Aluminum block vs iron block and BSFC?

[Number21]

I am attempting to find a good liquid cooled engine in the 30hp range to run from natural gas. I am trying to find something that will have the lowest BSFC. I expect to either increase the engine compression or add a turbocharger to increase efficiency and take advantage of the high octane of NG.

In this power range, I have found 3 major engine types to choose from:

1. Briggs and Stratton or Kawasaki aluminum block V-twin.
2. Geo/Suzuki 3 cylinder 1.0L aluminum block inline 3.
3. Briggs and Stratton .7L cast iron block inline 3.

I'm leaning towards #3, mainly because it has a cast iron block. Is an engine of the same design with an aluminum block going to have a higher BSFC due to the aluminum losing more heat? Or can that be controlled as long as the engine has a proper thermostat? Also, the Briggs engine is a converted diesel, so it should be able to handle turbocharging quite well. (turbo diesel is a factory option)
http://www.ebay.com/itm/131797201535

My other concern is number of cylinders. I think two is better than three. Is a two cylinder engine likely to have a better BSFC than a three cylinder of the same displacement?

Are there any other engines I should consider? I would also think about the Kubota 3 cylinder gas engines, much like the Briggs, but I can't find anywhere to buy one that is new.

[SteveU.]

Search up wikipedia's article on b.s.f.c.
Good read. You will see that clear back in the 1930's German and certain British internal piston combustion engines were getting grams per hp b.s.f.c. that are hard to match even today. Problem. These were huge bomber aircraft and submarine engines with no personal individual usage.

My own personal useage I have found NO DIFFERENCE in base range possible b.s.f.c. in my water cooled aluminium versus cast iron. Much more diffnence in the bore to stroke ratio's. Cumbustion chamber designs. And much more diffnence in the actual rpm/loads range the engine is put to use in. Then ultimately the operator makes as big a difference than all of these put together.

My been used opinions:
for your ~30 hp go with the three cylinder. All cast iron. Kubota DG1000. Already natural gas, spark converted. Then no power sucking balance shafts; drive chains and gears. Even spaced power pulses. Use an electrically driven cooling fan. Thermal switch controlled.
Two cylinder/twin cylinder in this horsepower range and the pistons must be large. Needs large valves if only two. Big bores really benefit from four, even five valves to feed it. And that adds costs, complexity. You turbo possibility adds that too, with a must have higher more expensive quality lubricant and oil cooler to live. Service costs will eat some of your fuel-not-used savings!
Again my opinion: cylinder displacement up to 400 cc per cylinder seems to give the best balance of all factors with manufactures getting their highest (lowest numbered) b.s.f.c. for small engines. So for moderately slow speed like 1500 rpm loaded you'd need a 1.2 L four cylinder.

The link you put up is actually for a Diahatsu manufactured engine. Sure looks to have a cast iron block, aluminum cylinder head. Just what you do not want. A head gasket blow'er with any problems and power pushing.

MUCH more important than an ultimate b.s.f.c. is where are you going to get service information, repair and rebuilding parts. B&S will be slow, slow going clear back to Japan.
Why I say Kubota. Or a Yanmar. Both have world wide direct dealers/servicing.

Aircooled and I'd say instead all aluminum W/cast iron bores. Kawasaki V-Twin for the best b.s.f.c. currently.

Internationally recognized branded named: "Pay once. Cry Once. Then use, and enjoy."

Regards
Steve unruh

[Number21]

Thanks for the information. I hadn't noticed the aluminum head on the Briggs, (Diahatsu) I don't like that. Is there anywhere besides a Kubota dealer at full MSRP to buy a new 3 cylinder engine setup for spark ignition? There are none that I can find on any of the surplus markets. Only ones on ebay are beat up used engines. I might consider a diesel Kubota with NG fumigation, but I need to do some math on that.

The engine will be used to pump water out of a creek, and I'm going to use a heat exchanger in the creek to get rid of engine heat. This way there is no fuel consumption from a fan. It's also kind of an experiment for a cogenerator I want to build later on, I want to try some different things with the engine (like changing the compression ratio) and see how it effects fuel consumption. I'm also thinking about trying some things like ceramic and anti friction coatings in various places.

