Any news on gas engine CUTS?

[buickanddeere]

Most folks who dabble in the industry know the best diesel engines have roughly 15% better thermal efficiency than the best gasoline engines....this isn't news.

Further, folks defending gas engines always seem to forget that the overwhelming majority of gasoline sold in the U.S. these days has ethanol in it, which lowers it's energy content by around 3% when you're talking 10% ethanol content.

So, we have a diesel system that is 15% more efficient going against a gasoline engine that is hampered by fuel that gives it 3% less efficiency, and that puts the difference in the ballpark of 18% in favor of the diesel.

The only way to do apples-to-apples as you ask would be to put similarly developed diesel and gasoline engines in the same machine and compare PTO outputs. Everything else is really just a guess.

Gasser in the past have had their efficiency limited due to detonation that occurs with compression and thus expansion ratio's above 8 to 1 ratio. Now DI gassers have a 12 to 1 expansion ration and no concerns about detonation. Diesels go higher on the compression ratio in order to cold weather start. Efficiency improvements start dropping rapidly per unit of compression after the 11-12 to 1 ratio range. The extra power required to make the extra pressure on the compression stroke and the extra compression heat made and thermal efficiency lost limits the gains on the expansion stroke. Take a look at the difference in power and efficiency of the Chev 5.3 port injected vs the Chev 5.3 direct injected.
Lets not forget an engine makes power on the pressure difference between the compression pressure and the combustion pressure.
Lets compare the DI turbo Chevy Cruze eco gasser for $21,500 and obtains 26 city, 31 combined and 39 highway. $1000 a year in fuel according to the EPA test. vs the Cruze diesel turbo for $25,295 , 27 city, 33 combined and 46 highway, $1300 a year in fuel according to the EPA. Tell us here ,where the diesel advantage is. Lets also consider that gasoline with only 88% as much energy per gallon as diesel being very close to the diesel mileage. Certainly cheaper to purchase, cheaper to drive and cheaper to service the DI gasser.

 

[GManBart]

Gasser in the past have had their efficiency limited due to detonation that occurs with compression and thus expansion ratio's above 8 to 1 ratio. Now DI gassers have a 12 to 1 expansion ration and no concerns about detonation. Diesels go higher on the compression ratio in order to cold weather start. Efficiency improvements start dropping rapidly per unit of compression after the 11-12 to 1 ratio range. The extra power required to make the extra pressure on the compression stroke and the extra compression heat made and thermal efficiency lost limits the gains on the expansion stroke. Take a look at the difference in power and efficiency of the Chev 5.3 port injected vs the Chev 5.3 direct injected.
Lets not forget an engine makes power on the pressure difference between the compression pressure and the combustion pressure.
Lets compare the DI turbo Chevy Cruze eco gasser for $21,500 and obtains 26 city, 31 combined and 39 highway. $1000 a year in fuel according to the EPA test. vs the Cruze diesel turbo for $25,295 , 27 city, 33 combined and 46 highway, $1300 a year in fuel according to the EPA. Tell us here ,where the diesel advantage is. Lets also consider that gasoline with only 88% as much energy per gallon as diesel being very close to the diesel mileage. Certainly cheaper to purchase, cheaper to drive and cheaper to service the DI gasser.

The EPA doesn't use ethanol gas in their tests, although they claim to factor that in when they publish their mileage figures....so they're guessing a little bit.

The glaring omission in your comments is that the diesel Cruz has 151hp @4,000rpm compared with 138hp @4,900rpm for the gasser. Even more telling is that the diesel has 264lb/ft of torque at 2,600rpm to the gassers 148lb/ft at 1,850rpm. That means the diesel is going to perform much better, and still get better mileage. This is what we call an apples-to-oranges comparison again.

I'd be glad to pay $300 more per year for a car that performs significantly better when you're talking cars that are on the low end of the power-to-weight ratio.

Further, the price per year fuel figures are based upon theoretical fuel costs, not actual costs. Until the recent huge drop in gasoline prices, diesel wasn't much more expensive than regular gas around here.

