hey guys, i am new to the forum but i have been visiting the site for all of my diesel needs for the past year or so but i have come across a new problem that i cant find an existing post for relating to my problem so here it is
last night i pulled the stock injectors out of my 92 cummins and i put in some rebuilt injectors with 55hp nozzles that i got off a certified bosch service guy here in town. my issue now is i seem to have less power now? i dont get it. i went from having 30 pounds of boost out of my hx35 to 23 pounds of boost and less smoke. throttle response also seems to be a little lower as it takes longer to spool up the turbo to build that 23 pounds. so i am lost... what happened to my truck?

 

First off, give us some more information about your set up and tuning. Is your timing stock or advanced. Did the bosch guy give you any details about the injectors? # of holes and size, spray angle, pop pressure? How long is the nozzle measured from the sealing face of the injector body. What thickness washers did you use when you installed the injectors? All of these things add up to how the system will act.

 

the only things i have done for tuning are fuel pin turned 90 degrees clockwise and the fuel screw turned in about 1 turn, and the smoke screw is turned in about3/4 of a turn, the truck never smoked much just when i matted the throttle from an idle. he didnt give me the specs on the nozzles, pop pressures are the same as a stock injector so 245 bar. i dont know the exact length but the copper washer on the sealing side of the injector was about half the thickness of the ones i pulled out so the nozzle actually comes out a little longer than what was in there originally which i believe would actually bring the nozzle closer to the piston? does that mean i techincally have retarded timing now?

 

Check your fuel pin, turning it 90° doesn't always get it to the deep side of the pin. The stock nozzles are longer than any others I've been able to get measurements from, so the thinner washer is better. Placing it back into the correct position. I would suspect your timing is retarded because of the increased fuel and possibly a higher pop pressure. New or rebuilt injectors will have a higher pop pressure than those that have been in service for a while. So you may want to start small timing bumps until you find the point your combination likes.

 

alright, i will give it a shot, thank you for the advice, how much should someone have to tamper with the pump so start getting some smoke? i know my hx35 spools faster than the stock h1c but with injects and a mild pump adjustment shouldnt i expect some smoke?

 

I know that people like the smoke....... but tuning your truck to smoke isnt tuning it. Your just throwing un burnt fuel out your exhaust by pouring in more than the turbo can clean up. With that being said.... getting a lift pump that can give plenty of (gph) and a performance Fuel pin and with an extra turn on the screw should have it belching...... just know that you are robbing yourself of power with this "tune"

 

Like dodgeramit10 said, smoke is mostly over fueling. Added timing does help some, but it's a chasing game. You need to tune it so you only get a puff of smoke that clears up quickly as the turbo spools. All of your components and adjustment need to balance out in order to get the best power and economy out of your engine.

 

I am all for efficiency, all I meant before was with the stock injectors all I was getting was that puff and now I'm not getting anything really. Also as an update, I just towed my racecar 130km and there is a rather steep long grade on the way to the track so pedal to the floor 25 pounds of boost and I barely broke 1000 degrees on the pyro where as before 25 pounds would get me to just under 1200, leads me to believe I'm not getting full fuel... Injector pump issue?

 

if the only thing you have changed was the injectors you probably had bigger injectors than stock and put smaller ones in there. ide put the -stockers- back in there and see if the performance comes back.

 

pop off pressures usually get raised with bigger injectors. if you have not compensated your timing by advancing it that may also be a solution.