I'm also curious if I can't use the hot water from the engine and cold water in the creek to generate some power with a thermoelectric generator. I'm also going to install a small turbine in the creek eventually.

[glort]

I agree with Steve on a lot of his points.
I'm also confused as to what the real objective is here.  You seem to want to squeeze every last drop out of fuel efficiency and go to trouble and expense said efficiency would likely never recover.

I often look at the price of efficiency or economy.  As an example, a mate of mine is a car dealer. The brand he sells has models in petrol and Diesel versions.  People want the diesels about 4:1. When My mate asks why they want a diesel, they inevitably site better economy.  He looks at their 4 yo trade in with 40,000 km and points out with the mileage they do, they will never come near recovering the $6K price difference through the better economy and by the time they go to trade in again, they could be more than $3K better off buying the cheaper petrol model and the cheaper than diesel petrol fuel even if they do get less miles.
And that's not taking into account the much higher servicing and maintence costs of the diesel models.
Some people get it, some don't.

He doesn't care which one he sells, same profit in it for him, no shortage of either, just trying to actually do the right thing by the customer.

I wonder about the exact same thing here.
If you are actually concerned about running costs, maybe focusing on the BSFC is giving you a tunnel vision of the big picture.
You are talking head work or turboing, ceramic coatings etc, non of which is going to be cheap, especially if you aren't doing the labour. IF you are and it's a bit of fun as well, different story.
Straight off i think, " What will the fuel saving be between turboed and not and, how much fuel would the turbo modification buy and what would be the time frame to recoup that cost and get ahead?
Again, as Steve points out, then you have the oil and maybe more frequent changes, another component to wear and repair and so it goes.
My understanding is there is going to be a pretty small difference between the consumption in a turboed and non turboed engine especially in a stationary role of constant power delivery and what could be minimal boost anyway. 

I'd also be looking at things like the Geo engine that can be had cheaply.  Not every used engine is going to be cllapped and in my experience here at least. I can buy a set of pistons and  rings for a 350 Chev cheaper than some small Briggs engines.  Again, if the cost difference between a decent used Vehicle engine and a new stationary engine is put into fuel offset, You may find the efficency Difference is going to off set a lot of hours running at a higher consumption ( as marginal as that may be).

I don't know about the states but here we have vehicle engines that are set up for gas from the factory. Being computer controlled and gas fuel injected, I'd reckon you might have a hard time beating their efficiency  even with a much smaller converted " Dumb" engine.  The purchase price of those would be cheaper than a lot of industrial engines and running slower would not hurt their life expectancy either.

As for the the thermo electric, what sort of power are you looking to generate? 200w Or 20 KW? I'm not aware of any practical setups to make power in the KW range with thermo but if there is, I'd be interested to find out about it.
As my understanding of thermo is themore heat difference the better. I'd suggest you may be a lot better off to run the exhaust through the hot side of the thermo than the hot water.  Cool exhaust is going to be a couple of hundred oC, hot coolant is going to be 98 oC tops.

If you weren't planning to, with a bit of experience with boats, even in fresh water i'd say you would be wise to run a heat exchanger rather than direct water for coolant.  That way you can run proper coolant with anticorrosion properties.
The HE wouldn't have to be much, submerge a car radiator  in a box with screened creek water running through and you'd be more than fine.  Probably at the HP you are after, you'd be able to run a length 6-12 ft length of 2" pipe in the creek, Maybe exhaust pipe with a 180o bend, and still have plenty of cooling capacity.

I'd love to have a place to play with Microhydro.  You can make power with pretty much any moving water if you set up for what you have.
A friend just bought a property that has a creek running through it and I'll be very interested to see what that is like.

Let us know what you go with on this.

[SteveU.]

O.K. good you have lined out your intneded use parameters.
As glort inffered there is a huge differnece in a narrow range speed stationary and a must-have 10 to 1, even 20 to 1 speed/laoding range in a vehicle application.

