Author Topic: Fuel Consumption LPG vs Gasoline  (Read 10747 times)

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ChrisOlson

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Fuel Consumption LPG vs Gasoline
« on: September 14, 2012, 09:09:59 AM »
We had a really bad power day on Thursday so the bank didn't get charged good. The auto-start didn't start the generator - we would've been fine for another day.  But I've been itching to get a real world fuel consumption run on our new Honda generator doing battery charging.  So I started it and ran it for 2.5 hours to see what it would do.

I don't have a good way to measure genset power production directly (yet), but I can measure on the DC side going into the batteries.  I put 6.0 kWh into the batteries in 2.5 hours, which at 90% charging efficiency I figure to be about 6.7 kWh at the genset.  There was other loads on in the house at the same time, and I estimated those at about 370 watts ave for the 2.5 hour run, which would be another .9 kWh direct from the genset at Power Factor 1.0.  That would be a total of 7.6 kWh produced by the genset over 2.5 hours, or roughly 3.04 kVA average output for the run.

The generator burned 141 ounces of 91 octane (non-ethanol blend) fuel for the 2.5 hour test.  That figures out to a fuel consumption rate of .44 gal/hr.  The BTU content of the fuel is about 114,500 BTU/gal, or 33.56 kWh/gal.  So overall efficiency figures out to 20.6%.

That's roughly 3% better efficiency than the LPG generator could do on its best day.  It's not quite as good as a diesel generator can do.  But it's in the ballpark.

As a comparison to a larger diesel, our 250 kVA Cummins prime power set burns 19.8 gal/hr @ 70% load.  That figures out to 23.3% efficiency.

One other thing I did was add an auto-throttle controller for the Honda.  The Honda has built-in auto-throttle, and can't use it for startup because it takes to long to get the engine up to operating temp for warmup, and the voltage and freq is low for the inverter to sync with it while it's idling.  But for shutdown it's nice because it cools the engine and generator down quicker - and doesn't load up the cylinder from the spark suddenly being shut off with the engine running at rated speed during cool down.

I did it by having a Coleman Air board monitor the genset battery voltage.  When it first starts the voltage is below 13 and it takes the charging system on the engine a bit of time to get it up to 13.2V where the controller engages the auto-throttle with an ice cube relay mounted in the gen enclosure.  It works really good.  It required tapping into the wires on the auto-throttle switch and connecting them to the Common and NO contacts in the ice cube relay

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bob g

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Re: Fuel Consumption LPG vs Gasoline
« Reply #1 on: September 14, 2012, 11:15:15 AM »
Chris

just for reference

purpose built DC gensets in the 4-7kwatt class powered by diesel engines have no problem attaining 25% overall efficiency.

i would expect the cummins to be better than what you report too.


there are a variety of in class diesel DC gensets designed to do direct battery charging that are very efficient, much more so than the best of propane/nat gas or gasoline units.

i understand your cold winter startup issues, probably precludes your using one of the DC gensets, but maybe during the warmer months one might be useful?  redundancy?

have you considered one such a unit?  if not why not?  cold weather start issues?

bob g
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large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
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ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #2 on: September 14, 2012, 11:43:32 AM »
have you considered one such a unit?  if not why not?  cold weather start issues?

Two reasons:

- Redundancy.  We got a big Ronk manual transfer switch.  I can flip that and completely remove the inverters and battery bank from the picture, and keep the house and shop alive on genset power.  This is used in the event of an inverter failure, or some instance where all the batteries have to be pulled offline.  Can't run the house on a DC genset

- Load Management.  Our inverters can put out 8 kW max continuous and some of our loads are bigger than that.  But those heavy loads are intermittent, and usually short.  We depend on the genset to start up and take the peak off those heavy loads so the inverters can use both battery and genset power to run them.  Can't do peak load management with a DC genset.

Some people will say, well put in bigger inverters and more batteries.  Running the genset for the hours required for peak load is much cheaper in the long run than batteries, if you do the math on it.
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bob g

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Re: Fuel Consumption LPG vs Gasoline
« Reply #3 on: September 14, 2012, 03:49:50 PM »
" Running the genset for the hours required for peak load is much cheaper in the long run than batteries, if you do the math on it."

can't argue with that

bob g
research and development of a S195 changfa based trigenerator, modified
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ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #4 on: September 14, 2012, 07:28:18 PM »
I'm happy with the efficiency of it compared to LPG and satisfied that it will lower our operating costs of the generator, long term.  Yes, some diesel generators can do better.  However, at today's prices gasoline is cheaper per kWh in this Honda than diesel is in our big genset, even though the big genset is more efficient.

