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

[Boostwerks.com]

... Ok it has nothing to do with Cummins, but it sure does pull like one.

With over four years in the making the Boostwerks XJ is finally turbo’d! I’ve been testing the rig for a little over a month now and have only good things to say. I’m running about 8lbs of boost which has been more than enough power to pull on my buddies boxer powered Subaru legacy. Not to mention that I’m on 33 mud terrains and still have the 3.55 factory gears. I’ve been working on this project for a long time and have put more time and thought into it than any project that I’ve done to date. I’ve compiled this thread for your viewing pleasure with over 170 pictures! The pictures detail the entire build process, and include all the parts I’ve used in the setup. I hope that this build thread will disprove some of you doubters as well as inspire some to tackle your own boosted 4.0L project.

Background:
The road has been long and paved with many unforeseeable challenges, but the results have been well worth the effort. As some of you know, I had first tried a manifold based turbo setup for a customer several years ago, but the fitment wasn’t the greatest. Next I developed a remote mount turbo setup that mounted the turbo right behind the transfer case, but like the first setup, this also proved to have fitment issues and the amount of work involved to make it work simply wasn’t worth the cost. After dealing with these problematic first two setups, I decided to revisit the tried and true manifold based setup. With several simple changes to the manifold’s design, I was able to eliminate the fitment issues to comfortably fit a turbo capable of over 500whp, while at the same time keep my AC!

I am a huge stickler for reliability, which is one reason why this setup has taken so long to develop. IMO it’s not worth building something that you won’t feel comfortable driving high up on the mountain or half way across the country. I decided it was worth the extra cost for high quality components and placing them where they would work in harmony with everything else. I hope this build sheds some light that a fairly inexpensive, yet reliable turbo setup is indeed possible for the 4.0L XJ.
Well I think that’s enough introduction and overview. Let’s get on with the build!

Parts list and pictures:
- (Freebie) Boostwerks Manifold
- $650 Borg Warner 57 trim T3/T4 with P trim turbine
- $210 Tial 38mm external WG
- $220 Tial 50mm BOV
- $300 3” Down Pipe and full 3” exhaust with Dynomax ultraflo mufflers
- $40 2” stainless charge piping
- $150 Small Water to air IC
- $100 Bosch IC water pump
- $75 B&M 10x11 Heat exchanger
- $350 AEM FIC 1913 piggy back controller
- $155 AEM ECU patch harness
- $275 40lb Ford Motorsports injectors
- $210 AEM UEGO wideband
- $30 -4AN oil feed line
- $30 -10AN oil drain line
- $40 Various silicon couplers
- $30 Various fittings for oil and water lines
- $70 MSD SS coil
- $30 1 step colder NGK V power plugs
- $50 AEM dryflow filter
- $45 Felpro manifold and oil pan gaskets
- $15 3” flexible silicon intake tube
- $50 Heat wrap for the down pipe and fuel lines
- $50 DEI gold foil
- $50 Boost Gauge and pod
- $20 Misc install goods (copper spray, acetone, antiseize…etc)

Basic parts required: $2120
+
Extras/hop-ups: $1290
= Rough total: $3,410

*Keep in mind this is the price for all new parts. A good turbo system can be built for considerably less on a budget by sourcing good used parts.*

 

[Boostwerks.com]

 

[Boostwerks.com]

Now for the build…

Step 1. Engine Management
- The engine management was probably the biggest hurdle for me and this project simply due to the available options out there. I needed to maintain the factory OBD2 reliability, while also being able to precisely tune the engine under boost. I had looked at several different options out there including the split-second FTC1, Unichip, and the AEM FIC. After a lot of research I had decided to go with the AEM FIC controller, primarily because they had developed a unit to work specifically with Chrysler/dodge/jeep ECUs. I also liked how it has several different ways of outputting and interpreting sensor signals. When it came down to it, the AEM simply has a better capability to $ ratio than any other piggy back options out there.
- AEM has also produced a very nice ECU patch harness which makes wiring the FIC as easy as it could possibly be. I highly recommend one for anyone who is looking to patch into the factory harness.
- The install was very easy and painless. I installed the system first to ensure that it was wired and functioning properly.

