Just curious about CS 80mm exhausts

I am basically happy with the exhaust I have, so, my question is basically academic. But I'm curious about CS's 80mm exhausts. They have them for the MS3 and the MS6. But their downpipes for the MS3 and MS6 are 3". I don't know of any competitor making an 80mm downpipe either. So, what is the point of having an 80 mm exhaust connected to a 3" downpipe? What is the purpose? I also figure that 80mm mandrel tooling and pipe is harder to come by and more expensive here in the Imperial units states. Thus making it more expensive for no purpose that I am understanding.

Now, I know that CS also makes a cool 3.5" turbo-back exhaust for the MS3, but that is a different animal. Just asking about the 80mm exhausts. What is the point? Just curious. Thanks.

 

80mm=3.1" for arguments sake they're the same thing so what are you getting on about wondering why you'd want the same sized DP and catback? Why they don't just list them in Imperial for all the exhausts is or list it as 80mm(3.1") is a question I cannot answer.

Now a slightly bigger DP than catback is fine, you can make 300 whp+ with a down pipe and stock catback, I think my buddy hit ~354whp like that.
The hottest air coming out of the turbo will consume more volume slightly bigger turn off the bell mouth is good for flow. How much the exhaust gas cools on the way down the DP I don't know it's cooler by the time it's exists the tips.

Ethier way 0.1" is really nothing to write home about and it probably benefits turns and flange ID

 

Eh, closer to 3.15", but, true, not a big difference at all. (I did say the question was "academic")

But CS actually lists it as a selling point. From their description on their cat-back. (Same verbiage on their MS3 and MS6 cat-backs)

• Mandrel bent, true 80mm piping for increased flow and more power from your engine

Which differs from the DP selling points:

• Polished 3" 304 stainless steel piping for corrosion resistance and reduced heat transfer

I just don't understand why. As I said, I'm pretty sure that here in the states, 80mm piping and 80mm mandrel tooling is more expensive than 3". And the MS3 version indicates it also comes with 80mm tips, which again I'm sure are more expensive than 3". And the 80mm mufflers are probably more expensive than 3". For no discernable purpose.

But we are talking the reverse, a (slightly) bigger cat-back than the DP! That doesn't make any sense to me. Sure, it is insignificant. I'm just perplexed as to why.

How I even came to ask the question was I came across a CS YouTube video about their MS3 3.5" exhaust. In the comment section on the video, they did claim to be working on an MS6 version. Whether they actually will make it, who knows. Even if they did, it still probably won't interest me as their MS3 3.5" exhaust is for their 5-bolt flanged turbos and I assume that if they made an MS6 version it would also be 5-bolt. But, just seeing their MS3 3.5" exhaust video caused me to decide to peruse the CS site just to see what they have, and I noticed that 80mm oddity and wondered why.

 

Something even more curious. I discovered that they also make, for the MS3, a 3.5" to 3" downpipe.

Mazdaspeed 3.5" Downpipe Kit - YouTube

In the video, they say, "the entire length of the downpipe is a full 3.5 inches and reduces down to that 3 inches at the very end". Okay. And they state it is compatible with 3" and 80mm cat-backs. They do specifically state them as being two different things. Okay. But, then, shouldn't they have actually made it reduce down to 80mm at the very end? If they are going to the trouble to make a 3.5" downpipe, and they had previously gone to the trouble to make a roughly 3.15" cat-back, wouldn't it make the most sense to make the reducing downpipe go down to the 80mm instead of 3"? You may say it is insignificant. But again, they went to the trouble to make it 80mm and advertise it as an advantage, so why not actually make use of that advantage in some small way? It just boggles my mind.

 

Some of this comes down to material selection and manufacturing processes. In the grand view of things the 4mm (0.125") difference will not be noticeable or measurable. So 3" vs 80mm is essentially the same for 99% of builds.
Now...the 3.5" (89mm) has a full turbo-back option or downpipe only option.
- The downpipe only option is a 3.5" that reduces down to the "standard" 3" options that most all aftermarket cat-back exhaust are. Its also fits the CS 3.125" (80mm) exhaust perfectly.
- The full turbo-back exhaust must be purchased as a complete turbo-back because the designs intention is to have a constants 3.5" diameter from turbo to Tip. No reductions/restrictions in the system.
Both setups do use the OEM 5 bolt flange but its a v-band connection from the cast bell mouth to the rest of the piping so you could get a fabbed bell mouth for a v-band turbo. I know Jimi @ DTP has done it before.
Also the 3.5" systems have proven to provide faster spool and more peak power (especially on higher power builds) .

 

The site pictures are nothing compared to actually hands on unboxing and seeing the shining excellent pipes. Now my chassis is straight, but with the all bolt flanges was worried on fitment. CS uses a oem style of cut in half donut on the downpipe to cat connection for alignment to allow any additional adjustment. Once I had system in loose from downpipe to exhaust tips (with one bolt to hold gasket) was completely shocked, surprised and very happy that all the connections were perfect. As you can see from the photos the flat gaskets for the bolt flanges just rotated into proper position for second bolts
Incredible looking... I had to leave on stands a couple of days for other purposes.. I still used creeper to stare at it any chance possible.