 

[buickanddeere]

The EPA doesn't use ethanol gas in their tests, although they claim to factor that in when they publish their mileage figures....so they're guessing a little bit.

The glaring omission in your comments is that the diesel Cruz has 151hp @4,000rpm compared with 138hp @4,900rpm for the gasser. Even more telling is that the diesel has 264lb/ft of torque at 2,600rpm to the gassers 148lb/ft at 1,850rpm. That means the diesel is going to perform much better, and still get better mileage. This is what we call an apples-to-oranges comparison again.

I'd be glad to pay $300 more per year for a car that performs significantly better when you're talking cars that are on the low end of the power-to-weight ratio.

Further, the price per year fuel figures are based upon theoretical fuel costs, not actual costs. Until the recent huge drop in gasoline prices, diesel wasn't much more expensive than regular gas around here.

So what about the power and torque. The average driver doesn't even know. Both vehicles accelerate up to highway speeds without being floored.
$300 a year for fuel. I don't hear you being glad about the extra cost of the diesel option. Nary a peep either about paying the dealership to work on that emission diesel.
The DI gasser has displaced the diesel in the light to medium duty market.
The price of diesel has been more expensive than gasoline for the past eight years in the US. How and when do you expect that to change?

 

[buickanddeere]

Most folks who dabble in the industry know the best diesel engines have roughly 15% better thermal efficiency than the best gasoline engines....this isn't news.

Further, folks defending gas engines always seem to forget that the overwhelming majority of gasoline sold in the U.S. these days has ethanol in it, which lowers it's energy content by around 3% when you're talking 10% ethanol content.

So, we have a diesel system that is 15% more efficient going against a gasoline engine that is hampered by fuel that gives it 3% less efficiency, and that puts the difference in the ballpark of 18% in favor of the diesel.

The only way to do apples-to-apples as you ask would be to put similarly developed diesel and gasoline engines in the same machine and compare PTO outputs. Everything else is really just a guess.

What is the price difference between gasoline and Diesel per gallon?
Why won't you acknowledge that diesel efficiency drops when the engine is not constantly operated at full rpms and full load? I gave you the results of the Nebraska test of the partly to fully loaded IH 105C . We are awaiting you comments regarding diesel efficiency in the light duty puttering around CUT application. Nor have you said a peep about initial purchase and service costs on that Tier IV diesel.

 

[GManBart]

So what about the power and torque. The average driver doesn't even know. Both vehicles accelerate up to highway speeds without being floored.
$300 a year for fuel. I don't hear you being glad about the extra cost of the diesel option. Nary a peep either about paying the dealership to work on that emission diesel.
The DI gasser has displaced the diesel in the light to medium duty market.
The price of diesel has been more expensive than gasoline for the past eight years in the US. How and when do you expect that to change?

So the folks that don't care about significantly better performance don't buy the diesel....simple. Those that want the extra performance can have it...nobody is forcing them.

If they made that Cruz gasser so that it put out the same power and torque as the diesel (if possible) it would use significantly more fuel than it does now, which would make the fuel economy difference even larger than it is.

You're talking about an engine powering a tractor, but you use a Chevy Cruz engine to make your argument...that's pretty funny. Looking at the specs between those two engines, it's obvious which one would do a far better job of powering a tractor, all while getting better fuel economy....and it's not the gasser.

Diesel can cost more than gas because there's more energy per gallon in it, and the engines get more out of each gallon of diesel...again, these facts aren't news.

 

[GManBart]

What is the price difference between gasoline and Diesel per gallon?
Why won't you acknowledge that diesel efficiency drops when the engine is not constantly operated at full rpms and full load? I gave you the results of the Nebraska test of the partly to fully loaded IH 105C . We are awaiting you comments regarding diesel efficiency in the light duty puttering around CUT application. Nor have you said a peep about initial purchase and service costs on that Tier IV diesel.

