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

[jeep-power]

Do you have the ability to post a video or two as well?

I have one of it flexing the suspension on a loading dock, but none of it driving, yet. I'll take video at the dyno, on Thursday.

 

[nectarXJ]

Do you have the ability to post a video or two as well?

X2. :thumbup:

 

[Seiler]

I have one of it flexing the suspension on a loading dock, but none of it driving, yet. I'll take video at the dyno, on Thursday.

Awesome! :thumbup:

 

[jeep-power]

I set this to "public", so everyone should be able to see it.

VIDEO OF DYNO

lower blue lines are from when the engine was naturally aspirated. Double lines are two turbo pulls.

6PSI of boost, 92 octane pump-gas, 4.2 bottom end, '92 4.0 head, stock 4.2 cam, 2000 intake, Megasquirt MS3Pro w/ distributorless coil.

 

[nectarXJ]

Fantastic!! :clap:

 

[nectarXJ]

Hey boostwerks, I'm loving this thread! This has totally got me sold on the idea of a turbo for the XJ.

Anyhow, my 4.0 (2001) just broke a piston skirt and needs a rebuild (or swap). Instead I'm thinking of getting a reman'ed 4.0 from somewhere like Jasper or Golden. I'm very interested in installing a turbo eventually.

If I were to have a reman'ed engine built with performance in mind for a turbo eventually then what sort of engine parts / specs would I be looking for?

Also, I don't intend to hit the drag strip or anything, but if I'm going to fork out $$$ for a reman'ed engine then I might as well do it a bit better than stock (right?). It sounds like 6 to 8 lbs of boost is about the most a stock 4.0 can handle reliably. What would be considered a mild "step up" from what a stock build could handle (10 to 12 lbs)? What would the engine need to be able to handle this (is it worth it)?

What are the pros and cons of increasing the boost on these 4.0 engines? Excluding everything behind the engine (trans, tc, drivelines, rearend, shafts, etc), would this be a lot more maintenance than a stock setup? Could I expect robustness and longevity (once dialed in / tuned / setup right)?

Anyhow, just wondering if it's worth the extra $$$ in the long run or if I should just stay stock. I know the grin factor will go waaaay up and that is a "pro" in my book not a "con".

Thanks

(...by the way awesome welds!)

 

[Seiler]

I set this to "public", so everyone should be able to see it.

VIDEO OF DYNO

lower blue lines are from when the engine was naturally aspirated. Double lines are two turbo pulls.

6PSI of boost, 92 octane pump-gas, 4.2 bottom end, '92 4.0 head, stock 4.2 cam, 2000 intake, Megasquirt MS3Pro w/ distributorless coil.

That video is awesome! Where's the freaking drool smiley when you need it.

Thanks for sharing that!

 

[child9]

Is it me or does the "100.86 HP" seem a bit odd?

 

[Alexia]

Is it me or does the "100.86 HP" seem a bit odd?

A stock 4.2L 258 with a stock 4.2L head made around 150 horsepower at their peak. With drive train loss factored in that number is not far off.

 

[jeep-power]

A stock 4.2L 258 with a stock 4.2L head made around 150 horsepower at their peak. With drive train loss factored in that number is not far off.

for clarification sake- the NA 100HP pull was on the same setup (4.2 w/ a 4.0 head). It was running the factory EFI/computer from a '92 XJ.

 

[Boostwerks.com]

Looks great Peter! Nice flat torque curve as well! Thank you for taking the time to post up your results!

for clarification sake- the NA 100HP pull was on the same setup (4.2 w/ a 4.0 head). It was running the factory EFI/computer from a '92 XJ.

It also looks like it was a low rev pull. Combined with drivetrain loss, that sounds about right.

 

[PseudoSport]

What are you guys running for timing under boost? Does anyone have a picture of their timing map they can share?

 

[SolarBell]

General recommendation is to retard one degree for every pound of boost, but that changes depending on fuel and altitude. The one map I've seen (but don't have to post) maxes out at 8 degrees at 10 pounds of boost.

 

[Truckedup]

Great turbo write up.I have the tools and experience to do this...and want to...except....I have a nice rust free 99 two door....But NY state plugs in the ORB2 vehicles to a computer during the annual state inspection...So I have to find a way to cheat the system. Or sell it and buy a 95 or older that they don't test....I don't want to sell....

 

[rav]

Great turbo write up.I have the tools and experience to do this...and want to...except....I have a nice rust free 99 two door....But NY state plugs in the ORB2 vehicles to a computer during the annual state inspection...So I have to find a way to cheat the system. Or sell it and buy a 95 or older that they don't test....I don't want to sell....

I have the same jeep. So you think a turbo will not pass the emissions inspection?

 

[Truckedup]

I have the same jeep. So you think a turbo will not pass the emissions inspection?

NY isn't testing actual exhaust emissions, just the stored computer info...so

I think it will if the engine isn't modified (other than strength upgrades) and the boost is maybe 5 PSI?
I'm thinking the extra fuel used to keep up with the turbo airflow should set off fault codes?
And devices to retard the timing during high boost have to intergratedinto the engine management somehow...This should trigger more codes.
I know fault codes can be cleared with a scanner tool... but...?

 

[SolarBell]

Done correctly, an FIC with the turbo should handle the extra fuel and air, and have the ECU not throw any codes. The FIC is designed to intercept the signals and tell the ECU what it thinks it should see even if the engine is doing something different. For the ignition retard, the FIC does nothing more than add a delay to the crank / cam signals so that the ECU triggers when it thinks it should. Same with the injectors - the FIC will pulse the injectors longer when the ECU triggers them, and the ECU thinks nothing of it.

 

[Truckedup]

Done correctly, an FIC with the turbo should handle the extra fuel and air, and have the ECU not throw any codes. The FIC is designed to intercept the signals and tell the ECU what it thinks it should see even if the engine is doing something different. For the ignition retard, the FIC does nothing more than add a delay to the crank / cam signals so that the ECU triggers when it thinks it should. Same with the injectors - the FIC will pulse the injectors longer when the ECU triggers them, and the ECU thinks nothing of it.

Thanks, FIC is? And can be bought? I'm familiar with basic car electronics but not the fine details.

EDIT, I found the FIC info in this tread,yeah reading helps lol

 

[blkbird95]

For those with 96+ emissions, NYS inspection will be fine as long as you are running the stock computer, there are no codes and your readiness monitors are complete. I ran my 98 XJ 4.0 turbo through since 2008. I was using the Aeromotive DFMU for fuel and Crane ignition for timing retard. It runs like stock until you get into boost. There are better methods for the fuel and timing now.

Brad

 

[jeep-power]

What are you guys running for timing under boost? Does anyone have a picture of their timing map they can share?

x2-- does anyone have ANY ignition map for a 4.0 or 4.2? :helpme:

Boost-- is that manifold gasket the Victor MS16315?