Step 2: Manifold Fabrication
Details:
Built from schedule 40 304 stainless which is THICK! I wanted a manifold that was virtually bullet proof since it needs to withstand a lot of daily driving and very high heat. I also used laser cut ½”
mild steel head flanges and CNC machined turbine and wastegate flanges. The manifold was entirely tig welded and back purged for 100% penetration and contamination free welds. Once welded I had the head flanges milled flat to properly seal the manifold once torqued to the head. This will also relieve any built in stress due to the welding.
Like previously mentioned, the turbo manifold project has been a huge challenge for me. Obviously since AMC decided to put the intake manifold on the same side as the exhaust greatly complicates a manifold based turbo system. At first it may seem like there is plenty of room for a turbo, but once components are placed and reinstalled this room quickly disappears. However, the final design that I ended up with I think is the placement possible. The turbo is tucked up tightly to the block, which gets it as far away from the chassis as possible. It also puts less of a strain on the manifold by reducing the leverage the turbo has on the manifold. The turbo is as far back as possible, yet will easily accommodate a 3” down pipe.
The other variable for the manifold is where to put the external wastegate. An internal wastegate is possible depending on the turbo. However, the Borg Warner turbo that I wanted to use with this setup is an external gate turbo only. I also prefer to use an external wastegate due to its ability to control boost a lot more efficiently compared to an internal. The problem however, is they take up a lot of room. Not only do you need to account for the room of the wastegate itself, you need to account for where the dump tube will be routed. I ended up placing the wastegate on the other end of the log which ended up being a perfect location. It takes up wasted space behind the water pump/power steering pump, and allows room for a re-circulated dump tube, or an easier open atmosphere dump tube. Since this is a daily driven rig, I wanted the quiet operation of a re-circulated dump not to mention the legality of having it a closed system.

 

[Boostwerks.com]

 

[Boostwerks.com]

Step 3: IC fabrication
For the sake of room I decided to go with a small air/water IC. An air/air core would normally be first choice due to simplicity, but the XJ has a very tight engine bay and I didn’t want to have to remove the A/C.
I chose a core capable of flowing about 450hp (conservatively rated) with inlets and outlets on both sides. After a rough mock up, I welded a 90deg elbow on the inlet, a ½” NPT bung for water fill, a 1/8” npt bung for a future temp sender, and finally the Tial BOV flange.

Step 4: Down pipe and exhaust fabrication
The down pipe and dump tube fabrication was probably the trickiest part of the build. I wanted to fit a full 3” down pipe along with a 1.5” re-circulated wastegate dump tube (easier said than done). The down pipe wasn’t all that bad. It just needed to clear the driveshaft, upper control arm, the bell housing. The dump-tube however, needed to clear the turbo, manifold, oil drain line, engine block, along with being shaped in a way it could be installed or removed with the turbo and other components already in place.
The exhaust on the other hand was fairly straight forward. I used a V band connection after the 3” flex section. I used a 3” dynomax race muffler, along with a 3” ultraflo muffler. Some of you might freak out that I’m not using a cat, but in my experience I’ve been able to tune the vehicle so that the emissions have been comparable to that of a factory vehicle with one installed. Utilizing E85 as the fuel will also help. However, if I’m not able to tune it as cleanly as I’d like I will install a high flow 3” cat.

 

[Boostwerks.com]

 

[Boostwerks.com]

Step 5: Final install
Once I had a rough mock up of each major component I was going to use, I could begin the final installation. The installation was fairly straight forward. I began by removing all the components that I would need to install the setup. First I removed the oil pan, and welded a 10AN bung on for the oil drain line. I made the mistake of putting it a little too high on the pan which later made the drain line fab a pain in the ass. If I would had put it down about another half inch, it would have saved me a lot of headache later on. I hit the bung with a couple coats of paint and reinstalled it with the felpro blue silicon gasket.

Then I began working my way from the inside out. Installing the turbo and wastegate is much easier if bolted to the manifold before installing onto the motor. I used permatex’s copper spray adhesive on all gaskets, along with studs and lock nuts to suck em tight. Before bolting the manifold to the head, I stuffed paper towels into the ports to block any gasket debris that might get in there while I scrap off the old gasket. Once the head has been scrapped, I rubbed down the mating surfaces with acetone to remove any gasket residue. Like the turbo gaskets, I coated the manifold gasket with a couple coats of copper spray before installing. Using the two outer studs as guides, I installed the manifold with WG and turbo installed. I then torqued down the middle manifold bolt to synch up the manifold to the head.