Ever since they invented ULSD (with the associated extra cost), when it comes to operating costs you have to examine it very closely when trying to choose between diesel and gasoline power.  Diesel fuel was 70 cents more/gallon than gasoline here last winter.  Right now it's 26 cents more per gallon.  The efficiency of a diesel doesn't make up for the additional cost in fuel at that price differential.
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MagicValleyHPV

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Re: Fuel Consumption LPG vs Gasoline
« Reply #5 on: October 31, 2012, 08:47:20 PM »
We had a really bad power day on Thursday so the bank didn't get charged good. The auto-start didn't start the generator - we would've been fine for another day.  But I've been itching to get a real world fuel consumption run on our new Honda generator doing battery charging.  So I started it and ran it for 2.5 hours to see what it would do.

I don't have a good way to measure genset power production directly (yet), but I can measure on the DC side going into the batteries.  I put 6.0 kWh into the batteries in 2.5 hours, which at 90% charging efficiency I figure to be about 6.7 kWh at the genset.  There was other loads on in the house at the same time, and I estimated those at about 370 watts ave for the 2.5 hour run, which would be another .9 kWh direct from the genset at Power Factor 1.0.  That would be a total of 7.6 kWh produced by the genset over 2.5 hours, or roughly 3.04 kVA average output for the run.

The generator burned 141 ounces of 91 octane (non-ethanol blend) fuel for the 2.5 hour test.  That figures out to a fuel consumption rate of .44 gal/hr.  The BTU content of the fuel is about 114,500 BTU/gal, or 33.56 kWh/gal.  So overall efficiency figures out to 20.6%.

That's roughly 3% better efficiency than the LPG generator could do on its best day.
Hi Chris,

This subject interest me greatly. I assume you tested two completely different generators - one on propane, and a second on gasoline? Also, if the LPG prime mover wasn't properly modified and tuned for lpg, then that would undoubtedly skew the results. To be clear, my aim to not criticize your choice of fuel, but rather the conditions under which the comparison was made. Do you real feel it was valid?

ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #6 on: October 31, 2012, 08:50:54 PM »
Yes.  The LP generator was a Generac EcoGen 6 kW.  Designed from the ground up to burn LPG:

http://www.generac.com/Residential/EcoGenSeries/6kW/

With any given engine, the brake thermal efficiency with LPG will always be lower than using gasoline in the same engine because the flame front speed is too slow with LPG.  The other bad thing about LPG for an off-grid generator is the size of the tank required to store the same amount of energy you can store in a 5 gallon can of gasoline.  For us, with LPG at $1.90/gallon and gasoline at $3.40/gallon, and considering the much higher fuel consumption with LPG (and additional cost), the gasoline fueled generator is a no brainer.  If you can buy LPG at much lower cost/BTU than gasoline or diesel, and can put up with the big tank sitting in your yard to fuel a generator, then it may pay off.

But as it stands at present, gasoline is a better buy/BTU than either diesel fuel or LPG.  Diesel fuel is 65 cents more/gallon here right now than gasoline is.  So neither can compete, despite a diesel's higher thermal efficiency, in cost/kWh with the gasoline fueled genset.
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« Last Edit: October 31, 2012, 09:28:09 PM by ChrisOlson »

MagicValleyHPV

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Re: Fuel Consumption LPG vs Gasoline
« Reply #7 on: November 01, 2012, 02:34:02 AM »
Yes.  The LP generator was a Generac EcoGen 6 kW.  Designed from the ground up to burn LPG:

http://www.generac.com/Residential/EcoGenSeries/6kW/
Knowing Generac, and this example's CR of 9.5 to 1, I'm dubious they optimized much of anything. LPG prudence starts at 10.5 CR, and I have one engine (now w/360 hrs) at 11.8 CR. And unlike your Honda, I seriously doubt it has variable ignition timing. I see this genset is also belt driven.
With any given engine, the brake thermal efficiency with LPG will always be lower than using gasoline in the same engine because the flame front speed is too slow with LPG.
It's not that definitive - not by a long shot. I would urge a copy of "Analysis of combustion and flame propagation characteristics of LPG and Gasoline fuels by laser deflection method" by, Ki Hyung Lee, Chang Sik Lee, Jea Duk Ryu and Gyung-Min Choi (2002). In it, I quote, "Comparison of flame propagation between LPG and gasoline showed that the flame speed of LPG is faster than that of gasoline at the range of lean or stoichiometric equivalence ratios." It goes on to stipulate that once the gasoline mixture is en-richened beyond stoichiometric, indeed it becomes slightly faster. But you and I both know what 'rich' mixtures lead too, especially at altitude... don't we?



ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #8 on: November 01, 2012, 12:44:07 PM »
Actually, though, all spark ignition engines run on the rich side of stoichiometric - especially engines that operate at continuous full power like generator engines.  You can only play with lean mixtures on engines that operate at low or partial loads - and that is not generators.

When you start raising compression ratios you also end up with another can of worms - starting in cold weather.  A high compression SI engine is no better starting than a diesel at 30 below.  A medium compression ratio 8-8.5:1 SI engine will crank and fire right up without preheat at those temps.

So what it boils down to is that the LP generator didn't work for us.  When it's 30 below and you've been fighting for two hours to get a standby generator running it's starts getting old real quick.  First, the tank won't make enough pressure to keep the engine running.  So you heat the tank up to get pressure, and then the carb turns into an iceball, freezes up and it quits.  Now you need a carb heater.  So you say "screw it", go brush the snow off the top of the little Champion gasoline portable generator, pull the rope and it fires up and "just works".  That's when you reach the realization that you're fighting the wrong battle.

Part of the requirement of a standby generator in extreme cold, when we run ours the most, is reliability.  I could come up with a whole page full of reasons why a diesel generator, in theory, is more reliable and efficient than our gasoline fueled Honda.  But if you can't get the damn thing started at 30 below all those theories are moot.
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MagicValleyHPV

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Re: Fuel Consumption LPG vs Gasoline
« Reply #9 on: November 01, 2012, 03:06:11 PM »
Actually, though, all spark ignition engines run on the rich side of stoichiometric - especially engines that operate at continuous full power like generator engines.  You can only play with lean mixtures on engines that operate at low or partial loads - and that is not generators.
I'm not inclined to lump all SI/IC engines into a single, fit-all category - just too many variables. Many, especially the current EFI SI crop, are specifically designed to accurately follow the engine's feeding needs - lean at no loads, stoich at partial loads, and proportionally rich when the load demands it. Even most carbed engines have multiple mixture circuits to safely accommodate a reasonably broad and safe workload. It's also important to point out, that many genset manufactures intentionally tune their units to the 'rich' side, simply to inhibit premature damage when ignorance decides to load his unit to max.. at sea level.. on a scorching 105 degree day. So what if it uses more fuel than is needed... they're not the ones footing the fuel bill. So reality is, not all SI engines always run rich - stating otherwise, defaces verifiable exceptions.
When you start raising compression ratios you also end up with another can of worms - starting in cold weather.  A high compression SI engine is no better starting than a diesel at 30 below.  A medium compression ratio 8-8.5:1 SI engine will crank and fire right up without preheat at those temps.
Not unlike other small engine manufactures, Honda (shown below), employs a cute and very effective "Automatic mechanical decompression" gizmo (located on the camshaft). In my case, a simple spring swap to this gizmo was all that was necessary to lower my static CR about 50% (it deactivates @ about 600rpm). I really doubt even a trained Honda tech would suspect that my engine is any different internally than OEM. But that's not all. I also installed the very same variable ignition coil that your Honda has. My initial is set @ 5 BTDC and swings to 'all in' @ about 2k (this is for LPG only).

I've not experienced -30 in years where I live. I do however, see -5 periodically. Under those chilly conditions, I honestly don't experience the hard starting problems expressed. If it ever does dip much below that, I have no qualms red-necking a little starting heat.       



So what it boils down to is that the LP generator didn't work for us.
No dispute from me - only you know what works for you.

 

ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #10 on: November 01, 2012, 06:24:02 PM »
I'm not inclined to lump all SI/IC engines into a single, fit-all category - just too many variables.

Well, you get what I'm saying - at the air/fuel ratio that prime power SI generators run at you are on the rich side out of necessity.  Otherwise you'll end up with skyrocketing cylinder head temps, burnt valves, recessed seats and a host of other issues.  The flame speed (and thermal efficiency) of LP fueled engines is lower under these conditions - and that's the conditions that off-grid generators are required to run under.

