, dieselgman for the CA110 loaner!!!

Video perhaps tomorrow when I can get some extra hands.

Bruce

[32 coupe]

Good deal Bruce !!!!
It looks like you are making progress now !

Gary

[Tom]

Your making progress and power, awesome!