 

[Boostwerks.com]

With the manifold installed I started installing the down pipe and dump tube, but first I wrapped them up with DEI’s titanium heat wrap. I also installed the bank 1 O2 and the AEM’s wideband O2 sensor.

For the intake tube I used a 3” flexible silicon tube from Mcmaster. It has a high abrasion resistance and can take continuous temps of 300+ F. I cut a small section of 3” stainless tube and attached the AEM dry flow filter.

Once the dump tube was installed I could then install the 10AN drain line. I also installed the -4AN feed line.

With everything under the intake manifold buttoned up and ready to go, I installed DEI’s heat sleeving over the critical components that are a little too close to turbo/manifold. Those include the fuel line, vaccum line, fuel tank breather line, and oil feed line.

 

[Boostwerks.com]

Before installing the intake manifold however, I took time to install DEI’s gold heat barrier to the underside of the manifold. The film has a high temp adhesive and is as easy to install as packaging tape. The highly reflective tape will help reduce heatsoak since the manifold and turbo components are so close to the intake manifold. I decided to block heat from soaking into the intake manifold rather than wrapping the turbo manifold. The turbo manifold will typically get red hot, and wrapping it will only increase the likely hood of cracks forming. I then plopped it back on the head and torqued all the manifold bolts back to factory specs working from the center out.

With the intake manifold back on I could start hooking back up the sensors and the fuel system. I lubed up the ford injectors installed them in the rail first, then the manifold. Once the rail is bolted back down I reinstalled the plugs.

The intercooler and charge piping was up next. I started from the turbo and worked my way to the throttle body. This definitely has be the shortest charge piping I’ve ever built for a turbo setup. I used 2” stainless tube from the turbo to the intercooler. From the intercooler to the throttle body I used a 90deg, 45 deg coupler with a 90deg aluminum elbow between them. I also went ahead and installed the Tial BOV and ran the vaccum line for both the BOV and the WG.

 

[Boostwerks.com]

With the IC installed I could go ahead and plumb the lines for the water cooler. I decided to go with Summits push lock fittings and 12an rubber hose. I also installed the B&M heat exchanger on the driver’s side of the A/C condenser, and the Bosch Cobra water pump in front of the factory horn. As for the wiring, I used a fuel pump relay kit for a fuel pump from summit and wired it up to the same circuit.

Step 6: Tuning
I had decided long before the turbo build that I would utilize the AEM FIC controller in this build. AEM has put a lot of R and D into these units and produce a unit that is specific to the Dodge, Jeep, Chrysler ECU. Unlike other piggy back units on the market, the AEM has the ability to “clamp” factory sensor signals by limiting the signal sent to the factory ECU. This allows for part throttle tuning, and prevents the ECU from seeing boost. Another great feature is that it has the ability to change the method it uses to interprets the information in a map. For example, you can have a sensor signal (O2 signal for example) read by the FIC changed either by a percent, an offset value, or a fixed output value. Several weeks before I bought the FIC, AEM had announced that they were now producing ECU patch harnesses and the jeep was included on the list! This allowed me to wire in the FIC entirely into the patch harness
Before even building the rest of the turbo setup, I installed the FIC and patch harness to ensure that it functioned properly and so I could get acquainted with how to tune it. My first impression of the unit is that it’s a LOT more impressive than any other piggy back I’ve ever used. It’s almost standalone like in its functionality, yet it does require a slightly different approach to tuning which is typical of most piggy backs. For any piggyback system, its imperative that time is spent to tune the unit so that it works in harmony with the factory ECU. If not, you’ll quickly find that the factory ECU will start to take over (short and long term fuel trims for example).
It did take me some time to get the narrow band sensor O2 map correct so the factory ECU doesn’t pull out the fuel that I keep adding, but with a little time it was easily accomplished. Once the basics are set, the unit is very easy to tune and user friendly. It has real time map tracing and data logging which makes tuning painless.

