I am now on my 3rd set of injectors in 35k miles. Every time I've gotten a new set I got the old ones checked out and they always came back with cracked tips. A couple weeks ago I towed 25K combined load 150 miles in 100+f weather and kept the egt's between 1200-1450 the whole way. Now I have excessive hazing, high fuel consumption, and gray smoke. I pulled an injector earlier and the end of the tip is blue like it got really hot. Is it possible that the high heat is killing my injectors? I would like to experiment more but injectors get expensive. Anybody have any ideas?

 

The Cummins engine is rated for a 100% duty-cycle with 1250*F EGTs.

1450*F "the whole way" is not 1250*F "the whole way".

Sorry.

 

It's been a long day. I did mean 1200F constant with short periods of 1450F.

 

That should be OK. I wouldn't let those short periods get longer than a minute though.

What's the injection-pump's timing at? A little bump past stock, a lotta bump?

 

Interesting! I have the same hazing problem, and my DDP injectors have blued tips. I called them, however, the never called me back.

 

I have the timing bumped an 1/8". Too much timing did cross my mind. I know on the old idi engines too much will break the tips of the glow plugs off.

 

That amount of heat won't cause tips to crack unless they were a bad design from the get go.

Otherwise cracked tips are generally due to water in fuel.

 

Even in 100* heat thats some high EGT's considering the mods and bumped timing. The 40hp injectors and 1 turn on the fuel screw should account for no more than +70hp. Add the bumped timing, free flowing exhaust and intake, and you shouldnt be much higher than stock EGT's under full load. Loaded with timing also keeps more of the heat in the cylinder, so cylinder temps of 1250* may be 1200* EGT at stock timing. While 1200* EGT's at higher timing can have closer to 1400* cylinder temps. Those arent exact numbers, but just a general guess. Thats why advanced timing vs stock for the same EGT, the cooling system works harder to keep the higher timing cool.

I suck at explaining some things, hope I didnt screw this up too much. My suggestion though is to either limit your continous EGT closer to 1100* with added timing, or 1200* closer to stock timing.

 

Can anyone advise about the blued injector tips? It is possible that that was part of the hardening process afer DDP modified them, and since they never call me back, I am truly curious. I seriously doubt you could get an Injector red hot and not sustain other damage, however, I have been surprised before!
The Injectors I removed pretty much behaved the same as the DDP's, only more so. (Smoke, hazing at idle)
And if someone at DDP is reading this, you have great products, however, your customer service is less than great.

 

Hardening, I believe,, has been known to make certain types of metal brittle. Might want to make sure that DDP knows of the process and hopefully has a remedy to correct this. Water in the fuel can blow the nozzle tips off and air in the fuel will cause the needle to contact the nozzle from the inside. Although, if you had air or water in the fuel, I think you'd notice a significant change in performance.