In reply to alfadriver:
Hopefully in the future no one had to get anywhere in a hurry. With each new generation of diesel we get they become a bit less reliable. It seems like most of the emission reduction comes from having them sitting in the shop.
In reply to Wall-e:
It will get better. Don't worry- plenty of money in getting the diesel emissions right with fuel economy and power.
Not sure why you think tech will be bad and or static for the future.... Gas engines are more powerful than ever AND cleaner than ever.
In reply to alfadriver:
Light gas. Most of the people who are interested have V6 and small V8 vans. (Crazy factoid: For a long while the E250 with the highest GVWR was a 4.2l model. Probably created specifically for a certain fleet operator. Yes they are SLOW and usually loaded well past the GVWR)
Think cable/telco type places where they can refill overnight while at the depot.
Our demo vehicle is a 4.8l Sierra. (Some GRMers have seen me driving it) You cannot tell if it is running on gasoline or CNG unless you look at the switch.
In reply to Wall-e:
It is wonderful to not breathe clouds of soot every time a municipal bus goes by. I was actually reflecting on this this on the way home from work, stuck behind a bus. The back of the bus was CLEAN and in good shape. When I was a kid, the bus would be nasty and the license plate would be illegible because whatever acids or other crud in the exhaust destroyed the paint, leaving it bare metal. Growing up, I thought county license plates were uncolored because they were all like that.
The change isn't as noticable if you watch it happening, but if you look back to the way things used to be... we're doing a hell of a lot better and yes it was absolutely worth it.
alfadriver wrote: It will get better. Don't worry- plenty of money in getting the diesel emissions right with fuel economy and power. Not sure why you think tech will be bad and or static for the future.... Gas engines are more powerful than ever AND cleaner than ever.
I am reminded of what gasoline engines went through in the 70s. We went from running cleaner by making no power (hands up, who remembers 120-150hp Diesel one-ton trucks? Back when the standards were LAX?) and now we have trucks in the 400+hp and 800ft-lb range, with cleanliness.
If the trucks were detuned to pre-clean Diesel levels, they'd probably last forever and not need so aggressive of an exhaust scrubbing regimen. But people need to be able to tow a house straight up in top gear without slowing down from 80mph, or something.
Hell I remember when Class 8 trucks had under 200hp...
alfadriver wrote: In reply to Wall-e: Not sure why you think tech will be bad and or static for the future.... Gas engines are more powerful than ever AND cleaner than ever.
15 years of watching new buses come in with more breakdowns than the ones before. We have 20 year old buses that run great every day and brand new ones that can't get here from the manufacturer without the help of a tow truck. It seems a lot of what is being put out isn't quite ready.
Are the heavy trucks running CNG spark ignition or compression ignition?
Are they clean sheet designs or adapted from existing conventional engines. The LPG engines that I'm familiar with are all only a half degree of separation from gasoline engines.
Do the CNG fuel systems have problems with contaminates fouling things up like LPG systems?
Someone, Knurled I think, mentioned that CNG engines leaked a lot of oil, and moisture build up in the crankcase was an issue. That sounds like a crankcase breather problem more than a fuel problem to me, could someone explain that a bit more in detail? It doesn't make sense that CNG would carry more moisture into the combustion chamber than ethanol, and as far as I know e85 engines don't have a problem with moisture build up.
Wall-e wrote:alfadriver wrote: In reply to Wall-e: Not sure why you think tech will be bad and or static for the future.... Gas engines are more powerful than ever AND cleaner than ever.15 years of watching new buses come in with more breakdowns than the ones before. We have 20 year old buses that run great every day and brand new ones that can't get here from the manufacturer without the help of a tow truck. It seems a lot of what is being put out isn't quite ready.
That's not the law's fault.
Given how I heard many of the large diesel companies were dragging their feet, this doesn't surprise me. What sucks is that they don't see that a few here in the auto industry have figured out that you can use the rules to your competitive advantage. The maker right now who does the best will have a huge chunk of the market.
and as Knurled pointed out, I'd rather not breathe the gasses that caused so much damage to the back of the buses. I can't imagine what that does to living tissue.
In reply to HappyAndy:
RE: the oil issue- it could be that the combusted gas chemistry changed enough that the oil just isn't compatible. That happened to exhaust systems in the 80's as oxygenated fuel was introduced. It happens.
