Well, I guess I've got the most experience in this area on this forum, so here goes. Sorry it's long.
I actually called KB to try to buy the kit when they put it in the Performance West Liberty Patriot. IIRC, it was using a custom intake manifold and they didn't know if they were actually going to ever produce them because they didn't think there would be enough demand to do a manufacturing run of the manifolds. That was a show vehicle, so I doubt it was ever driven enough to run into the weaknesses that can cause failures. I don't think they ever got very much out of it either. According to their dyno graph, their stock KJ was making way more power to the ground than mine when stock, but was much slower. Looks like their dyno graph is adjusted to have the stock KJ make 80% of the mfg engine claims to the ground, even though it was kind of a pig. Maybe they already had the 245/75R16 MTR's on it. Either that or the torque management was still in it, or they ran it at different boost levels than they dyno'd it.
Anyway, after strongly considering dropping in a built 4.7, Profinish-Proglass juiced it up. The hood went on, and the N2O went in. A 35 hp shot of N2O worked smoothly, but didn't make that much difference on a 2+ ton vehicle. A 50 shot felt like a nice V8. A 75 hp shot didn't work right. The computer would freak out with it. It wouldn't shift correctly, or at all sometimes. Had to use an RPM window switch to fix that. The only way it would work about half the time was to do a 35 shot run, followed by a 50, and then the 75. The 50 was a lot of fun though.
Then an APS converter, Transgo reprogramming kit, and 4.10 gears made a nice difference, but the 75 shot still wouldn't work right. Then, KRC Performance got B&G Chrysler to create a flash for the 3.7 for me. That made it work. They made an aggressive flash with the torque management deleted. With the same settings it put almost 40 more hp to the ground with the same N2O and gas jets, and worked up to 100 hp which were the largest jets I had. It was making huge power. The KJ was amazingly fast. It was hillarious. Couldn't wait to have the direct N2O system, cams, pistons, and custom tuning at KRC in a few months.
Unfortunately, a slight tuning mistake combined with pushing the 3.7 to it's limits caused the short block to be sitting in my garage right now with 2 scorched cylinders. That was after a year of sporadic short 50 hp shots, and then a few 75-100 hp runs.
The good news is you can actually build a 3.7 for some serious power. Just make sure that you get upgraded pistons, rings, the right cams, and the right programming. You can also work on the heads. A little machining made a difference on mine. Make sure you upgrade your torque converter and valve body. If you have the factory LSD, you may want to replace it. My Trashlock didn't last a year after the Frankenlift. Between the heavier tires and rims, and the amount of torque mine makes it just didn't stand a chance. It split apart and took out my pinion bearing. I was actually looking at dropping a built up D44 in the rear when I was running the N2O because I thought I was going to tear up the rear. If it had been turbo or supercharged, running that much power all the time would have torn it up in no time at all. Now I'm just hoping the DTT and HD axles handle it once I go to the 206 cams, custom JBA headers, and high flow cats next summer. I think they will though.
If you're really interested in putting boost on it, you should talk to KRC. They can get the cams, pistons, programming from B&G, and kit for you. They're not the cheapest out there, but they know their stuff. They have a lot of experience with the 4.7 that is really closely realated to the 3.7.
_________________ June 2001 Liberty Limited 4X4
Frankenlift II Premium, Al's Upper Arms, 245/75R16 C Silent Armors on Moabs, RL Skink Super Sliders, Rear DTT, Riddler Diff Cover, Fastman Throttle Body, Profinish-Proglass Hood, Borla Dual Outlet Exhaust, TransGo Reprogramming Kit, APS Stall Converter, 4.10 Gears, B&G Chrysler PCM, Lots of Line-X, etc...
Last edited by KY Liberty on Thu Dec 04, 2008 7:20 pm, edited 1 time in total.
|