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After the first "baseline stock" track outing (ECR, Oct 11, 2008) in a new 2008 EVO X "MR" we noted that after 2-3 hard laps the transmission would overheat during each 20 minute session. This was with a totally stock suspension and drivetrain - so why didn't any of the million magazine articles praising the EVO X's flappy paddle semi-automatic "DSG" style transmission mention this after their many on-track tests? Well apparently it only happens when 1) driven harder the most automotive journalists can muster (yes, that was a jab!) and 2) when drivers employ Left Foot Braking. But ... with no clutch pedal, what sane racing driver wouldn't use LFB on track? That's one of the big pluses of these 2 pedal transmissions - the ability to let each pedal have its own foot. Colin McRae said it best about LFB use (video).
Well we found out from talking to a local Mitsubishi dealer than when the brake pedal is even lightly pressed ("covering the pedal", which is what you do when you are using a Left Foot Braking technique) the clutch is semi-disengaged... allowing for clutch slip and rapid transmission overheating. One automotive journalist did in fact have this happen during the press testing barrage, but it was overlooked. Well, Hanchey track drove the car like it should be driven - using LFB technique. That could have caused some of the overheating problem, but we wanted to improve transmission cooling just in case it reared its head again at the next track event (less than 5 days after the first event was run) or at the next autocross, where he WOULD be using LFB, by damn. What's the point of buying a $40K performance car if you have to drive it like Mr. Magoo??
L: EVO X with fog lights covering up the oil coolers. R: Fog light housings removed and coolers exposed to more airflow!
The EVO X "MR" models' trans overheating woes are well known on the interweb with track drivers already, and even acknowledged by Mitsubishi dealers and Mitsu corporate. They promote the Super Sport transmission mode "for track use" but didn't quite get the cooling right on their first iteration (and even had a production halt in February on the MR to address this). We aimed to improve that instead of waiting for a "factory update".
So, after that initial track day where 3 hot laps was about the limit before "trans over temp...SLOW DOWN!" alarms would chime, we knew something had to be done to the cooling. There aren't a lot of solutions yet, so Hanchey decided to come up with his own.
After a look at the shop manual he noted problems in the ducting and location of the SST transmission cooler, and thus where some of the problems probably stemmed from - insufficient air flow to cool the heat exchanger, which was buried behind a fog light assembly, a wonky looking air duct, and cooling air that exited into the left front wheel well. Brian suggested adding a cooling fan to the back of the cooler and I suggested removing the fog lights - in the end we did both.
After Hanchey sourced a stout looking 5.2" diameter fan from Spal that was made for this type of use, we tore into the installation late one night at the shop. We thought we might be able to get away with a quick 30 minute install, but access to the front of the cooler was very limited, so off came the front bumper. I wanted an excuse to take a look under there for large lead weights or other ballast - something to explain this 3600 pound curb weight! - and we did indeed get to uncover a few things about the EVO X with a look under the skin.
The front bumper removal was the hardest part of this project, but a glance at the shop manual helped us track down the thirty or so fasteners that held the bumper cover and lower shrouds in place. Once it was off we could see that Hanchey had chosen the perfect size fan from Spal, and it went on with the included fasteners, plus a few washers and some rubber hose used to make a compliant seal between fan and heat exchanger. This was a "sucker" fan, so its mounted on the back side of the cooler. There was ample room to the fender liner to fit the fan in there, no worries.
Once the fan was in place, we removed both fog light assemblies. Good riddance to unnecessary bling - we don't have "fog" in Texas and their dead weight was covering up a good portion of two important oil coolers (engine and trans oil). We put together the wiring for the fan quickly. This included a relay and fuse for the higher current fan circuit, and a switch under the dash for the "low power" side of the relay. There was an unused 12V switched circuit in the factory fuse panel under the hood, right above the cooler & fan.
Total costs: About $100 for all of the parts, about 2-3 hours of time (possibly more if you are not familiar with removing bodywork and doing 12 volt wiring).
Another open track event was run the following weekend (same track, same format, same ambient temps; BMW at ECR). This showed the results we wanted to see - ZERO trans temp problems and improved lap times. At the end of each 20 minute lapping session the new trans cooler fan was run for several minutes while the engine sat at idle, and heat was POURING out of the heat exchanger - so the fan was definitely moving some air, and helping.
I guess we can chalk this on up as a successful mod. Here's the step-by-step install guide picture gallery: http://vorshlag.smugmug.com/gallery/6321704_Wm79c
We will go back and add a new/improved duct to the trans cooler (sheet aluminum), then make some mesh coverings for both fog light openings soon. I will update this thread when we add those final bits.
Cheers,