I am not against all aluminum water cooled engines at all.
I had a 1987 Suzuki Samurai four cylinder that taught me out of my aluminum prejudices. DO need to use the best low-silica coolants though or have pinhole-cavatation eating up your coolant side castings. So maybe not the best for a creek water system.
Plus here in my Pacific Northwest mountain valleys Samurai's and Geo's bring a 2x, 3x premium and and need to be secured with dogs and lot's of guns.
Fuel hogging cast iron V-8's a dime dozen.

The Kubota natural gas engine is a cool $3,00-4,000 USD here. Discounts only for buys of 10 or more. Once when they discontinued them you could get the smaller DG672 engines for under $2,000.

For your natuel water cooling I still say you's be better with an all cast iron engine.
USA/Canada the still can be had Chrysler 225 cid inline sixes can be had cheap. Parts still cheap, cheap.
Fellow on the old Lister Engine Forum who set up one of these in his urban house basement on street gas producing 20 kW/el handily. He would laugh his ass off on the big single hopper fellows fighting mountings, in-ground distance transmitted thumpings, and lighting flicker.
These are as durable and efficient as any small inline six ever made for a 1500-1800 rpm use.

Regards
Steve Unruh

[mobile_bob]

matching power to the available load is probably going to have more of an affect on the bsfc numbers than just about anything else.

most if not all, engines have a very narrow window where the bsfc numbers are best, much outside this narrow window and the bsfc can vary over a surprisingly large range.

in my experience with small diesels, particularly the s195 and its variants, the best bsfc number happen right at full max load for whatever your intended rpm range is.  if you can keep the load up, the coolant temps high, and have a means for protection so the engine can run unattended, you can get some really good bsfc numbers out of the 195.

if i were to want to pump water, as you suggest, i would probably want to get things matched to where the full load capacity is pretty close to what the actual load will be... however

there is always the issue surrounding reliability, so there is a trade off that you likely will have to work out the details of.

getting maximum bsfc numbers while running the engine at max output likely doesn't equate to best engine life.

this is something i would keep in mind when looking at advertised bsfc numbers, i would want to make sure how, and under what conditions the advertised numbers are derived from.

remember Sears hp ratings?  defined as,  the absolutely max hp an engine can produce for perhaps one second before going thermonuclear.

bob g

[glort]

I am not against all aluminum water cooled engines at all.

While I would never say all aluminium engines/ heads are bad, I don't think there is any question that in severe service or just operating out of normal parameters, iron engines are far more resilient and tough.

I still remember about 5 years ago dragging my big trailer across a mountain range and wondering why my Iron Nissan Diesel was blowing so much smoke even when not under full load.  It was a bit down on power but otherwise everything seemed OK. I put it down to bad fuel I had topped up with on the trip in.
I crawl up some of the steepest mountain roads in the country, get to the top and feel a bit cool in the cabin so put the heater on. There is no heat. I'm thinking if there is no heat, there is no coolant.  Sure enough, I pull into a servo, carefully undo the radiator cap and proceed to put 3/4 of the cooling capacity's water in it. At that stage I'm wondering very much I'df I'm going to even get the last 80Km home.

In looking for leaks and finding none, I discovered the spring in the radiator cap had failed and the thing had obviously ejected all the water that way.  I also worked out it must have happened on the way up the mountain on the outward trip as I hadn't put any water in it since leaving home and it did seem a bit off when I got to where I was going.
I still marvel how I dragged that trailer 200KM with the thing smoking and carrying on obviously because there was no water ( hence I didn't get a high temp reading on the gauge) and replacing the radiator cap had the thing going perfect a couple more years till I sold it. It didn't use oil or water or do anything else other than run fine.

My father has a Subaru Wrecking yard and like most cars so equipped, the ally heads are a weaker point.  Once people cook the engines, 8 times out of 10 the heads go soft and are good for nothing other than my YT aluminium melting vids.  There is a test the re conditioners do to tell if the heating has made the heads lose their hardness and those that have can't be recoed. Well they can, but you'll be forever blowing gaskets which would be pointless. On the flip side, The aluminium cased bottom ends are fine.  For shits and giggles, we rebuilt an engine that had got so hot it melted the plastic in the knock sensor that is bolted to the top back of the engine for a yard runaround.  The thing runs quiet as a mouse and while of course not logging up many miles, it uses no oil and starts and runs perfect with just a pair of high mileage heads slapped on the thing.

