I was looking to reproduce a similar system to the Amuse but w/ SS piping. I wasn't able to locate the ID of the piping used from the cat to the can - I know HKS uses 60mm after the Y. Anyone know the Amuse ID or OD?

Curious if a straight 3" from the cat back to a single outlet would be beneficial. Has this been done before? I could whip up a crush bent (yuck) 3" steel fairly quickly to test on the dyno with a Dynomax or Flowmaster muff. I dunno what it would sound like or what the dyno will say, but I have all the parts laying here from a previous project car, so why not. More or less, if we see some positive results, I'd sent the details to Thermal Research or the like to possibly fabricate a quality 3" full SS cat back; single out.

If there is some interest - I'll tackle it this weekend and post the results. Let me know what you think.

 

Unless you're using some form of forced induction (turbo,supercharger,etc.) then you're probably going to lose power with a 3" exhaust, even if it's only cat-back. I wouldn't go any larger than 2.5".

 

According to Mugen (instructions with the ECU) the recomended diameter is 2.4" if I remember correctly. They also say how long it should be.

We used to have a 2.5" custom made exhaust with a N1 muffler but later changed to a Js Racing which is done in SS and is around Mugen's specs. I haven't dyno the car but witht he J's the car feels better on the bottom end. I have to find some time for dyno testing.

 

I like your idea but I think 3" would be way too big. I'd love to see the results from 2.33", 2.5", and 3 inch. I'm betting the 2.33" would be the best.

Any chance of you taking a shot at doing this?

 

Amuse is 60mm piping.

 

That's a good point - maybe build 2 or 3 single-out exhaust systems in varing sizes and see what the dyno says. The bends from the cat back are not hard to duplicate; it wont be pretty but it will work just as well.

Since Honda splits the exhaust - the overall ID is greater than 3". I didnt know the Amuse was a single at 60mm. That's almost like cutting off one side of the Y on the stock exhaust and capping the cut. Not taking into account the mufflers; the backpressure on the Amuse must be higher than OEM.

I'm running the car with Chin at Atlanta Motor Speedway this weekend - so I'll get the results in after that.

 

The exhaust that I'd like to see would be identical to the Amuse Ti exhaust, except it would have a resonator in it before the muffler to quiet it down some.

I'd definitely be up for something like that. As others have said, a good exhaust starting point would be the Mugen specs and take it from there.

 

First, ContactPatch - the stock exhaust is most certainly NOT 3". I haven't measured it, but it looks like it's about 2.25" or so. But DEFINITELY not 3". 3" exhaust is strictly for high displacement engines and turbocharged engines.

S2KRob, the Amuse exhaust DOES have a resonator before the muffler.





As you can see, the Amuse exhaust does not actually have any bends in it - it just has a bunch of straight pieces welded together. Kinda ghetto. I'd rather have slightly heavier stainless exhaust with smooth transitions and mandrel bends.

 

I might not have clarified it correctly - the stock exhaust is really about 4.5" ID after the Y. Take into account both pipes at approx 2.25 each - the stock exhaust is *much* larger than a single 60mm Amuse or even my testing on a 3" single (like the Amuse).
The OEM mufflers come into play on the stock system, but I think that is why we are not seeing a jump in HP on freeflowing dual systems. The OEMs might keep the pressure in check.

Only speculation, but maybe the A/F dual systems are too large. The cat restriction has some effect on the calc, along with the header - but on a NA 2.0, testing on a single out system and varing the sizes from 2.25 to 3" could lead to some favorable results. And maybe not. Only one way to find out.

 

Actually, dual 2.25" pipes translate to a single diameter pipe of 3.2" or about 90mm, not 4.5".

This is based on the assumption that 50% of the exhaust flows out each muffler, probably not a good one.

Of course, the real restriction in the stock exhaust is BEFORE the split.

So, yes, the Amuse will definitely outflow the stock exhaust.