If you have a grid backup generator, then you're running at only 50% load max continuous and it is no longer a prime power generator.  Then LP fuel (or natural gas) becomes a viable option as it has many advantages - it can be stored indefinitely without breakdown or going "stale", it extends oil change service intervals (since most home owners don't service their own standby generators this saves money).  But at the same time those generators are short lived units - usually 1,500 hours and they're junk.  They're sold under the premise that they only get run for exercise and once in a blue moon during a power outage for a few hours.

Off-grid generators, OTOH, are usually expected to run 10,000 hours without a problem.  You're hard pressed to get that out of an LP fueled engine without having the head(s) off at least once.

Quote
If it ever does dip much below that, I have no qualms red-necking a little starting heat.

One of the requirements for us is that our generator is used for peak loads.  It is auto-start.  If the load on the inverters hits 9 kVA the master inverter calls for gen start within 6 seconds and expects it to be at rated voltage and frequency at 10 seconds, syncs its voltage and freq with the gen over the next 10 seconds, and finally expects the generator to accept full rated load within 20 seconds after calling for help.  At 20-30 below that requires a generator that starts - there's no time to preheat it.  And when you're off-grid you can't waste power constantly keeping a genset warm so it will start like you can when you got grid power.

There's various reasons the LP-fueled EcoGen was a total failure for us.  And the type of fuel used, and it's characteristics, was one of the major ones.  It's no fun at 30 below having the power go out because the gen didn't start when the inverter called for it.  And then you're outside for two hours heating a 500 gallon LP tank with charcoal to get the pressure up in the tank so the generator will run.  Even underground LP tanks don't work at those temps because the usage is above ground and as soon as the fuel vaporizes it freezes up valves, regulators, carbs, you name it.

I know a lot of people use LP with great success and think it's the best thing since premarital sex.  But those people don't experience the conditions we live in here in the winter time - and those conditions are when the generator power is the most important for us.

We (I) made a mistake installing a LP-fueled generator.  When I went to rectify that mistake I looked at diesels (Cummins QD-series).  But the energy input to get a diesel started in the winter time negates any efficiency advantages it has.  So gasoline fuel was the only viable option for us, because experience has shown me it's the only thing that works when we need it most.
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MagicValleyHPV

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Re: Fuel Consumption LPG vs Gasoline
« Reply #11 on: November 01, 2012, 11:32:06 PM »
Well, I'm beginning to think that because of your usage, your situation is more the exception than the rule. Most off-gridders quickly come to realize that conservation is vital to keeping expenditures in check. If you have the funds available for a high KW, push-button world, that's cool - I don't. Sadly, what directly effects both of us, is the antiquated electron storage. This 20's circa technology essentially forcing many of us to rely on more costly, greasy-fingered alternatives. Running a genset at 20-25% efficiency is flippin' nuts, irregardless of the reason(s). 

And me,.. I just sat down one day and penciled a list.

Living downwind from a Sante Fe hump yard for 10+ years blessed me with a perpetual intolerance to diesel - five miles behind a semi and I'm stuck with a migraine for the rest of the day.

Not so bad with gasoline, but I still end-up smelling like a refinery after every refill. And my clothes are banned from the living quarters if I so much as spill a drop. Unlike LPG, I'd be forced to use even more fuel just to restock - not to mention, that storing much more than about 25-30 gal on the property isn't particularity comforting to me. If not the hazards, it's thieves. I also have grandkids.

I understand propane, and I've done numerous installs.... NOT bolt-on conversions.  And because of its advantages, I learn to deal with, and try to minimize the disadvantages. No, it's not for everyone, and I certainly don't claim that it is. It's just the most tolerable compromise I've found so far for me.

MagicValleyHPV

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Re: Fuel Consumption LPG vs Gasoline
« Reply #12 on: November 02, 2012, 03:54:55 AM »
Just for ***** & giggles, I plugged in some raw data on one of my genny engines. Please understand that this a computer generated simulator and may or may not be accurate. The sample chosen is a Honda GX240 (8hp) 242cc - sea level - 70 degrees amb. No other changes were made beyond what is noted below. (Of particular interest, is the Thermal efficiency and the EGT. Also note the difference in cylinder pressures (validating the increased CR on propane).

Gasoline 86 oct, 8.3 CR, 20deg        LPG 105 oct, 10.8 CR, 28deg

« Last Edit: November 02, 2012, 04:05:32 AM by MagicValleyHPV »

ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #13 on: November 02, 2012, 07:21:57 AM »
Skewing data with different compression ratios is sort of purpose-defeating.  If you bump the compression ratio on the gasoline engine to 10.8:1 then it again wins across the board.  Or take it a step further and bump the ratio to 14:1 and burn Turbo Blue racing gas in it.

