I installed my 60mm compressor wheel and housing from Gillett last week and a 4" intake and BHAF. I didn't do any tuning right away as I wanted to see the results from just those mods. My EGT's were a hair lower throughout the range but not much to write about. The only thing I noticed is it seemed to cool down/idle cooler. Max boost was about the same, a bit more lag, but you could feel the improvement when it started making boost.

Now came some tuning. I went a turn and a half more on the fuel screw. It wanted to runaway so I backed it off a half turn. My boost is now up from 28 to 35psi. The really cool thing, is that the EGT's have stayed exactly where they were when it was tuned milder. I can feel a definite improvement over what I had before. My EGT's would quickly head toward the death zone when I had it tuned similar with the stock turbo. Now It has a hard time breaking 1200 deg unloaded.

Now my question. I know my pump is not maxed. I am about two turns in on the fuel screw, pin is about stockish and the star wheel turned in a bit. The next half turn on the fuel screw caused it to runaway. Is there something else, like fuel pin or starwheel, that I should be tuning that will deliver fuel differently to where it won't want to runaway? I used to run it at two and a half turns, but the starwheel wasn't messed with. I understand how the fuel pin causes runaway, but I haven't learned how the rest of the pump works in the case of runaway.

-Steve

 

If the pump is at runaway, then that's it for big power gains for free Starwheel/smoke screw andjustments are pretty much driveability/personal taste things. Not any big power to be had there. MAke sure your fuel cone actually has the deepest part facing the radiator. You can do some grinding on it if you don't mind permanently altering it. 35psi is a good place to be with your setup. Are you running the 18.5 exhaust housing? Have you maximized throttle travel? How about timing? My truck likes a ton of timing...

 

My fuel cone is about opposite of the deepest setting. I played with it quite a bit when I had the stock compressor and didn't gain much other than smoke and temperatures so I hadn't played with it yet. I will give that a try. I am running the stock 18.5 housing. I haven't checked throttle travel since I adjusted it this time. Good idea, I will do that. Timing is something I am unsure about. I haven't personally touched it.

The pump was brand new and installed by highly knowledgeable Cummins mechanic just before I bought this truck from my friend. The Cummins guy told him he would set it up for reliability and mileage so I don't know where it is. It starts like a champ in the winter so maybe it isn't advanced any. I will have to look back into that some more. Time to get the snap-on wrench on it's way.

Thanks a lot.

-Steve

 

If the fuel cone has the shallow profile towards the radiator, then you're in for some fun when you rotate it. That profile has a direct relation to control collar travel as boost comes up. With your old compressor, you weren't moving enough air to burn the extra fuel, so all you got was smoke and heat. Now with the extra air, you'll be able to take advantage of that fuel and make more power with temps that are still reasonable. On a mild (sub 350rwhp) 12valve, anything more than a steady grey haze at full boogie is just a waste.

Sounds like the timing is at or near stock. Not a bad place to be while you dial other things in.

 

Okay thanks I bunch. I will look into those things tonight and report back.

I also have to say that the how-to's from this site made the install and the intake very easy. Thanks guys.

 

I've done many of the mods in the sticky many times and I still refer back to the writeups often--very good info to be found there

 

Do you have a 3200rpm spring in the IP?

If not, you'll enjoy having that in place.

 

I have one sitting at home, but haven't gotten to installing it yet. I am really thinking I need to.

-Steve

 

Just for fun, I rotated the fuel pin back around to the most extreme setting. At the same time, I backed out the full fuel screw a full turn. Max boost went from 35 to 40 psi, and it became much more drivable. Also, it has a bit less haze at lower RPM's. I can now get too hot with no load if I would like. It is a lot of fun though. I really need to get the 4" exhaust if I am going to be towing much.

 

Consider getting a 14cfm n/w housing. Spool up and milage will be even greater.