supercharging?

Rocker7 · **Posted:** Thu Jul 27, 2006 5:39 pm

I have a spare supercharger off of a 3.8L Ford Thunderbird. I will within the next few months be adapting this honey to my '02 Libby. Doesn't appear to be too difficult, of course with some fab. I figure about a sixty hp gain with a 5-6 psi boost. Should be very torquey. Let me know what you guys think.

JFortier777 · **Posted:** Thu Jul 27, 2006 6:36 pm

PICTURES!

PICTURES!

Jeepjeepster · **Posted:** Thu Jul 27, 2006 6:48 pm

Thats not alot of boost, but have you heard about the pistons/rings not being able to handle boost? Dont know if thats to much for them or not?

KW AV8R · **Posted:** Thu Jul 27, 2006 6:51 pm

IIRC, there are issues with installing a supercharger on the 3.7L we have. It had something to do with the placement of the top ring on our pistons. I think the ring was too close to the top of the piston meaning with a supercharger, it will just blow off this ring. I'm sure there is someone on here that knows more about this and will chime in soon so you might want to hold off on this for a bit.

FreedomKJ · **Posted:** Thu Jul 27, 2006 6:56 pm

You know, I find claims of problems with supercharging the 3.7L to be a little strange. The 3.7L V6 is built exactly like the 4.7L V8, and there are superchargers for sale for the 4.7L. So why would the 3.7L have any issues?

KW AV8R · **Posted:** Thu Jul 27, 2006 7:03 pm

This might be a good reference. I know that these people spent a lot of time doing some extensive research with reference to superchargers.

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=124

pokey555 · **Joined:** Fri Jun 09, 2006 2:47 pm **Posts:** 50

As with adding forced induction to any vehicle, a proper tune is essential. 5-6lbs more than reasonable for a factory build engine with powder metal rods and hypertenic (sp?) pistons. In the search for more power it is easy to get greedy and increase the pressure resulting in broken internal parts. If you are planning installing forced induction plan to spend money in supporting hardware like fuel pumps, injectors, an dyno tune, colder range plugs, wires, and ignition system (distributor, coil packs or C.O.Ps) Another thing to consider is the current engine static compression ratio (I am assuming between 9-10 to 1). If the engine has a lower static compression ratio more pressure and timing can be used. ~9lb is generally accepted as the upper boundary to use on a factory NA motor with a dyno tune. Just remember, if you plan on adding forced induction to any vehicle be prepared to buy a "built" motor, due to the addicting nature.

Rob

Guyute1210 · **Posted:** Fri Jul 28, 2006 1:17 pm

Send a PM to KYLiberty. He has had his KJ at the strip, and had it programmed, etc. He's probably the expert here on the KJ's with Forced induction.

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

You'll need to get your computer reprogrammed by B&G if you want it to work. They're the only one's I know of capable of doing it. You will need the torque management turned off or you won't be able to produce more than around 50 extra hp no matter what you do. Not even with a 125 hp wet shot of N2O. The computer will cut back the power. You'll want to upgrade your injectors, and go to some colder plugs. You should also upgrade your torque converter, and do a shift kit, or it will shift really badly. It's going to take some custom air/fuel curves and a lot of dyno time. It's also going to blow your stock motor before long. You're going to end up needing a built motor. Non-built 3.7's and 4.7's won't hold up to forced induction long because of the piston and ring isssue. The rods might handle it, but they tend to snap at a little more power than you're talking about, so I would recommend upgrading them too.

SavageSS27 · **Posted:** Sat Jul 29, 2006 5:40 pm

OK, so it seems like it's gonna cost way more money than it's worth to really upgrade the stock engine, what's the easiest way to get, say 300-400HP in the KJ using the stock trans (shift kit and new torque converter)???

Or a simpler way to ask that question is probably "what V8s will mate up to the 45RFE and be able to put out 300-400HP?"

Would the 5.9 fit? I've seen some really nice 5.9 GCs

spoonplugger1 · **Posted:** Sun Jul 30, 2006 9:50 am

Your front diff will never hold up under that much power. There have been 4.7s put in the Liberty. Haven't heard of any bigger engines. You can do anything with enough money, but what will the resale be?

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

If you're not up for spending $10k on a motor swap for a 4.7 that will be dangerous in a front end collision, you're pretty limited. As someone who used to run 335 hp and 400 lbs of torque out of the 3.7, I think I know a little about its limitations and abilities.

Your best option for everyday use with more power is to change your ring and pinion gears in the rear from 3.73s to 4.10s. Pull the front differential from a 4 cylinder for the front. Send your ECU to B&G Chrysler and have them program it, or get a spare ECU from Autocraft, have them write your VIN to it, and send that to B&G so you keep the stock ECU as a spare. If you have the sentry keys, you will need to get them programmed if you replace the ECU or it will only run for 2 seconds. Get a torque converter from APS Precision with the multiplier changed from 1.93:1 to 2.53:1. Get a stall around 2500 rpm. Also get the performance shift kit for the valve body. Do a cat-back exhaust, and upgrade your air intake. Some headers should also help, but I haven't ordered the JBA's yet, so I don't have details on them yet.

