I had another member tell me:

"the 3rd injection event/cat like the 04.5+, which cause worse mileage and dirty oil"

It was in regards to what year has the best drivetrain of the 03-05 5.9 2500/3500?

What is this 3rd injection event???

 

As I understand it, 04.5 and later 5.9 trucks sometimes have an injection event after top dead center, which doesn't create extra power but serves to get the cat hot enough to not clog up.

When the 600 first showed up, there were threads about them getting slightly lower mpg. I think there was also something about a reflash to improve things.

 

So- what is it, and how does it create the heat???

 

The 3rd injection event is part power and part emissions.

The power part is what gives use 325 HP and +600 fl\lbs TQ across a broad rpm range.

The emissions part is designed to cut NOX emissions by replacing part of the combustion charge with oxygen depleted air.

The 3rd event does not fire all the time, only when predetermined variables are met. It generally occurs under high load and/or high rpm scenarios.

Contrary to misinformation, it is NOT needed to make the CAT work. The CAT is designed to minimize NOX emissions which occurs at high cylinder and subsequent EGT's. In fact, too much heat and EGT's will damage the CAT to the point it wil no longer functioning correctly and will impede exhaust flow.

 

Didn't know that.. but makes sence at 1800rpms WOT while towing I cant break 1200*.. but same hill same load 1 gear lower at 2500rpms I am at 1300* with less LOD....

I also think it fires when the engine is below operating temp as my EGT's are about 100* warmer while the engine is below 200*...

Smarty Jr reduces the 3rd event... they tried to cut it completely and they lost hp and increased EGT's so parts of it are good.

 

Thats more a lack of fuel and boost than anything. The fuel maps are setup so you don't get more fuel until you get the rpm's and boost to warrant it.

Put a drive pressure gauge on the truck and you can see where the 3rd event kicks in and starts firing. It varies depending on load but I usually do not see a spike in drive pressure until after 2500 rpm's.

 

:third injector event........ Occurs after the cylinder has reached top dead center. Why? For the cummins to meet the CARB emissions without a EGR, which rule the auto industry for the North American Continent. How? the third event continues combustion temps on the downward stroke. The purpose is to create a high temp burn before the exhaust valves open, which further lowering the emissions. Not intended to heat the cat which the new 6.7 do! By the way the exhaust valves don't let all the combustions gases out. The cam is timed to retain a portion for the next compression cycle. Simply put..... a in cylinder EGR! We have to always remember that our engines are manufactured first and foremost to meet emission standards dictated by California. Some of the big tricky gains in horsepower are made by altering the cam lobes! This happened on the 04.5 and up model years. By the way the valve were upgraded to a high temp inconel to accommodate this. So you notice the oil absorbs more soot and turns black as soon as you change the oil. However the HP went up from 305 to 325? The best in the aftermarket business, Marco from our favorite programmer SMARTY tried to eliminate the third event. THE KNOWN RESULT result was a loss of HP. ... Remember this guy is a European trained emissions engineer. Okay what the heck was the question or point I'm trying to Make

 

Explain that gauge please....

 

A drive pressure gauge measures the pressure of the exhaust in the manifold. This is the pressure that drives the turbo. You generally want to keep this as low as possible but drive pressure will go up as boost goes up so you try to keep the boost to drive ratio around 1:1.

Its usually measured with a 100lb boost gauge. The connection to the manifold goes through some coiled copper tubing before connecting to the boost gauge. The copper tubing cools everything so you dont melt the plastic boost tube and it also usually contains some oil or something to dampen the gauge.

 

So the 3rd event raises this substantially?

 

Using stock 4" exhaust, stock manifold and turbo, CAT, and a Borlah muffler I see boost to drive at 1:1.2 at cruise speeds up to 1:1.5 under moderate acceleration. As soon as the 3rd event hits the ratio immediately goes to 1:2, or higher. I only have a 60 lb gauge and anything over 30 lbs of boost hard pegs the drive pressure gauge.

The good news is a turbo upgrade will bring this back down to a better ratio. The emissions setup is not just one piece but several working together. With the 5.9's its a parts swap to substantially change how it works, for the better.

 

Oh, now you went and said the E word!!!


Now we will have 3 pages of posts claiming it doesn't exist on a 5.9 Cummins.

 

I wonder how my Smarty Jr will affect this? I know it drops EGTs substantially.. but never thought about drive pressure.

 

Thanks for the good info! Hmmmm- Kitty, here kitty??