If the evo didn't have a cat to begin with then I not surprised that there wasn't any gains. I sure that the modified evo had a straight through muffler as well so there would be much of a restriction.

I think the whole point of a cut-out is so that you can keep the stock exhaust ( or whatever exhaust ) with a cat to keep the noise down, but when you want the extra horses free up the exhaust by bypassing the cat.

 

I agree, did the evo tested have a tbe already?

 

I agree with you...It would be a big benefit on a stock exhaust system. I seem to ask "why?" a lot these days when I see some of the so called mods on cars come through the shop..

 

Just thinking, a cutout wouldnt effect the cars tune if you have it tuned open but drive around with it closed most of the time would it? I would expect it wouldnt because tbe's and switching tbe's usually dont effect the cars tune.

 

I've already discussed this with the original poster of this thread in PM's... but for the knowledge of everyone else...

In my honest opinion, in order to gain the most power out of a cutout, the cutout has to be placed as close to the turbo as possble AND must be placed in the direction of the flow of exhaust gases. Granted, having a 3" hole in your downpipe at a 90 degree angle from the direction of exhaust flow will still allow exhaust gases to be expelled more quickly than normal due to the fact that exhaust gases will attempt to travel in the direction of least resistance, despite the angle and change of direction needed. However, I believe that if the direction of flow of the exhaust gases is in a very close angle to the openning of a cutout, the momentum of the exhaust flow will greatly aid in expelling exhaust gases at a much quicker rate.

With this said, in theory, a cutout will make more power than a full TBE of any size only if the TBE the cutout is installed on suffers from high amounts of exhaust gas pressure. An easy way to explain this is to take a coffee stirrer and blow as hard as you can into it... notice the back pressure of the air you're blowing. Next, put a fairly nice sized hole on the side of the stirrer as close to your lips as possible, then blow and notice the increased ease of blowing air through the straw. Consider the straw a 2.25" exhaust for the sake of this example. Now find a fairly nice sized drinking straw and try blowing into it. Consider that straw to be a larger diameter exhaust. Once there is little to no backpressure left inside the exhaust/straws, the cutout generates no additional power.

Hope this all makes sense.

 

this is what i need to know also~!!!!
anyone got answer for this?

 

In my wifes WRX I did a custom dyno tune with the cutout open, and drive around most of the time on the street with it shut. Gas milage is great, and the car runs awesome.

Keith

 

sounds good