2003 Mitsubishi Lancer Evolution VIII - DME And Turbo XS - O2 Housing And After-Cat Exhaust And Downpipe

On inspection, there seemed to be few differences between the stock cast-iron O2 housing and the new DME tubular welded piece. Both turbine outlet and wastegate outlet diameters were about the same size. However, the housing outlet is bigger to meet up with the 3-inch downpipe. Internally, the wastegate merge orifice that combines the flow from the wastegate into the main exhaust flow seemed no bigger than stock. This could be a potential cause of boost spikes if the car was tuned to higher boost levels. But our dyno tests showed no signs of boost spikes even with a target boost pressure of 16-18 psi. Power-wise, the new O2 housing was good for another 15 whp up top while peak torque at 3750 rpm (where the stock turbo reaches its initial peak boost) decreased by 1 ft-lb. This loss came from the stock boost controller reducing the target boost pressure because it was near the stock programming's predetermined limits.

Jon feels that proper tuning and a boost solenoid restrictor that allows higher boost levels would significantly increase the marginal benefits of the DME O2 housing and Turbo XS plumbing.

With Exhaust And Downpipe
Gains Made
+ 17.9 Hp
+ 16.1 Ft-Lbs Torque

Before 233.3 whp and 241.7 ft-lbs
After 251.2 whp and 258.8 ft-lbs

With Exhaust, Downpipe And 02 Housing
Gains Made
+ 15.3 hp
+ 1.0 ft-lbs torque

Before 251.2 whp and 258.8 ft-lbs
After 266.5 whp and 257.8 ft-lbs