I took the unit injectors for the Cummins ISM in to be tested and resealed and they asked me if I wanted larger nozzles. This is a commercial diesel injector specialist. They told me it's an easy and cheap 50 hp for $500 without touching the ECM. So the ECM guys told me 50 hp would be $1500 without touching the injectors. I was under the impression that the ECM dictated the volume of the injection event based on a feedback loop, but perhaps I have that wrong?
Most diesels don't have feedback into the ecm/pcm until recently. They rely on a preset fuel map for power. They have all the air they want. The fuel dictates the amount of power produced. Most diesels are fine with a "modest" nozzle size upgrade before you have to get larger pumps and reprogramming of injector events, the tuning window is really small.
Ranger50 said:Most diesels don't have feedback into the ecm/pcm until recently. They rely on a preset fuel map for power. They have all the air they want. The fuel dictates the amount of power produced. Most diesels are fine with a "modest" nozzle size upgrade before you have to get larger pumps and reprogramming of injector events, the tuning window is really small.
+1 on this, basically a modest bump in injectors is fine, you will run out of turbo before fuel.
Feel free to reach out, it's a bit much to type but was in the diesel performance industry for a long time and did a little teaching about it.
Agreed. Most ECMs are a pretty simple fueling map with no feedback. It will continue to use the same pulsewidth and pressure and have no idea you're injecting more fuel. The turbo reacts sympathetically with the increased mass and spins harder (obviously within the parameters of its map) and depending on the turbo and fueling, it gives you a window. You can defuel a certain amount before the turbo becomes undersized, and you can overfuel to a certain point before the turbo can't give anymore and you're in coal-rolling territory.
I'm not that familiar with ISMs. I know they came out in 94, but quickly got a version of Cummins CELECT fueling system which got more complex. Not sure if it includes any feedback or not.
Ok great. So I will get the bigger nozzles then and not bother with ECM tuning. I think of a 2000 motor as being pretty new but in reality it is primitive in terms of engine management.
Especially for diesels pre-2008 EPA changes.
It's one of the reasons I love diesel. Ridiculously simple.
We have a 2004 Duramax in the family. Dad went 30-over with replacement injectors and did zero tuning at first. It ran like a charm and the ECM had no idea what was going on.
It did make some black smoke. Factory ECMs retard injector timing several degrees from optimal for NOx reasons so he ended up going all-in with a 5-position chip, intake, exhaust, and lift pump. With the advanced timing, even with crazy fueling on level 5, the only smoke it makes is a wee puff below 2000 rpm. By then the turbo adds enough air. We toyed with adding a later VATN hairdryer, but determined it wasn't worth the effort.
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