I'm not a 'tuner', I'm an old school engine guy.. Motorhead. Car Nut. Mopar Fanatic.
First, if you have the 3.7, I don't think I'd bother turboing it. If you have the 4.0, here's what I'd do..
Pull the motor, have custom rods and pistons built for it, that dish and at the same time, improve the swirl. This lets you get more boost without detonation. Next, I'd say drop the engine CR while you're doing this to around 8 to 8.8, no higher.
You'll need to seriously alter your timing and fuel curves for this, so I'd suggest whacking the stock computer and going with Megasquirt, or something similar.
The weak spots in this plan are:
1 crank - high boost will result in some broken bits.
2 trans - if you have the auto, there's going to be issues with power and controlling it. If manual, that'll help some.
3 emissions inspections.
if I REALLY wanted the horsepower, I'd just shoehorn a Hemi under the hood and run with it.
The 4.0 is a relative of the 3.5, which was a respectable and decent engine. But they were not overbuilt like Mopar engines of old - gotta be all light and "modern" you know.
I have the old 2.5 buzzy 4 cylinder in a caravan with a 5 speed - all factory. And that engine WILL take a heap of abuse and keep running. And I have an old Poly 318 in a Power Wagon. Built like it was meant to keep a ship from drifting at sea... Forged steel crank, rods that would make Chevy blush in embarrassment, massively thick bearing webs in the block, full floating piston pins, cylinder wall thickness so massive you can bore nearly 1/8 inch and still have a solid wall. Heads made of so much iron it's all one man can do to lift them. It wasn't enough to have a forged crank. They HARDENED THE JOURNALS on top of that! That motor doesn't make a lot of horsepower in stock trim, but it can be hopped up, and it'll make full horsepower, WOT, for hours and hours and hours. The engine was used in agricultural equipment. The mechanics told me a 350 chevy would die in less than a season of use, these engines lasted multiple years and rarely ever broke.
Now, the difference is, that 318 made 160 horsepower in my truck, and 240 hp in the harvester. And it weighs a LOT more than the 4.0. You can't have "indestructible" and "light" at the same time.
One of the most bulletproof V6's on the road today is the chrysler 3.3 pushrod engine. Many of them run several hundred thousand miles and still are healthy. But people have tried turbocharging them and the result is that they break themselves into smallish parts.
So, while I love the idea, and I know you could make it "work", do you REALLY want something you can break easily? It would be a lot of fun when it wasn't broken... But how much are you willing to pay for that "fun"? Find an old Neon and make it a project instead. Faster, more fun, and less costly.
