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Thread: jeep Cherokee 4.0 supercharger project

  1. #1
    Junior SCH Member
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    Aug 2011
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    Smile jeep Cherokee 4.0 supercharger project

    Hello all,

    I am a mechanical engineer and an amateur petrol head .
    I am the proud owner of a 2001 jeep Cherokee 4.0 with a manual transmission which I consider a test bed for all my tuning related projects.Its got many bolt on modifications so far : 62mm throttle body, intake, tube headers, high flow muffler.

    The next step is initiating a forced induction project for my jeep , here are my thoughts and criteria , please let me know what you think.

    1. I decided to use a supercharger and not a turbocharger mainly because the jeep has a very tight engine bay, where the exhaust manifold is mount in the worst location ever under the intake manifold. I simply dont have the skills and resources to fabricate a custom manifold to mount a turbo is this very tight area. I was barely able to install a tube header in that area.

    2. I am planning to run a boost pressure of 8 psi. Its just an educated guess based on the technical literature I read on the topic, this boost pressure is equivalent to around 1.5 pressure ratio which should be more than adequate for all supercharger types, and should give me a decent increase in power.


    3. I want the installation to be as simple and neat as possible with minimum permanent modifications to the car. I want to direct my focus to the supercharger sizing and fuel delivery of the system rather than custom fabrication.


    4. I am on a limited budget for the project, around $1,500. most of which should be spent on the fuelling system and the blower itself ( a used one )

    5. I need everyone's help here to share their info about which type of supercharger to use in the 4.0 jeep engine ( Roots, twin-screw, centrifugal ). My personal preference is to use a centrifugal type simply due to space and simplicity of installation. I am thinking the area where my air filter now sits where I install some sort of bracket for a pulley that is in the same plane as the power steering pulley.
    I know the dis-advantages of the centrifugal being poor low RPM boost but I think if I size it properly I should be getting useful boost as early as 2500-3000rpm. I like the idea of the centrifugal as well because as many technical books say, it allows me to keep the stock location of the throttle body in addition to being compact. Hood clearance is virtually non-existent in the jeep engine to the extent that the pcv grommet sticking out of the valve cover makes contact with hood insulation as hood closes:)


    6. I am lost in the different brands/ family's of the centrifugal e.g: paxton, vortech, etc. I can read a compressor map and correlate it with my engine flow figures. Just need some help where to look.


    7. I dont know if running at 8 psi would need an inter cooler or not: air to air or air to water? is the temperature gain at that boost really that significant? I live in Egypt and ambient temps in summer can reach up to 104 F. However the jeep is running fine now although the intake is sucking very hot under hood air.


    8. How can I accurately calculate my engines volumetric efficieny at various RPM points say 2000, 3000 , 4000 and 5000 rpms?. The generalized data I have is that the jeep engine has about 77% VE at the torque peak and 70% at the red line. Follwing this assumption my initial calculations say that the engine has a flowrate of 245 CFM at the redline.

    9. For fuelling I am planning initially to use AEM Fuel/Ignition piggyback controller. But I dont know what injector size would be suitable for that kind of boost. My stock injectors are rated at 21 lb/hr with 49psi of fuel pressure. how big should the new injectors be? In addition I dont know how the jeep Manifold Absolute Pressure sensor would react to boost? My initial guess is that it is designed to read vacum to atmospheric only.

    Appreciate your thoughts and directing me to which forum section I should post in if this is not the correct one.
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  2. #2
    SCH Owner Michael's Avatar
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    Welcome to SCH!

    Glad to have you aboard! Your project sounds very interesting - I don't think I've heard or seen anyone supercharging a 4.0 Jeep Cherokee. You may be entering uncharted territory here.

    But that's not to say it can't be done. I'm an Engineer myself, so as far as I'm concerned, as long as the numbers work out and the laws of physics and thermodynamics aren't bent too badly, anything is possible... LOL!!

    Unfortunately, I just finished typing a very long posting with my suggestions and thoughts regarding your project, but it all got lost when I hit the "Post Quick Reply" button below. Needless to say, someone at vBulletin is getting an email from me very soon along with our web hosting service company!

    But I'll try to summarize my thoughts while I still remember them:

    1. Your decision to supercharger vs. turbocharging is sound as most systems don't add any permanent changes to a vehicle. Some will argue that in order to maximize performance and life-longevity with respect to supercharging a vehicle is to tear-down the engine and build it using high-grade parts, sized and spec'd for the application at hand. And while that's very true, unless the engine is excessively worn out, or you're looking to run extremely high boost (upwards of 20psi), or you're entering competitive racing, generally there's no need to do this. As such, most supercharging systems can easily be removed from a vehicle without any trace that it was ever there in the first place.

