Originally Posted by SMSP from this [url="https://honda-tech.com/zerothread?id=200438"

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This is an interesting thread to say the least. Everyone is entitled to their own opinions....even me. Thanks to the guys with the + comments.

Here are pictures of zyg's exhaust which is very similar to George's except I used (2) 45 degree bends before the axle on George's versus zyg's (1) 90 degree bend. Both of these exhausts used 2-1/2" tips. The exhaust on the yellow ITR used the stock tip which could be adjusted slighlty more for direction. Please note that the stock ITR tip on the stock ITR muffler is welded on at an angle.




I always read that exhausts don't give any power just noise. This is probably true in most cases. But not all exhausts are built the same way. When I spec and build my exhausts I also take a common sense approach to it. One thing I know that's true is that just because a system is flashy does not mean that it will perform and make power. I also don't like to use silencers since they defeat the main reason (to me) for buying an after market exhaust and that is to release more power.

Most of the JDM systems are 60mm OD (2-3/8") some of the US systems are 2-1/4" (Thermal, Magnaflow and Comp Tech). The new Type One is 63.5mm OD (2-1/2") and the Kakimoto R is 70mm OD.

I'll try to give some comparisons between these systems. I can't comment on the HyTech system since I've never seen one but I suspect they do some of the same things I do because it's the right way to do it and they'd take the extra time to build it that way.

My exhaust is 2.50" OD, 16g 304L stainless steel with an ID of 2.37". I use a straight thru Magnaflow 2-1/2" resonator and muffler. There are no bottlenecks and no joint/section is smaller than 2.37" ID. However, 2-1/2" cats have a 2-1/2" ID outlet and this would cause a mismatch with 2.37" ID tubing. So I taper flare the inlet of the B pipe and use the exact same flange as I do on my cats.



Therefore the ID of my B pipe inlet is between 2.50 and 2.56" and thus no mismatch. In the above picture of the exhaust system, if you look at the flange set up for the muffler you'll notice the tubing of the B pipe extends past the flange and gets inserted into the muffler inlet. This is done to prevent any chance of the flanges from misaligning and causing turbulence at that point.

How does this compare to other systems available?

Stock ITR is 57mm OD (2-1/4") with multiple bottle necks. The worse being at the B pipe inlet which is 1-3/4" ID. The B pipe necks down to around 2" or 2-1/16" OD at the B pipe to Axle back joint and the muffler tubing is 54mm OD and then necks again to 52-53mm right before it enters the muffler.

Tanabe RM is 60mm and has a 1-7/8" ID x 2" long bottle neck at the B pipe inlet and it's resonator uses perforated dog ears that extend into the flow path. The 2 joints after the resonator are 2-1/4" ID.

APEXi is 60mm and has a 2-1/4" ID at the B pipe inlet, I'm not sure of the rest of the system but I believe the 2 other joints would also be 2-1/4" ID.

Comp Tech, Magnaflow and Thermal are 2-1/4" OD systems like stock but without the bottle necks for the most part.

Kamimoto R is 70mm OD and has a B pipe inlet ID of 2.50" ID <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emthup.gif" BORDER="0"> but the resonator is not a straight thru from what I can tell from the picture.


Type One is 63.5mm OD (2.50") with a 2.37" ID in the tubing. However, the B pipe inlet necks to 2-1/4" and then opens to the 2.37" ID, the resonator is straight thru but the flanged joint after the resonator is also 2-1/4" ID. The outlet of the B pipe (for the axle back joint) is set up to bolt to stock or the Type One axle back to bolt to the stock B pipe and therefore uses the stock donut. This tubing necks down to 2" OD with a 1-7/8" ID.

N1 Axle Back is 60 or 63.5mm OD and has a 2" ID inlet in order to bolt to a stock B pipe. (This is the joint that Ross was talking about having me fix).

So, I feel my exhaust performs well because the muffler and resonator are straight through with nothing protruding into the flow path, there are no abrupt diameter changes and no joint mismatches. This promotes increased flow and reduces back pressure. The size and configuration of the Magnaflow muffler that I use plus the long resonator does one of the better jobs of quieting the exhaust compared to these other systems that use smaller diameter cans in the axle back portion.

I don't have any back to back testing with my system versus any of the above but the results that George, Neo, Zyg and others have had do suggest that there are gains to be had with the system. BTW, one of my 2-1/2" exhausts with a 2-3/4" tip is currently supporting a 230+whp B20VTEC street car.

I should have a video of the ITR used in the header test this past Dec with my header and cat back so you guys can hear it. However, it was taken during a dyno run so it's inside a building.

Oh, one last thing, when we removed the 2" bottleneck in a Tanabe RM B pipe on an ITR with a Toda header and Car Sound cat the customer picked up 4whp in VTEC.

SMSP - Who has an optional 5" tip that comes with a chrome grill, chrome wheel lips, chrome door edge guards and chrome surround for the windshield, back and side glass at no charge. This makes the car look just like your father's old 1979 Buick.