Tweaking Kubota engines for more power...?

[RobJ]

I should probably let it go, but I'll make one more point that counters the predictions of doom and gloom. There's a lot of design margin in low-rpm engines. As an example, tractor manufacturers are apt to offer a model with a normally aspirated engine rated at say 45 hp, and another model with the same basic engine and a turbo, rated 15% higher, and still another with an intercooler etc. rated even higher than that. They are all likely to use the same crank, pistons, transmission, etc. A small up-tick in power will not kill it. It might reduce its average rebuild life from 8,000 hours down to 7,500 - but if it accomplishes the objective its exactly the same economy as buying bigger. Adjustment of the fuel pump rack travel isn't always available - but it's one way to get a small increase in top end power.

What you say is true but when you add a turbo you also add more air to balance the extra fuel. A non turbo engine can run exhaust temps of 900 degrees, a turbo version can produce more power but still maintain exhaust temps of 900 degrees. Talk to the diesel truck guys that add the chips, most all..and they should..add an exhaust temp gauge. Pulling a trailer up a long grade with a 150+hp chip and you can melt a brand new PSD.

I've posted before that the same exact engine can be rated differently, continious duty, such as a generator set, water pump. And a intermitting duty rating, usually a truck, maybe a tractor. These know the load will be heavy but not on all the time. When I was a mechanic I replaced a v12 diesel in a very large crane that was designed and built in Europe(hills and such as terrain). They shipped it to the gulf coast, flat land, and burned up the motor between Houston and Beaumont. We installed a new engine, had the pump sent out and reset to a continious duty setting, and sent themon their way. When I ran stuff on the dyno with all the hookups you can really see what's happening to an engine.

And never let it go!!

 

[hill]

I doubt that engine longevity is high on the list of concerns of a regulating agency like the EPA, and a lean burn condition will most always result in higher temperatures. High temperatures put holes in diesel pistons when under load.

A little more fuel can serve to cool combustion temperatures and improve cylinder wall lubrication as well as increase output power somewhat. Might well increase engine longevity as a result.

 

[ripplefct]

Put a turbo on it... A turbo diesel is a happy diesel. I did a samll mits. 15hp 4x4 tractor. Put a really small turbo on it, got about 6 lbs of boost. What a difference. Then again Im at 5000 ft above sea level. Im probably just getting back to the factory spec's at sea level. But... It still made a big difference. And it sounded neat.

Rip.

 

[Rebel]

I doubt that engine longevity is high on the list of concerns of a regulating agency like the EPA, and a lean burn condition will most always result in higher temperatures. High temperatures put holes in diesel pistons when under load.

A little more fuel can serve to cool combustion temperatures and improve cylinder wall lubrication as well as increase output power somewhat. Might well increase engine longevity as a result.

Sorry, but in a diesel application this is not the case!

A diesel engine is classified as a lean burn engine. There is no method used to control the amount of air getting into the combustion chamber. The amount of air getting into the engine at a fixed rpm is constant regardless of the load the engine is under.

More fuel equals more heat.

 

[medicshawn]

The amount of air getting into the engine at a fixed rpm is constant regardless of the load the engine is under.

More fuel equals more heat.

That's what a turbo's for to add more air.

You could also cool the intake air with water/Methanol, propane, nitrous

 

[hill]

Are tractors considered constant RPM applications? I suppose more so than cars and trucks they are but still most of us use our accelerators for something other than a convenient place to hang our hat or rest our foot, as the case may be.

I guess I should have used 'more mixture' instead of 'more fuel' but considering that the with an interest in the reduction of burn product to the atmosphere the EPA isn't placing restrictions on amounts of air, but only fuel in the dictate to clean output by ever and ever leaner mixtures, adding a little more fuel than they'd prefer us to use can benefit both our output and our engines in the manner previously described.

 

[RobJ]

Sorry, but in a diesel application this is not the case!

A diesel engine is classified as a lean burn engine. There is no method used to control the amount of air getting into the combustion chamber. The amount of air getting into the engine at a fixed rpm is constant regardless of the load the engine is under.

More fuel equals more heat.

Correct, it ain't no gasser.

 

[RobJ]

That's what a turbo's for to add more air.

You could also cool the intake air with water/Methanol, propane, nitrous

also correct, more air, more fuel, more power...

A normal intercooler uses ambient air to help cool the compressed air of a turbo. Looks like a radiator...mostly.

 

[RobJ]

Are tractors considered constant RPM applications? I suppose more so than cars and trucks they are but still most of us use our accelerators for something other than a convenient place to hang our hat or rest our foot, as the case may be.

I guess I should have used 'more mixture' instead of 'more fuel' but considering that the with an interest in the reduction of burn product to the atmosphere the EPA isn't placing restrictions on amounts of air, but only fuel in the dictate to clean output by ever and ever leaner mixtures, adding a little more fuel than they'd prefer us to use can benefit both our output and our engines in the manner previously described.

I don't know if tractors are continious duty engines, I never worked on any of those. Without the facts you could almost make a case for both.

The new truck diesels run the new LS diesel. I'm not sure they "lean" the engines out because that would just reduce the HP. The new Ford 6.4 still has plenty of hp. But they require the engine to clean up after themselves and this cost mpg. The Fords (and others I presume) do a "regen" on occasion. This dumps extra fuel in the cylinder after the firing stroke to heat up the exhaust and burn up soot caught by the diesel-particulate filter. That's about all I can explain about it. Downside is the new 6.4l diesels get much less mpg than the old 6.0 and 7.3. And it has many guys who enjoyed a diesel before switching back to gas. I'm sure that diesel costing almost $.50 a gallon more as I saw yesterday has a little to do with it to. I also think the new diesel option is about $7000 these days.


You can google regen. Here is a Cut-n-paste from a web site...

Active ReGeneration Attacks
During our testing, the truck went into its Active Regeneration mode after a few acceleration passes. Active Regeneration is Ford's way of cleaning the 6.4L's new diesel-particulate filter (DPF) mounted in the exhaust system. The DPF is required to trap soot produced by the engine to meet the current diesel emissions standards. You can think of Active Regeneration like the automatic oven-cleaning setting on your kitchen stove, except in the 6.4L, diesel fuel is injected into the engine after the main combustion to superheat the DPF. The whole process is controlled by the factory engine computer and is triggered when the DPF in the exhaust system begins to clog. We suspect the added power of the Bully Dog programmer could produce more exhaust soot and may cause the engine's computer to trigger Active Regeneration more often. How often the engine goes into Active Regeneration will depend largely on how the vehicle is driven.-