Technical Documents

Water Spray Kit For Evo X MR And SST Transmission Models

MRT develops, fits and tests a water spray kit for the EVO X with SST transmission (that has no kit factory fitted). For some unknown reason Mitsubishi chose to omit the water spray function on these models, it is however fitted to the GSR (5spd) model, like the one that MRT uses for R&D.

Using the right parts and some common sense, EcuTeK software, and some modifications, MRT have provided a solution that is genuinely sought after that will be a huge benefit to many owners of this model.


Intercooler Spray KitThe water spray system on the EVO like the earlier models has 3 nozzles that direct water onto the front mount intercooler. This water then improves the efficiency of the intercooler thru evaporation. The real benefit is then a lower inlet charge to the engine and more power.


On the Models with the SST transmissions, an extra (custom made) nozzle can be fitted to also spray onto the transmission cooler that is located on the front left hand side of the car, just behind the bumper bar. These models when driven hard are known to run high trans temperatures and in some situations can overheat causing the Transmission ECU to remove drive whilst it cools down. A good example is in skid pan situations where transmission loads are high and air speed is low, as the cooler has no electric fan it relies on road speed and air flow to cool the oil that passes through it.

(There are several aftermarket larger SST trans cooler kits, the downside being they cost thousands, require a lot of labour to fit and wo’t work at high speed in some cases. Some come with cooler fans, The upside is they work with no air flow and at zero road speed, the downside is the fan causes a restriction to air flow above 80 km/hr. Water on the other hand works in all cases.)


On the SST models the rear washer tank is smaller than the models with a water spray kit and has no provision for a intercooler spray pump.

Note: The water spray function will not work unless the factory ECU has had a software update (via EcuTeK) to enable the “Auto” function to work and in “Manual” mode some other small mods are required.

Obviously the (MR) car needs the following to make the kit a reality (Please note this is a basic list and not everything is listed):

Water Spray Switch

  • Rear tank
  • Rear tank cap
  • Main hose
  • 3 x nozzles
  • 3 x nozzle clips
  • Front hose kit
  • Relay
  • Fuses
  • Auto / man OEM dash switch
  • One way valves
  • and more


  • Nozzle for SST trans cooler (MRT made)
  • Hose for above
  • Shut off valve for above to allow choice of use
  • Electric solenoid to stop water leakage when spray is not in use (Factory check valves are unreliable)


The factory fitted fog lamp covers over 50% of the SST trans cooler we recommend the following if you want to maximise your SST trans cooler performance.

  • Remove the LHS fog cover and replace with:
    • the factory mesh grille and outer garnish
    • fill the lower space with an alloy tray to direct air to the cooler and stop “leakage” around it.

Water Spray NozzlesThis (water spray) kit is very labour intensive to fit and requires the car to be substantially dismantled to run all the hoses from the rear to the front as well as to modify the wire harness and fit the nozzles at the front.

The end result is well worth it as the test car showed significant reduction in the cooling required after a track test (as in cool down laps or driving around the pits) as the car performed well with the water spray on the intercooler in “auto” mode.

For use in day to day conditions where the sst trans cooler may not be needed, we fitted a valve to control water flow to the optional MRT sst trans spray, this also saves water!

Note: The EcuTeK upgrade by MRT uses a whole new set of triggers to ensure best performance of the Intercooler water spray function in both the GSR and the MRT fitted MR models kit.

This kit can be purchased from MRT as:

  • Ready to fit with all parts and info.
  • Optional SST trans cooler parts.
  • Fitted by MRT.


Ever wondered why the water spray on your Evo 7, 8 9 and 10 wo’t work in auto mode?

The reason is the factory settings and triggers are set in such as way that your car will never turn it on! One example is the engine temp has to be over 105 degrees to trip just one of the many trigger points! Read the following document to understand why….

The solution is a MRT EcuTeK ECU upgrade that gives, Power, Torque AND revised water spray settings!

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