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Right now while we are tuning and later for track use, we are using AMS’s test pipe to connect the down pipe to the Greddy RS exhaust. AMS’s test pipe is made of 3” diameter 304 stainless with stainless flanges. Later for street use we will go to a high flow cat to help keep things clean.
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| The AMS downpipe also has a provision for an extra O2 sensor for tuning. We like how AMS has thought of adding extra bungs for convenience even if you are not using all AMS parts. |
Due to the rear mounted turbo on the EVO X installing the downpipe was a little harder than on the Evo IX. We had to stand in the engine compartment to reach some of the bolts connecting the turbine housing to the downpipe. Still the installation was not that bad, just a little more time consuming than usual.
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| This view up towards the turbo shows how tight of an area the downpipe has to fit through. The tight quarters makes installation a minor pain in the ass. This is where we like the older Evo a lot more! |
Once we had everything in place, Naji Dahi of Looney Tuning once again lent us a hand. With EVO Scan we again logged our car while doing power runs. The car responded well to the down pipe and test pipe immediately making 16 more hp. Looking at our logs showed that the turbo made boost about 200 rpm sooner as well. Unfortunately we also logged knock again and to eliminate it we had to pull about two more degrees of timing from the high load, high rpm areas of the map to get rid of the knock. Our power gains remained the same even with retarding the timing but all owners of 2010 and later Evo X’s with lean spool need to note that if you are running an intake, exhaust and downpipe, you need to tune your ECU or you will probably experience engine damage even if running stock boost!
As an experiment, we reflashed our ECU to the stock program and did a power pull. We could actually hear audible knock before the ECU could pull timing and registered a knock count of 19! This would probably damage the engine if you drove at the track or did an extended run at full throttle.
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| You can see the high quality of the casting here. The flex tube is also high quality and has a reasonably smooth interior for good flow. |
Now that our car was uncorked, Naji did a light tune for power. Naji tweaked the boost solenoid maps to slightly increase the boost so we would spike the boost at 25 psi and taper to 18 psi by redline. The Evo X has a turbo with a larger exhaust housing A/R with the same turbine wheel as the Evo IX but the compressor wheel is very small. The result is a turbo that does not respond as well to turning up the boost like the older Evos.
