I maintain there is a setting somewhere in the code that would allow you to disable pre/post injection. I also think that pre/post injection is calculated either in the software of the ECU or in the injector driver(s). But I have some questions:

1) Is pilot injection ever a fixed duration? (such as cold startup)
2) Is post injection ever a fixed value?

I'd just like to see what the injection cycle looks like, actually.

Andy

 

"I maintain there is a setting somewhere in the code that would allow you to disable pre/post injection."

I don't think there would be a software switch if that is what you are saying, but you never know. The ISBs probably use the same code base and they do NOT have a post injection. All these engines have a pilot injection event. I suspect table entries.


"I also think that pre/post injection is calculated either in the software of the ECU or in the injector driver(s). But I have some questions:

1) Is pilot injection ever a fixed duration? (such as cold startup)
2) Is post injection ever a fixed value?"

I doubt it because the desired volumes for each change as the engine operates at different points in the fuel map. A desireable pilot shot at idle might be 4mm^3, whereas at part throttle it might be 10 mm^3 and at higher RPMs and loads it might be zero. Furthermore, the actual volume delivered depends on rail pressure and duration, and the ECM timing only controls duration, so for sure the duration is not constant at different map points.

"I'd just like to see what the injection cycle looks like, actually."


Get a scope with a current probe (or make your own) and have a look. It helps to have a digital storage scope because of the relative slow speed the events repeat at.

 

After reading all the previous posts here, I find it is exactly as I thought! Whew. LOL
Frank

 

Huh ? You've already disabled the 3rd injection event in software ?

 

Just curious SD, have you verified there is indeed a "3rd" event? This came up years ago when the CRD came out and a checked one at work with a lab scope and there were only two events. Haven't heard of a change in that, but I haven't asked anyone at tech either, or checked one in a long time.

 

Check out this thread in Diesel Ram forum. Turning off the 1st and 3rd injection events does seem to be possible for some impressive mpg gains but the one who knows how has apparently left the cummins fold.
http://dieselram.com/cgi-bin/ultimat...;f=29;t=002817

 

[QUOTE=Superduty]"The ECM doesn't sense airflow (no mass airflow sensor). It uses boost pressure and IMT to determine how much fuel to put in to keep it from going too lean."

Not trying to be smart, but isn't the sensor in the elbow behind the airbox a MAF?

 

No , that is a IAT inlet air temperature sensor .

 

Under certain conditions the pilot and post injections are turned off. One I can think of is rpms above 25-2600. This injection events are no longer effective at higher rpms.
Superduty,
I would have you contact Oregonpharmer over on the dieselram.com forum but he's now in Chile. He was able to turn off the extra injection events.
Best bet is to contact Marco over on the TDR. He's located in Italy and is very well versed with the Cummins ECM codes.

MikeyB

 

I read the thread over there and I don't believe a word of those claims. Who is OP and why do people stick up for him? Maybe I'm missing something.

Marco did work on the older generation of ECM's on the 2nd gens. The 3rd gen is a very dfferent animal.

Andy

 

OP is Oregonpharmer. And I too have a hard time believing the mileage claims towing that big a$$ trailer. I have no doubt that what OP did helped mileage, but not like that!!!

 

"Just curious SD, have you verified there is indeed a "3rd" event?"

Nope. I am going by what people tell me.

I'm really busy on other projects these days, so this is a in my spare time endeavor. I'll put a scope on and check for sure some day. The 3rd event might not be present at idle either. One might have to put the truck under a load to see it.