1 Attachment(s)
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.
