Diesel differences

[grsthegreat]

My 1994 dodge 6.0 Cummins gets nearly 27mpg. You mean the smaller ones don’t get much bettet

 

[ovrszd]

My 1994 dodge 6.0 Cummins gets nearly 27mpg. You mean the smaller ones don’t get much bettet

I must have missed that one?? Didn't know Cummins made a 6.0 that was used in Dodge?

 

[ptsg]

VM are good engines. My old 1962 crawler had a 2 Cylinder VM aircooled engine. Land Rover uses VM engines on a bunch of their SUVs.

Here we have a:

2016 Mitsubishi Outlander 2.2L 150HP 4 cylinder turbo diesel, I can squeeze about 41 MPG out of it.
1994 Mitsubishi Pajero or Montero in the US with a 2.8L 125HP 4 cylinder turbo diesel, it does around 26 MPG or about 18 MPG towing about 5800 lbs (Tractor + Trailer + loader + mower).
2015 Renault Clio 1.5L 90HP 4 cylinder turbo diesel and it does about 65 MPG easily.

We had a 2009 VW Golf with the 1.6L 105HP. I can't remember the mileage but it was relatively bad for that car. I believe it was around 8 MPG. It was a pure mess with that DPF. Constantly giving problems and going into limp mode. We sold before all the VW scandal. Came to find out later, that that car was affected by that.

 

[Rebeldad1]

My 1994 dodge 6.0 Cummins gets nearly 27mpg. You mean the smaller ones don’t get much bettet

Lets see... you are in Idaho. I bet on a really quiet morning I can hear you start your truck here in Washington

 

[Industrial Toys]

I don't own one anymore, but think that Yanmar are one of the finest and smoothest engines you can buy. Has something changed?

Working on an Isuzu generator and for smoothness it will put all my Kubota powered generators and "Steiner" to shame.

Ooops, I lied. Still have a single cylinder air cooled Yanmar generator. Loud and horrible but ultra reliable.

 

[nova3930]

Beginning about thirty-three horsepower most tractors have Diesel Particulate Filters.
A few Tier IV compliant tractors between 26 and 75 hp use DOC (Diesel Oxidation Catalyst) conversion. Mahindra is one. Mahindra has DOC of similar construction to DPF. Both DPF and DOC are honeycomb ceramic filters which supercede a muffler.
The DOC forces engine exhaust over a honeycomb ceramic structure coated with platinum, palladium, and rhodium. These catalysts oxidize carbon monoxide and hydrocarbons into carbon dioxide and water at hot exhaust temperature.

Mahindra has a DOC oven hot all the time, DPF tractors have an oven hot intermittently. There is no free lunch.

Diesel DOC emits dirty exhaust until hot, which would not be allowed in USA road vehicles. Or possibly Mahindra evaluated the $30 billion (and counting) costs incurred by VW for falsifying diesel emission tests and decided its truck technology is not clean enough for export.

Trying to reconcile all this with what I know about diesel combustion and on road emissions from my various Cummins engines.

Tractor designs only utilizing a DPF, the engineers have probably decided to run relatively rich mixtures and/or are running LOTS of exhaust gas re-circulation (EGR). Those factors reduce combustion temperatures, reducing both NOX and CO at the expense of soot production, which they then clean up with the DPF.

A design utilizing a DOC without DPF is probably running a relatively lean mixture with less EGR, reducing soot and hydrocarbon emissions at the expense of CO and NOX, the CO being cleaned up by the DOC. In the case of the Mahindra with the common rail direct injection, they're probably using multiple injection events to control the combustion process and thus emissions. As I understand their system it's roughly equivalent to an on road truck of the early to mid 2000s vintange. The 03-07 5.9L cummins was a common rail direct injection system with EGR and DOC.

The thing I"m seeing that I guess allows for just using a DOC or DPF and not both is that Tier IV has a combined standard for NOX and hydrocarbons instead of being separate values as in on road requirements. It gives a lot more flexibility in meeting the standards.

I'd also hesitate in directly comparing a DOC with a DPF in their operation. A DOC operates effectively at 300*C+ when a typical diesel EGT is in the 700-800*C range, with bursts over 1000*C. A DOC will operate all day every day just by operating the engine, they don't require any extra fuel.

A DPF in comparison typically requires 900*C just to start consuming soot and requires much higher to consume soot faster than it's produced. That's why they have regen cycles at all. Diesel is injected late in the exhaust stroke where it combusts in the exhaust effectively, driving up the temp to burn the soot. Even then the things still plug up eventually.

Given my experience with on road engines, I'd take a common rail direct injection engine with a DOC over a DPF equipped vehicle all day every day. DPFs are the most problematic emissions component on modern on road diesels. On top of that I wouldn't want a DPF without SCR to allow combustion parameters that minimize soot production to start with.

That's just my general view of the various methods, I don't have any experience with the Mahindra system. All my experience comes from the on road world.

 

[nova3930]

I don't own one anymore, but think that Yanmar are one of the finest and smoothest engines you can buy. Has something changed?

Working on an Isuzu generator and for smoothness it will put all my Kubota powered generators and "Steiner" to shame.

Ooops, I lied. Still have a single cylinder air cooled Yanmar generator. Loud and horrible but ultra reliable.

I've got a Mustang 940 skid steer with a yanmar 4 cylinder diesel in it. 1989 model with who knows how many hours. Been rode hard and put up wet it's entire life. I haven't run it in a month and i know I can roll out there right now and have it fire right up on the first key turn. I would take a Yanmar over any other small diesel in existence.

 

[nova3930]

My 1994 dodge 6.0 Cummins gets nearly 27mpg. You mean the smaller ones don’t get much bettet

I must have missed that one?? Didn't know Cummins made a 6.0 that was used in Dodge?

He's talking about the Cummins 5.9L. Specifically the all mechanical 12V version of old. IMO the finest diesel engine ever produced by anybody anywhere. If not for emissions Dodge and half the commercial world would still be putting them in trucks.

 

[Industrial Toys]

I have under two hundred KMs on my 08, 6.6, but aside from glowplugs it has been flawless and I am very thankfull for that. It does like it's Diesel Fuel though.

 

[Molalla1]

Very well stated.

It sure was overzd . . . I have a 3500 '06 Ram with a Cummins . . . and just before the regulations really set in (probably why they went from the trusted 5.9 to the newer version) to make up for the power loss due to regulations.