Natural Gas Carburetor Conversion for Small Engines

Ozzb, excellent! I just got off the phone with them and they can hook me up for under $250 bucks.

Gas conversions often do have aheat problem as ozzb described. The little hondas are easy to strip down and check for burned valves or overheated pistons. If the pistons are overheating you can get higher hot strength pistons. For valves get them coated in ceramic, the racing shops can arrange this easily.

A simpler option is to drill a hole in the inlet, plug it up with felt and place a nipple for a tube to an oil container. You want to use diesel or thinner oil. The Vacuum sucks the oil into the chamber in minute quantities stopping the rings from wearing and cooling the inlet valve. You will need to put a little gause (from a fuel filter or tap)on the inner most part so the felt doesn't suck in too! You could use petrol but it tends to evaporate and stuff up the mixture, it doesn't lubricate much either...

Have you thought of Grid Connected Solar? the battery bank would allow more economical running of the generator, your fuel bills would be down or negative and the whole system would make you pretty well self sufficient.

Which brings up the last option... Alcohol fuel or old chip oil for small diesels???

You have a good engine to start with. That engine is all over the place. Have you searched to see if Honda ever sold these engines, or similar ones that ran on CNG? That should get you some leads. Another place to look is your propane dealer. They are in the business of selling propane. If they want to sell propane, they will help you look.

Another thing to consider. Propane generators produce more power than CNG. A generator that makes 13KW on CNG makes 15KW on propane, or gasoline. Do you have pre-piped CNG at your house? That would be the only reason I would recommend CNG. I am planning to have the local propane distributer set a 100 pound propane tank here, and running my barbecue grill off of it as well as my standby generator. These companies are in existence to deliver propane. Once the storm is over, they will want to be delivering propane to their customers. My question is ,how long will the 15KW generator run on 100 lbs of propane at an average of 50% load?

Yep, I expect to lose about 15-20% in power output on CNG, I'm thinking that I probably should upsize on the genset to compensate and hang on to the smaller one for utility use. I expect a bunch of generators will start showing up on craigslist and the pawn shops in the near future as people start looking to sell them to pay for repairs. I have CNG already plumbed into the house, but I don't have propane (nobody in the neighborhood does.) so CNG is a no-brainer. I expect to run Synthetic oil in the unit so extended high temps should not cause a lubrication issue. Besides, finding somebody to come out to fill the tank in the aftermath of a storm is probably no easier than finding a gas station with gas and power. CNG never shuts down.

Hello Rorschach,

Yep, I expect to lose about 15-20% in power output on CNG

You may recoup the power using a turbo?

What do you think...

Probably could, but we are still talking about around a 25 hp engine for a 11 KW rig. that would be a mighty small turbo. I also suspect the cost of retrofitting the unit with a turbo would be such that I could have bought a 25Kw rig. I also suspect the engine might not take to being blown real well.

Okay but then it may not serve well to expect greater power from either. I was considering the possible fuel saving...

Perhaps hydrogen enrichment?

You'd have to talk to Al Gore and T. Boone Pickens about getting rich off hydrogen....=D

try www.oildrum.com

After Wilma, Katrina and Ernesto, the local propane trucks were up and running after about two days. I was impressed with their effort.

Rorschach, hoping it is OK if I piggy-back on your thread...

I too was impacted by Ike and am at about the same point in thinking through things. At about a gallon an hour, gas became a concern very quickly. I have come across the same resources that folks pointed to in this thread.

The generator that I have was left by the previous owners of the home when we moved in. It is a Generac Guardian Ultra Source Portable Generator rated at 15kW. It hooks up directly to the home. Given that it i already here, I would like to use it if I can and was planning to have the CNG that runs to my house run to a spot near the electrical tie-in. I have not spoken to Hendricks, but propane-generators.com does appear to have a kit. Emails to Generac dealers have gone unanswered.

My question really has to do with the heating and wear problems discussed in some of the responses. Would I see the same type problems with a conversion on this generator? Any other concerns that you can think of? Any help would be appreciated.

Thanks in advance... Dave

Dave, I've heard good things about Generac. Apparently they wind their generator heads with twice as many poles so that the engine can run at 1800 rpm instead of 3600 rpm. That means the engine is not working as hard and the engine is actually oversized for the load. (engines of that type are rated based on the torque available at the highest rated speed, so to get 15 KW at 1800 RPM, you actually need an engine that would be rated closer to 25 kw at 3600.) Again, the engine has a lot more margin. the downside is that they are heavy and large for the power output. Honda built generators (vs a no-name generic generator with a Honda prime mover) and some Yamaha ones are actually DC generators that feed electronic inverters, so instead of having to run at a fixed RPM all the time like most gensets, they can throttle up and down to meet the load. That means fuel consumption and noise is much lower. But I understand that they come with a hefty price tag too.

Funny, I have heard the opposite at the SmokeStack board(the one I referenced later here) Many of the guys there refer to them as Genercrap. It is said they use either proprietary or no name components(well, unmarked at least) in their units and their technical support is non existant for all but the newest sets. Even then, they are not very likely to be of much assistance for anything other than how to install them. Reportadly, they are not helpful if you are trying to identify parts and/or repair their units.