Final Thoughts:

My first WOT pull resulted in a grin from ear to ear and an evil laugh that I couldn’t control for the next 5 minutes. I have a full 8lbs of boost by 2600rpm, and it pulls like an angry silver back gorilla on steroids! Even with 33’s and the stock 3.55 gears it pulls HARD! The turbo spools very fast, and provides good low end torque even out of boost. The sluggish power I had with 3.55 gears with 33’s is now gone, even under low load. Under WOT the tone is deep and sounds almost exactly like a 6BT! The Borg turbo on this setup is very happy and seems sized perfectly. I’m currently cruising around on 91 octane, but as soon as some dyno time can be scheduled I will swap for E85 and see what kind of power she makes. However I don’t think I will raise the boost level for reliability reasons, not to mention that I think it has more than enough power now.
I hope this build inspires some of you who are up for a challenge and have always wanted to turbo their XJ. I hope it will also shed some light on how a decent and reliable setup can be built for less money than you think. I’ve included parts and options in my build that I wouldn’t necessary consider “required” for a moderate turbo setup.

What I learned:

1. Once the intake manifold is installed, it is nearly impossible to get to the 4 bolts underneath that hold both manifolds on. I was finally able to reach up from underneath with a wrench and torque them down.

2. I need to see if I can swap in a longer shifter cable, since the current cable is VERY close to the down pipe. I had heat wrapped the cable but I’m still sure that it will melt over time if it remains in the same location.

3. Don’t mount the oil drain bung too high on the pan. This seems to be a theme with me since I had made this same mistake on the last two builds. The bung needs to be as high on the pan as possible, but not too high as to make the drain line a pain in the a$$.

4. Check your gaskets! The Felpro manifold gasket I had purchased didn’t match my exhaust ports even though it was the specific PN for a 99 model year. A couple minutes with the die grinder though and it was all AOK.

5. The 4.0L HO motor absolutely loves boost! Overall the setup fit like a glove, and all the components seem to be working in harmony. Drivability is great, and it’s easy to forget the extra power is even there.

I will have more updates at the end of the week; hopefully with video and a dyno graph to share as well. eace:

 

[Twisted_Dakota]

Sweet build wand turbo mine? I am serious....

I kept having to reload the page because you were still uploading pics....

 

[old_man]

It is a pleasure to see what a craftsman can do. Your build is a pure thing of beauty.

 

[wy_jeep]

Excellent build. I appreciate that you used quality parts (v-band PTE turbo, Tial BOV/WG, etc). I can't wait to see the results. :clap:

 

[southernrebel20]

Awesome build! One can tell from your attention to detail that you put a lot of time and thought into this project. It looks great, and I can't wait to see dyno numbers on your setup. What, if anything, have you done internally to your motor? Is it an all stock 4.0 or did you rebuild it, blueprint it, etc.

 

[DieselSJ]

Amazing work.

Couple questions - are you using a separate reservoir for your IC? Have you done any testing to see if the B&M cooler is keeping the water temps down?

I'm asking because of my turbodiesel install into my SJ. I don't have room for an air/air setup, so I've been looking at air/water setups.

Thanks!

 

[urban yan]

a) looks good.
b) it's about time

 

[moto_ridah]

Great build and tutorial, looks like something I could do.
Do you have any dwg's for that exhaust manifold flange? or solidworks files?

 

[Talyn]

Nice work!

Where did you find the DEI heat shield?

 

[Boostwerks.com]

Thanks guys. I appreciate the kind words!

The motor is bone stock with about 128,000 miles. I've thought about building a mild stroker to go along with the turbo setup, but for now I'd like to see how well the stock 4.0 holds up over the long term.

The intercooler has it's own cooling circuit. I don't have a resivioir because I didn't feel the need for one. If the fluid exchanger is large enough, and the pump has good flow the system will maintain control of the intake temps. It's not like an engine cooling system where it is in constant battle with the engine to maintain a certain temperature.

I havn't done any water temp readings yet, but I have done logs of the IATs. Under boost I had 110F, which is substaintial considering the IATs at idle were 150F on a 85deg day.

I don't have a drawing for the flanges, but I can however source them for you. Just let me know.

Summit carries the entire DEI product line.

Thanks again guys,
Bryson

 

[dgrigorenko]

bryson.... amazing work! again nice job on the attention to detail and doing it right the first time. i like it a lot