Thermal efficiency is a function of the compression ratio as well as the fuel.  With a given set of parameters (compression ratio, valve timing events, spark timing, stroke length, mean piston speed), fuels with a lower energy density will always exhibit lower thermal efficiency.

In operating cost, the cost/BTU of the fuel is the determining factor with any given engine on a generator that is ultimately going to determine cost/kWh.  LPG is on the low end of the scale.  Gasoline is somewhere in the middle, diesel is typically the best.

When it comes to having the funds available for a high KW push-button world, yes, we have spent considerable money on our system.  The first seven years here weren't all that great and I lost track of the number of times I had to get up at 3:00 AM and start a bone dead gas charger at 30 below because the inverter was singing its low voltage tune and the furnace blower in the house was about to quit.

We decided there has to be a better quality of life and embarked on a mission to make our system totally automatic so that we can enjoy some of the same conveniences as folks who have grid power have.  That cost us roughly $50,000 over the past three years - $10,000 on a 58 kW battery bank alone.  And I don't make any excuses for that - it's what we wanted because we enjoy fishing and hunting, and other activities more than babysitting an underpowered system for our house all the time.  And it got old having to run around at night worrying about too many lights being turned on, and the TV going, etc..  We don't have to worry that anymore and today we even have a security light that comes on automatically at dark that illuminates our whole back yard.

We went from the theory of conservation being the way to "make it thru" to not believing in conserving renewable power, but making more of it.
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MagicValleyHPV

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Re: Fuel Consumption LPG vs Gasoline
« Reply #14 on: November 02, 2012, 12:38:56 PM »
Skewing data with different compression ratios is sort of purpose-defeating.
Not at all Chris. "Purpose-defeating" is feeding propane to an unmodified gasoline engine, and expecting lower operating costs because the fuel is cheaper. I would not even consider propane if I could not fully exploit its virtues - milling the head was $35 and the replacement head gasket was $4
If you bump the compression ratio on the gasoline engine to 10.8:1 then it again wins across the board.
Wrong answer. "Winning" is proof of concept. Suffice to say, 10.8 CR on a 86 pump will buy you a basket full of shrapnel... long before the batteries reach float. As an ol' drag racer, I'm shocked you even suggested it.

 


ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #15 on: November 02, 2012, 02:17:07 PM »
Suffice to say, 10.8 CR on a 86 pump will buy you a basket full of shrapnel

Well, that's not totally accurate.  High specific output normally aspirated marine engines like the Sterling 750 (10.5:1 compression) produce 700 brake hp on normal everyday 87 octane pump gas with 10% ethanol from 588 cubic inches:
http://sterlingperformance.org/engines/750-horsepower-pump-fuel-engine/

And these are polyspherical combustion chamber engines - not hemi's.  The bottom line is that technology has improved by leaps and bounds over what it was when I ran the 426 Hemi in my Roadrunner almost 35 years ago.  They used to light the fire on one side (wedge) or in the middle (hemi), let it burn, and then try to quench the pressure rise in the combustion chamber to prevent auto-ignition of the remaining charge on the other side (wedge) or on the outside (hemi).

With modern electronic controls engineers found out you can use polysphere chambers with the right bore/stroke combination and mean piston speed and push the limits with cheap fuel to levels never thought possible in 1980 - without any adverse effects.

The Honda iGX engine in our new generator is just such an engine - it takes the technology in small air-cooled engines to the next level with an onboard computer that communicates with the machine it's driving to constantly adjust the engine's tuning and operating parameters.  This allows the engine to react to changes in load faster and get fuel efficiency never before possible from an engine of it's class.  The iGX achieves 15% better fuel economy than the previous GX-series did, driving the same loads (and meets 50 state emission requirements while doing it).

It's a totally drive-by-wire engine.  There is no mechanical linkages on it, no mechanical governor.  Its ECU constantly keeps track of engine speed and load (by calculating throttle opening) to adjust ignition timing for peak fuel efficiency.  Like I said in my original post here it's really close to a diesel genset in efficiency - not quite as good - but really damn close.  And the fuel cost/kWh (at present prices of fuel), that I've measured, is less than either LPG or diesel.  LPG is currently $1.90/gallon here.  Diesel is $4.14.  Gasoline is $3.40.  When you take into account the energy content in the fuel vs efficiency of the engines using the various fuels, and losses in the generator to the measured load (Power Factor), it's going to be hard to beat even if gas goes up to $4/gallon and the prices of the other two fuels stay the same.