The price difference varies over time, and by location. In much of the world diesel is less expensive than gasoline, so it only takes a slight increase in fuel economy to pay for any increased purchase price....which is why we see diesels as the norm for most of the world. Historically, diesel has been less expensive than gasoline, and part of the reason for the change is the expense required for U.S. fuel producers to change to ultra-low sulfur fuel....that cost goes to the consumer. Also, diesel fuel has lower taxes than gasoline. All of those things are subject to change, but what isn't subject to change is that diesels are more efficient and diesel fuel has more energy per gallon in it.

The cost of diesel emission control equipment will drop as the technology matures, and more units are sold...this is pretty simple economics.

If someone thinks they can make a gasser tractor that will work out well they should give it a whirl. If you think the folks on this forum know more than the folks making tractors for a living, that's a pretty arrogant thought. If they thought they could sell more tractors, or make a higher profit margin by offering gassers, they would.

There has to be a reason why they haven't....hint, it's because they probably won't work as well, won't be as efficient, won't last as long, and they won't sell enough of them to ever recoup their costs for testing, developing, designing, tooling, etc.

 

[PoorPlowboy]

Torque demands ? What ? How did gasoline farm tractors in the past and light equipment today operate ? They made torque . Actuly torque alone Accomplishes nothing.
Take a look at the Nebraska test for tractors with gasoline and Diesel engines in the same model. The gasser made as much or more torque and HP per cubic inch as the diesel.
Gas engines are not concerned with glow plugs, turbos, 30,000 psi injection systems, particulate filters, urea injection, cold weather gelling of fuel and cold weather starting .

Gassers are plagued by no legal means to transport bulk fuel for them. In my area, it is against the law to transport more than 15 gallons of gasoline in marked and approved containers. That won't get me through a full day of mowing with my '46 M. Its also plagued by points and condensors, rust in the fuel tank (all my diesels have poly cells) and fouled spark plugs if not kept in tune. There's drawbacks to them all, no matter what fuels them.

 

[PoorPlowboy]

It is illegal to carry gasoline in a bed mounted fuel transfer tank. I dont enjoy climbing on top of a 6ft tall hood to fill a tank 5 gallons at a time. My gassers are relegated to hobby tractors.

 

[PoorPlowboy]

Gasoline is out. Natural gas is in. Cummins is converting just about every engine they make to a gas head offering.

You are being redirected...

A 3.3L 4CYL DI turbo LNG would make a fine little tractor motor if the fuel infrastructure was there. It would probably make 250+ horsepower.

 

[john_bud]

Tractors are meant to be run for hours and hours and hours, over many years. Modern DI gas engines max out around 35% efficiency. Modern common rail diesel engines can take that figure up to 50%. 15% better efficiency will pay for itself over time when you're talking extended run time over many years.

That's really what the argument boils down to.

Good point. But diesel engines w the epa stuff is a thousands of dollars premium. Then the fuel costs 25-30% more per gal.

I have 3 diesel tractors, 1 gas tractor and a diesel truck. In the winter, the modern diesels start good enough w glow plugs and grid heaters. But the old gaser fires up just by choking and it's 6v! The truck tows heavy and diesels rock at that ... but... given the total cost picture, my next truck dang sure won't be diesel. Higher initial cost, higher maint costs, 25% better mpg - but 30% higher fuel cost. There is no payback that I can find.

I'm sure if they engineered a small stout gas engine for a tractor it would be popular in many diesel applications.

 

[MHarryE]

Gasoline burns best at a 14.3:1 air to fuel ratio. When running at part power, the throttle plate us closed limiting the air entering the cylinder so when fuel is introduced the combustion will be at 14.3:1. The effect, when running at low owner, is like sucking through a small diameter straw. It takes power, in the case of a straw lung power, in an engine it is lost power. The diesel is not throttled because it is not limited to a 14.3:1 ratio. It has a clear passageway always able to breath in a full gulp every piston stroke.