The 2.5 Subys mainly have trouble with head gaskets as there was a manufacturing defect for a few models but once replaced, they are pretty much right for the rest of their service lives... which is a long one.
If they are overheated, then the heads need to be tested but if caught in time before they are cooked, then a skim and gasket replacement is all that is needed. It's rare for the 2L engines to have this trouble.
There are many makes and models of cars here that are scrapped after a short life because ally heads become so hard to get because they all fail and everyone wants them, they are scrapped after 5 years or less.

The main advantage with Aluminium in engines is weight and 9 times out of 10, that's only a concern for Vehicles.
I'm not aware of any ( although there may be some) large stationary engines designed for long hours made from aluminium. Where weight isn't a factor, I thing iron is the better choice of material for an engine.

I also agree with the idea of the inline 225 sixes which was what I was thinking in theroy as well.  A large underdriven engine in stationary use can be just as fuel efficent when set up properly as a smaller engine and of course far less stressed aiding longevity. Like the old slow Listers, having a low RPM also allows for longer burn times which helps efficiency.  I know the Diesel engine in my truck was also used in forklifts, busses and various machinery as well as stationary use.  To this end, there are a number of different cam shafts available to suit the given application. It may be possible with a popular vehicle engine to have a variety of camshafts available and select one for something like towing that may better suit the stationary use and efficiency.

As I said, the difference between the optimal fuel efficiency on an expensive setup and an easily achievable one one a much cheaper system might be maybe a Dollar a day and if the efficient one is going to cost a couple or more thousand over a less efficient engine, The the payback time is going to be a long one and possibly never achieved economically with other things factored in.

You'll need to do your numbers carefully!  :0)

[Number21]

I also agree with the idea of the inline 225 sixes which was what I was thinking in theroy as well.  A large underdriven engine in stationary use can be just as fuel efficent when set up properly as a smaller engine and of course far less stressed aiding longevity.

Do you really think it is possible for an engine as large as an inline 6 to be as efficient while running at say, 1800 RPM, with a 15kw load, than a 3 cylinder running twice as fast with half (or less) the displacement?

Could I lean the A/F ratio on big engine way out to reduce the horsepower, and run the throttle wide open to reduce pumping losses, without burning the engine up?

I've seen a range of fuel consumption on NG engines from 8,500 BTU/HP to as high as 10,000 BTU/HP. At 30hp, that is a difference of up to 45,000 BTU/hour that could be saved!

I've thought long and hard about converted car engines but I always run into a few major issues -
RPM control - I can add a governor but for a good one you're looking at $500 or more. (Somebody please prove me wrong)
Size - they are always way bigger than needed, the best I could find was a 1.0L Geo.
Output shaft - Need custom adapter to bolt anything to the flywheel, might be able to use the front pulley.

Car engines are always cheaper - I keep coming back to the 350 Chevy, I can buy a brand new one, not rebuilt, with a 3 year warranty, no core, for $1400 shipped, but it's way bigger than I need. I could also get a remanufactured Geo 1.0 for about $1600 if I had a core. But when you add the parts listed above, and consider they are less fuel efficient, they might start costing the same as an industrial engine.

I've considered looking for CNG powered junkyard engines, but, they aren't very common here, and I don't think any of the brains would be applicable to me in that situation. With low pressure natural gas, there is no fuel injection, so I can't see any need for a brain, just need a carburetor/mixer and RPM control. Most of them are low compression dual fuel capable anyway, not really optimized for NG.

My other option is to simply use a diesel engine with a diesel pilot ignition and the rest natural gas. This way the engine is already high compression, and maybe turbocharged, easier to find, and, built in speed control. No spark plugs either. I have to calculate if the increase in efficiency outweighs the higher cost of diesel fuel.

