5.9b or 6bt tune and performance

[bansil]

The last tidbit perked my eyebrow....spill the beans

I am not planning mods until next year when I upgrade the tranny

[chev49]

i dont have the link in my mind right now, but there is a website for modified diesel engines, and the 5.9 is discussed a lot. injection pump mod for one...

[nevrenufhp]

Yep, it's super easy to modify. Slide the fuel plate forward, tighten or replace the governor springs, and have a shop advance the timing a little. Turns it into a monster. I just did the fuel plate & tightened gov springs about a month ago to an F600. Wow, that thing moves! It's certainly overpowering the AT545 trans though. I instructed to the driver to let off the pedal during shifts.

[bansil]

Check out
http://www.cumminsforum.com/forum/

[caseythenose]

Keep in mind that playing with the gov springs will not matter with an auto behind it.
The plate will make a huge difference, but you can't top every hill at 45-50PSI out of the turbo all day long and expect your headgasket to last long.
If you are looking for the safest mod for a 12 valve, I would suggest a very modest plate, allowing it to fuel a bit heavier without sending 50PSI down its throat.
Some of the dump truck guys in canada were using propane injection with a switch under the pedal. When floored, it would feed the engine propane at a point where it cooled the charge (and of course, added fuel) with great results. (I have not seen how they were set up, but they claimed this allowed the autos to remain in high gear for the long climbs when they juuuuuuust by a hair would lose lock previously. The thing that perked my ears was the EGT control doing it with the propane. From what they said, there was zero change in EGT.)

What trans do you have behind your engine?

[nevrenufhp]

Yes, the gov springs will make a difference with an auto. It likely wont on an otherwise stock truck. You need more fuel and timing to get to use the extra rpm. Every little bit helps, and it actually does help.

[caseythenose]

Originally Posted by nevrenufhp

Yes, the gov springs will make a difference with an auto. It likely wont on an otherwise stock truck. You need more fuel and timing to get to use the extra rpm. Every little bit helps, and it actually does help.

Spring kits/adjustment makes the engine fuel out to a higher RPM range. How does that help you when your trans is in the next gear 150 RPM before the springs would make any difference?

[nevrenufhp]

It fuels harder to the point of shifting, and you can carry each gear a couple more mph. If it shifts at 2400, and the engine can rev to 3100, it needs a kickdown cable adjustment. It makes a difference is all I'm trying to say. Test it out, and you'll see it get up to 40mph faster than before.

[caseythenose]

Originally Posted by nevrenufhp

It fuels harder to the point of shifting, and you can carry each gear a couple more mph. If it shifts at 2400, and the engine can rev to 3100, it needs a kickdown cable adjustment. It makes a difference is all I'm trying to say. Test it out, and you'll see it get up to 40mph faster than before.

We did with the 12 valve 4 and 6B's in the bread fleet.

What we found was...unless you adjusted the trans (and the procedure I am not familiar with, it was done by the shop we used for Allison repairs) it made no appreciable difference. When the transmission was adjusted to shift at a higher point, as you suggest, it made the shifts kind of violent and very unpleasant in everyday driving. It was as if the "kickdown cable" had become too sensitive. The shop was never able to find a happy medium.

Perhaps on a 1/4 mile run, the truck would get to the finish faster if you adjusted the trans to shift further up in RPMs. In daily driving, the guys that did the test were happiest with them shifting at the normal points, which made messing with the springs unnecessary.