Diesel differences

[Industrial Toys]

I'm gonna have to SHINE mine up! Engine not so bad, but the powder coat garbage on the base needs attention.

HATE having nice generators and the power never even flickers!

 

[nova3930]

Indirect injection diesels normally have a higher compression ratio that direct injection. Also as soon as you install a turbocharger the compression goes down some more.

Yep, there's any number of compression ratios that will work on a diesel engine depending on the requirements. Lower compression ratio is one way to help control NOX emissions if that's a requirement. Conversely higher CR will drive up efficiency.

 

[finn1]

Indirect injection engines will always have a higher compression ratio than direct engines. Remember, these are compression ignition engines that rely on the heat generated by compressing air in the cylinder. Indirect injection engines loose a large amount of heat to the cylinder head water jacket as the air is throttled into and out of the precipitation chamber. Higher compression ratio is thus required to reach the auto ignition temperature of the fuel.

Turbo engines often have lower compression ratios than ma engines to control cylinder pressure under high load, high boost conditions.

 

[electrycmonk]

fascinating thread. thanks for the history lesson folks.

 

[troverman]

My Kubota B2920 had a 1.3L, indirect mechanical injection. It required a long glow plug warm period to start in colder weather. The engine was loud and rattly at idle; smoother at higher RPMs. Always ran very well.

My Kubota L2501 had a 1.7L, direct mechanical injection. This tractor started amazingly smoothly, with no glow period needed much of the time. Very smooth engine. Idled nicely.

My Kubota L4060 has a 2.2L, common rail direct injection system. The glow period is automatically controlled. I feel the tractor starts less smoothly by far then the L2501. However, after that, it idles very smoothly and quietly.

There seems to be some misconception on DPF equipped machines...at least Kubota uses a combined DOC and DPF unit. It also uses cooled EGR which is electronically controlled by a valve, as to when and how much EGR is reintroduced.

Using a DPF is the more costly and sophisticated method of controlling emissions, and ultimately the better method for engine longevity. I'd vastly prefer a DPF over a DOC-only system. Yes, the DPF requires occasional additional fuel consumption to perform an active regen. However, it doesn't require high EGTs all the time like a DOC and actually does a better job of reducing emissions. Mahindra is a cheap tractor, and thus you are getting the bare bones minimum in order to meet EPA requirements.

I've also had a variety of diesel pickups - Ford and RAM. I love all of them.

My 2018 RAM 3500 Cummins 6.7L was noisy to start, noisy upon sudden throttle input; it would shake when you started it up and shake when you shut it down. My Ford 6.7L trucks were smooth and quiet. My new 2019 RAM 3500 Cummins high output has eliminated the shakes and is as quiet or quieter than a Ford. Too bad, I like some diesel grumble.

I've never had any DPF issues on any of my trucks or equipment. It's also nice not having soot on the loader arms near the exhaust exit, or breathing it all day.

 

[nova3930]

Using a DPF is the more costly and sophisticated method of controlling emissions, and ultimately the better method for engine longevity. I'd vastly prefer a DPF over a DOC-only system. Yes, the DPF requires occasional additional fuel consumption to perform an active regen. However, it doesn't require high EGTs all the time like a DOC and actually does a better job of reducing emissions. Mahindra is a cheap tractor, and thus you are getting the bare bones minimum in order to meet EPA requirements.

DOCs begin to operate efficiently at 300C, that's not a high EGT for a diesel. The 600C+ temps required for a DPF are much more detrimental, even in short bursts. 675C is generally considered the maximum before permanent engine damage.

A DPF is more efficient at reducing SOME emissions, namely soot. It does nothing for CO, SO2 or unburned hydrocarbons. Conversely the DOC is essentially the exact opposite.

Electronically controlled common rail direct injection is the most advanced diesel fueling system available. Specifically the Bosch systems that Mahindra is using are the best of the best. Cummins, Ford, Duramax, Mercedes Benz, BMW, Volvo, etc etc etc ALL use Bosch common rail systems to meet emissions, so calling it "bare bones" is a little off base. By precisely controlling the combustion process less after treatment is required.

As I said earlier, there will come a day when ALL of the manufacturers are using common rail direct injection with DPF, DOC, EGR and SCR to control emissions. It's just a matter of time.

 

[pmsmechanic]

As I said earlier, there will come a day when ALL of the manufacturers are using common rail direct injection with DPF, DOC, EGR and SCR to control emissions. It's just a matter of time.

Hopefully not!!!!

Can Diesel Finally Come Clean? - Scientific American

 

[troverman]

DOCs begin to operate efficiently at 300C, that's not a high EGT for a diesel. The 600C+ temps required for a DPF are much more detrimental, even in short bursts. 675C is generally considered the maximum before permanent engine damage.