A little bit longer explanation about what I am doing:
I recently bought several acres with a creek where the natural gas is just $0.52 per therm. Immediately I only need an engine that will pump water, at varying RPMs. Over the next few years, I am going to be developing this property into a mixed use residential/commercial development. There will be perhaps 20 different rental units and I'll be responsible for supplying them all with electricity, hot water, hot air, and cold air. Long term plans include a dedicated trigeneration building. There will be multiple individual generators, for redundancy, and in the summer the waste heat will be fed into an absorption chiller to create more air conditioning. (North Carolina, hot at least 6 months of the year) I intend on investing a great deal of money into this system, but expect monthly paybacks.

This system will not be built for a couple of years, but, in the mean time, I want to settle on an engine I can use for that project, and do some experimenting with it. I want to find out under what circumstances I can get the best BSFC, and, what does it take to get the engine there. I will be doing careful monitoring for both fuel consumption and any other hourly running costs. Also somewhat of a reliability test. I need to find out for myself what really makes the best BSFC under my circumstances, not just some theory I read somewhere.

Simply increasing the compression on an engine is really easy, has little effect on engine life, and could substantially increase fuel efficiency for a dedicated NG engine. Any dual fuel gasoline/NG engine running on natural gas is not doing so efficiently because of the low compression ratio needed for gasoline. Thermal efficiency relies heavily on compression ratio. It's not very hard to take the head off, have it shaved a little, and bolt it back on, though it will void a warranty. I'd also like to go through the engine and do a little porting and polishing, mass produced engines always have rough spots inside and efficiency can be gained spending some time smoothing everything out.

Also, a turbo with low boost levels could basically raise the compression ratio without actually cracking the engine open. They are only a few hundred bucks and not very hard to install. Most of the engines I am considering do have a factory turbo diesel as an option, so I know they can handle it...and I can probably find OEM parts.

[Number21]

As for the the thermo electric, what sort of power are you looking to generate? 200w Or 20 KW? I'm not aware of any practical setups to make power in the KW range with thermo but if there is, I'd be interested to find out about it.

I really do not know what is possible, other than one time many years ago I remember reading an article where they built a 1KW thermoelectric generator powered by exhaust heat to replace the alternator on a semi truck. If I could make an extra 1KW I would be very happy with that. (in addition to a small turbine generator)

I am interested in modules like this:
http://www.ebay.com/itm/172159943602
They claim with a 100 degree difference, just one of those modules produces 3.2 watts.

Say the creek is running at 70 degrees in the summer. And I have 220 degree engine water. That's a 150 degree difference. Even better in the winter. Whether it is actually economical to do or not I am not sure, just want to play with it. If the idea actually worked, I could make more hot water with wood, or waste motor oil, and turn that into power!

It has been my dream to own property with a creek since I was a small kid, and I'm going to do everything I can to extract every last bit of energy and geothermal heating/cooling out of this creek. It makes a lot of my land unbuildable, and therefore, I expect the creek to pay rent.   I have not had time yet to measure flow rates and temperatures of the creek.

[Number21]

Do you really think it is possible for an engine as large as an inline 6 to be as efficient while running at say, 1800 RPM, with a 15kw load, than a 3 cylinder running twice as fast with half (or less) the displacement?

Could I lean the A/F ratio on big engine way out to reduce the horsepower, and run the throttle wide open to reduce pumping losses, without burning the engine up?

I wrote a couple big long posts, although this was the main information I wanted to focus on. Anyone know? I'm kind of an inline 6 geek, if I could use one of those efficiently, I would be very happy.

I appreciate all the detailed replies!

[Number21]

This is some fuel consumption information I found on the Arrow engine website. Their engines are all optimized for natural gas, not gasoline.

K series - big single cylinder that looks like a converted imported diesel:
At 4hp and 650 RPM, it burns about 8900 BTU/HP.

