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8.3 turbo discussion

dmetalmiki

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We have a pump, injectors, air filter and intercooler threads so let's talk turbos! First question is what size is the stock turbo?

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(I have wheels..what size are the stock wheels?)..(turbos..) for WHICH vehicle. Just asking.
 

Csm Davis

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Okay it is a HX40 but what size A/R housing is that, and what size compressor wheel is that, what size impeller is on those?
(I have wheels..what size are the stock wheels?)..(turbos..) for WHICH vehicle. Just asking.
The vehicle is the 939A2 with the 8.3L Cummins as in the title but what other military vehicles use that engine?

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patracy

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HX40's are inherently weak due to their shafts. (Same as a HX35 only with larger wheels)
 

patracy

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Okay really want to talk about those stock dimensions if anyone has them.

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There's several flavors:
6 blade = 56/86 or 60/86
7 blade = 60/86
8 blade = 58/83 or 60/83

7 blades with the extended tip are the "best" 40 out there. If there's such a thing.
 

patracy

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That's determined by the turbine housing. If you're hoping for performance from a 40 on a 8.3 you're starting off on the wrong foot. People put 40s on 5.9 Cummins. But more often end up swapping to a better turbo.

What is your power goal?
 

Csm Davis

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That's determined by the turbine housing. If you're hoping for performance from a 40 on a 8.3 you're starting off on the wrong foot. People put 40s on 5.9 Cummins. But more often end up swapping to a better turbo.

What is your power goal?
Need to find out exactly what we have to start with before we start throwing parts at it most turbos that come stock on an engine can put out more air than that engine can use. As for my power I am looking for I am going to be looking at what the highest factory settings were and see about getting something close to that, pretty sure 375-400 will be max but I will be upgrading lots of parts not just one.

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Csm Davis

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There's several flavors:
6 blade = 56/86 or 60/86
7 blade = 60/86
8 blade = 58/83 or 60/83

7 blades with the extended tip are the "best" 40 out there. If there's such a thing.
Also as you have shown here there are many different HX40 and unlike Garrett finding out the A/R of the compressor housing is a pain. And I see many folks not just you knock the HX40 as not being a good turbo but I don't see lots of people who have had problems with them, but do see lots of upgrades that are available to increase output and reliability of a few issues. I am not trying to argue but do want the facts for everyone to be able to make the call as to what they might want to upgrade or not. A small up grade if we have it on ours would be to trick the waste gate by changing how much pressure it sees and that only cost about 20 bucks, or add a HX50 as a compound setup and blow the heads off for a 1000 bucks. I personally would like to try both but don't want to do it without the starting point.

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patracy

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Need to find out exactly what we have to start with before we start throwing parts at it most turbos that come stock on an engine can put out more air than that engine can use. As for my power I am looking for I am going to be looking at what the highest factory settings were and see about getting something close to that, pretty sure 375-400 will be max but I will be upgrading lots of parts not just one.

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You can of course push a turbo with more fueling to achieve more power. But a 40 isn't the best sizing for a 8.3 out of the box. It has a T4 foot. The problem you're going to run into trying to push the 40 is EGTs. Especially under load. Cummins specs the HX40 to 280hp, which is conservative. But real world you're looking at about 300hp tops before drive pressure and outlet temps are harming you instead of helping. (The function of a turbo is also it's downfall. It becomes a restriction on the exhaust side, and once it exceeds it's map the compressed air temp is so high, it negates any gain) Now something like a HX50 or HX55 is spec'd up to 370hp conservatively. This would get you closer to your goal.

I know this is a little off topic, but you want 375-400hp. What's your plans for the 654 Allison? They're only rated to 300hp/800ft-lbs.
 

patracy

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Also as you have shown here there are many different HX40 and unlike Garrett finding out the A/R of the compressor housing is a pain. And I see many folks not just you knock the HX40 as not being a good turbo but I don't see lots of people who have had problems with them, but do see lots of upgrades that are available to increase output and reliability of a few issues. I am not trying to argue but do want the facts for everyone to be able to make the call as to what they might want to upgrade or not. A small up grade if we have it on ours would be to trick the waste gate by changing how much pressure it sees and that only cost about 20 bucks, or add a HX50 as a compound setup and blow the heads off for a 1000 bucks. I personally would like to try both but don't want to do it without the starting point.

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There's a lot of 40 failures out there. I've stayed away from the 40 intentionally due to their shared HX35 shaft size. You could buy a "boost elbow" to increase boost pressure. This simply reduces the pressure sent to the wastegate allowing for higher boost. That'll help squeeze a little more out of the 40. (But again you're talking 300 tops)

As for compounds/twins. A HX40/HX50 compound would be a terrible setup. (Too close in size) A compounded turbo setup needs the secondary to be massive. You'd be better served with a HX40 (if you insist on keeping it) and something like a HT3B or HT4B under it. A HX40/HT3B could support 600hp.

And on a side note, studs are a VERY good investment with the cummins when it comes to playing with boost.
 

Csm Davis

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You can of course push a turbo with more fueling to achieve more power. But a 40 isn't the best sizing for a 8.3 out of the box. It has a T4 foot. The problem you're going to run into trying to push the 40 is EGTs. Especially under load. Cummins specs the HX40 to 280hp, which is conservative. But real world you're looking at about 300hp tops before drive pressure and outlet temps are harming you instead of helping. (The function of a turbo is also it's downfall. It becomes a restriction on the exhaust side, and once it exceeds it's map the compressed air temp is so high, it negates any gain) Now something like a HX50 or HX55 is spec'd up to 370hp conservatively. This would get you closer to your goal.
And this is the stuff I am after but I am one of these bullet heads that wants to see it all and I bet there are others like me.

I know this is a little off topic, but you want 375-400hp. What's your plans for the 654 Allison? They're only rated to 300hp/800ft-lbs.
Run it until I rip it in half then upgrade unless you want to give me a 7speed Allison. By the way think 50 year old CSM driving his own truck not 20 year old private Beetle Bailey driving Army owned truck.



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Last edited:

Csm Davis

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HX40's are inherently weak due to their shafts. (Same as a HX35 only with larger wheels)
Would the problem be with guys jacking with them or in stock usage?
I haven't noticed a lot of guys fussing about the turbos failing on the 8.3. The shaft size shouldn't be a big problem on a big slow diesel military truck unlike the little hotrod dodge idiots doing burnouts and tractor pulls.

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