So who has bumped the power on a 6CTA cummins

racing4funn

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I want to do some of these eazy mods on my 93 tractor. I've had some heavy modded dodges in the past and I always ran a high pressure fuel gauge, a EGT gauge, and a boost gauge. That way when I make changes I can verify what's going on. A diesel lives and dies by the EGTand it goes up with the fuel going up and I might be loaded up to 35k pounds behind the tractor.

Are any of yall running gauges? Or yall using smoke or feel? Any good place to unstall a high pressure gauge and what would the high side of the pressure stock?
 

Mother Deuce

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Back in the days of OO dump trucking. We were all pump artists... at least we thought so. There are pressure issues to deal with. We were running them hot and inefficient. As an extreme example a friend of mine running a 400 Cummins had a 00 button and about 8 or nine throttle shims in the pump. The truck was a bullet for a while. It was running raw fuel up the stack. The pressures were high and the head bolts would stretch allowing gasket failure. I agree that they will take some additional fuel without damage. However the gauge suggestion would be wise. At the very least manifold pressure and a pyrometer. Have fun!
 

YOUNG GUN

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Has anyone actually posted results on turning up the fuel on the 6CTA 8.3 Cummins in the A2?
If so, I haven't found it... Which leads me to...

I'm installing digital pyrometer and boost gauges today, then I'm going to turn it up and see what I can get out of my A2.
I've done a lot of talking with my local Cummins shop and another local shop that rebuilds the pumps, so I feel like I've done my due diligence as far as research goes, does and don'ts etc...
My truck has the MW pump (not sure if all of them do or not).
I'll post results when I'm done.
 

Motiracer38

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Please do post results. I have yet to find a step-by-step guide that yields a respectable amount of power gain. Most of the 8.3L information is on P-pumps and very little is on MW pumps like all A2s have. I'm getting sick of pulling 35mph up the hill to my house.
 

YOUNG GUN

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Please do post results. I have yet to find a step-by-step guide that yields a respectable amount of power gain. Most of the 8.3L information is on P-pumps and very little is on MW pumps like all A2s have. I'm getting sick of pulling 35mph up the hill to my house.
I've put together a step-by-step guide to do this, so we'll see how it works out...
Unfortunately, I don't have a dyno to give real HP number increases, however I do have this one darn hill that I know if I hit the bottom @ 60mph, I'm only doing 40mph when I reach the top... This will be my test :lol:

I'll post results when complete.
 

nevrenufhp

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I'm going to be doing one this weekend, and putting in gov springs too. I'll try to get pix and video of results. Yes, also an MW pump. He wants his 5T to go over the Grapevine at better than 35mph.

You guys know you can subscribe to a thread without making a post that says 'subscribed', right? A little "subscribe to this thread" tab pops down from the top of this page, from the "thread tools". Right under the page 5 of 5 thing.
 
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nevrenufhp

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Installed 3k GSK, timing advanced a few degrees, throttle stop adjusted, fuel screw on top adjusted. First video shows the strangeness of the MW-pump. After adjusting the fuel screw on top, it will go into a heavy fueling mode(35 pounds of boost here and lots of power), until it hits around 2200rpm. Max effective rpm is up to 2600 after the GSK, up from 2300 before. There is a full fuel adjustment, but you have to take off the back half of the pump.
http://www.youtube.com/watch?v=XtJWO9Zevec
http://www.youtube.com/watch?v=3n6iTwoxkRo



 
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nevrenufhp

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It's not mine. The guys doing the truck are members here, but dont have the time to post the build. I saw the photo album, and there are a bunch of build pix. Takes money to spend money on a truck like this. There will be a build thread on it, I was assured. Should go over 35mph up the Grapevine now.
 

Iggy913

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The fuel pump on the early 90s Cummins CTA 8.3 is an MW pump. It's the same fuel pump as what's used in later CTA 8.3s as well, the difference is how the fuel pump is governed. The MW pump uses a governer that can be adjusted with a few different screws to increase fuel flow and rack travel. The later CTAs share the fuel plate style governer like the 94-98 12 valve 5.9 Dodge/Cummins motors. To my knowledge there are no 939A2s that got the fuel plate style governer, only the MW style.