VR330 330ci inline 6:
Roughly 8200 BTU/HP at 1600 RPM and 60HP

VR330 with crossflow head:
7717 BTU/HP at 1400 RPM and 55HP

VR220 220ci inline 4:
8100 BTU/HP at 1800 RPM and 45HP

Compared to other gensets, using a 3L 4 cylinder gasoline/natural gas engine at 25% load, burns closer to 11,000 BTU/HP. I don't think using an inline 6 at a fraction of it's rated horsepower would be very efficient.

The best fuel consumption was with the cross flow head in a 330CI inline 6, but 55hp is too much. Cut that in half (inline 3) and it would probably be just right. If I could get anywhere near 7700 BTU/HP, I would be very, VERY happy!

[SteveU.]

Well O.K. again your above "my situation' explanation has helped narrow in the possibilities.

I had been wonder mightily just how you could have supplied natural gas AND a rural creek to work with.

Yes absolutely in a narrow speed load range of operation a cast iron only four bearing,cam-in-block, crossflow head,  inline six could beat a three cylinder GM/Suzuki's fuel gas use butt. The trick of it is the use/LOADING of the larger slower speed engine. Off-loading parasitic fan and water pumping loads.
You point out well the steps and difficulties of modifying for stationary use any auto based engine are all true. These alligator problems have eaten up many a man. The Harrison Ford in Mosquito Coast, "lost in the details" effect is Real and bites down hard.
So why do it?
Lots of already set up natural gas generator sets used/new out there that would fit the end result of your overall project much off-the-shelf better.
www.centralmainediesel.com their NG gensets are as affordable as you will find new. Look for these systems used, locally. You just add the heats harvesting.
www.marathonengine.com for their unified Ecopower, tri-energy systems. Use their efficiency's at least for achievable goal settings. They do district systems too.

You far underestimate the work to set up a durable long term usable engine turbo system. Whole books written how to start to match up the impellor to the turbine side for each engine and that engines intended power use curve. And it usually takes manufacturers phase I, phase II, phase III to get the engines internals beefed up and pistons undersides oil spray cooled to live long term with a turbo. You do realize you will need to add an external oil cooler too? Manufactures just bolting slapping it on were GM's, and others, early engine death problems.

Turbo's, superchargers, carburetors are not like wheel and tire over-sizing slap-it-on, or Nos bottling-up, and drive it away. Takes lots of systems cut-fitting, primary/secondary controls use/tuning in to get them working smoothly, reliably. Alligators.
NG fumigating injected diesels - BIG Alligator. You then get to repair maintain two whole different systems. Are you a diesel injection mechanic? You will have to learn to be.
In addition to your whole system projects of an HVAC, refrigeration, pipefitter, sheetmetal specialist. Only the Gov'Mint, or a pocket billionaire can afford to hire out for all of these.

S.U.

[Number21]

Yes absolutely in a narrow speed load range of operation a cast iron only four bearing,cam-in-block, crossflow head,  inline six could beat a three cylinder GM/Suzuki's fuel gas use butt.

Are there any readily available automotive inline 6s with a crossflow head? That's the big sticking point with the inline 6, most of them are not crossflow. The Arrow engine I was talking about above would be great but I'm sure far out of my price range and dealer only. A CNG converted Cummins 4BT or 6BT engine from a bus on ebay would be fantastic, but none available right now. I've seen them in the past.

I wonder if the same would be true for a V6 with a cross flow head, for example, the 4.3L GM Vortec engine? Could I run that engine super lean on natural gas with the throttle near wide open?

I can get a reman 4.3L for under $2000. If I spent some money on a stub shaft and governor system, it can easily be transferred from engine to engine and probably last forever. With that in mind an automotive engine might be a better idea because long blocks are usually available for cheaper than industrial engines.

So why do it?
Lots of already set up natural gas generator sets used/new out there that would fit the end result of your overall project much off-the-shelf better.
www.centralmainediesel.com their NG gensets are as affordable as you will find new. Look for these systems used, locally. You just add the heats harvesting.

My first goal is to settle on an engine I can use multiples of in the future. I want one engine I can use for a variety of things, from my water pump test to later trigeneration needs. They won't strictly be electrical generators, they will also have belt driven A/C compressors. The first one I buy for my water pump will be a test of what is possible in the future.

