***BEFORE YOU DO ANYTHING READ FIRST***Unlike the 3.5L/6g74 swap where you can easily swap the engine in and run with it, the 3.8L/6g75 engine swap
requires tuning. Why is tuning this engine swap so important? The 6g72/74 is a 9:1 or 9.5:1 compression ratio engine, but the 6g75 is a 10:1 compression ratio. With the increased compression ratio, ignition and fuel is very important to have set properly. The ignition timing in the Galant Ecu (intended to run the 6g72 engine) is not sufficient to control the differences needed to properly run the 6g75 engine. From side by side comparisons of the Galant 6g72 Ecu ROM file and the 6g75 ROM file there are a number of areas in the ignition maps that are different by 4-7* or more. Along with the ignition timing, the fuel maps referenced in the Galant Ecu are also insufficient to adequately fuel the larger engine displacement. The 6g75 actually runs rich from the factory, but with the increased combustion chamber (CC) size on the 6g75 heads, and higher compression ratio this engine will require more fuel than what the Galant Ecu will supply at most ranges of the RPM or Load sections.
**Performing this swap and driving without properly tuning this setup will result in potential engine failure. Do so at your own risk!For more information on tuning for this engine swap;
viewtopic.php?f=12&t=690 Motor Mounts/BracketsThe stock 6g72/74 motor mounts (passenger side) are direct bolt ons, all other motor mounts are also direct bolt on.
The alternator bracket from the 6g75 is different from the 6g72/74 as far as how the alternator attaches to it. You can use the 6g75 alternator bracket, and the 6g75 alternator as direct bolt-ons. The 74 passenger side motor mount would be needed in order to run the 72/74 alternator. If you want to use the 72 alternator, engine mount, and bracket you will run into an issue with the top bracket not lining up correctly. You can drill the bracket in the needed location as the 72 bracket can still work. You will need a washer between the top bracket and alternator that will keep the belt aligned properly.
Fuel SystemThe 6g75 series engines (MIVEC and Non-MIVEC) use a returnless fuel rail system. The 8th Gen Galant fuel rail uses a return style system which means you have the fuel supply line feeding into one side of the fuel rails, and a fuel return line coming off the other rail. The other difference on the 6g75 fuel rail is there is no fuel pressure regulator attached to it like the 6g72/74 fuel rails. As I understand this difference it will require the use of an "external" fuel pressure regulator such as an Aeromotive or other brand Adjustable Fuel Pressure Regulator (AFPR).
With regards to the returnless fuel rail, some have tried modifying the 6g75 rails to become a return style, though it is not as clean and there is a better route. The 6g75 fuel rails also have a different angle of how they mount to the lower intake manifold. The 6g72, and 6g74 fuel rails will not bolt up to the 6g75 lower intake manifold. You will need to use a 74 lower intake manifold to give a clean installation and full use of the return style fuel system on the Galant. This also allows you to upgrade to other fuel rails that fit the 3000 GT engine.
Ignition SystemThe 6g75 series engines use a distributorless ignition system via a COP (Coil On Plug). In order to drive this ignition system you would need to obtain the newer ECU, or run a full standalone engine management system. Now a note on the use of the newer ECU in order to drive this ignition system is that everything is run off a "CAN" based program instead of the OBD like our 8th Gens. That means if you swap to the newer CAN based ECU, the instrument cluster and everything has to be swapped in.
You can retain the use of the 6g72/74 distributor and mount it onto the 6g75 engine in the same location (rear bank) as a
direct bolt on.The next issue with mounting the distributor here is the 6g75 coolant crossover pipe will not mount up. You will need to obtain the coolant crossover pipe from the 6g74 in order to mount the distributor on the rear bank. The relector wheel on the 6g75 is different than the 3 blade type design on the 72/74 engines. You will need to swap in the 72/74 reluctor wheel in order to run the distributor.
IntakeThrottle BodyThe 6g75 uses a DBW (Drive By Wire) throttle body which is completely different than the 6g72/74 cable driven throttle body. Now since we do not have a way to operate this throttle body (or a desire honestly), you can simply swap the 6g72/74 throttle body over to the 6g75 manifold.
Upper/Lower Intake ManifoldsThe 6g75 lower intake manifold will not accept the fuel rails from the 6g72, or 6g74 (Refer back to "Fuel System" section for more details). The "best" approach/combination of parts here is going to be the 6g74 lower intake manifold.
The upper intake manifold on the 6g75 just from looking at it is very "free flowing" and the plenum area is not "squished" either. For N/A or FI applicatons the 6g75 upper intake manifold will work fine. If you have upgraded to a Diamante, XG350, or Eclipse GTS upper manifold, you can use all of these manifolds. This is confirmed from bolting on the stock 6g72 upper manifold to the 6g75's lower manifold;
Exhaust ManifoldsThe 6g75 exhaust manifolds cannot be used for the swap on the 8th Gen Galant due to how the rear manifold is designed (the 4th Gen Eclipse manifolds may be different but will have to verify). The rear manifold goes down and away from the engine, as in it will hit the 8th Gen's steering rack or firewall because of how it is made. You can swap over the 6g72/74 manifolds, or a set of the RPW headers as well. Now on the headers there will be some modification needed to fit correctly (IIRC it was something with the mid pipe, or due to the height of the 75 heads the header tubes need to be lengthed...not sure). The photo below will give you an idea of how the rear manifold runs away from the engine (6g75 is on the far right sitting on the tire)
Good starting point to find used 6G75s: http://www.car-part.com(Found mine for $500 w/140K miles, better deals are out there, but prices aren't that bad)
Models and production years the 6G75 is available;2003–present Mitsubishi Montero
2004–present Mitsubishi Endeavor
2004–present Mitsubishi Galant
2006–present Mitsubishi Eclipse (MIVEC Engine)
FSM information on the MIVEC System;http://mitsubishieclipseforum.com/IMG/M ... _MIVEC.pdf
