Mitsubishi Ralliart Colt Turbo / CZT Colt with 4G15 DOHC Mivec Turbo

Dummies Guide to Vehicle Modifications!

The Mitsubishi Ralliart Colt Turbo / CZT Colt came out of the blue and literally, blew everyone’s mind. A front wheel drive new style hatch back, its one of those shapes you either love or hate. There design though, produces extremely good handling compared to many other front wheel drive vehicles, and there gutsy 115kw engine in a very light weight car out accelerates many competitors. We can honestly say having been driving and modifying these, they are a fantastic vehicle to own and modify. We have spent considerable time with a R&D vehicle to work out a range of working modifications, and the results of these can be seen under our dyno sheets / customer section.

These vehicles were only released in Australia as a 5 speed manual. They have there quirks, with a noisy clutch being common and fly by wire throttle body technology. The DOHC Mivec engine comes on boost very hard very early with its baby TD03 turbo. Electronically controlled boost means it starts off high and tapers off very fast from factory.

This section is to be used as a guide in your modification – we will be breaking this into sections to provide a well balanced vehicle. Additionally the modification package will be setup so that as you increase the power of the vehicle, your alternative items like brakes etc are matched to your new power level. This guide has also been done in an order which provides successive gains from the modifications power wise. Jumping say to number 20 first, may result in a LOSS of power until you have done other items to match its effect.

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.

RPW has done a huge amount of R&D work on this vehicle, for dyno results on various modifications as outlined here, please read the following link before you read much further for the full background test on this vehicle.

Basic Mods to start on the vehicle

1. Air Cleaner Mods

The stock air box is not badly set-up, with a partial cold air feed from the front bonnet area. We have found that for the majority of owners, fitting a K&N replacement Panel Filter is the best option. On the front bonnet, there is a rubber strip which if removed from around the same area as where the filter funnel is located, can further improve air flow into the air box.

We tested the K&N Filter charger kits, which replaces the air box with a pod filter setup. We found that this setup, with it mounted inside the engine bay, resulted in a loss of horsepower from engine heat soak.  This result would be evident from any open air cleaner setup fitted to the vehicle.

For those who plan on upgrading there inter-cooler to a front mounted unit (More information on this later), RPW has manufactured a cold air pipe kit which locates a Ram-pod Filter into the same position of the original inter-cooler. This has the benefits of increased cold air induction, and increased air flow.

Gains from air-box / filter only is around 1 – 2kw. Gains from true cold air kit / pod filter set-up is around 3 – 5kw.

2. Exhaust system Modifications

The  stock exhaust systems on the colts is a very restrictive system. There are three exhaust upgrades which dramatically improve torque, horsepower and throttle response compared to factory. The overall result of these mods are a drop in peak boost / torque / hp by 500rpm and improved rpm range. We recommend modifying the exhaust in the following order.

1. 2 1/2″ Cat back exhaust system – replacing the stock system with a 2 1/2″ mandrel bent system has significant improvements. The factory system runs a secondary cat converter for emission purposes, fitting of a cat back should include the removal of this unit. Since there are no o2 sensors after this unit, there are no CEL issues. This could be increased up to 3″ diameter if the vehicle was running significantly more modifications than a normal colt.

RPW manufactures a 2 1/2″ cat back bolt on system which retains factory sound levels inside the cabin, but has a significant improvement in sound outside the vehicle. This has recently been upgraded to a Version 2 system for lowered vehicles to accommodate the clearance issues associated with the rear suspension on these vehicles.

2. Front Pipe Kit – the second piece of the exhaust system. This bolts onto the back of the dump pipe housing, includes a primary cat converter and then has a small section of pipe work that leads up over a cross member and then bolts up to the secondary cat converter. This unit is extremely restrictive and small and replacement of this unit alone drops peak boost / rpm by 500 alone.

RPW has manufactured two bolt on items for the colt vehicles. For those utilising factory ECU’s and are not planning on performing any tuning work, the Version 1 Front pipe in a 2 1/4″ diameter with in built Ceramic Cat Converter works perfectly. The release of the Version 2 Front pipe which has been upgraded to 2 1/2″ diameter piping and a Metallic High Flow Cat Converter. The version 2 can only be used with Factory ECU Retuning due to the increased airflow will create immediate CEL issues.

