Food for thought

gmctd · **Posted:** Tue Dec 02, 2008 11:42 am

The 3.7 is a reliable engine - it is very powerful and fuel efficient for it's size because the 2v\cyl heads breathe excellently, also making the engine a perfect candidate for turbo-charging - don't believe it? - millions have been sold in single and dual-turbo versions: check out all the turbocharged\waste-gated V6 engines in 2-door and 4-door coupes and sedans from the Mitsubishi (and Chrysler) stables - your 3.7L V6 is just an up-sized Mitsu 3-liter V6 - the recent Mitsu Montero V6 was at some displacement near 3.7L, iirc, tho not turbocharged

- the ECM will handle positive manifold pressures based on feedback from the Manifold Air Pressure sensor, also referred to as the Boost sensor - the upgrading parts are out there in local boneyards, and all that may be required is an upgraded ECM program that works with pressure above Baro, rather than below - vacuum, all important to a gasser (patooie!) engine, is just any pressure level that is less than Barometric, or atmospheric, pressure

- stock feedback from the O2 sensors and knock sensor should pull fuel before extensive damage can occur from extreme fuel\air ratio lean-out, and a relay could be added to the warning indicator on the instrument panel to control the wastegate as further protection

- you would also need to deal with EGR, as the valve is expecting vacuum in the intake, as well as specific exhaust gas pressures which will increase drastically when adding the t\c

- you would also need a charge-air cooler, which DCJ thoughtfully provided in the KJ CRD, an exact fit to those less-fortunate KJ versions using that other fuel

- your 3sp\od auto trans is unique unto itself, and no factory upgrades are likely possible - you will need to check in the aftermarket segment such as Transgo and Suncoast (sorry, my bad on the confusion between 42RLE and the 42RE 727 concatenation)

- the manual transmission may require the clutch\pressure plate from the V8 version to manage the extra power, also the aftermarket segment should have some upgrades

- check it out, should be no hill for a stepper - that's my story and I'm stickin' to it................

Note - the 4-cyl and some Mitsubishi V6's have 4 valves per cylinder - this version has only two per, derived from the base V6 in all lines - turbocharging applies to the 4 banger as well as the bent 6 in any valve cofiguration

The concept is sound, whether 2v or 4v per cylinder - your engine is an air pump - there are three ways to increase airflow\volume (and fuel rate ) in any air pump\engine in order to increase it's output:

- increase displacement: bore and stroke
- increase rpm: camshaft, valves
- increase applied pressure: turbocharger or supercharger

The last method involves little additional engine modification as the original cam timing, crank (stroke) and pistons (bore) work well with increased pressure to 15psig, even more if the engine is of modern design - if the engine is 140hp at one atmosphere (Bar) 14.7psia, then power can be nearly doubled at two atmospheres (2 Bar) 30psia, or 15psig Boost, as the engine is now pumping twice the volume to which can be added twice the fuel - more air\fuel = more btu = more power - the turbo is essentially free power, operating off the normally wasted btu in exhaust gasses - a supercharger requires parasitic drain from the crankshaft: takes bunches of horsepower to drive that auxiliary air pump

The turbocharger is the easiest route to power, and your engine, at various stages in it's past, was factory-equipped with one or two turbochargers - find the stuff and adapt it - easy enuff, compared to similar upgrades on other engines - try it, you'll like it...............

edited for erroneious data - 'nuther words, a misteak

JJsTJ · **Posted:** Tue Dec 02, 2008 12:15 pm

There was a supercharger built for the early 3.7L's by Kenne Belle but it didn't work out as the top ring groove on the pistons is too near the top of the piston and IIRC they were breaking that ring and/or top of the piston under boost. Wouldn't the turbo cause a similar problem? (Sure different pistons could be swapped in if available.)

So who is gonna be the 1st guinea pig on this idea?

gmctd · **Posted:** Tue Dec 02, 2008 12:16 pm

Any idea of the max pressures that KB setup was cranking out?

JJsTJ · **Posted:** Tue Dec 02, 2008 1:09 pm

gmctd wrote:

Any idea of the max pressures that KB setup was cranking out?

6-8 psi? Can't find the info online now.

gmctd · **Posted:** Tue Dec 02, 2008 2:27 pm

Be interesting to read any articles on that system, particularly those that discuss failure mode

tjkj2002 · **Posted:** Tue Dec 02, 2008 8:53 pm

I beleive the kit was set at 4-6 psi,very low so as not need to lower the compresion to handle more bost then 8psi.

Ask KYLiberty,he blew up a 3.7 with a 100hp shot of NOS,about the same as 4-6psi boost from a supercharger.

Guest · **Posted:** Wed Dec 03, 2008 12:21 am

the KJ 3.7 is not at all related to the Mitsu 6G72/73/74 V6s.

The architecture is nowhere near the same. Take it from somebody who has owned them.

dieselenthusiast · **Posted:** Wed Dec 03, 2008 12:52 am

Gmctd, what the heck are you doin’ talkin’ about gasoline engines? Are you ill? :shock:

Guest · **Posted:** Wed Dec 03, 2008 1:40 am

And for the record...IIRC the Mitsu 6Gxx jumped from the 3.5L to 3.8 liters.

Also, The Mitsu pickup is a reskinned Dakota, so don't bring up the fact that it has a 4.7 and a 3.7.

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

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.

gmctd · **Posted:** Wed Dec 03, 2008 10:03 pm

Ah, confusion, contentious conflict and chaos - my work here is done..............

So, ok, my bad on several points - musta had too much eggnog - the 3.7L 90* DCJ V6 is obviously not just an upsized 60* Mitsu V6 - it is close enuff in displacement to use one of the Mitsu turbos for mild power upgrades, and the parts are readily available in most boneyards - about that piston land position preventing puffing, I'd need more info on the pressures and rpms where any breakage occured - a turbo is no extra load on the engine, where a supercharger is increasing load as rpm and Boost increases, resulting in less net power - where you may get 45 extra hp from the exhaust-driven turbo at a certain Boost level, the crankshaft-driven supercharger will require 45hp to make that same Boost, which is a tremendous load on the pistons for nothing but overhead, which means you won't feel it in the ole buns dyno - plus, the turbo output can be ducted thru a charge-air cooler for reduced manifold air temperature - cooler air is denser air, meaning reduced Boost levels will give same power as higher Boost levels of heated air - stock engines live longer at reduced Boost levels

My bad on the trans also - the 42RE is baby brother to the 48RE behind the Cummins, but which would have made the drivetrain too long for the KJ platform, so they used the 42RLE, a derivative of the FWD 4sp trans beside the 3.7L in the minivans

I've just had this on the back of my mind for some time now, so any hard information on the 3.7L failing under Boost, as has been mentioned on other forums, would be appreciated

And thanks for your input, KY

BTW, I've also been planning some shenanigans with that 231cuin Montero V6 in another platform................

Guest · **Posted:** Thu Dec 04, 2008 2:58 am

gmctd wrote:

3.7L in the minivans

3.8L...

Food for thought

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