Selecting the Super Charger
As I said at the start of the thread, putting a super charger on my TJ, with it?s short wheelbase and what I use it for really can?t be justified under any other category then ?I wanted it!?
In stock form my 4.0L and gearing provided all the power it needed for the off roading that I do. Now it just has a lot more! And I must say a lot more fun to drive, so far on road.
I narrowed down my choice to an ?AutoRotor? type super charger. AutoRotor type compressors are available from Kenne Bell and Avenger.
After checking both of these similar designs out and getting an understanding of the pros and cons that each company?s unit presented I settled in on the Avenger Super Charger.
As luck would have it, while at the SEMA show in Las Vegas I sat down next to Jack and Ed, the owners of Avenger Superchargers in the hotel lobby coffee shop. While enjoying morning coffee and a bagel I had their undivided attention for an hour and all we did was talk about this unit.
After returning home I contacted the folks at Kenne Bell to try and learn all I could about their design, which is basically the same with a few additional twists. Here are the differences, pro and con as I see it between the two systems.
Kenne Bell Unit
Only Available for 1999 and up 4.0L
Self contained ?splash? oiling system for the Blower
Re-programmed PCM for Air/Fuel and Timing
Larger Fuel Injectors
Water to Air Intercooler
Avenger Unit
Available for all 4.0L TJ?s (2.5L too)
Pressurized Blower Oiling System via engine oil system tap
Oil return to engine via ?punched? hole in oil pan
No PCM code changes, uses built in (inside the stock PCM) ?Flash Mode? to re-learn correct A/F and Timing
Larger Fuel Injectors
Water to Air Intercooler
My thoughts
I liked the fact that the Kenne Bell unit comes with a bunch of experience in building these units for all kinds of applications. I particularly liked the PCM re-programming to re-map the A/F Ratios and Ignition Timing Management.
What I didn?t like is their 100% unwillingness to even entertain the thought of doing this for the PCM in my 1997 TJ.
At Blaine?s suggestion I gave some thought and investigation into converting my TJ to the 1999 or newer PCM but this would involve a complete re-wiring harness, including all sensors, the harness and the PCM. If I had to I would have done this, but I decided it wasn?t worth the cost or my time.
I also did not like the self-contained ?splash type? oiling system built into their blower. It just bothered me.
I don?t have any evidence this wouldn?t work great. I just feel that any oil used to lubricate and cool parts that are moving this fast should be pressurized and filtered.
I realize that a case can be built to say; ?Yes but, engine oil can be dirty and that might cause a problem too.? Good point! But one I am willing to live with for the benefit of a pressurized and filtered oiling system to the blower bearings.
One of the things that really bothered me about the Avenger System was the need to ?Punch? a hole (Above the oil line) in the oil pan, to be used for the low-pressure oil return to the engine. The process to do this is to use a ?Round Air Chisel? to punch the hole and then to tap the hole out and thread a fitting in
I have to tell you I my first thought on this was ?Mickey Mouse?!
But I figured my worst-case scenario, if this didn?t work to my satisfaction was to drop the oil pan, drill the hole out, and then weld a ?bung? onto the pan for the oil return line fitting.
It is unnerving to do this, but it worked out great! (Read that; It worked to my satisfaction quit well, and I can be picky at times.)
I will tell you more about this later. (If you knew how soft the metal is that makes up your oil pan you would never even consider driving it out of your driveway without a skid plate there!) (Heck I?m afraid now to even tighten down the oil pan drain plug like I used to now!)
In fact, the decision for me was almost made by defaults. I couldn?t get the Kenne Bell Unit cause they won?t program my PCM for it.
What helped me accept this was learning about how to ?flash? the PCM in my TJ to let it learn or adapt to the new air/fuel volumes.
Also, I figured if the a/f ratios do not manage themselves via this ?adaptive? process then I will just tune things myself.
I do have the tools to measure and record A/F Rations against the RPM band and various other sensor readings. All I will need to do is acquire a ?piggyback? Air Fuel Controller. A?PEX makes a great unit that I have investigated to do this. I do not plan to go down this path any farther unless or until I am convinced it is needed.
More later as time permits.
Frank