So the Idea would be 6-6.5 pounds of boost would add about 38% more power.
235hp -> 325hp +90hp
295tq -> 405tq +110hp
Could use an Eaton M90 supercharger, custom machined adapter plate to bolt SC to heads.
Needs to fit under the stock hood, no holes or scoops.
Just to clarify, there is no product for sale here.
I recently bought a 2000 WJ with the 4.7L engine and looking for another project. Just thinking, gathering info about this engine and dreaming.
Just the technical stuff.
M90 has 90cu.in./revolution x 2.75:1 pulley ratio x 2engine revs/engine cycle then divided by 287 CID of engine = 1.72 pressure ratio
1.72 PR x 14.7 = 10.65 psi theoretical maximum boost.
2.5:1 pulley ratio = 1.568PR x 14.7 = 8.35 psi theoretical maximum boost.
So the M90 is big enough for a low boost 6-8 psi system. At this low boost the engine should live a long life even with adding nearly 100hp.
I think when all is said and done, you will find the cost far outweigh's the benifit.
Anyone can bolt on a blower by making a few brackets and pulleys, but thats just 5% of what needed. Making it work in all situations and conditions and remember i think you have to get CARB complinace if you plan to sell your product for on road use.
Software alone to make it work would cost a lot, if its even doable.
It's been tried several times, cost, realiability and complexity have always killed the idea. And there were some big players like Kenny Bell
I wish you good luck, but a one off support model can turn into a nightmare.
You're right, bolting it on is the 'easy' 5%. Machined adapter plate to bolt to heads, plenum, adapter plate to SC, possible front snout shortening to align up the pulleys, machining back of SC to fit adapter plate for TB, elbows and hoses for inlet. Keeping it under the hood is tougher.
Tuning?
There are hard ways or easy ways. 8 bigger injectors, 2 bar MAP sensor and tune to control the fuel and timing retard under boost. Probably needs to be done on a dyno or with data logging and mail order tune and adjustments. Use SCT tuning suite and handheld to load. $$$. Plus you need some sort of intercooling to keep Intake Air Temps in check.
On the 4.0s we use an additional injector and controller which is basically a stand alone ecu to control the 9th injector while in boost and it also intercepts the crank position and cam position sensor and delays the signal the provide boost timing retard. So the engine runs just as stock when not in boost. Cold starting, idling, cruise, etc is just like stock until boost comes in. The fuel from the 9th auxillary injector goes thru the SC and provides chemical/liquid intercooling removing 60-100* from the charge intake air temps. No tubing for FMIC or complicated water to air intercooler. Simple.
I am only suspect of the transmission. I have no experience with the 45 or 55 RFE and only hope they are not junk like the 42RLE.
I used to run about 12lbs of boost in my GTP with the M90 before I needed an intercooler. But I ran a stacked inter cooler underneath the M90 with a cowl hood. A cowl hood wouldnt look bad if done right on the WJ. And from what I hear, the 5-45RFE is a pretty stout transmission. It comes behind the Hemi in Dodge Ram pickups
There was a guy at the drag strip (Cecil Dragway) in north east Maryland that had 2005ish grand Cherokee with a supercharger. It ran 11's in the 1/4 and was very impressive. Never even herd it. Just a woosh and it was gone.
I think that part of the problem with SC kits in the past was they were running too much boost, no intercoolers and bad tuning.
The 4.7L pistons only have 1/8" top ring lands and are very sensitive to heat, hot combustion temps, detonation and lean mixture. These piston lands would break with their kits and every manufacture jumped out of the 4.7L SC business. They blamed the 1/8" piston lands.
I blame the SC companies themselves.
Low boost 4-5 pounds, fuel liquid intercooling with 150* IATs, boost timing retard. This will live.
4-5 pounds boost will add 25-30% more power. 235hp-> 295-305hp and 295tq-> 370-385tq, +60-70hp and +75-90tq. That works.
I think that part of the problem with SC kits in the past was they were running too much boost, no intercoolers and bad tuning.
The 4.7L pistons only have 1/8" top ring lands and are very sensitive to heat, hot combustion temps, detonation and lean mixture. These piston lands would break with their kits and every manufacture jumped out of the 4.7L SC business. They blamed the 1/8" piston lands.
I blame the SC companies themselves.
Low boost 4-5 pounds, fuel liquid intercooling with 150* IATs, boost timing retard. This will live.
4-5 pounds boost will add 25-30% more power. 235hp-> 295-305hp and 295tq-> 370-385tq, +60-70hp and +75-90tq. That works.
Yes the factory piston design with the 1/8" landings are an issue even in stock engines with the higher than usual combustion chamber temps. Airram sells some new design ones that have 1/4" landings, however they are for oversized bores only, you'd have to bore the block beyond standard to go with them.
When I rebuilt my engine last year I wanted to get the new designed pistons but found out they were not available in stock bore size and I could not justify boring my block just to go with the newer design, so std bore factory style pistons went back in it.
I like your idea of a low boost though. If I was to spend the time and money on a low boost project I'd probably put the HO cams in my engine, and go with the oversized bore in order to use the 1/4" landing pistons to help keep temps under control.
There isn't much options on exhaust either, no headers that I know of for these things. I did do some minor porting on my rebuild, mainly just gasket matching however there was quite a bit of material removed from both the exhaust manifold and exhaust port of the head in doing this. The intake side I did not touch. She does seem to be peppy but I do not have access to a dyno to have actually compared any difference it may have made.
I've been hoping Edelbrock will come out with an E-Force SC for the 4.7L. They recently released a new aluminum head for the 4.0L so it would seem they are not afraid of tinkering with engine platforms that are no longer in production.
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