A DPF is more efficient at reducing SOME emissions, namely soot. It does nothing for CO, SO2 or unburned hydrocarbons. Conversely the DOC is essentially the exact opposite.

Electronically controlled common rail direct injection is the most advanced diesel fueling system available. Specifically the Bosch systems that Mahindra is using are the best of the best. Cummins, Ford, Duramax, Mercedes Benz, BMW, Volvo, etc etc etc ALL use Bosch common rail systems to meet emissions, so calling it "bare bones" is a little off base. By precisely controlling the combustion process less after treatment is required.

As I said earlier, there will come a day when ALL of the manufacturers are using common rail direct injection with DPF, DOC, EGR and SCR to control emissions. It's just a matter of time.

That's the point of the DPF - to remove soot. Keep in mind, as I mentioned, Kubota (and Deere) are using both DOC+DPF. The DOC handles catalyzing certain pollutants while cooled EGR reduces NOx and the DPF nearly eliminates soot. Total measurable emissions will be less on a DOC+DPF system.

Frankly, the Bosch fuel system being the best of the best is debatable. Bosch knowingly allowed their ECU's to have a cheat mode on the VW TDI engines. The Bosch CP4 high pressure fuel pump used on LML Duramax engines and 6.7L Ford Powerstroke engines is considered one of the least reliable fuel pumps on the market, causing catastrophic damage to the entire fuel system upon failure. In fact, to update you, Duramax engines no longer use Bosch at all, as of 2017. They have switched to a Japanese made Denso fuel system. Conversely, Cummins has an all-new 6.7L diesel for 2019 which has moved to the Bosch CP4 pump, same as Ford. As of 2018, they used the much more reliable CP3 system, which flowed more fuel volume but at less fuel pressure than a CP4.

Any of the common rail systems are "precisely controlling the combustion process." Mahindra has nothing special here...if you have an engine that is over 26HP, you must have electronically controlled common rail injection. Everything does now.

 

[nova3930]

That's the point of the DPF - to remove soot. Keep in mind, as I mentioned, Kubota (and Deere) are using both DOC+DPF. The DOC handles catalyzing certain pollutants while cooled EGR reduces NOx and the DPF nearly eliminates soot. Total measurable emissions will be less on a DOC+DPF system.

Thanks for mostly repeating me. A DPF without SCR is pretty much the worst setup you can get. That's basically an on-road setup from 2008-2012 which are known to burn massive amounts of fuel and have bad reliability problems with the DPF. Comparatively common rail with EGR and DOC is an early 2000s setup which are very robust. If you can meet the emissions requirements without the DPF, there's no reason to have it, whether it's overall cleaner or not, especially without SCR.

Frankly, the Bosch fuel system being the best of the best is debatable. Bosch knowingly allowed their ECU's to have a cheat mode on the VW TDI engines.

Bosch is a hardware provider. They're not responsible for implementation and programming.

The Bosch CP4 high pressure fuel pump used on LML Duramax engines and 6.7L Ford Powerstroke engines is considered one of the least reliable fuel pumps on the market, causing catastrophic damage to the entire fuel system upon failure.

Primarily caused by Ford and GM not properly specing the vehicle fuel filtration system to meet the pump requirements. Other applications of the CP4 with proper filtration work just fine. Basically if any pump fails you're going to have massive fuel system damage. nature of the beast.

In fact, to update you, Duramax engines no longer use Bosch at all, as of 2017. They have switched to a Japanese made Denso fuel system. Conversely, Cummins has an all-new 6.7L diesel for 2019 which has moved to the Bosch CP4 pump, same as Ford. As of 2018, they used the much more reliable CP3 system, which flowed more fuel volume but at less fuel pressure than a CP4.

Wasn't aware of the Duramax swap, but that still leaves a large portion of diesel applications that use it, including a big chunk of European manufacturers. I knew Cummins had swapped to the CP4 for a variety of reasons, again with no known problems, probably because the Ram setup has dual fuel filters, one rear frame mounted with water separator and one front engine mounted.

Any of the common rail systems are "precisely controlling the combustion process." Mahindra has nothing special here...if you have an engine that is over 26HP, you must have electronically controlled common rail injection. Everything does now.

If Kubota uses it, good for them, they're ahead of the curve, although I'm unaware of any particular reason you have to have it. I never said it was anything special, just that it's a preferred engineering solution to an emissions requirement over other fixes. If your controls are programmed correctly you can meet emissions without the problematic DPF. Multiple injection events give multiple burn initial conditions, controlling both mixture and combustion temperature to reduce both soot and NOX. Looking at some of the designs, it appears as if DPF is being used as a bandaid to avoid changing the engine substantially.

 

[nova3930]

Hopefully not!!!!

Can Diesel Finally Come Clean? - Scientific American

Interesting setup. Modified fuel injector to complement multiple injection events. I would still expect some after treatment to be required just because of the push to "near zero emissions" that seems to be moving forward....