In reply to HappyAndy:
The CNG engines in big trucks are heavily modified diesels. They often share a block, crank and connecting rods with their diesel counterpart but that's about it. Pistons are different as are cylinder heads. Cams are often different. They are spark ignited via a coil-on-plug setup and the fuel is typically injected into the intake manifold near the throttle body vs a throttle-less diesel with direct injection.
I think most of the headaches that edizzle mentioned are slowly being ironed out. The engines he had access to were for the most part early development engines in prototype or alpha stages. By the time they hit showrooms, they seem to be much improved. That trend should only continue as they become more and more common and the tech gets more mature. Think about how refined gasoline engines were at the same point in their development and how far they've come. I think it's reasonable to expect similar improvements with CNG.
STM317 wrote: In reply to HappyAndy: The CNG engines in big trucks are heavily modified diesels. They often share a block, crank and connecting rods with their diesel counterpart but that's about it. Pistons are different as are cylinder heads. Cams are often different. They are spark ignited via a coil-on-plug setup and the fuel is typically injected into the intake manifold near the throttle body vs a throttle-less diesel with direct injection. I think most of the headaches that edizzle mentioned are slowly being ironed out. The engines he had access to were for the most part early development engines in prototype or alpha stages. By the time they hit showrooms, they seem to be much improved. That trend should only continue as they become more and more common and the tech gets more mature. Think about how refined gasoline engines were at the same point in their development and how far they've come. I think it's reasonable to expect similar improvements with CNG.
In the test cells we ran some newly developed engines but we also ran current product (i ran cells from 2012 to 2015). So some of those CNG engines we ran are the same as the ones on the road today, most likely with some misfire fault codes and leaving oil spots anywhere it parks. But again thats the whole point of running in test cells, development.
i do agree with you in the fact they they will get better, that how pretty much any automotive technology works, look at gasoline direct injection, once it became big in cars many engines had problems with carbon build up but now many auto manufactures have remedied that. I would never own a CNG engine right now, but in 5, maybe 10 years? i would probably consider it.
In reply to edizzle89: Exactly. At some point in the future, the regulations for diesel will be so tight that it's no longer feasible. By getting the bulk of the development done on CNG now, the CNG engines they'll need to meet future regs will be ready to go when they're needed.
I fail to see how the fuel type is relevant when it comes to oil sealing. They even manage to make shaky Diesels that don't drool everywhere, so sealing tech is not an issue.
In reply to Knurled:
the one think I can think of post combustion chemistry.
For instance, I know that back in the 80's there was a lot of concern for ethanol and it's by products of acetaldehyde which I think was responsible for turning part of the oil components to acid. That was fixed with an adjustment of the oil makeup.
The only other thing I can come with is increased blowby, which blows seals out... dunno.
(that from the fact that CNG isn't oil, so it adds nothing the bores, which may increase bore wear... I'm making this up as I go along...)
HappyAndy wrote: Someone, Knurled I think, mentioned that CNG engines leaked a lot of oil, and moisture build up in the crankcase was an issue. That sounds like a crankcase breather problem more than a fuel problem to me, could someone explain that a bit more in detail? It doesn't make sense that CNG would carry more moisture into the combustion chamber than ethanol, and as far as I know e85 engines don't have a problem with moisture build up.
All of the hydrocarbon fuels are combinations of C and H. Methane (the primary component of CNG) is CH4. LPG contains hydrocarbons in the C3-C4 range, meaning C3H8 (propane) and C4H10 (butane). Gasoline typically contains hyrdrocarbons in the C4-C12 range, like C8H18 (octane) up to C12 (dissolved tars, napthas, etc)
Each step up the chain, there are more carbon bonds. When they combust with oxygen, its the breaking of those bonds that releases energy. More carbon bonds = higher energy density. Methane is not very energy dense, so to make a stoichiometric combustion event it takes way more of it to equal the output of gas or diesel. When you increase the amount of carbon, you're tagging along a disproportionate amount of Hydrogen in the molecule. More hydrogen combining with oxygen means more water produced.
Long story short... have you ever put a pan of water on a gas stove and saw the whisps of condensation on the outside? Burning the smaller hydrocarbons makes a lot more water. Hence the sludgy oil.
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