I just replaced the stock plastic DV in my VIII with the aluminum JDM MR. The stocker was leaking pretty good and there's a noticeable change for the better. I learned the next day that a number of Evo's came from the factory with their DV's installed backwards. And I put the new one in the way my stocker was - backwards.

I wound up getting a little compressor surge, but the car ran much better. I went and turned the DV around; the car sounds more normal now, but I'm wondering if it doesn't pull quite as good now after a test drive. Its kind of a seat of the pants subjective thing I guess. I need to drive it some more.

Can it run better with the DV in backwards? If so is t harder on the engine?

 

Just put it in the correct way and be done with it.

 

It is harder on the turbo.. Mine was in backwards from the dealer..

 

sorry for my ignorance, but how is it backwards?

 

Your turbo will definitely spoolup quicker with the DV installed backwards. The stock DV's, including the metal MR piece start to lift off the seat at 11 PSI. With the thing installed backwards, your car's torque and midrange power should be improved as well.

 

so the bov is just installed 180 on its mount? how does this make a difference?

 

With it spun 180 the boost keeps the BOV closed, like the HKS SSQV. This used to be an old group N trick back in the days when the BOV wouldn't hold boost.

 

My old one was backwards, held boost great, part throttle was BAD.

 

With the DV valve installed backwards it won't open at all. On the other hand with the DV oriented correctly, the pressurized air pushing on the valve face lifts the valve off its seat compressing the spring and recirculating the pressurized air back into the MAF pipe. I realize that this was not a very good explanation...sorry!

 

The DV doesn't really have a proper "mount" or flange per se. It has two very similar ports oriented at right angles to each other. In fact, they are so alike, that it is easy to install the port that sources off the UICP into the MAF pipe and vice versa. Both ports are the same diameter and length. They are so similar looking that the assembly line workers at the Mitsu factory end up installing the thing backwards all the time.

 

so I just purchesed a 9 BOV......is it better to install it "correctly" or "backwards"?

 

As should be obvious installing it correctly will not create the part throttle hiccups. Also that chopping sound is the result of sudden stops on the compressor wheel which is bad and could lead to premature turbo failure.

 

Alright, i just looked at a image of the BOV and i now understand how it could be installed incorrectly, thanks for answering my questions.

 

Install it correctly so that it will function as designed. If installed backwards you will eventually damage your turbocharger.

Before removing your present stock DV mark a "M" with a marker on the side that connects to the MAF. Once you remove it then compare the new DV and orient it in the same manner.