FWIW I have not had personal experience with them myself. So, I cannot vouch for the accuracy of the above statements. It is just what I have been told.

Ian, I am referring to the info I've heard about the larger stationary units, they may very well have a low end line that is crap. I don't know.

Here's a little info for you.

Here is a link to a top cylinder lubricator and there are others but you do need one of these to get the life out of your engine. www.ampcolubes.com/index.html

I was going to give you some btu figures when I came upon this page. It looks like it will give you some good info on propane and CNG. http://www.yamaha-propane-natural-gas-generators.com/fuel_consumption.htm

Good luck,

Randy

That was a great site with plenty of hard to find information on propane usage. Thank you.

I might also add that you might do a little price comparison between propane and CNG. It appears that CNG is about 1/4 the price of propane (around here anyhow) I'm a little suspicious that CNG conversion is more expensive.

Randy

I'm a little suspicious that CNG conversion is more expensive.

Why is only a different size orifice "jet", injector etc..

Here is another site that may help answer some of your questions. There is a wealth of information generator related here. While the site may be targeted towards antique gensets, most of the information is applicable to newer units too. That and it is just a cool site, if you like generators.

http://www.smokstak.com/forum/forumdisplay.php?f=6

Thanks for the info on smokstack.

I have been told by a manufacturer's rep. that recent EPA regulations make it illegal to convert a small gasoline engine to a different fuel, and that the manufacturer does not offer any conversion kits.

That would depend upon the type fuel, the objective is towards cleaner air and I don't believe you'd be violating the principles and objectives of the ruling by converting to cleaner fuel.

bwire, there you go trying to apply logic and common sense to something that the government did. Haven't you learned anything in all your years? =D

No harm in using their rhetoric as a defense

As others have mentioned, using gas will cause the engine to run hotter, the valves will have probably the worst problems, followed by the piston......

My recomendation is NOT to convert if you want long term reliability.

Buy an old [or new] generator without an engine. Look up Mike Brown's Steam Engines and check out the smaller steam engines and boilers. Also check the Green Steam Engine site. You can put any kind of liquid or gaseous fuel into the boiler, you can even use wood or charcoal a fuel. After a hurricane there is plenty of wood.

Conversion means reworking the carburetor to suck a mix of air and NG or propane from a gas chamber or building a gas injector that will put gas in the cylinder on the intake stroke.

I am struggling with a related project. How do I figure out the right air / fuel mix for propane in a small burner for a heater. (scratch built) Its calculating the right air inlet ( draft tube ?) going to burner head from the point at which the porpane orifice injects the gas.

I've been thinking about going a hybrid route. Using the smaller genset to charge a battery bank and then run a decent sized inverter from the battery bank. I've heard good things about Xantrex but I have to wonder how much they cost compared to some of the no-name, generic Chinese ones. That would also allow me to charge the battery bank with any number of different technologies as well, Solar, wind, etc.

I've found a 17 KW one but I haven't been able to contact anyone about pricing and availability yet. The specifications seem strange, it LOOKS like it is actually a 9.8 KW continuous rated unit that can surge to 17 KW. It also puts out 240 V, which means I can in theory run my A/C system too. I figure that the AC system (a 4-ton unit that MIGHT have a 10 SEER rating at best) will pull about 4.8 KW running and 9.6 KW starting. So this unit should be able to do the job and still run the lights and such. I figure I'll need to connect a couple of 12-V deep cycle marine batteries in series.

What do you guys think?

9.8Kw, 97% eff.@24V=420AMPS!! You'd better have one big battery bank as well as some big ole honking powercable!

Seriously though, I am not sure as to how practical that would be. Perhaps, a better idea would be to run a smaller inverter(or two?) and one or two smaller window A/C units, to cool a few selected rooms. You would have much more control of battery loading than that big 4 ton unit cycling off and on.

Still, a 10Kw inverter power system would be cool to see

I figure automobile batteries can do 850-900 amps instantaneously for starting, and the alternators are rated for 80-100A output max. Granted that automotive starting batteries have thin plates with a lot of surface area for maximum instantaneous power whereas deep cycle batteries have less surface area and thicker plates. So I figure something in the neighborhood of 450A for say 30 seconds or so should not be out of the range of possibility for a couple of large 12V marine deep cycle batteries in series. Say with #00 wire for interconnects. I might need to put four of them in series/parallel but that would probably be the most I'd need. I'm thinking a couple of BCI group 4DM batteries in series should be more than enough.

I'm starting to think though that I'm going to end up costing more than an off the shelf 11KW standby rig going this route.

ok, I'm looking at this for cost estimates:

Generator 3.5 KW, approx. 2.9KW after conversion (already owned, cost $270 used.)

Conversion to CNG manual start $250

5KW Cont./10KW surge inverter with integrated 10A/24V charger $719

Cutler-Hammer 100A manual transfer switch $259

Qty. 2 BCI group# 4DM batteries @ approx $150 ea. (estimated) $300

#1AWG 25' booster cables (to be cut up for jumpers) $105

Subtotal (minus genset already owned) $1633

A 6KW continuous pre-packaged stationary CNG Genset for comparison purposes costs $1900

I'm starting to think rolling my own might not be a wise decision.

