So who has bumped the power on a 6CTA cummins

[YOUNG GUN]

Maybe he was just being extra cautious...
What do you think would be safe continuous boost, and how about EGT's?
I'm just learning as I go

 

[nevrenufhp]

Before the turbo, 1350* sustained, or 1300 for conservative side. Upping just the fuel on these pumps should NOT make it run that high, unless there's a problem(air restriction).
He was telling you safe and cautious, at 30 pounds. It can take 30 pounds at 100% duty cycle. I would put the actual limits the same as a 5.9(6BT), with 45 pounds of boost on the stock head bolts.

 

[YOUNG GUN]

Does a 200-300F drop pre turbo to post turbo sound about right?
I've got my probe installed about 1.5" after the turbo where they recommended.

Also, to do the real fuel adjustment you've gotta have a special socket inside a socket tool, I can post a couple pics of what I made if that's helpful.

 

[nevrenufhp]

Yes, that's about right.
I remember seeing the nuts up inside the AFC. Thought of trying to make my own tool also. Yes, what does your home brew tool look like? I may just buy the real one, and rent it out.

 

[YOUNG GUN]

I've heard the tool costs about $200, but I could be wrong.
I just took a 14mm & a 10mm deep socket and turned down the OD on the 10mm and bored out the ID on the 14mm; I'll either use vise grips for the 14mm or tack weld a tee handle on it, and use a regular 3/8" drive short extension with a ratchet on the 10mm.
It only took me about 10 minutes on the lathe and $14.00 in the 2 Armstrong sockets.

 

[chp925]

hey nevrenufhp
i have a 90 m923 that is a dog off the line where would be the best place to start with adjustments.
thank you
rob

 

[nevrenufhp]

A dog off the line, back out the screw on top a few (about 5)turns, plus the full fuel that Young Gun described a few posts back.

 

[chp925]

thank you for the fast reply well i have work to do tomorrow i'll let you know how it goes
thank you
rob

 

[nevrenufhp]

One note on the full fuel nuts; It wasn't mentioned yet, but both nuts will need to be backed out, once you break them loose. They are on a stud, and are basically jammed together to make the rack stop, and limiting the fuel. I'm 99.8% sure that if you back them all the way to the last threads, it still wont get hot enuf to hurt it.

 

[insas]

So I tightened the gov springs 4 clicks and backed out the top fuel screw 3.5 revs.... my truck now idles at 1070 rpm instead of 500... is that about what the rest of you are getting?

Thanks!

 

[TurboMustang370]

So I tightened the gov springs 4 clicks (720deg) and backed out the top fuel screw 3.5 revs.... my truck now idles at 1070 rpm instead of 500... is that about what the rest of you are getting?

Thanks!

I would not be running the truck like that. Something is not right.

 

[Bolkbich]

Its fine to run the truck like that. I didnt like the high idle so i only went 2 click on the gov springs.... idles around 725 or so. When the idle is too high it slams into gear then it tries to hold the high idle and pushes the truck too much. Slamming into reverse on a m939 makes me worry about the T-case.

 

[nevrenufhp]

It's normal for it to raise the idle rpm after tightening the gov springs. Adjusting the idle is as simple as a bolt with a jamb nut. Cycle the lever with the engine off, and you will see it. Idling at 500 is not good either, it should be at 650 in gear. Go for the 4 clicks, and back off the idle adjustment.
Each click is a quarter turn. You would be at 360* on each nut.

 

[dochowz]

I'm rolling a 90 A2...looks like this friday will be tinker day!

 

[YOUNG GUN]

UPDATE:
Finally did the "real" fuel adjustment... Holy crap!
I backed it out about 2.5 turns and adjusted the "no air" screw, and this thing screams!
I'm taking it easy on her and watching all the important gauges, but it's quite impressive compared to stock.
Hills that I used to get passed on constantly by semi trucks are no longer, they're left in my dust/smoke

Definitely need to get more air into her though, anyone have any good air intake mods?

Also, the inner socket must be modified to fit the "special" outer jamb nut on the fuel adjustment... see attached pics.

 

[nevrenufhp]

All that, and no pump pix? We like the action shots.

 

[Sambor]

How about you or neverenuf posting some pics of each adjustment on the 8.3 so us dummies can follow along. With all the tubes/pipes/linkages it might be useful. I turned up my fuel under the plug on top of the pump and it made a BIG difference. Haven't done the gov yet. According to the tach, it is set at about 2-2100. What would be a good safe max for it? I don't have a pyro or boost gage installed yet.

John R Dunn
Weatherford, Texas M931A2

 

[Brad Nitzke]

I would pipe in a Charged Air Cooler. the way it is now that air gets really hot. Cold air means more air. Just saying.

 

[Suprman]

The governor is set stock at 2100 rpms. It is my understanding that the 8.3 motor can safely spin well into the 3k's but the drivetrain wont like it. I went one click on my gov springs it gave me another 100 or so rpms without any idle issues.
Will

 

[Moto2four]

Does the 8.3 have a waste gate? If it does, I can't find it. I've looked all over for it. The only line I see is the oil feed line.