Too little fuel?

[BreckenridgeCruiser]

Thanks to all that helped with my altitude questions. Especially BrownBear!

So, now that I have brought my engine below the smoking point at rev, a new question has arisen...

Q) Can I bring down the fuel too much in a diesel?

In a gas motor, if the mix is too lean, you can burn things up... Is that a risk with a diesel? Or does power just die down until the engine runs poopy (technical term )?

Thanks all!

K

 

[Diescipel]

OK I'm still a newb but I'll give it a shot...

No, diesels and gassers do not behave the same way with regards to fuel. Diesels are fuel throttled so whatever volume of air is present will do the job for combustion, but you will have problems/symptoms. At altitude the engine cannot draw in enough air to match the fuel hence you get the black smoke (unburned fuel because there's not enough air to match it). Turning down the fuel helps to match the fuel to the available air. Another option is a turbo which increases the air.

I think the only issue you will have if you turn your fuel down too far is you will lack power. Too much fuel is what leads to high EGTs in diesels.

HTH
Hope I didn't get it wrong.
B

 

[brownbear]

I agree fully with the explaination above. Too little fuel will just be less power. There is no such thing as a lean mixture in a diesel such as a gasser.

So no worries, at least the hippies will leave you alone now!

Congrates you got it figured out to in or out....

 

[BreckenridgeCruiser]

Thanks! I did bring it down quite a ways and it does not smoke anymore. A little white smoke at high rev when she's not fully warmed up, but not much more...

Thanks for the info about the fuel load. One question about your post. if these trucks are Fuel throttled, why does my acceleration linkage go to a butterfly (venturi) on the intake? How does the truck know to fuel throttle? Is this like some mechanical Mass Air flow sensor or something?

Thanks again!

K

 

[brownbear]

pnuematic fuel sensing across the butterfly. See the two lines? they sense are across and move the diaphram accordingly

 

[BreckenridgeCruiser]

That's really cool! Thanks for the info!

K

 

[Martin White]

I've been adjusting my fuel mix over the past couple of days, and I've noticed a drastic drop in power as you lower the fuel. So I'm looking for the sweet spot between fuel economy and power. But I've noticed the engine seems to run fine whatever I've done to the fuel so far. EGT's have dropped noticeably as the fuel is turned down.

 

[Diescipel]

I've been adjusting my fuel mix over the past couple of days, and I've noticed a drastic drop in power as you lower the fuel. So I'm looking for the sweet spot between fuel economy and power. But I've noticed the engine seems to run fine whatever I've done to the fuel so far. EGT's have dropped noticeably as the fuel is turned down.

Yep, this is classic diesel behavior as I understand it.

This is why the local diesel tuner shop around here has a dyno--this is the trick: increase the fuel just to where the power is where it is supposed to be and no more. Easier if you have a dyno because you are not doing so much trial and error, adjust and drive. I hope to save up enough money this winter to get my injectors serviced and then to have this shop adjust my fuel for optimum effeciency--power and economy.

Cheers,
B

 

[Martin White]

I've also noticed that with lowered fuel, the engine sounds different. A bit quieter, and idles a bit lower, with no other changes.

 

[brownbear]

Yep, this is classic diesel behavior as I understand it.

This is why the local diesel tuner shop around here has a dyno--this is the trick: increase the fuel just to where the power is where it is supposed to be and no more. Easier if you have a dyno because you are not doing so much trial and error, adjust and drive. I hope to save up enough money this winter to get my injectors serviced and then to have this shop adjust my fuel for optimum effeciency--power and economy.

Cheers,
B

Hey that sounds great doing it on a dyno. I wonder where my closest one is.....

I'm sure in Vancouver.

 

[Lantec]

Hey that sounds great doing it on a dyno. I wonder where my closest one is.....

I'm sure in Vancouver.

AWD dyno is up at rocket rally at squamish

 

[Martin White]

It would be really interesting to see a dyno vs fuel printout. I'm wondering if power increases linearly with fuel or if there is a curve. I suspect we're dealing with some kind of curve and that there is going to be a very obvious "optimum" point. But I haven't seen a chart like that on mud so far.

 

[brownbear]

Definately a diesel doesn't use all the fuel in certain circumstances. So I imagine you will surely hit a point where the economy and power come together. But I would also presume the egts would be the limiting factor. And for different altitudes more so.