Fuel economy

[Petervs]

Hi Jon,
I am not an expert on pre DDEC or DDEC 1 systems, but I can not imagine that the fuel supply is controlled directly by the throttle position. The engine would flood out if you opened the throttle too quickly, the metering control has to sense the air pressure in the cylinder or going into the cylinder and respond to that.

Perhaps someone else will have a definative answer.

Peter VS

[Jon Wehrenberg]

Peter,

On mechanical engines (pre DDEC) the throttle position determined how much fuel the injectors supplied. A wide open throttle at low boost (low RPM) resulted in unburned or incompletely burned fuel (black smoke).

On DDEC I the same condition could temporarily be created. The computer was not as sophisticated as on later versions, and until the turbo spooled up you could roll out the black smoke with excessive throttle.

Our later versions will only allow fuel quantities that can be almost completely burned.

[Just Plain Jeff]

All the above ignores the PBF factor, which can be deliterious as to fuel economy.

[Jon Wehrenberg]

JPJ, Don't you have some mail to sort?

[Gary & Peggy Stevens]

I know I saw a post just yesterday about the difference between the ULSD and our older diesel fuels, but can't find it.

So I am posting this website on this post site, HOPE you don't mind.


http://www.clean-diesel.org/

Gary S

[lewpopp]

Doesn't the "potentiometer" come in there somewhere?

[JIM CHALOUPKA]

lewpopp;Doesn't the "potentiometer" come in there somewhere?

Lew, The elaboration of your query.

Automotive jargon: Throttle position switch. = Electronics jargon: potentiometer.

Personally I think you new that!

JIM

[Jerry Winchester]

In the older mechanically governed 8V92's there was actually a piston that pushed oil out of a tube with a small hole it it that acted as a buffer between mashing your foot in the throttle and the fuel system going to full fuel. If you wanted to improve your pull from the stop sign, just drill the hole bigger, but be ready to face the fact that the sun was going to be blocked out by the black smoke.

The Cummins PT fuel system used an aneroid valve that sensed turbo boost pressure and adjusted the fuel flow accordingly. Mack "Maxidyne" engines had a similar feature on their high pressure injection pump.

I think this is all for naught in the new engines as the sensors and computers keep this all in check with electrons and or 1's and 0's.