Just because you don't seem to have enough choices. Let me throw this out to you. Inverters seem to gain cost per watt as they grow larger. Batteries drop in price as power goes up. Two 800 watt inverters are cheaper than one 1500 watt inverter.

The best answer for being prepared is an automatic standby generator, that will power the entire house. That is $3,000 to 3,500 plus installation. If you are able to pick the essential items in your house, and power each one with an inverter, possibly some low powered lighting shared on one inverter. With the lower power, the cables become less expensive. A 1500 watt inverter will run a dual burner hot plate, or a microwave oven. An 800 watt should run your refrigerator, and another one for your TV, and related equipment, unless you have a high powered amp used with it. One good group 31 battery should allow a days worth of use between recharges on each inverter. Another way to store energy is to pick up UPSs when available. Depending on the size, they will keep a refrigerator working for at least a day. If you get slick, you can use the battery charger to maintain the other storage batteries. (If they are 12 volt battery packs.)

You will need to run your 3.5-2.9 Kw during the day to recharge the other batteries, but that is not too hard, just stagger the charging to recharge them all.

Actually Bob, I was thinking along those lines myself. instead of powering the whole shooting match with one massive inverter, powering individual branches with smaller units running in parallel. Perhaps a number of "modified sine" inverters for the lighting and outlet loads, and one or more pure sine inverters for branches with electric motors like the AC system and the fridge and freezer and the washer and dryer. It makes the transfer switching a bit more complicated, but not a lot. It would mean a whole bank of DPDT relays/contactors. I noticed that the 16kw Generac units that Home Depot sells for $3500 have separate circuits to power just the branch circuits that you want.

800W won't even come close to running my fridge BTW, I've got a little 900W two cycle Coleman genset I bought a few years back thinking it would run the fridge too, but it can't start the compressor, it will BARELY run my freezer. 1-1.5kw I figure is the minimum the fridge needs to start and run. it COULD be that it is because the little genset is an inverter type and the output isn't pure sine either. That could be part of the problem.

During Andrew we got our hands on a bunch of 800 WATT inverters. All but two people were able to run refrigerators on them. One of those people had a refrigerator that belonged in the Smithsonian. So I had assumed the other was an old high power user also. I looked at my 2 refrigerators. One is 3.5 amp, but the other is 6.5 amp so I guess you do need a bigger inverter.

What about UPSs, how will they work in a power outage when used with a 60 watt light bulb?

"What about UPSs, how will they work in a power outage when used with a 60 watt light bulb?"

You need to be careful with using an UPS for continuous duty. Many of the inexpensive UPS for home computers use marginal components at best. They were intended to run a PC for only a few minutes, so you can save your work and shut the PC down safely. They will burn up quick if you use them for an appreciable load for a longer duration. The larger, comercial (read, expensive) units are built for continous (quasi continuous?) use. They use bigger heat sinks and larger power semiconductors (more of them, too) as well as better built transformers. The 39 dollar units from places like WalMart and Office Depot will not last long, powering anywhere close to their max ratings, for any length of time.

Thank you for the reply. That seems to imply that they would be best at supplying some lighting reserve.

For a small light they may live for a while.

Back in '04, when Charlie, Jeane and Frances cale through. I used a cheap 250 VA ups to power a small 13" TV with an antenna several time with no ill effects. Granted, it only drew about 40 watts and I never ran it more than about 10 minutes at a time. I couldn't stand listening to the AC power alarm much longer than than that, anyway

With some shopping, you should be able to find a 16kW LP (15kW NG) generator with an automatic transfer switch for under $3500. That is with a weather resistant housing. It will run a 5 ton AC, or two 4 ton units.

You could get a commercial UPS and expand on it's battery bank as well as charge it through other, offline means.

The units here at work have a separate battery cabinet, with (18) 12V Deep cycle batteries 216VDC.

Granted these are massive 100Kw 277/480V Continuous duty 3ph units. But they do come in more manageable sizes. ie 7-25Kw single phase. The key here is the DC voltage level. ie 25Kw(216V@120A vs 24V@1075A)

You ever notice a pencil and paper can really ruin a good brain storm?

Randy

True 'nuff.... but there may still be some economies to be had. As it is, I am still $300 cheaper and I haven't optimized much yet. Plus there is the added advantage that I will have a more stable power output, even if it is a "modified sine wave" instead of a true sine wave. Of course I also haven't built the enclosure yet either. I think I can shave at least a hundred bucks out of it here and there which should pay for the enclosure. I also have a rig that I can charge with solar power too if I choose to later.

Stand by getset and while you're there checkout PTO gensets and maybe that steam engine idea isn't so bad

If you live in a flood zone, take that into consideration. For one, engines don't run too well under water and if the house and it's wiring get wet, you don't want to run a generator at all.

Flood zone is a non-issue with me. I'm far enough inland and far enough away from the creek that flooding is really not an issue.