3. Dump Pipe Housing – the dump pipe which comes off the back of the turbo, is like most systems, restrictive and small. The internal diameter of the factory unit is approximately 1 7/8″ and has terrible internal airflow designs. Replacement of this with a better designed unit with either a 2 1/4″ or 2 1/2″ internal diameter unit has tremendous improvements in throttle response and boost characteristics.

We manufacture two models, depending upon which front pipe unit has been fitted to the vehicle. Optional Ceramic coating is recommended with these units due to the removal of the heat shielding.

Gains from the exhaust mods in total is around 20kw at the flywheel, with a reduction of peak boost/torque by 500 rpm. 

3. Suspension Upgrades

The factory suspension set-up on these vehicles are extremely well done. They handle well, go around corners like a rail car, and generally do everything we expect of them. But like all systems they can be improved. Factory set-ups run front strut braces, rear torsion bar set-up and decent coil springs.

  • Replacement of the factory springs with some lowered units has significant improvements in handling. These are available usually as 30mm lowered units – we use King Springs for the colts and cannot recommend them enough.
  • Fitting a rear sway bar kit to improve cornering and reduction of body roll
  • Fitting of anti lift polyurthane bushing kits to both front and rear suspension
  • Coil over strut kits are available by most major manufacturers, this has significant advantages in handling and is suitable for both moderate road use and all forms of racing.

4. Drive Line Modifications

The drive line on the colts are very good from the factory. Utilising a combined drive by wire throttle body control, electronic traction control operated through the ABS system.

This set-up works quite well but the Front Wheel drive set-up does need more help to avoid wheel spin issues. The main drive line modifications would be as follows

1. The gear shifter on the Colt utilises a very long shifter throw as well as is awkwardly mounted requiring the driver to have to reach for it. RPW provides a modified exchange unit which not only shortens the throw forwards/backwards and sideways, but retains the stock height. This is important so that the driver does not need to reach any further forward to change gears.

2. Fitting of LSD System – the factory set-up with a front wheel drive turbo is a necessity no matter what power level. There are currently two options of LSD available being either a clutch style unit manufactured by Cusco. This provides very high levels of traction, but also has side effects of typical noisy operation and the “Clunking” when turning corners at low speeds. The other alternative is a Quaife ATB unit which is not as positive in its engagement as the Cusco units, but provides the same results without any side effects.

RPW has successfully worked with Quaife and has now fitted these to Colts with great results. Improved traction, and a more positive feel on steering with greater road feel. This is a very easy job to do and can be done in around 8 hours.

3. The factory clutch on these vehicles does not hold up to increased boost well. They are noisy, prone to failure from the factory and are unfortunately, a necessity for replacement for any user contemplating any track work or increased boost levels. At this stage these are not yet readily available but a combination flywheel / clutch package is not far away from being released.

5. Brake Upgrades

The brakes on the colt are excellent from factory. 276mm single piston callipers on the front with a 260mm single piston calliper set-up on the rear. But like all Mitsubishi models, any decent hard braking results in immediate warp age of rotors and eventual brake fade.

1. Replace both front and rear rotors with slotted rotors and replace front and rear brake pads with EBC Green Stuff pads. Improves braking tremendously for the majority of applications and is good for both street users and occasional track use

2. Upgrading of the front and rear brake lines with stainless steel braided lines. Reduces expansion of hoses upon braking,  providing better feel to the brakes. Easy to fit and perfect for any track work. There are some Japanese brands as well as RPW manufactured units.

3. Upgrading of front rotors to a twin piston calliper package, combined with EBC green pads and slotted rotors on the front increases braking efficiency by around 50%. These should be used with new manufactured brake lines.

4. Larger brake packages can be provided with after market 300mm and larger four / six piston packages but these all require after market rims to provide appropriate clearances.

6. Tuning Solutions

The factory ECU on the colts is very smart and controls items like the drive by wire throttle body, boost control, fuel and ignition curves.

It has shown clearly that piggy back systems do not work with the colt factory ecu bringing up multiple Check Engine Lights.