There are no aftermarket companies that I'm aware of offering power increases for the MW governed trucks, and it's because you have to physically adjust the pump to make it provide more fuel, there is nothing to sell you.

Companies like TST and others, or yourself if your so inclined, offer fuel plates that have different profiles ground into them which allow more fuel flow. The TST "Power Kit" for a fuel plate governed truck is simply a fuel plate with one of several profiles ground into it and a brass elbow that screws in the front of the turbocharger. The elbow has a set screw in it and simply restricts the amount of air between the turbo and the wastegate. That restriction basically fools the wastegate into thinking the truck isn't producing as much boost, it remains closed longer which provides more boost to match the increased fuel from the new fuel plate making everything happy.

As nevrenufhp has pointed out you can accomplish the same thing as the "Power Kit" mentioned above in our MW governed trucks by adjusting the fuel flow screw(s) he has shown in the video early on in this thread. If your nervous about adjusting the fuel pump simply keep a log, "fuel screw turned out 8 turns clockwise" close the pump back up and go for a drive. If you like it leave it alone or go back to the way it was before: use your log, open the pump, and turn that same screw back down 8 turns, your back to stock. I would install both boost and pyrometer gauges before attempting to adjust the fuel pump. It's really the only way to see how the changes your making are affecting the engine itself, and not just the seat of your pants feel.

You can also buy a brass elbow with the set screw in it. Again whip out your log book, turn the set screw in a full turn so that your restricting the hole and go out for a drive. With both the boost and pyrometer gauges you could accurately see how the changes you were making affected the truck. You will need more boost to help keep the increased fuel flow from the "adjusted" fuel pump happy. I'm not going to quote exact figures here, maybe someone with more experience on these motors will comment on what your looking for in terms of maximum sustained EGTs, maximum EGT spikes, and maximum boost.
 

nevrenufhp

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I forgot to add the other easy adjustment. This gives a little more travel for the rack overall, and hopefully less smoke. Just pull the tin cover off from the 2 bolts, and back out the screw in the middle(all the way CCW) with a 3mm allen wrench.
 

YOUNG GUN

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View attachment MW FUEL PUMP ADJUSTMENT.pdfI installed my pyrometer and boost gauges, but I've only had time to make the rack adjustment shown on Low buck diesel power website... the actual fuel adjustment is proving to be a real pain; the screws have proved very difficult to get out on the back of the pump that hold on the tin cover.
As it was explained to me; making the adjustment shown on Low Buck, you essentially are making the rack go to full throttle when you stomp the pedal instead of getting there in a regulated manner, so you'll only have that extra fuel for power under that condition (stomping on the pedal from 0-100% very quickly). I made this adjustment and it works as described; It's kind of a half-ass way of doing it IMO, but it does work, it's just a little odd.
Remember that hill I was talking about in my previous post... Cleared the top at 52mph, so it definitely made a difference.
I now have a good idea of the full potential.
She certainly Rolls some Coal when you stomp on it, but the "no air" adjustment screw should help with that.

Stock Max Boost: 23.4 psi / Max Boost achievable with Low Buck Adjustment: 32 psi

Stock Max EGT Post Turbo: 800F / Max post turbo EGT achievable with Low Buck Adjustment: 1,000F

My local Cummins shop said Max sustained EGT post turbo should be 1,000F Max assuming a 200-300F drop from pre turbo temp; I'm sticking with the lower temp of 900F Max sustained for now. They also said max boost for that engine stock should be about 24psi, and advised not to go over 30psi continuous.

I'm far from an expert on diesel engines, so feel free to correct/add to the information I'm posting on this; I'm only going off of what I've been told by people that work on these engine & pumps and that I assume are knowledgeable; Even the "experts" have differing opinions...


BTW: No offence intended to Low Buck's method or info whatsoever, I'm just sharing my experience with that particular adjustment shown assuming I understood it correctly.

I've added the instructions I made up from talking with the pump people, let me know if this looks accurate.
 
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nevrenufhp

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I'm not offended a bit. Glad you found what you did. The stuff I wrote about was stuff I discovered on my own. Seems like there are so few places to get info on an MW. It's a great description of what the top screw does.
Not sure I agree with the guy saying to keep it under 30 pounds.
 
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