With generators, you can get lost in trying to prove (as an example) that a diesel is more efficient than gasoline, and fail to see the big picture which is cost/kWh.
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MagicValleyHPV

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Re: Fuel Consumption LPG vs Gasoline
« Reply #16 on: November 02, 2012, 04:20:56 PM »
Suffice to say, 10.8 CR on a 86 pump will buy you a basket full of shrapnel

Well, that's not totally accurate.  High specific output normally aspirated marine engines like the Sterling 750 (10.5:1 compression) produce 700 brake hp on normal everyday 87 octane pump gas with 10% ethanol from 588 cubic inches:
http://sterlingperformance.org/engines/750-horsepower-pump-fuel-engine/
Get real Chris, we're not discussing (at least I didn't think we were), 5 digit custom builds or vintage elephant motors here. We're talking budget, mass produced imports and backyard hacks. As good as Honda's are, I wouldn't even consider putting gasoline in one of mine because I KNOW the monetary waste that would undoubtedly result. And you believe otherwise?

The Honda iGX engine in our new generator is just such an engine - it takes the technology in small air-cooled engines to the next level with an onboard computer that communicates with the machine it's driving to constantly adjust the engine's tuning and operating parameters.  This allows the engine to react to changes in load faster and get fuel efficiency never before possible from an engine of it's class.  The iGX achieves 15% better fuel economy than the previous GX-series did, driving the same loads (and meets 50 state emission requirements while doing it).

It's a totally drive-by-wire engine.  There is no mechanical linkages on it, no mechanical governor.  Its ECU constantly keeps track of engine speed and load (by calculating throttle opening) to adjust ignition timing for peak fuel efficiency.[/color]
The ECU communicates with the electronic governor yes, but NOT the engine timing.

You need to study the schematic again - it's in your Owner's Manual on page 73 and 74. Here's a digital copy if can't find yours;

http://m.powerequipment.honda.com/pdf/manuals/00X31Z236000.pdf

Show me where the ignition coil (labeled "D-CDI") is connected anywhere to the ECU. It's not. There's 4 terminals on the CDI coil

2 are 12v supply (connected directly to the starting switch)
1 is Oil Alert (a shut down in case of low oil level)
1 LED terminal (which is NOT connected)

And here the little gem in question PN 30500-Z5K-003 (which is currently on my vintage GX240 sans ECU). And my inductance timing light verified its variable abilities.

 

But that's not all; Honda boosted the CR .3 points on your iGX270 motor by simply installing a .010" stamped steel head gasket (from 8.2 to 1, to 8.5 to 1). The new gasket PN is 12251-Z5K-003, I have 5 handy, if you need one. They also altered the camshaft lobe profiles.

The amusing part is, they-re not even made in Japan anymore -  try Thailand.

Like I said in my original post here it's really close to a diesel genset in efficiency - not quite as good - but really damn close.  And the fuel cost/kWh (at present prices of fuel), that I've measured, is less than either LPG or diesel.
Again, you cannot realistically expect valid data using only two samples. Samples I might add, that share completely different specs. Not only are the tested sample's outputs different, but your Honda has half the engine displacement of the Generac. And you even admitted to 'estimating' the load data on the Honda. And you accuse me of skewed data?

I'm done here.

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Re: Fuel Consumption LPG vs Gasoline
« Reply #17 on: November 02, 2012, 07:26:40 PM »
As good as Honda's are, I wouldn't even consider putting gasoline in one of mine because I KNOW the monetary waste that would undoubtedly result. And you believe otherwise?

I don't exactly know what your program is - evidently find it unfathomable that somebody uses a gasoline fueled generator and is happy with it.  Well, you're going to have to live with it.  Because I won't have another propane fueled generator around here even if they start paying me to use one and promise to send me a Christmas card.

And BTW - there is no 12 volts to that ignition module.  I had to install a separate slave relay on the generator for it when I wired the gen for auto-start.  I mounted the slave relay in the housing behind the ignition switch and it is powered up when the GSM supplies power to ECU.

Quote
The ECU communicates with the electronic governor yes, but NOT the engine timing

The ECU IS the electronic governor.  It uses various inputs to determine throttle opening (including a CT on a generator application) and calculates load based on engine speed vs throttle position.  While you may be using the default failure mode or standalone timing curve on your hacked up engine, on the generator the ECU controls ignition timing.  The trigger circuit for the CDI goes to the ignition switch and is hooked to the ECU when the switch is turned on.

