What did you do to your Grand today (ZJ/WJ)?

[5oclock]

Isnt the logic [of small engine diesel ] not giving the diesel excess air at "part throttle" to reduce oxides of nitrogen?
Pumping losses are also quoted as a reason not to "over boost" at part throttle. However we have seen a big reduction in engine oil soot in older direct injection jap diesels by small amounts of part throttle over boosting, [ like say 3lb increase ] which suggests more complete combustion inside the engine, which suggests better fuel economy.
All of our experience is with diesels under 5 litre displacement not monsters like you work with. 1350hp per cylinder is pretty serious ,as is 6x15= about 90 psi boost!!!! Are the engines you are working with using compound turbo/superchargers?

[JeanLuke]

Originally Posted by 5oclock

Isnt the logic [of small engine diesel ] not giving the diesel excess air at "part throttle" to reduce oxides of nitrogen?

Almost, but not quite. The reduction in NOx is achieved by a reduction in temperature. The reduction in temperature is achieved by a reduction in O2, which is achieved by replacing some of the intake air with exhaust gas (enter EGR).

Deezelweazel is correct in that increasing air will increase EGT. It will also (as a consequence) increase NOx, about which most won't care... until you get hauled in for testing.

[Deezelweazel]

They are Caterpillar VM 46DF - twin turbochargers, single stage- but dual stage intercooled- otherwise the intercooler would crack because of the massive temp drop.

I'm an instructor for Control and Monitoring electronic systems.
We have about 6 of those engines here for training purposes.

Remember?
We get exhaust added to reduce NOX. If you perform an EGR delete, you get more air into the engine, as a result combustion temperature is increasing...

Does that give us a performance difference? Nope... Better Throttle response? Nahhh...
You would recognize that, if you also cleaned the complete intake manifold at the same time, valve rods have been replaced and maybe with a fresh set of injectors. If the injectors are worn, you wouldn't feel any difference. Fresh air supply alone is not helping into better combustion.

Soot can be caused by many causes, mostly improper combustion. Mostly condensation or faulty injectors or spray pattern. Faulty valves, bad timing and so on.
Even air humdity can play a role.
In our case: Playing with the tumble flaps- they are there for a reason. Especially during part load. This created swirl creates the necessary movement inside the combustion chamber to provide fresh air everywhere inside the chamber.

Most 4 valve per cylinder engines operate like that, increasing combustion efficiency by 10% as a neat side effect.

[Adrian D]

Originally Posted by Deezelweazel

Quote:
„ If lowering the mixture in part load (more boost for the same fuel) you might get better economy when cruising.“

via GIPHY

Adrian, you still learned nothing…

Air is neccessary, but gives you nothing. For every degree you increase part load boost,
you increase EGT‘s.
Due to uneven laminar flow in part load, you increase them by 3 to 5 degree per increased degree in the intake.

Better throttle response? Inject more fuel! In a sprint you drive the intercooler into saturation - intake temp reaches with ease 200degrees after (!)IC. Even with modified IC you will still reach 140 degrees.
Trade off:Saving on fuel? Obviously not!
When you want to regain a bit efficiency with bigger tires, you need to regear your diff ratio.
Reminder: The NAG 1 can deliver 400Nm of torque. The 1310 u-joint can handle 176Nm continuos, 1080Nm short term max! The steeper the angle the less torque.
The stress on engine components with the extra heat is wether desirable nor any good regarding reliability.
We have here about 30 (Caterpillar)engineers working on thermodynamic procedures.
And our engines produce around 1350hp per cylinder at 6 bar of charge air pressure…

In part load EGT‘s can raise into the sky!

I got a giggle out of the image, thanks for that. And I'm always open to learning

I wasn't sure about the change in mixture, that's why I added the "might".

Care to elaborate more on why in part load a leaner mixture increases EGTs?

For throttle response it would definitely be a feature of injecting more fuel, a more aggressive slope of the pedal position to driver wish conversion in the ECU is how I've seen it done.

[Deezelweazel]

Laminar flow in the exhaust is not equal during low load conditions. It has nothing to do with leaner mixtures.

In industrial applications therefore the individual cylinder EGT's are monitored and have a different alarm trigger value at different loads.
By the way- how many sensors are involved in a modern engine?
Yes, you are reading correctly: up to one thousandthreehundred sensors are involved...

Higher Boost at part load is a serious problem, it increases EGT due to turbulences after manifold and also brings in way more heat into the intake manifold. Luckily adding boost does not do any harm combustion wise- it's all about the thermal load.
Think: maybe "only" raising intake temps by 10 degree- that in turn will create a rise about 30 to to degrees at the exhaust. Not good.
It's ok- if you speed up the engine, then the flow is sufficient and fast enough. This creates speed and heat- you can use at the turbocharger.
This is an example: single Turbocharger weight: 2 ton
Intercooler: 1ton.
Overall weight: close to 350 ton

[5oclock]

That is awesome! I checked the VM45DF out on the CAT website, it sure is BIG equipment you teach on Deezelweazel.

[freerider170]

Fitting a auxiliary transmission cooler. Not finished yet, but close.

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