Also, most of the "cheap off the shelf" natural gas gensets are simply gasoline engines converted to NG. They are not efficient. I have researched a number of generators based on the 3.0L GM 4 cylinder, and without a crossflow head or high compression, it is not very efficient on natural gas. Companies like Arrow offer more efficient natural gas optimized gensets, but they cost a fortune. I'd rather put together my own system.

In addition to your whole system projects of an HVAC, refrigeration, pipefitter, sheetmetal specialist. Only the Gov'Mint, or a pocket billionaire can afford to hire out for all of these.

The future rental units will all be setup for hydronic heating and cooling. There will be various thermal storage tanks in the system. Each heating and cooling system will have a standard backup like a natural gas fired boiler and an electrical hydronic heat pump in case any of my trigenerator systems fail. I can handle most of the necessary work and engineering for compressor refrigeration systems, plumbing, hydronic HVAC, ect. I have fun doing this kind of stuff, especially if I can make money at it. 

[glort]

A little bit longer explanation about what I am doing:[/b]
I recently bought several acres with a creek where the natural gas is just $0.52 per therm.  Over the next few years, I am going to be developing this property into a mixed use residential/commercial development. There will be perhaps 20 different rental units and I'll be responsible for supplying them all with electricity, hot water, hot air, and cold air. Long term plans include a dedicated trigeneration building. There will be multiple individual generators, for redundancy, and in the summer the waste heat will be fed into an absorption chiller to create more air conditioning. (North Carolina, hot at least 6 months of the year) I intend on investing a great deal of money into this system, but expect monthly paybacks.

From what you are saying, I think the time to start investing that money is now.
You need to be painting the outline of the big  picture then colouring it in as you go IHMO.  I can understand that perhaps you want to start small and learn but that doesn't seem a viable thing here.  You are going to be needing a lot more than pissy little single/twin industrial engines here with the loads/ functions and most of all RELIABILITY this is going to require when you have 20 families/ businesses relying on you.

I think it all needs to be mapped out NOW and you are going to need an expert to work out the loads and requirements of what you are going to need.
That said, worrying about costs on this " toy" engine seems bit of a moot point. What you are talking about is a multi million dollar development so if you are worrying about the $500 cost of a governor for an engine and one that could be far more in line with your ultimate needs than immediate ones, I have to wonder about the likelihood of this all coming off.

I'm as far away from an expert on this as could be but I'd also be pretty willing to bet with my very limited knowledge, what works for a small "domestic" size setup has probably little to do with anything upscaled and relevant to what you are ultimately talking about. You may come up with something that works small scale but can't be workd into a redundant system easily or doesn't have the required controls etc to supply mains power or connect to the grid etc. You Could be then right back to square one and all your development and experience ( and investment) is out the window.
I think concentrating on the engines economy is being extremely tunnel visioned atm.  There is a vastly bigger picture that needs to be taken into account.

That I believe is going to require a LOT of infrastructure to set up and again, I believe is a job for experts to make it all work and interlink. If you can't afford to pay a consultant or system designer for that part of the plan, Then look out when you are trying to do the rest.  They aren't going to let you put in factory units or homes without a LOT of plans and design for every part of the infrastructure and that is going to involve a lot of people whom aren't going to work for nothing. 

My advise would be go with what you will ultimately use NOW so you have the development stage of the rest of the project to sort out the bugs and learn it all.

Really sounds like a huge undertaking and needs to be done on an appropriate scale and design level.

[Number21]

You are going to be needing a lot more than pissy little single/twin industrial engines here with the loads/ functions and most of all RELIABILITY this is going to require when you have 20 families/ businesses relying on you.

I think it all needs to be mapped out NOW and you are going to need an expert to work out the loads and requirements of what you are going to need.
That said, worrying about costs on this " toy" engine seems bit of a moot point. What you are talking about is a multi million dollar development so if you are worrying about the $500 cost of a governor for an engine and one that could be far more in line with your ultimate needs than immediate ones, I have to wonder about the likelihood of this all coming off.