Otherwise where do you think the ECU gets its engine speed information from?  Rough guess and hope it's right?

From the manual:
Honda iGX engines feature an integrated ECU (electronic control unit) with a self-tuning regulator (STR) governor system.

The innovative ECU monitors and controls engine functions including Throttle, Choke, Ignition Timing, and Oil Alert.  On some models, it also offers programmable governor and throttle modes for unprecedented flexibility.  A diagnostic LED helps with trouble shooting.  Stepper motors precisely control throttle and choke position.

This allows the engine to communicate with the machine it is powering.

    Operation is automated
    Control becomes surer, faster and easier.
    Enables drive-by-wire remote control operation of the engine, regulating functions such as starting, throttle, ignition timing and diagnostics.
    Engine speed can be programmed and varied based on the equipment application's load and speed requirement.
    Easier for inexperienced users to operate
    Easily maintained - Ideal for rental applications

--
Chris
« Last Edit: November 02, 2012, 11:11:11 PM by ChrisOlson »

badkins100

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Re: Fuel Consumption LPG vs Gasoline
« Reply #18 on: September 30, 2013, 10:23:01 AM »
It's an old thread, but I wanted to add my 2cents on why propane is better in my situation.  I have used gasoline generators for over 40 years down here near the Gulf Coast. When I was younger, I had carb issues all the time, but eventually learned to end that by just running them once a month or so and replace my supply fuel every year and treat it.

Hurricane Katrina flooded our Gulf coast refineries and shut down rigs in the gulf, and there was no gasoline for several days, and even then, you would stand in line for 4 hours and they would only let you have 5 gallons.  Wife and I had to eventually bug-out after I used my 40 gal. fuel supply and then emptied my 85 gallon boat tank.

We have no natural gas here, even though they have pumped trillions of cubic feet of it from under us.  Propane supply is very dependable and our company assures us of uninterrupted propane supply. Those of us who have generators are on a computer printout that pops out to the drivers as soon as any tropical system gets close or is aiming at us. They top everyone off. Then after the storm, as soon as the road is clear, they will be making daily runs to keep everyone full.

I installed a 16kw professionally converted to propane and had my propane company bring me a 250 gallon tank. Once that was piped into my shop, I sent my little 3kw carb off to be modified for tri-fuel, emptied and cleaned the gasoline features, and piped the little generator into propane also.  Then I got a wild hair and converted my older Coleman (Briggs) 10kw to tri-fuel. I also cleared that gasoline system.  Hopefully I will never have to put gasoline in them again.

So with me, it is mainly about the unlimited supply of fuel. It is also normally cheaper than gasoline down here, and a huge plus is not having to store, treat, rotate, and handle gasoline again.  I will probably lay in 20 gallons if a storm approaches, but after the storm, it will go into the Suburban because it loves the stuff. ;D  My two big gens like fuel, so if running gasoline, it is a near every-other day concern with having to fill up 6 gallon gas cans.  With propane, if the lights are out, the guy will come to me and when he leaves, I will have 200 gallons of fuel safely stored and connected to the generators.

After Hurricane Fredric, the bridge coming to the island was knocked down. Only way on and off the island was boat/ferry, or small aircraft.  They built a new higher bridge and say it will be there forever. ::)  While the new 3 mile long bridge was being built, our propane company barged over a large tractor trailer type propane tank, along with a delivery truck which stayed on the island. When the transport tank got low, they brought in another one on another barge, and just swapped them out.

Bruce S

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Re: Fuel Consumption LPG vs Gasoline
« Reply #19 on: September 30, 2013, 11:18:18 AM »
One of the threads that this one was a tangent from was about his woes with LPG.
Where he is located, during the winter , it is SOOOOOOO cold, the LPG is too cold to gas up, therefore no reasonable way to start his genest. For him gasoline's superior cold starting abilities outweigh everything else.
His home depends on this genset to power his off-grid home/farm.
His posts are very detailed and have quite a lot off information for someone in the same boat.
Cheers;
Bruce S
You can educate out ignorance, you can work out of poverty, BUT you cannot fix "stupid".
author "Bruce S"

badkins100

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Re: Fuel Consumption LPG vs Gasoline
« Reply #20 on: September 30, 2013, 11:57:10 AM »
I thought about the cold, and maybe altitude, as a deterrent to using propane by some.  Yeah that makes gasoline better than propane in those situations. We have only seen 32 degrees for about one hour in the past several years. ;D  Our main concern is keeping the air conditioning on for a good part of the year. We see a lot of snow, but only if we watch the Weather Channel. ;)

ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #21 on: September 30, 2013, 02:12:39 PM »
I thought about the cold, and maybe altitude, as a deterrent to using propane by some.  Yeah that makes gasoline better than propane in those situations.