There are two tuning solutions available for the colt at this time

(A) Remapping factory Engine Control Unit (ECU)

(B) Fitting a full after market Engine Management System

For the majority of customers, limiting themselves to stock turbo’s or slightly larger turbo’s the stock ECU can be tuned happily to accommodate a large range of modifications without any issues. RPW was the instigator of having the factory ECU cracked open and we are the most experienced factory ECU tuner on colts in Australia. They have a unique style which your average tuner, especially on boost curves, fail to understand as they lack the experience on this vehicle platform.

For those planning on going further, we have successfully worked with Haltech to have the Haltech Elite 1500 ECU work very well on these vehicles. With full control over every feature of the vehicle, without any issues. This is currently the only full after market ECU which can control both the fuel, ignition and drive by wire throttle body and not have any issues with the vehicle going into limp mode. Most other systems only have partial control, with no control over the DBW throttle body and thus having to try and “Trick” the factory ECU into still working.

6. Boost Control & Blow Off Valves

Boost control is factory ECU operated using a combination of two boost restrictor pills and a solenoid. The actual system works extremely well and we highly recommend reading the RPW R&D section for a full explanation of how it works.

Unfortunately until the factory ECU is re flashed with an updated tune, there is no way to alter the boost level significantly on the vehicle without causing a Check Engine Light due to the factory ecu having both a boost cut limiter, and a torque limiter function.

With the ability to remap the factory ECU completely, with the factory ECU also having boost dedicated by lower and higher gear ratio’s, closed loop (ECU Feedback system) it is already more sophisticated than any simple bleeder system or some after market systems.

Unless you remap the factory ECU to suit, you cannot use any form of marketeer boost control system and nor do you need to. Its just another ECU trying to do what is already available from the factory.

The only boost modifications that need to be done are

  1. Fitment of 3 port boost control solenoid enabling very accurate control of boost. These are available as a direct fit system
  2. Upgrading of the waste gate actuator (Factory 7 psi spring) to a after market unit with choice of 14, 17 and 21 psi springs. This enables smoother boost curves and reduction of over boosting when pushing above 15 psi boost levels.

The original blow off valve is a limited plastic unit. Fine for stock boost levels, but as soon as you start increasing them a larger steel based unit is required to stop boost leaks.

The most common upgrade is to fit the Mitsubishi EVO Lancer MR Metal unit which is a direct bolt in replacement, although we also use the GFB plumb back model units as well.

Note that the factory unit is a plumb back design and under no circumstances, should you attempt to fit a externally venting unit to the vehicle.

Being a Air Flow Meter operated unit, any externally venting unit will create issues with air fuel ratios, flat spots, idling and finally the big old check engine lights and limp home modes. You have been warned.

7. Inter-cooler Upgrade & Cold Air Feed

The factory inter-cooler is not a bad unit – for stock factory. The small unit is hidden on one side of the vehicle with granted, good air flow.

Arguably replacement to a larger front mounted unit into the front bumper of the vehicle has tremendous improvements in air flow and cooling of incoming air charge. This is especially important as boost levels are increased.

A small 400 X 300mm unit is perfect for the vehicle, not requiring large amounts of fabrication. Larger units can also be used but are of questionable value merely increasing boost level lags with no additional cooling benefit.

We have worked with the Australian Ralliart Colt users to provide pre manufactured bolt on inter-cooler kits or piping only which do not require any vehicle modifications to fit.

The factory pipe diameters on the vehicle varies from 1 1/2″ up to 2 1/4″. Our kits retain a 2″ diameter all the way from turbo to throttle body for consistent airflow.

The only thing we highly recommend, do not utilise cheap Chinese manufactured units that you can buy for $200.00. Get a high quality Unit which flow well without restrictions, but don’t go too large as this will create issues with fitting around the front bumper, as well as create more turbo lag.

Just because it is bigger than your factory unit, and its cheap, does not mean that it will improve the cooling effect of the vehicle.

RPW recommends upgrading at the same time the air filter setup. Remounting the filter with a K&N pod filter, into the now vacant position where the original inter-cooler was located.