Next the Otto cycle. In general, industrial engines are limited to the same peak combustion pressure. The Otto cycle has a lower compression ratio because heat, in theory, is added at a constant volume until this peak is reached, let's say 2000 psi combustion chamber pressure. That hot air expanding drives the piston down, but while it is driving the piston down the combustion chamber is enlarging and the pressure is dropping. In the Diesel cycle the air is compressed to the peak that the Otto cycle sees, and then heat is added at constant pressure. That is while the piston is descending fuel continues to be injected, combustion continues, and the combustion chamber pressure stays high. At 90 degrees where the torque of the crank throws is at the point of maximum lever arm, the piston is still giving peak push while an Otto cycle is down to half piston force. A tractor is used where this type of power is really needed, and is why they are now virtually all diesel.

Forty years ago the company where I worked, building self-propelled combines, sold the same combine with a 350 cu. in. GM gasoline engine or 292 cu. in. Allus-Chalmers turbo diesel. The gasoline engine had a higher power rating but when it came to grunt time, usually when a slug fed into the cylinder, the gas engine would promptly croak. The diesel would usually grunt and pull the slug through. In a few years the gasoline engine disappeared despite the higher power rating and significantly lower cost. After all, to handle the grunt the diesel was capable of producing, everything needed extra beef.

Things have progressed, but the Otto cycle is still the Otto cycle and has its limitations although much has been done to improve the crappy carbureted engines of the past. Gasoline still burns at 14.3:1 although mixed with ethanol that ratio changes. Engines can sense the difference and compensate, something a carbureted engine can't due without tweaking. Until the latest diesels nothing much has been done to improve their performance. Now with common rail systems and piezoelectric injectors, fuel injection can be controlled to the gnat's *** greatly improving what you can get out of each cycle. When I moved to Cat one of my first products had a 4 liter engine topping out at 107 HP. With Tier 1 we didn't have to change much and it still topped out at 107 HP. With Tier 2 we did some major redesign to the block but retained much of the original fuel system and got 133 HP. That stayed with Tier 3 when we introduced a common rail system because we were getting our feet wet. Now at Tier 4 that 4 cylinder is replacing the 6 liter 6 cylinder engine we used for our 175 HP machine - the 4 now maxes out over 175 HP. By changing from a 6 to a 4 we actually reduced the installed power plant cost. Piston ring scrub creates about 25% of the total friction so cutting 2 cylinders reduced that wasted energy. With the ability to control the injectors we can keep the combustion chamber pressure fairly constant throughout the meaningful work part of the piston stroke. Perfect? No way. Still lots of room for improvement. Would love to be like the big guys working with the GE90 powering the next generation 777X where they work with ceramics that can handle constant temperatures triple what we see.

 

[buickanddeere]

So the folks that don't care about significantly better performance don't buy the diesel....simple. Those that want the extra performance can have it...nobody is forcing them.

If they made that Cruz gasser so that it put out the same power and torque as the diesel (if possible) it would use significantly more fuel than it does now, which would make the fuel economy difference even larger than it is.

You're talking about an engine powering a tractor, but you use a Chevy Cruz engine to make your argument...that's pretty funny. Looking at the specs between those two engines, it's obvious which one would do a far better job of powering a tractor, all while getting better fuel economy....and it's not the gasser.

Diesel can cost more than gas because there's more energy per gallon in it, and the engines get more out of each gallon of diesel...again, these facts aren't news.

Are you denying that ULS diesel has cost more than gasoline per btu than gasoline since 2006?
Are you saying the either the diesel or gas Cruze uses more HP to drive down the road 55mph?
Are you saying that Uncle Bubba putting around on his rural estate on his CUT is a HD application?
Are you saying the diesel cruze is cheaper per mile to operate ?

 

[buickanddeere]

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So the folks that don't care about significantly better performance don't buy the diesel....simple. Those that want the extra performance can have it...nobody is forcing them.

