Turbo Satoh S373 Beaver III

[Ilikeurtractor]

So I found this on Wikipedia:

"The full load limit of a diesel engine in normal service is defined by the "black smoke limit", beyond which point the fuel cannot be completely burned. As the "black smoke limit" is still considerably lean of stoichiometric, it is possible to obtain more power by exceeding it, but the resultant inefficient combustion means that the extra power comes at the price of reduced combustion efficiency, high fuel consumption and dense clouds of smoke."

The problem with the above statement is how "black smoke limit" is defined, which the article does not explain or link to explain. Which means what I consider the "black smoke limit" may be different than what the guy next to me does. I have a hard time accepting that once the black smoke limit is reached the burn "is still lean of stoichiometric" because I would think black smoke means pure carbon molecules are in the smoke which, if they are in carbon form, have not combined with oxygen to release the associated energy by doing so.

I am curious as to why a gasoline engine of the same displacement as a diesel, given the same bore and stroke configuration, almost always (always?) has more rated power at the same speed since they are both theoretically taking in the same amount of oxygen despite the diesel having a higher thermal efficiency (i.e. it should produce more power inherently.) I'm guessing it at least partially has to do with this issue of eventual black smoke with diesels as "peak" load occurs, where the fuel and air mixture is not mixed well enough to achieve full combustion, and little carbon guys go out the stack without their oxygen partners attached resulting in a loss of liberated energy. Certainly a turbo helps with this problem.

 

[GrocMax]

Diesel Tuning. A/F Ratios etc..

Nice colored graph of where 'smoke limit' is.

 

[Ilikeurtractor]

Interesting data. So "smoke point" is it "smoking like a coal train" - lol. I actually would have thought it to be the point of onset of visible black smoke. I'm sure the EPA would rather have it that way. Thanks for sharing.

 

[Ilikeurtractor]

So as a final point for me, I think I had a different view of what stoichiometric is until now. I took stoichiometric meaning both there is enough oxygen to burn all of the fuel present and it actually does fully combine which would be more accurate for an Otto cycle engine. As applied to how a diesel works, there is enough oxygen present, it just doesn't combine because lack of time/mixing. Therefore even though the smoke limit is below the theoretical stoichiometric value for diesel fuel, the actual resultant combustion of the fuel during the power stroke is not at the stoichiometric value as far as the fuel is concerned (but the cylinder contains enough oxygen). I would think this would result in high CO values which a diesel is not known for, but maybe only at the smoke point, or around there which is not a typical operating point based on the graphs so it is not an issue. Or the CO eventually combines anyway, just outside of the power stroke (leading to high EGT???) Hmmm.

 

[GrocMax]

BTW the adjustment screw on the side cover of the pump is like an idle buffer/anti-hunt/minimum speed spring and does not increase rack travel significantly across the entire operating range.

 

[Ilikeurtractor]

If you're anxious to increase fuel here is some information to help - sorry it's a low quality scan. Looks like you just remove the funny linkages that restrict the rack from the full setting and have fun I have no idea how much more fuel will actually get injected. Probably a good thing you have the EGT to watch. I know a good source for transmission parts if you need it.

 

[GrocMax]

Mine doesn't look like that, the intermediate lever and spring 'angleich' is not present. I figured out a way to get external adjustment, install a very light coil spring with an adjustment screw to take spring tension off the overinjection return spring lever. That spring's rate appears to be what sets max fuel for a given governor position (its what pushes back against the governor to reach equilibrium), taking spring rate off it in a controlled fashion should result in a global fuel increase at load without a bunch of negative impact, and can be easily undone. In other words, a smoke set screw has been installed.

 

[Ilikeurtractor]

I haven't had a K3A or B fuel pump out of the engine yet but that was the information I had for those engines. Apparently there was more than one version.

 

[GrocMax]

Mitsubishi K3G Manual (Page 7 of 148)

K3G engine very similar, fuel section starts on pg 70. Governor about pg 105. Real simple setup, there are no adjustments. Adj. screw on side cover is called 'damper adjustment' its just a very light spring to keep low speed hunting down.

 

[Ilikeurtractor]

The KE engines only have one moving plate that is the "stopper" for the rack (smoke limit.) I never messed with it but I think I would just take it off and see what would happen (rely on the clutch and foot pedal to limit load/fuel temporarily until I understood the results better.) It may not even supply enough more fuel to cause a problem with a turbo installed. I would like to think it could though just to make it a more appealing modification.

 

[GrocMax]

Removing it is a really bad idea rack could jam stuck wide open.

 

[Ilikeurtractor]

Keep some rags handy to shove in the intake

 

[GrocMax]

I'm having evil thoughts about making an aneroid/boost compensator out of a Holley 4 bbl carb vacuum secondary unit, its about the right pressure range to do it.

 

[Ilikeurtractor]

Do you have any data showing how much fuel the pump can supply at full rack (without limiters)? It would be interesting to know how much theoretical power you could achieve from it. I suspect the same pump was used on all K3 engines with different configurations of limiter linkages being the only difference. If that is true then the pumps should be capable of delivering a lot of fuel. Maybe the pumps had different available cylinder sizes though (?)

 

[GrocMax]

We know the plunger diameter is 6.5mm, take the total injector cam lift subtract about 3-4mm, compute volume, compute mass per stroke, multiply by RPM/2 and multiply by 60, there's the mass per hr, divide by BSFC (mass per HP per hr) = HP.

A WAG estimate at 6mm plunger lift and .330 BSFC is between 80-100HP sticking to a 3000 RPM rev limit.

I suspect they used the exact same pumping element on a wide variety of engines of various sizes and just changed the stopper lever and injectors.

 

[Ilikeurtractor]

Well that gives something to work with for sure.

 

[GrocMax]

You need to know what the exact effective stroke (fill port close to spill port open) is, that guess could be off quite a bit.

 

[Ilikeurtractor]

I wonder if the effective fill/spill is the same for all series of engines? Or if they are more closely matched to the particular engine? Seems like the cost to make them unique probably wouldn't justify it. Easier just to limit the rack I suppose.

 

[Ilikeurtractor]

According to the manual I have the fuel injection rate for a K3A at "smoke set" is given to be 20.5 mm^3/stroke (+/- 1mm^3). At "start set" it's 30 mm^3 (+/- 5mm^3). I don't know how much this changes as the rpm varies but it must to some extent otherwise it wouldn't be specified I suppose (although I would think it would be pretty independent of speed). If we assume the engine to be 30% efficient and the fuel to have a heat energy content of about 140,000 BTU/gal then the power available at smoke set would be about 24 hp. At start set 35 hp. In the extreme case of 35 mm^3 it would be 41 hp. All of these values are at 3000 rpm. So plenty of gain to be had just by getting to the smoke set value. I wonder what the actual power of the non-turbo'd engine is at smoke set? It should be close to the 24 hp unless the efficiency tanks as it gets there. Then the next questions would be how much boost would be required to get a 30% efficient conversion of the fuel at the start set and is this possible without grenading the engine in a short amount of time?

 

[GrocMax]

I wonder if the effective fill/spill is the same for all series of engines? Or if they are more closely matched to the particular engine? Seems like the cost to make them unique probably wouldn't justify it. Easier just to limit the rack I suppose.

Can't be, they vary widely in size thus max fuel requirements. Just switching the stopper lever you can set max fuel for a wide variety of cylinder sizes. K3M is twice the size of the K3A.