cummins ntc 350

Get any comparison to an electronic engine out of your head, it will not lug and you should not lug it, 1500rpm hard bottom limit especially turned up and then prolly best not to pull below 1600, rpm will not hurt these engines and you need to use it.

 

In less some one altered it an NTC air fuel control does not allow full fuel intel about 1500 RPM, the bottom limit.
I believe compression ratios changed along the way as turbos and cooling of compressed air improved.
High compression and high boost makes high power but it is not Gomer proof. Engine builders have to make it so they stand up to anyone. Must be set up so Gomer will not melt the pistons out of it.
Don't remember 400's smoking bad when cold intel about 1985, was told it was for emission compliant engines.
Why lower comp and add more fuel. More boost equals more oxygen in cylinder so more fuel can be added and maintain the proper air fuel ratio.
When I was in a seminar, 1985?, a Cummings engineer explained the 315 would out preform the 350 in rolling hills because it had more HP and torque over a broader RPM range than a 350. It looked good on the grafts but never drove one much. Just to say you can spend money and go backwards.
Used to put 400 injectors in 350's on a regular basis and had none of those problems. Sorry I have no numbers I was just the do guy.
Adding 200 RPM worth of shims and dropping the fuel button by two sizes is a fairly safe power increase in my opinion.
Don't stand on it for long periods and install a pirometer.

 

Ive allways ran then 1700 to 1800 going down the road. 2450 to 2500 max rpm. But never ran more than 290 fuel pressure.

 

If you mean you are up shifting at 1600 and dropping to 1200 RPM you and backing up! If you have that truck in high gear at about 1300 RPM, held on the floor, it should start to come to life around 1500-1550. That RPM is your minimum working engine speed.
Some engines in this series were factory set at 2450 so do not fear that, not saying that's were you want to run all day.
They usually start to waiver a little about 150-200 RPM before maximum goverened speed cutting back HP.
If you have a 1900-2100 engine that extra 200 RPM makes that range fully usable and well with in the range of the engine.

 

You do not want to lug these engines. Like i said 1750/1850 cruising down highway. If you go up a hill of any size and it starts to drop under 1700 you need to down shift. If you wait for 1600/1500 you have waited to long and will need to downshift again. If you have a pryometer you will see it rising fast at this rpm. Now as long as tach is going up you can temporary be in these lower ranges. Just be light on pedel and let it pick it back up. And watch pryometer. Step on it to hard and you start scoring pistons and liners. These engines only know what you right foot is doing. No computer to protect it from you.

 

Guarantee your N14 will eventually have main cap fretting issues from being pulled that low, they are only a 6"'stroke engine and aren't meant to have their guts pulled out like a cat.

I have no problem running an 855 up to 2400rpm on a shift, at 2200 that gives you 600 working rpm if you use 1600 as lower limit.