If they made that Cruz gasser so that it put out the same power and torque as the diesel (if possible) it would use significantly more fuel than it does now, which would make the fuel economy difference even larger than it is.

You're talking about an engine powering a tractor, but you use a Chevy Cruz engine to make your argument...that's pretty funny. Looking at the specs between those two engines, it's obvious which one would do a far better job of powering a tractor, all while getting better fuel economy....and it's not the gasser.

Diesel can cost more than gas because there's more energy per gallon in it, and the engines get more out of each gallon of diesel...again, these facts aren't news.

Are you denying that ULS diesel has cost more than gasoline per btu than gasoline since 2006?
Are you saying the either the diesel or gas Cruze uses more HP to drive down the road 55mph?
Are you saying that Uncle Bubba putting around on his rural estate on his CUT is a HD application?
Are you saying the diesel cruze is cheaper per mile to operate ?
Are you saying that after looking at the Nabraska tests that the diesel burns less fuel in a Light Duty application than a gasser ?

As for MHarryE who is decades behind the times. The DI gasser operates at 14.7 to 1 which is a term called Stoichiometric . In fact the DI will go into a lean burn mode under some circumstances .
What is this talk of combustion occurring 90 degrees after TDC is desirable ? It's too late for efficient mechanical conversion of combustion chamber pressure to torque . Combustion that late just causes over heating as more cylinder wall is exposed to absorb heat. Ever hear tell of a gasser running hit due to retarded timing?
Ideal combustion efficiency occurs as close as possible to TDC when the combustion chamber volume is smallest.
This also gives the entire expansion stroke/power stroke to use combustion chamber pressure.
This is where common rail injection of diesels is a win as the entire load of fuel can be injected over 5 degrees of crank rotation instead of over 45 degrees rotation. Less kick back on the compression stroke as combustion is starting at 5 BTDC instead of 15-20 BTDC.
Are you aware that the DI gasser uses variable cam timing to control airflow ?
Are you aware that when a diesel , boiler fire box of gas turbine is operating at less than 100% power . The excess in throttled airflow reduces engine thermal efficiency by cooling the combustion and carrying heat out the exhaust ? Are you aware that some diesel reciprocation and stationary gas turbine applications throttle the intake to improve efficiency at less than 100% power.
Are you aware that when comparing Two similar engines such as the gas 4020 and the diesel 4020. The torque and HP is near identical? How can you compare the 292 or 350 Chev calmed to make power from 1800-4500rpm to a turbo diesel calmed shorter to make power from 1200-2200rpm?

 

[buickanddeere]

Gassers are plagued by no legal means to transport bulk fuel for them. In my area, it is against the law to transport more than 15 gallons of gasoline in marked and approved containers. That won't get me through a full day of mowing with my '46 M. Its also plagued by points and condensors, rust in the fuel tank (all my diesels have poly cells) and fouled spark plugs if not kept in tune. There's drawbacks to them all, no matter what fuels them.

Who is talking about some old M with points and a carb ? The conversation is about the cost and practicality of a DI gasser for light duty use for putting around use in a CUT. Vs the cost of gasoline -diesel fuel , the tier IV emission equipment and future emissions equipment service at the dealership.
Do you take your M to the dealer for new points ?

 

[paulfun9]

The main problem with this is we have no fuel engines built today for the use. Simply taking a gas powered engine like a 350 and changing the cams to increase the Mean cyl pressure at the intended useable RPM is not a sufficient comparison. A real test would involve building one from scratch and throwing out the rule book as most know it. Using more complex combustion chambers and off the wall bore and strokes coupled with todays computer controlled injection systems you could build one **** of a good gas powered engine for a tractor. Would it be justified between cost to build , maintain and fuel consumption? That is the real question.

 

[buickanddeere]

What is the cost between building a Tier II 35HP diesel for a CUT and a Tier IV diesel? What is glow plugs, particulate filter, EGR service and urea injection service cost going to be in 10yrsrs time ?

