Mitsubishi Challenger / Pajero / Triton 96 - 05 with 6G72/74 3.0/3.5 SOHC 24v engine.

Dummies Guide to Vehicle Modifications!

The Mitsubishi four wheel drive range of vehicles have been very popular vehicles for many years. But looking around, there is still not many firms focusing on producing any reasonable products for the vehicles as well as any real documentation on what works and doesn’t.

To our shame, RPW must join this crowd (Up to 2010) as we ourselves, focused on the faster moving Magna / Lancer range of vehicles. We are again placing some much needed attention as of 2011 on the four wheel drive range to provide some price competitive options for the owner who wishes to drive around normally during the week, and go off road on the weekend. There is no reason why you can’t have your cake and eat it to.

The Mitsubishi four wheel drive range included the following model vehicles (That this particular document will be focusing on)

  • Mitsubishi Challenger
  • Mitsubishi Pajero
  • Mitsubishi Triton
  • Mitsubishi Shogun

These vehicles came out with a choice of Manuel or Automatic Transmission. There were also four engine choices being

  • Mitsubishi 6G72 SOHC 24v – approx 130kw
  • Mitsubishi 6G74 SOHC 24v – approx 150 – 163kw
  • Mitsubishi 6G74 DOHC 24v – approx 170kw
  • Mitsubishi 6G75 SOHC 24v – approx 170kw
  • Mitsubishi 6G75 SOCH 24v Mivec – approx 185kw

The Mitsubishi V6 engine is a very robust and strong engine, and in this model is usually detuned due to the heavier loads they are under especially with compression ratios. We will focus on some of these items as we work through this document. The 3.0 motor unfortunately, due to its over square bore / stroke combination, is not particularly suited to heavy loads tending to suffer from lack of torque and requiring frequent gear changes to overtake.

The 3.5 engine has always had a lot more low rpm torque and does everything quite well. The later model 3.8 engine of course, has much more improved torque and has to be the best four wheel drive version motor of the lot with its much longer stroke crankshaft.

We will not go into suspension or handling modifications, we will leave that to other specialist firms. Instead we will focus purely on the performance aspect of the engine tuning. This is where we excel and hopefully, with this guide, aid future owners with a better idea of what to do to achieve there goals for there vehicle.

RPW does not take any responsibility for people performing these modifications on there car without professional involvement. Check with your local government regulations before modifying your car as these items may not be legal in your country.

Recommended Modifications

Due to the focus on performance, and in some ways limited in range, there is no need to have different sections. The good thing about these four wheel drive vehicles, is that they only require a group of basic modifications to achieve everything the majority of customers would require. Outside of these basic items, you are incurring both very large expenses, as well as turning the vehicle more aware from the effective daily driver / four wheel drive vehicle and more focused on pure four wheel driving performance to the exclusion of daily driving. For those customers, this guide is still of some aid but would mostly require more one on one discussions with there chosen modifier.

1. Auto Transmission Cooler

We cannot preach this enough on Mitsubishi vehicles. If you have an auto, any model, this should be one of the very first things done to the vehicle. 99% of Mitsubishi transmission failures are as a direct result of the oil being overheated by the lack of factory cooling on the transmission oil. Regular changes every 20,000km should be done regardless on these vehicles.

Fitting an after market transmission cooler, of virtually any design, will improve transmission life and responsiveness by over 100%. The vehicle will shift more consistently, be more reliable and cost a lot less to repair in the future. This is a very easy thing to fit and as you modify the vehicle more, becomes extremely necessary. They are usually mounted in front of the radiator, although RPW has been using the B&M fan cooled units a lot more which have there own thermostatically controlled fan to further improve there reliability. Not all of the four wheel drive models have factory fitted transmission coolers.

This is particularly important for the Auto Models that do either heavy towing, or lots of four wheel driving. We recommend the following two options

  • For mostly towing vehicles / light four wheel driving a generic bolt on unit without any secondary thermo fans etc are more than enough. Mounted in front of your radiator for additional cooling, these work perfectly in situations where high air flow is usually occurring.
  • For vehicles doing particularly heavy towing or heavy four wheel driving, we recommend the B&M fan cooled units. With there own inbuilt thermo fan, when doing low load / high rpm four wheel driving, these provide additional airflow to keep auto trans oil as cool as possible for maximum protection. More work is involved both mechanically and electrically to fit these units, but they are superior in design and effectiveness in these situations.

2. Air Filters & Cold Air Induction Kits

The factory air box system on these vehicles is quite restrictive in there original design. But for the record, we do not under any circumstances recommend replacing the factory air box with a ram pod filter located in the engine bay. This is just plain ineffective as it sucks hot air and reduces performance. All modifications should be done with the stock air box.

Step 1 – Fitting a K&N Factory Replacement Air Filter with improved air flow and throttle response should always be the first thing done. We recommend K&N because it filters nicely and has good airflow. Foam or cardboard style filters are restrictive despite having better filtering ability.

