How To: Build your own 4.0L turbo Cummins (Beware...170+ pics)

Re: Re: How To: Build your own 4.0L turbo Cummins (Beware...170+ pics)

Boostwerks.com said:
Looks great! Fantastic job on the dump tube. It starts to get cramped in there really quick!

I'm using the factory 99 XJ bracket. I'll snap some pics for you later tonight. What model/year bracket is yours?
Click to expand...

Thanks Cobra & Boost. Yeah, it is tight, but it works! :D gonna look into some heat shielding, as well.

I think it is a YJ 4.0. This thing is going on so long, i am forgetting who & where i got parts from. :screwy:

Some pics will be great, thanks!
 
The dyno issues strike me as little odd. When I ran a mobile chassis dyno for Livernois Motorsports I must have dyno'd a hundred cars or more, and I simply put the shifters in "3" and slowly ran the vehicles up and started the pull at around 2500 to 3250 rpm to prevent a down shift. If I hit the gas and button to start the recording and the vehicle downshifted, I simply cursed at her, stopped the recording, went up a little higher when she shifted back into 3rd, and tried again until it took. This was just for acquiring peak torque and power numbers though, not any actual tuning. That said, I also just dyno'd my Jeep on the 14th and just posted a thread in Street Performance about it. I had no issues pulling the Jeepra in 3rd from ~2800RPM up to a little over 6k.

http://www.naxja.org/forum/showthread.php?t=1096616

Am I missing something?
 
child9 said:
Am I missing something?
Click to expand...

The complete torque curve and possibly peak tq below 3000 rpm.

If you lock it in 2nd gear, you can then do a dyno pull from 1000rpm to 5000 without it trying to downshift.
 
CobraMarty said:
The complete torque curve and possibly peak tq below 3000 rpm.
Click to expand...

Your text comes off a little smarmy there, Cobra. Easy.

You don't need a "complete" torque curve.

Does anyone have a dyno graph covering ANY range of rpm values? If not, then EVERYTHING falls under the "possibly" category, cause no one actually knows. We can't trust what we feel when we drive...that is speculation and almost everyone over-estimates what they have.

A quick google image search of a wide variety of supercharged vehicle dyno sheets shows torque peaks around ~4600 rpm and up. I can always be wrong (and often am, just ask my wife), but I haven't seen one bit of data showing a supercharged gasoline engine making peak anything below 3000 rpm.

As is illustrated in the graphs I recently posted, I had no problem starting my pulls at about 2300 to 2400 rpm.
 
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? IDK what horse you're riding on, but...:dunno: :cheers:

Your turbo Supra 24 valve 3L is not a low rpm/torque monster like the Jeep 4.0L, - stock, stroked or supercharged. For you with a peak tq at 4000-4500, starting at 2800-3000rpm is fine. On my S/C 4.0L, on the dyno starting at 2800-3000, the torque curve was on the downward slope, past the peak tq. My point is that on a twin screw with 7 pounds boost off idle, I want to see the whole/complete torque curve of the engine and where it peaks, like from 1000-5000rpm. My peak torque is below 2800 rpm. I am sure stroker 4.6L's also make peak tq below 2800-3000rpm. Jeeps don't make their peak tq at 4600 rpm's like most other supercharged vehicle dyno sheets.

To clarify, as for a 'complete torque curve', it means that I would want to see a least 1000 rpm before the peak torque and after until redline. For you a 2800-6000rpm dyno pull shows that just fine. For me a 2800-5000rpm dyno pull doesn't show where the peak torque is located and only shows the trailing/falling side of the torque curve. That is the dyno issue with dynoing a 4.0L with auto trans is the downshifting at 2800 rpm when flooring it.

We're talking about 2 completely different engines and completely different shaped torque curves.
 
How To: Build your own 4.0L turbo Cummins...

Threads going to shat.

!.:D.!
Sorry boostwerks :(
 
No worries Cobra, I wasn't comparing my engine to yours...merely the process of pulling an auto on a dyno and how that works regardless of engine. I was also expressing confusion about why you think your peak torque is below 3000 rpm. So far you say it is. So far I say no. Only one way to know for sure. :) Do you have a dyno sheet?

I apologize if anyone thought I was on a high horse or am rabble-rousing. That was not my intent, so let's please move on to dyno sheets, ok?

-Chad
 
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Peaks are for bench racers.

For a work horse or wheeling rig it's all about the shape of the curve.

If the curve is relatively flat from ~800 RPM through 3000 rpm it generates a chubby.

2¢
 
I do have dyno sheets, both stock and with s/c. I am telling you what they show. It will take some digging. I'll find them for you.
 
Some updates!

In the process of swapping tranny's I noticed several of the bearings in my transfer case had some play, but didn't have time to do a rebuild at the time. I purchased a full rebuild kit as well as a 6 pinion planetary set and wide chain. Upon tear down I noticed the oil pickup screen was clogged with little aluminum shards. Although there was no obvious signs of wear, the clogged pickup surely led to the bearing failure. I also picked up a novak shifter to replace the factory joke.

001.jpg


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006.jpg


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Also in the process of the tranny swap, I noticed the hard way how much of a pain in the ass having a 1 piece cross member and long arm setup is when it comes time to do any drivetrain work. To remedy this I spent a couple hours drawing up a removable center section to modify my current cross member. I haven't finished this yet, but should have more to show soon.

TransCrossmemberAssem.jpg


2013-03-28170412.jpg


In other news, my rear RP is F'kD! I made the mistake of going with used 4.56 gears instead of saving up for a new set. They have always been loud, but recently started making a horrible metallic "clang" noise when rotating the pinion back and forth. I'm also pulling the rear Detroit locker and throwing an ARB in it's place while I'm at it. I'll be broke for a while lol!
 
Alexia said:
Bump for what? :P

So, what do you think of putting a turbocharger on a 4.7L stroker with a 10:1 static compression ratio? I think a small turbocharger limited to 6 to 8 PSI of boost would work well.
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There were a couple members looking for the thread.

That sounds good except for the 10:1 compression. The tuning will need to be spot on, and it will require a higher octane to keep from detonating. I highly recommend keeping the compression low to give you more flexibility in tuning. The last thing you want is to find out that it needs more than premium pump gas to keep from pinging.

Don't get me wrong. I love high compression turbo setups, but the poor flowing, all iron 4.0 isn't the best motor for it.
 
Boostwerks.com said:
There were a couple members looking for the thread.

That sounds good except for the 10:1 compression. The tuning will need to be spot on, and it will require a higher octane to keep from detonating. I highly recommend keeping the compression low to give you more flexibility in tuning. The last thing you want is to find out that it needs more than premium pump gas to keep from pinging.

Don't get me wrong. I love high compression turbo setups, but the poor flowing, all iron 4.0 isn't the best motor for it.
Click to expand...

Mmm, yeah. Just considering turbocharging and my compression ratio in the stroker is right about 10:1. Interestingly it SEEMS to run fine on 87 octane, but I run 93 octane on it at the moment out of caution. Assuming the 87 octane bit is not a fluke I could get away with a high compression turbocharged setup.
 
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