 

[DavesTractor]

Other than the zingers one guy on this thread keeps firing at folks, I've learned a lot about the technical aspects of the differences between modern gas and diesel engines. We should keep up this discussion, but get rid of the back and forth barbs.

Some of you guys really know your stuff and it is enjoyable to learn. It's like getting a free mechanical engineering/thermodynamics course......

 

[GManBart]

Good point. But diesel engines w the epa stuff is a thousands of dollars premium. Then the fuel costs 25-30% more per gal.

I have 3 diesel tractors, 1 gas tractor and a diesel truck. In the winter, the modern diesels start good enough w glow plugs and grid heaters. But the old gaser fires up just by choking and it's 6v! The truck tows heavy and diesels rock at that ... but... given the total cost picture, my next truck dang sure won't be diesel. Higher initial cost, higher maint costs, 25% better mpg - but 30% higher fuel cost. There is no payback that I can find.

I'm sure if they engineered a small stout gas engine for a tractor it would be popular in many diesel applications.

Last year I was pricing a new Kioti DK50SE (as they were disappearing) and a new NX 5010....the difference was less than two thousand dollars more for the NX with Tier IV, and it also had a handful of improvements that would have bumped the price without Tier IV (advanced HST and a few others). So, I don't see a massive price change with the simpler Tier IV stuff required on our relatively small SCUT/CUT/Utility tractors....not like what you see on the big machines. There is some increased cost, no doubt, but it just doesn't seem as bad as many would suggest.

The critical variable is really the fuel cost. Right now diesel is more expensive than gasoline, for a number of reasons....one be government taxes. Historically, gasoline has been more expensive than diesel everywhere, and still is in the rest of the world. Here in the U.S. that changed when refineries had to spend a bunch of money to switch to ultra low sulfur diesel, and that cost has been passed on to consumers....it's been roughly 8 years. In the last year or so the price of diesel and price of gas got closer until the recent huge drop in the price of gas. It's very possible that in a couple of years the price of diesel will be down below the price of gas again, but we'll have to wait and see.

 

[GManBart]

Are you denying that ULS diesel has cost more than gasoline per btu than gasoline since 2006?
Are you saying the either the diesel or gas Cruze uses more HP to drive down the road 55mph?
Are you saying that Uncle Bubba putting around on his rural estate on his CUT is a HD application?
Are you saying the diesel cruze is cheaper per mile to operate ?

I've already stated why diesel has cost more than gasoline for the last 8 years. When the refineries pay off all those costs associated with implementing ULSD, the price of diesel should drop below gasoline again...just like it has in the rest of the world. Don't bother saying that once they set the prices higher, they will never come down, because I saw gasoline for $1.61/Gal the other day....hasn't been that low in many years.

I never said there was a difference in HP required to move either Cruz down the road. I simply said the diesel model performs better, and if people wanted that performance, they could buy it.

I never said anything about Uncle Bubba on his CUT. You don't know anything about how other people run their machines, so basing your argument off of that is pretty weak. Some, many, folks run their tractors at rated power the whole time they operate them. No, they won't put the hours on them that a loader in a rock quarry will, but that isn't the point. Run a similar size, power, weight gasser CUT the same way, and it's not going to stand up to it, or have as good of fuel economy as the diesel....period.

I said the costs to operate the diesel Cruz will vary with the price of fuel. It gets better MPG than the gasser, and when the price of diesel drops back below that of gas, there won't be a need to discuss any of this any longer.

Your entire argument centers around one thing...that diesel costs are artificially high right now. When that changes, there really won't be much to discuss about which system has the lowest operating costs over time.

I do find it funny that people claim higher maintenance costs on diesel tractors...most folks run them for many, many years with absolutely nothing required other than filters and fluids.

 

[GManBart]

What is the cost between building a Tier II 35HP diesel for a CUT and a Tier IV diesel? What is glow plugs, particulate filter, EGR service and urea injection service cost going to be in 10yrsrs time ?

I looked at several Tier IV CUTs that didn't have DEF systems....just a DPR and EGR.