While this is almost a year ago now, we have since switched to diesel prime power with gasoline for the peak load generator for the house.  Both gensets are housed in a temperature controlled, but otherwise unheated powerhouse.  Engine waste heat is used to heat the powerhouse in the winter to 70F.  The gasoline genset will start at -40 with just a 75 watt heat lamp shining on the cylinder barrel.  When we want to run the diesel prime set we first start and run the gas set and get it up to 70 deg in the powerhouse.  After an hour of heat soak at 70F the diesel can be started and take over on prime power.

We also have a 45 kVA Cummins diesel cogeneration set for our equipment shop.  That engine runs about 12 hours a day in the winter.  It is preheated with a 12V electric pump that pumps warm coolant, that is still warm from the day before, from the shop tank thru the engine's cooling system to get it started.  The pump is turned on with a timer at 5:00AM and when we get to the shop at around 7:30AM if we have 50 deg F return temp on the coolant coming from the genset it will start even at 40 below.

The way I look at it at present is that diesel fuel is the best buy per BTU at (currently) $2.11/100K BTU for off-road dyed red #2.  Gasoline is currently $3.29/100K BTU.  LPG is currently $2.31/100K BTU.  Diesels are by far the most thermally efficient.  But they are also the hardest starting at 30-40 below.  If you have a carefully designed system for preheating them that doesn't waste energy just preheating the engine, they are the best choice for off-grid standby or prime power, even in the coldest weather.  However, gasoline is the best choice for extreme cold when you need on-demand standby power with minimal energy input for preheat.  LPG is a non-starter in our climate.  Can't even cook with it reliably, much less fuel a genset.
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Chris

badkins100

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Re: Fuel Consumption LPG vs Gasoline
« Reply #22 on: September 30, 2013, 03:19:47 PM »
Great read. Down here, when it gets to 47 degrees with 80% humidity, we can't go out doors.LOL!  Yeah, you are in cold country. You guys can store propane in open buckets during winter. ;)

ChrisOlson

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Re: Fuel Consumption LPG vs Gasoline
« Reply #23 on: September 30, 2013, 04:29:02 PM »
The storage life of propane is great.  But when you can't get it out of the tank when you need it, storage life becomes a minor issue   :-[

At one point when we had the EcoGen we had charcoal pans going under the tank, plus a black blanket over the tank to try to trap heat from the charcoal and get whatever sunlight there was to warm the tank and vaporize the gas.  When I decided we had to do something different, selling the 500 gallon tank was easy - that was gone inside a week on craigslist.  The generator is another issue.  It's still laying on its side in back of the shop where I dumped it out of the skid steer bucket.  That generator was nothing but a hassle from the word "go".  I guess they got a recall on it to replace the engine because those were defective and they had several of them lock up.  I haven't worried about it recently.  I think it's worth more as scrap than it is as a useful genset.  Some day when I'm loading up scrap to haul to the junkyard I'll throw that Generac on the pile.
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Chris

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Re: Fuel Consumption LPG vs Gasoline
« Reply #24 on: September 30, 2013, 04:43:21 PM »
Here is an alternative fuel source.

http://www.gekgasifier.com/

badkins100

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Re: Fuel Consumption LPG vs Gasoline
« Reply #25 on: September 30, 2013, 05:31:32 PM »
I spent considerable time researching gasifiers.  Fascinating.  Do them right and they are little trouble at all. You remove the tar from the process by filtering it through woodchips,, then you can burn them once they get changed out. They can be installed and used indoors in a barn or shed too. Finding this site has really given me lots to dream about.  I will build my own ram pump sooner or later, even though I don't have a place to use it, but they are just too cool not to have one. 

Boondocker

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Re: Fuel Consumption LPG vs Gasoline
« Reply #26 on: September 30, 2013, 06:46:02 PM »
They certainly are intriguing.  What Iíve read, keep the reactor temperature high enough and the tar will be cracked down to combustibles gases.   

Here is an active gasification group.

http://driveonwood.com/.