Third Inj event

[JoeErickson]

I thought I read somewhere that the third inj event shuts down under certin conditions? I pulled my usual load this last weekend in 90 deg temps and ran cooler egt's then I have my other 3 trips down the same road. Nothing was changed on the truck and if anything there was more wind. Did my third inj event shut down or was it some other fluke thing like getting some good fuel? I guess I'd like to figure out what caused it, it was nice to run up the hills at 1100 rather then 1200-1300. .

 

[NDanecker]

I'm not sure about the event shutting down or being disabled under certain conditions. There are so many other variables that go into the EGT number that its hard to say. My guess though is different fuel.



I'm curious as to what others will say...

 

[MRosinski]

It would be nice to be able to shut off the 3rd injection, fuel mileage would go up quite a bit.

 

[klenger]

I suspect that the 2nd and 3rd injection events actually overlap when running under heavy load, but then I'm pretty stupid about mechanical things, especially diesels.

 

[mattymac]

I was told that the 3rd inj event shuts off at a certain rpm because the injectors cant fire that fast, something like 2-2100 rpm? Ive never seen or noticed a diffrence. Also Marco (madselectronics) reports that shutting the 3rd injection event off makes the 600's do some funny things.

 

[JoeErickson]

I woundered if it had something to do with heat, intake air temp over x amount and the third event shuts down or backs off? The first two trips were in 20-30 deg outside temps and the 3 trip was in 50-60 deg. It does'nt make sense to me why I would run cooler when it's 30 plus deg hotter outside.

 

[betterthanstock]

I thought I read somewhere that the third inj event shuts down under certin conditions? I pulled my usual load this last weekend in 90 deg temps and ran cooler egt's then I have my other 3 trips down the same road. Nothing was changed on the truck and if anything there was more wind. Did my third inj event shut down or was it some other fluke thing like getting some good fuel? I guess I'd like to figure out what caused it, it was nice to run up the hills at 1100 rather then 1200-1300. .

There are several things that go on.

1. Your thermocouple may be off in colder weather, since it reads the difference between the voltage at the junction in your manifold, and another reference voltage in your gauge, or electronics, or another thermocouple on your wiring harness to the gauge.

2. The third event is done to keep the catalyst hot, and to have enough excess fuel to keep burning off other gasses. In colder weather it takes more to keep it hot, so maybe the computer adjusts for that.

3. Colder air is denser, so assuming you traveled at exactly the same speed, your engine works harder to tow thru colder air.

4. colder tires have more rolling resistance, as does colder oil in axles, etc.



Was your mileage better in hotter waeather?

 

[JoeErickson]

Mileage was the same to . 5 mpg better. It would be interesting to know when the computer backs off on the third event, someone here should know.

 

[cerberusiam]

Mileage was the same to . 5 mpg better. It would be interesting to know when the computer backs off on the third event, someone here should know.

Consideridering what the 3rd event does I have my doubts that it is ever eliminated. From what I can see the third event is part power, part in-cylinder EGR, and maybe heat for the CAT. Not sure it is intended to heat the CAT as that may be just a by product of a late event. Eliminating it would introduce some interesting problems in maintaining power and emissions control across an rpm range. Initial impression is the ECU simply does not have that kind of control but without some source code it is really tough to tell what they intended.