"Turning down" fuel

[Martin White]

I'm not sure if that's the right terminology, but I have heard numerous times that EGT's can be dropped by "turning down" the fuel. If there is basically no smoke coming out of an engine at all, is there still "room" to turn down the fuel, or is it going to cause running problems?

It appears that diesel stoichiometry is more complex and with more variables than would at first seem apparent. How do you know when you've turned things down too far? Is it immediately obvious ie does the engine start idling roughly? Obviously from my question I don't know much about this, just trying to learn. It's tough as there isn't much specific available on this topic on this forum, just very general suggestions.

I know it's been suggested to turn it UP until you start getting smoke, so how do you do the opposite and find the sweet spot? If I lost some power but gained economy I may be interested in that. I've noticed my friends truck in which he gets better economy than me by about 20% does not run as strong as mine, so maybe this turning down business is part of the explanation. I'm assuming turning fuel down is going to have some effect on fuel consumption. Anyone have any data on this?

 

[brownbear]

none for your engine I bet.

Most talk about a 3b when they mention it.

Do you have a fsm? look up setting the max rpm, thats how they explain it in the 3b manuals.

Remember a diesel doesn't have a "mixture" so to say. More fuel introduced it accelerates, When it reaches On speed it holds there, decrease fuel it lowers rpm.

On a 3b when you adjust the max fuel you really notice trhe accelerartion diff.

 

[Lantec]

none for your engine I bet.

Most talk about a 3b when they mention it.

Do you have a fsm? look up setting the max rpm, thats how they explain it in the 3b manuals.

Remember a diesel doesn't have a "mixture" so to say. More fuel introduced it accelerates, When it reaches On speed it holds there, decrease fuel it lowers rpm.

On a 3b when you adjust the max fuel you really notice trhe accelerartion diff.

So that screw that everyone adjusts is to adjust the maximum amount of fuel injected when the accelerator is floored or does it increase the amount of fuel injected as a whole?

 

[brownbear]

I think it increases it proportional accross the board. At least it feels that way. If you add to much fuel, it becomes quite peppy on the low end, but the temps are crazy when you push it harder.

Definately a pyro guage is a must if you play with fuel. Or say goodbye to the head.

 

[M John Galt]

What specific adjustment "turns down the fuel" on a 13B-T?

Where is this adjustment located?

 

[denis]

The "rotary" distributor style pump has a couple more adjustments than the inline style. The delivery quantity (backside screw above the pump head clockwise(+)) is adjustable independantly from the full-load stop (external stop on the lever assy).
On the inline pump with a pneumatic governor you can pretty much only adjust the idle (butterfly linkage) and full load (maximum speed, below the diaphragm housing clockwise(-)) stops short of messing with the internal springs.
I can't comment on the 13BT style pump with the mechanical governor, but I would imagine you would have about the same adjustability as the distributor pumps.

 

[Tapage]

In my case ( 2H ) I turn my diesel up .. my 2H acelerate ( I know is a mixture of gearing and diesel ) like a crazy race car in maybe 3 shifts .. obiusly, if I keep my pedal in floor the EGT come up as same as crazy speed that it can acelerate ..

In the highway at 120km/h i can hold 1200 or lityle less F temps .. ut I can go up easily pushing a little more diesel that in my casn don't means more speed but yes more smoke ..

 

[Martin White]

Ok so still no answers for a 1HDT? Anyone? The theory I do now follow, but how about for that specific engine?

 

[crushers]

Martin, a direct injection engine will blow a bit of black under hard acceletation or heavy work load... this is normal...

 

[denis]

You probably meant "an overfueled direct injection engine"

 

[crushers]

all the direct injected Toyota diesels i have seen have puffed black smoke under heavy load. not under normal driving but pulling hills, pulling trailers or hard driving...
the inderect diesels on the other hand don't seem to have this problem...