This will provide a significant cold air  fee, further improving the inter cooling effect.

8. Hard Pipe Upgrade

A popular upgrade, which could really be done at any time, is to replace the factory piping from inter-cooler to throttle body with an upgraded hard pipe kit.

This essentially replaces the pre fabricated plastic pipes / rubber hoses with mandrel bent piping and shorter silicone hose joiners. Long rubber hoses expand under boost pressure, and over time will eventually break down.

Utilising hard pipes, boost can remain more constant as long as sufficient silicone hose joiners are provided to allow for engine movement.

Upgrading the pipe from turbo to air box also has significant advantages, for those wanting noise the aluminium ones work well.

The silicone pipe kits flow the same, reduce heat soak and flow more more air due tot here smoother internal bore diameter.

This significantly improves throttle response and has a small horsepower gain at top end.

9. Turbo Manifold Upgrade

We are now getting into the more serious level of modifications. The factory turbo manifolds are showing a tendency to crack after a long period of use. With more colts becoming modified and used for semi racing and sprints, this is becoming more of a standard issue.

The factory manifold additionally, is a poor design manufactured for a mass production market with the restrictive factory exhaust and low boost. This is extremely evident when looking upon the almost log style manifold design.

An upgraded turbo manifold has significant gains in both design, function and reliability.  A well designed turbo manifold produces improved boost curves, improves flow by not only having better design runners, but by utilising thick steam pipe designs holds the heat and uses the heat flow to help keep the turbo spooled up.

With this in mind, we DO NOT recommend thin stainless steel style turbo manifolds as these produce good looks and can provide horsepower gains, but at the expense of longevity. The cheap Chinese ones are especially bad, even with additional welding they still crack.

Racing Performance Works designed our own tuned length, racing designed steam pipe manifold which has been proven on stock and modified turbines, available for factory TF035 and TD04 series turbochargers.

Working in conjunction with a good full exhaust system, this has the potential to create significant gains in horsepower over the factory set-up. The vehicle would require retuning with any manifold change.

Note that the turbo manifold upgrade running the stock boost levels would be fine with the stock fuelling system. Increase boost levels would definitely require fuelling upgrades, as specified below.

11. Fuel System Upgrades

This is the final level of what we would class as standardised upgrades for the vehicle. The aim being to ensure adequate fuel supply is provided for boost levels in excess of 17 psi and allowing for future upgrades of forged internals, camshafts etc.

The fuel system on the colt utilises a traditional fuel pump in the fuel tank, pumping up to the fuel rail, through the injectors into the engine. The fuel pressure is maintained by a fuel pressure regulator, and bled back to the tank.

The first step to upgrade is the fuel pump. Fuel pump volume is rated at 80 litres per hour. Perfect for stock output. We recommends upgrading to a minimum of a 160 LPH or higher pump.

There are several pump options being either a 160lph direct fit unit or bolt in 255 lph unit being either a Walbro or Duetchworks unit.

The next step is upgrading of the injections. The factory injectors are a 275cc unit, perfect for the standard boost levels on the vehicle.

Upgrading to some Mitsubishi 390cc units is what we recommend. Being a direct bolt in, these in conjunction with the fuel pump is more than enough for engine horsepower levels to reach in excess of 200kw at the flywheel.

We also now use the ID 750 injectors for many customers who are going extreme on there modifications or using E85 fuel.

The combination of these three fuel upgrades, will require significant retuning of the factory ECU.

This can be done, and done well with re-flashing technology, but is not for the amateur tuner.

This requires advanced data logging and experience with the OpenECU ECU software, and very detailed ECU Flash Definition files.

12. Turbine Upgrades

This stock turbine on this vehicle is very small being a TF035-12t.

The stock internals of the engine are capable of handling the stock turbo and the 1st upgraded size of a TF-35-15T which has a large intake turbine wheel.

Racing Performance Works has also manufactured our own turbo upgrade of a hybrid TF035-15T/TD04 which will also work to the limit of the stock internals and factory ECU with all the above modifications.

All these are direct fit units not requiring any modifications. For the majority of customers we recommend the TF035-15T turbine upgrade which will enable the vehicle to push to 210hp at the wheels on average.