Way, way off. This is why I tend to keep my posts vague, otherwise I get people answering questions I didn't ask and taking things way out of context. The topic here is I want the the most efficient 30hp engine I can find, that's it. I shouldn't have said why, it doesn't really matter. Let's just pretend I entered a "most efficient engine" contest.

Now, as for why you are incorrect:
Nobody is relying on this system. Like I already said, the units will be built with standard hydronic heating and cooling. This is simple stuff they have been doing for more than 100 years. Common, cheap equipment will be used to heat and cool the water on a constant reliable basis, and the grid will supply the same type of power. No, I won't be spending millions on this project, I find that quite laughable. I suppose it might approach near a million when I'm all done. (Appraised value, not what I actually spent) This system will use regular grid power and be billed to tenants at whatever that ends up costing. (via BTU meter measuring water delivered)

The cogenerator(trigenerator) is simply an add on. If it doesn't work, then the primary grid powered system continues to function as a normal, highly inefficient heating/cooling system. Given the cost of electricity, compared to the cost of natural gas, I can generate electricity for about the same cost as the power company, including engine maintenance. I can then sell this energy to tenants at the same price they would pay the utility. Now I have thousands of free BTUs to use as I please. I can use those free BTUs to make domestic hot water and heat living units, which again I can charge for. I can also spend about $40,000 on an absorption chiller to convert that hot water into cold water in the summer. All of my heating and air conditioning needs can be met with free waste energy, and, can be sold for a lot of money every month.

Having a completely hydronic system allows me a lot of flexibility, I can feed it with many different source of heating and cooling, with reliable backups. I could also supplement with a waste oil or wood burner, which I could even use to make air conditioning with an absorption chiller.

Yes, the equipment will be expensive, but I'll also get paid a few grand a month to have it. As for those "pissy little single/twin industrial engines", well, I never asked about anything smaller than 30hp, I don't consider that "a little pissy engine". Concerning efficiency and reliability, there needs to be several smaller individual generators, which can either work alone, or together. If one is down for maintenance I'll have a backup. If the power consumption at night is low I only need to run one generator, and during peak periods I can run two or more. As many as I need. Having one common engine means it's easy to keep parts and whole long blocks sitting around ready to go.

And yes, efficiency is a big, BIG deal. EVERY single BTU matters when you are running 30, 60, or 90 horsepower 24/7. Just a difference of 500 BTU per horsepower adds up really fast. The fewer BTUs I use the more money I pocket.

But let me repeat: I never asked about any of that. I simply wanted to explain why I am asking. The only topic here is high efficiency 30-ish horsepower engines. The simple economic problem is that the type of engine I need is mostly only available in very large power units, which I do not need. Supply and demand makes bigger engines and generators cheaper than the small-ish ones I am looking for. The ideal engine that I want, a 3 cylinder iron block with a crossflow head and easy availability of short blocks simply doesn't exist, so I'll have to come up with a compromise.

My advise would be go with what you will ultimately use NOW so you have the development stage of the rest of the project to sort out the bugs and learn it all.

That is exactly what I am asking for. At this time I do not need any cogenerator engines or generators. I do have an immediate need for a 20-30hp water pump (it will be variable speed) and since I need that anyway I want the same engine here that I'm going to be using over and over everywhere else. I'm not going to rely on what I read on the internet, I'm going to find a good engine, modify it the way I like, and then actually study it to see how that effects fuel economy and engine life. We can argue about theories all day but nobody really knows until you get out there, do it, run it, and measure it.

So, to sum up:
- Kubotas are nice but big money and not easy to find
- Briggs and other aluminum engines are cheaper, probably less reliable, but come with a 2-3 year warranty
- Most NG engines converted from gasoline are not as efficient as they could be
- Converted car engines have a few issues that must be solved, not impossible, but, also few car engines are available with cast iron cross flow blocks in smaller displacement

I said I would prefer a car engine because even though I would have to spend a lot on a governor and shaft adapters, those parts would last indefinitely and automotive long blocks (all the wear parts) are usually cheap to replace.