    2. Low-boost systems (ie. less than 10psi) don't need an intercooler, and more often than not actually suffer with one installed. The added volume from the intercooler and plumbing typically causes a drop in boost pressure as the supercharger tries to fill that space. Of course, this is all relative; a high-flow rate supercharger or a small volume intercooler mounted close to the supercharger maybe not see much drop in pressure. There are people on the site here that are running 6psi-8psi systems with water-to-air or water-to-water intercoolers that claim to see no drop in boost, so this isn't a hard and fast rule.

    Most people running low boost systems however, tend to prefer running water/meth injection instead of an intercooler. Water/meth injection adds no additional piping/volume and is only used when needed based on intake air temperature. They do have the disadvantage/inconvenience of having to refill the on-board bladder or tank every once in a while, but otherwise it's a very good option to consider. There's a great 2-part write on the subject in the Charge Cooling System section of the site. Definitely worthwhile reading.

    4. Your budget is a bit tight, but it's not impossible especially if you're looking to go used. If you can stretch your budget to about $2000, then I'd suggest looking at the gear-drive units from Procharger, Vortech, or Paxton (Novi). Extremely reliable units that often have room for increased performance later. In fact, if you can find an early Paxton NOVI 2000 on the used market, you'll be handing that thing down to your grand kids!

    If $1500 is carved in stone, then the Paxton SN units (SN60, SN89, SN93, SN2000, NOVI GSS) are all good options. They are ball-driven units, which run silent compared to gear drive units. This makes them great for daily drivers. But, they do require frequent fluid changes and are limited in their performance potential, about 6psi-8psi max. They are rebuildable as well, so a quick call to Paradise Wheels and you'll have all the parts you'll need to tear a unit down and rebuild it yourself.

    An Eaton/Roots type blower is also possible, but it will require considerably more fabrication to install. Look for a unit from the older 3.8 liter V6 GM engine, they can be had relatively cheap, and are quite reliable. They'll give you decent boost throughout the RPM band, unlike a centrifugal unit which will reserve it's boost for mid-to-high RPM.

    8./9. If you haven't done so already, I would highly suggest getting your hands on a copy of the book Supercharged! by Corky Bell. Look on Amazon.com; I think it's just over $20 right now. It will give all the formulas you need to calculate the VE of your engine, along with fuel system requirements, pulley diameters, boost ratio, etc... It's a must have for a project like yours.

    I know I haven't addressed all your questions, but I hope this helps at least get you started. And make sure to keep us posted on your progress too!

  3. #3
    Junior SCH Member
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    Subscribed just b/c I've owned to XJ's and curious how this goes!
    1987 Iroc-Z, ZZ4, xr276 w/ 1.6's, TPIS Miniram, 42#'s, Intercooled Paxton SN2000, T-56, 3.73's, Full Hotchkis/Koni suspension, C5 brakes, 17" ROH's

    1970 Skylark Convertible resto-mod, project on hold

  4. #4
    Junior SCH Member
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    Aug 2011
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    Shawn aka hemifever can tune your jeep for you with an SCT tuner. I also have a 2001 XJ and have a supercharger kit waiting to go on it.

  5. #5
    Senior SCH Member vinces427bb's Avatar
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    i have seen a roots style supercharged 4.0L cj5 at the drags
    it was pretty cool.

    here is an old thread in the jeep forum on this exact subject for reference material
    http://www.jeepforum.com/forum/f11/s...g-4-0l-513518/

  6. #6
    Junior SCH Member
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    Jun 2011
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    Hi 1982, I've done some research on force feeding a Jeep 4L engine and found the fuel control is the bottle neck. What other potential solution have you found to overcome the Chrysler speed density management aside from AEM?

  7. #7
    Junior SCH Member
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    Mar 2013
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    I Just finished my supercharger project, its an Eaton M62 mounted on top of the OEM intake manifold. The kits are for sale on eBay, and if your at 3000ft or above no timing changes are necessary. It does require a hole in the hood for an XJ but on a wrangler it fits without hood mods. Makes a safe but very noticeable 5psi.DSC05872 (Medium).jpg

  8. #8

  9. #9
    Junior SCH Member
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    Apr 2013
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    Here you go, all done and ready to go. Includes M62 supercharger, Split Second FTC pre-programmed plug-n-play, complete install hardware kit.
    www.jeepm62superchargerkit.blogspot.com

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