These upgrades will make your Liberty perform like a completely different vehicle. It will still be very reliable and usable as a daily driver that you depend on. If you still need more, your only realistic approach is nitrous. You will only want to run a wet 50 hp from 3000 rpm to 5500 rpm in 1st and 2nd. You will want an rpm window switch. Do not run it in 3rd. It is much harder on your engine than 1st and 2nd. Do not ever let it hit the rev limiter while on the juice. You should do all the accessories such as a bottle warmer, remote opener, gauges, blow-down tube, purge, and fuel pressure safety. One step colder NGK plugs will work fine. Do not use platinums. Oh, and be prepared to get your motor rebuilt. Racing is like off roading, you break things.

kickit_in4wheel · **Posted:** Sun Jul 30, 2006 8:20 pm

A little off the supercharging topic, but is it possible to have the motor rebuilt for a little more grunt? Assuming it only makes 210 horsepower, surely there's some untapped potential, once the computer restrictions are taken care of. KY Liberty- are there aftermarket cams & other engine internals available for the liberty? Would the 3.7 respond to larger injectors, a different cam, lighter custom ($ouch$) pistons, porting, etc? I realize it would be a costly endeavor, but I'd still like to know.

I've considered the 4.10:1 gears as well. I'm running the ever-popular Moabs and MTRs (heavy) and I was wondering, are 4.10s going to make my mileage go down, or up? Assume I'm just doing regular driving, not hard throttle. The tire diameter is larger, but using one of those gear ratio calculators and trying to keep the ratio the same as stock but for the larger tire, it recommended a 3.9X:1, which is unavailable. What affect would the 4:10s have on the low end torque, highway RPMs, and mileage compared to larger tires and stock 3.73s?

Myke · **Posted:** Mon Jul 31, 2006 1:51 pm

The 4.10 will add more torque, It will decrease your mpg on the highway since your cruising rpms will be a little higher. I don't know how much your going to lose.

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

With the 4.10's I ended up with slightly better gas milage in town (13.5 mpg raised to 14.5 mpg because I don't have to step on gas as hard to get same acceleration.) I lost about 4 mpg at 70 mph though. Back down from 24 mpg to 20 mpg on the interstate.

Yes the motor can be built for more grunt. It is very similar to the 4.7. I've discussed it at length with KRC. I'm still trying to decide if I should send the 3.7 block sitting in my garage to them for a complete build. If I do, we're putting in ceramic coated pistons, forged rods, raising the compression ratio to 10:1, and setting up a direct N20 shot under each fuel injector. It should be around the same power as the 6.1 Hemi when I flip the switch. It's just a lot of money, and the Libby is really powerful compared to stock right now.

shak · **Posted:** Tue Aug 01, 2006 12:37 am

ky liberty, are you selling your kj by any chance?

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

Sorry, no. I have way too much in it already. I have to drive this until the wheels fall off. Then I have to put them back on and drive it some more. Plus, I still have a ton of work before it's finished. I have a 7" motorized VGA touchscreen, a computer, gps, xm radio, amplifiers, sub, speakers.... sitting in a room right now that are waiting to go in it. I'm adding the headers after that, and thinking about upgrading the ignition, going to some Lincoln Navigator injectors, a larger throttle body, and having B&G reprogram my ECU. Next summer I'm getting a custom interior done with dark slate leather seats with sandstone suede inserts, and I'm going to either get the couple little dings taken care of on the paint since it will be 6 years old. And then get a couple coats of clearcoat to make it shine like a show car, or just get it repainted completely with the same color, just a lot nicer than stock. Then I have to decide if I should have the 3.7 block sitting in the garage rebuilt, or to do the OME lift and put on some 255/65R17's.

mvef · **Posted:** Fri Sep 15, 2006 1:56 am

FreedomKJ wrote:

You know, I find claims of problems with supercharging the 3.7L to be a little strange. The 3.7L V6 is built exactly like the 4.7L V8, and there are superchargers for sale for the 4.7L. So why would the 3.7L have any issues?

It may be the same, but with two less cylinders

mvef · **Posted:** Fri Sep 15, 2006 2:06 am

Rocker7 wrote:

I have a spare supercharger off of a 3.8L Ford Thunderbird. I will within the next few months be adapting this honey to my '02 Libby. Doesn't appear to be too difficult, of course with some fab. I figure about a sixty hp gain with a 5-6 psi boost. Should be very torquey. Let me know what you guys think.

I don't know if the engine and drive train is going to able to handle the extra torque :shock:

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

FreedomKJ wrote:

You know, I find claims of problems with supercharging the 3.7L to be a little strange. The 3.7L V6 is built exactly like the 4.7L V8, and there are superchargers for sale for the 4.7L. So why would the 3.7L have any issues?

Actually, the 3.7 is not exactly like the 4.7 minus 2 cylinders. The stroke of the 3.7 is 91 mm instead of 86.5 mm. This is very close to the bore of 93 mm for both motors. The rings are thin, and placed a little to high. There have been problems with the 4.7's blowing the rings with superchargers, but the problems are worse with the 3.7 since the stroke is a little longer, and closer to the size of the bore. All you really need to do to prevent it is get some custom pistons with better rings based off 4.7 pistons. KRC can get them for you. They also work a lot with B&G, so can probably help you with the programming with the different pistons and supercharger. You could also adjust your compression ratio at the same time so you could run 7 or 8 psi. What transmission do you have? The 42-RLE isn't going to like it very much at all. I assume that you have a heavy foot if you are wanting to superchage your Libby. I would budget for upgrading the torque converter and transmission if you have the 42-RLE. If you're lucky enough to have a 45-RFE or 545-RFE, you'll just need to upgrade the torque converter. The factory tc is a big weak point, and it is very inefficient. I would love to see a daily driver KJ that had a supercharger in it. Good luck with the project.

supercharging?

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