it really robs your hp on high rpms

 

More than you think. You're better off getting a magnaflow muffler

 

At your power level somewhere between 30 and 50 hp. This is based on a few dyno sheets I've seen.

-Paul

 

Wow thats a big chunk. Here I was thinking it was something like 10-15 hp.

 

If I remeber correctly, I think Al dynoed a car that lost 50 hp with the silencer.

 

The loss is high. Just think about it in terms of flow. 3" v. 1.75" (+/-) (what the silencer restricts down to).

Personally, I only run my Apexi active tail silencer (spring loaded - opens under WOT), when I am on long trips (over 2 hrs away). I notice slower spool-up, and a weak top end.

 

Yes, 30-40whp...may be even 50. We've seen dynosheets where a guy didn't know any better and had that thing in there, then when he took it out, he gained 40whp immediately. If people don't want loud, then don't get an exhaust. The silencer is worse than having the stock exhaust.

 

That may be true, but the silencer isn't a bad option for people that want to be quiet for daily driving and then pull the silencer out when they get to the track. I don't use my silencer often, but I do put it in for long road trips (4+ hrs).

-Paul

 

This is the part that puzzles me. IME, your statement is correct, as every aftermarket Evo exhaust I've heard has been way too loud compared to stock - they range from loud to louder. OTOH, the aftermarket for German cars is able to offer quiet exhausts, as well as loud models, both offering similar gains (eg. Milltek, Techtonics). There's an opening in the Evo market for a quiet product. With more and more municipalities enforcing noise ordinances, quiet high-performance exhausts will be the way of the future. I'm surprised no one has taken advantage of this opportunity.

 

No 3 inch exhaust is going to be quiet, and that is what is required for turbo cars.

NA Econocars only require 2.5" MAX (barely larger then stock).

 

Yeah, really, if it were possible to make a quiet 3" catless exhaust that makes 30whp, it would have been done already...

 

I've seen dyno results of 2.5", 2.75", and 3" exhausts on identical (turbo) cars and the outcome wasn't nearly as clear. I'm no expert, but there seems to be more at play than just the size of the piping. While the thrust of your comment may be correct (ie. the amplitude of a 3" exhaust), there's a distinct possibility that smaller diameter models may offer similar, if not better, performance relative to application, as well as a greatly reduced noise.

My point is this - if a firm were to offer a quiet Evo exhaust with dyno tests to illustrate the product's effectiveness, I bet they'd sell quite a few. Only a small number of manufacturers currently show comparative dyno results, and there may be a reason for it. Others seem to be selling of faith, which has little to do with a measurable standard we're up against.

 

Addendum:

Here's a 3" exhaust that's almost as quiet as stock. It's a shame it doesn't fit an Evo:

http://goapr.com/VW/products/apr_exhaust_mkvgti.html

Clearly, such a thing can be made.