Step 2 – The factory air box in basic design is already excellent. It filters well and has a half decent air feed into it. It usually has one large snorkel set-up, depending upon the model vehicle which feeds air from either over the top of the radiator or via an opening pulling air from behind the headlight system. The fundamental plan at this point is to try and increase airflow into the air box. This can be done several ways by

  • Removing the factory snorkel set-up and replacing it with an external system which pulls air from above the roof of the vehicle. If you can have the snorkel system facing into the wind this is particularly effective..
  • Removing the factory snorkel set-up and enlarging the hole which feeds into the air box. From here purchase some universal flexible hosing of at least 3” diameter and either re hook up to the original air box inlet (Where mounted over the top of the radiator) or relocate the opening in some way as to feed a greater volume of colder air into the vehicle
  • With some air boxes they run a secondary silencer system which is usually pot riveted onto the back or bottom of the air box. This is especially true of the triton range of vehicles. What we do on these is remove that plastic chamber off the air box, which then provides a new hole opening of around half the size of the main air feed into the air box. From here you can either get some flexible hosing and mount up to behind the grill somewhere, or our favourite, hook up a small bonnet scoop and hook the air inlet up to the bonnet scoop. Or even an external snorkel setup. The whole idea is to provide another air feed into the air box. The theory is simple – the more air the air box can get, the more air your engine can ingest and improve performance.

3. Exhaust System Upgrades

The Mitsubishi 4wd vehicles have quite a good system from the start. They generally run a 2 1/4″ mandrel bent system (In effective diameter). We say effective, meaning that in some points it can be slightly smaller, in other area’s slightly larger. The cat converters on these are a fairly good flowing unit as well.  At this point you must reach your first major decision on where you wish to go with the vehicle – in summary we recommend the following options

  1. Naturally Aspirated – You are only after mild improvements to make the car sportier, but don’t intend to do any real serious mods. This being the case stick with replacement of the stock exhaust with a rear muffler upgrade only. Fitment of a replacement rear muffler kit is worth on average 5 – 10kw by itself on average. This retains the factory resonators and cat converters, and will retain a factory sounding system with improved airflow. Ensure you use a oval shaped large muffler design for maximum sound reduction with maximum airflow..
  2. Naturally Aspirated – you are after mild to medium improvements to make the vehicle sportier, with slightly more than average vehicle modifications. This being the case, a replacement 2 1/2″ diameter replacement exhaust with a new resonator and oval shaped muffle design. Due to the large amount of room on the vehicle, with few bends we do recommend retaining a mandrel bent system but a press bent would still be fine. The cat converter should also be upgraded with a higher flowing metallic unit for maximum flow.
  3. Naturally Aspirated – okay you are an extreme Modder. Larger throttle body, camshafts the list goes on. In this case a complete 2 1/2″ mandrel bent system (for 3.0 customers) or a 3″  mandrel bent system (For 3.5 / 3.8 Owners), with the addition of a high flowing cat converter upgrade. The cat converter should be a metallic high flowing unit. For 3.8 owners, we do recommend going to 3” systems if at all possible for maximum results.
  4. Super Charged – no more need be said. A 3″ mandrel bent system with cat converter will be required. Keep the car quiet, no droning and has a great sound. Going larger than 3″ for any vehicle producing less than 600hp at the flywheel will not produce any further improvements other than to make more noise.

These can produce small gains with the basic systems of around 5 – 10kw at the wheels, with increased torque.

4. Extractor Upgrade

The stock system on these vehicles do vary greatly even between models, but as a general rule they are quite restrictive, especially in there flex pipe design which joins at a 90 Degree intersection, and is not a tuned length system. The later model vehicles are even more restrictive by there use of up to three cat converters, with one off each cylinder head and a third one further down the line. Needless to say, removal of this system to a more traditional single cat converter has very very large gains in terms of performance.

Due to the more general purpose design of these vehicles, the traditional design of a 3-2-1 system is utilised. This means that there is usually a 3-1 header off each cylinder head, which is joined into a Y Pipe and from there back into a single diameter pipe up to the cat converter. We can only say that no matter what model vehicle, any replacement of the stock header system (Especially late model) with nearly any header design will yield improvements. The amount of improvements very much depends upon the manufacturer. RPW has stayed with the Hurricane Exhaust systems for the majority of vehicles due to there good fitment, large pipe diameter design and high quality. There are other brand we also use when Hurricane units are not available.

For the later model vehicles, you will need to purchase additional Oxygen Sensor eliminators which are placed on the secondary oxygen sensors which used to read after the primary cat converters. This reduces the signal going to them as they are there primarily as an emission check to ensure the primary cat converters are doing there job. By fitting these eliminators, it reduces the amount of gases they see, which they then dutifully feed back a “Cleaner” value back to the ECU. The ECU thinks all is good and does not report a CEL issue. This sometimes may require tweaking as if they get too cold, they can bring up an error for not reporting properly. A general rule of thumb is to locate them in roughly same length away from the cylinder head as original.

