There is a duplicate of this thread in the General forum.

A couple of months ago I modified an illustration that I got from howitworks.com. But was not specific to the WRX, so I created one that is pretty darn close. As you can see by the diagram, you can locate everything you might want to upgrade.

 

Very nice diagram. I'll be printing this one out and saving for reference. As you can see, I'm new and this does a good job of pointing out the cats and their placement.

Looks like the up-pipe is a good area to improve upon the plumbing. I've read lots of comments on the up-pipe, but no specifics on what results can be expected. I assume spool-up is improved.

How about side affects??? Any negatives?

Terbeaux.

 

There are no bad side effect to a catless uppipe except:
- maybe getting a CEL (easy cheap fix)
- passing emissions

As for improvements it's hard to say any where from 5-15 depending on your others mods.

All I have right now is the uppipe and here are my results:

 

nice power improvement. Question: how come the hp curve is squiggly. How does that affect your acceleration. Is it wierd or inconsistant. Is it smooth?

 

Since this is a road dyno test, my first guess is that there are a couple of humps in the road increasing or decreasing acceration. Please note that the before and after were tested on different roads. I assure you my car drives smooth through all the gears.

 

I'm a little confused with this diagram. Is this right: The air from outside is taken in by the ram-air scoop, filtered, and pushed into the turbo which in turn is pushed PAST the intercooler for cooling by outside air (hoodscoop) and then fed into the engine?

So why are people taking off their Ram air scoop? They just put a short ram air filter (k&N or something) for higher flow?

 

I believe more than one source has shown higher pressure builds in the fender without the "ram air scoop" and just having hte plug in the fender hole for it.

It's been a LONG time since I've seen the data on it. Probably on the "other" forum.

Technically, the air is not "pushed" into the turbo. I think if you measure pressure in the inlet you'll find it's under vacuum and that the turbo is "sucking" the air in. But your description is otherwise correct.

 

Although there have been dozens of threads over the past year or two from people arguing both ways, I have not once seen any proven results that the resonator restricted flow at all. It would seem like it does, but even the guys at Cobb will tell you that the stock air system of the WRX is just fine, and you don't need to touch the intake system (other than maybe a high-flow filter) unless maybe you're pushing a lot higher boost levels and are doing some significant tuning.

... but you do get some cooler intake sounds by removing the silencer... i hacked mine out about 2 years ago when it was the hot thing to do, but i wouldn't say i noticed much in the line of gains... i'm not bummed that i hacked mine, but probably wouldn't do it today knowing what i know now.