If you plan on supercharging your vehicle (And why not) then header upgrade is absolutely mandatory and here designs with larger pipe diameters are most important.

This package adds around 5 – 10kw at the flywheel with increased torque and improved upper acceleration and rpm range (Late model triple cat converter setups gain closer to the 15kw range).

5. Throttle Body Upgrade

Time to look at improving throttle response again, looking at improving throttle response, even if you are going Supercharger later.

The stock throttle body on the 6G72/74 SOHC engines vary

  1. Early Model 6G72/74 – these usually run between a 55 – 60mm throttle body identified by there bulkier design and use of metal throttle cable linkage.
  2. Later Model 6G72/74 2000 onwards usually run a 57mm throttle body which is a new design compared to the older models. Identified by its use of a plastic (Black) throttle cable linkage.

The normal upgrade options are as follows

  1. Early Model 6G72/74 – upgrade options include upgrading to a 60mm, 63mm throttle body. The 60mm or 63mm involve the use of the stock units machined out with a larger butterfly. Some mild porting work on the intake manifold to ensure the larger diameter fits up fine.
  2. Later Model 6G72/74 2000 onwards – just like the earlier models, re-machining of the unit can provide an increased size out to 60mm. Mild porting work to the intake manifold is all that is required.
  3. One option for all models is a 65mm throttle body. This requires both new TPS and ISC Motors, and on some models a wiring change as well for the ISC Motor. This unit is significantly larger than the stock unit, and requires significant welding and reworking of the intake manifold for smooth flow.

These changes have significant effects on both airflow and throttle response. Going larger also provides more air for the motor to ingest. This will work nicely with exhaust modifications. Improved airflow results in better fuel economy, and better acceleration, mostly by no longer needing to open the throttle as heavily as normal. Fitment of a thermo block throttle body gasket, further reduces heat soak into the manifold / throttle body and helps provide cooler air into the engine.

This package adds 2- 5kw at the flywheel, but does improve throttle response and low rpm drive ability. The thermo block kit reduces heat soak and this allows the engine to maintain maximum ignition timing with max throttle response.

6. Computer Re-tuning

Re-flashing the factory ECU is NOW available for all models and is our preferred tuning option where possible. This allows maximun performance, maximun fuel economy and literally will cope with all but the most extreme modifications without any issues.

RPW is one of the few people in Australia which can do this. We are able to reflash most vehicles up to 2005 and for 2006 onwards, we are finalising software options for those right now.

Whilst re-flashing the factory offers superior tuning, allows the fuel and ignition trims to be adjusted for maximum performance. These also allow for vehicles running LPG gas systems to be further optimised with duel mapping especially with ignition timing.

The factory ECU utilises an advanced knock sensor set-up and can definitely be optimised for a gas setup but would take more work. In that situation, a combined re-flash / piggy back ecu system would be a better option for vehicles with LPG systems.

RPW has successfully fitted the piggy back systems to all model Pajero / Triton vehicles with great results for these form of systems.

Supercharging vehicles will have there own discussion on Computer Modifications.

7. Supercharger Conversion Package

What more can we say other than your a horsepower and boost Junkie. Welcome to the rest of the world. This combines extreme levels of torque and power, with neck snapping acceleration. It comes at a cost though, depending upon your throttle control, increased fuel economy, higher insurance and lots of money.

RPW has worked with Bullet Performance to manufacture a supercharger system for all late model 6G72 / 74 SOHC 24v models. Unfortunately this will not suit the DOHC models at this time.

This utilises a Eaton MP series supercharger, originally developed by TRD for Toyota Vehicles. The design runs anywhere from a 5 – 10 psi system and uses the following options

  • 5 PSI system is used with the combination of Reflash / Piggy Back ECU with / without larger main injectors and an auxiliary extra injector. This provides superior tuning as well as fine control for fueling and ignition timing under high air temperature levels. Most importantly, the factory Knock sensor remains in control to retard timing should detonation occur.
  • 10 PSI system using the same setup, but is further enhanced by a water/methanol injection system to reduce intake temperatures. The 10 PSI system is a definite need for upgraded larger injectors with a computer re-flash

Needless to say, a supercharger provides massive torque gains of up to 70%, and horsepower gains on average of 40% with 5 – 10 psi systems (Depending upon model vehicle and other modifications fitted). But word of warning, if you have not done any of the recommended modifications listed in this document, you will not get a good result from the supercharger.

Good idle, smooth power and massive throttle response is all to be gained, but all emission control features are retained (Excluding EGR). Externally there is no visible changes other than when you lift the bonnet. But this is not cheap, and is not to date compatible with any LPG Gas system.

Did you like our guide? Something did not make sense. Please let us know and we will try to update this with more relevant information etc. We hope this helps you plan your vehicle modifications in a more informed manner.