TrevorS

iTrader: (1)

In case of interest, here's a photo of the OE 'S'-Pipe. I measure the pipe ID as aprox 2.2" at the header end and aprox 2" at the scuba end.



Since the pipe bends are reasonably smooth and the header exit port is also aprox 2.2", I guess "upgrading" the pipe probably doesn't accomplish a lot, though I haven't actually measured the pipe at the scuba.

=====================Later==============================

I measured the scuba entry pipe OD as about 2.2". I figure in light of the bends, a 2.5" 'S'-pipe would probably be reasonable, but unless the scuba is deleted, 3" is really overkill. Wonder what the Weapon-R ID is?

ScionFred

iTrader: (1)

IIRC the biggest N/A hp/tq gains I've ever seen from a 2AZ-FE exhaust upgrade were from the CXR full 3" system. However, I'm quite sure that both hp and tq peaks were moved up the rpm scale and it was obnoxiously loud.

IMHO the biggest exhaust bottleneck isn't the 2.25-2" S-pipe, it's the 1.75" mid-pipe after the "scuba tank" and before the axle-back. Since the "scuba tank" exit is also 1.75" it too could be considered a major restriction. While a 2.5" S-pipe would provide some improvement, the bang-buck would be weak. I'd focus more on the scuba tank, mid-pipe and axle-back restriction and leave the S-pipe upgrade as the final piece of the puzzle.

TrevorS

iTrader: (1)

My exhaust piping from the rear of the Scuba is 2.5", so I wouldn't mind bumping that curvy 'S'-Pipe to match (given the right price ), but I really can't see me fooling with the scuba.

xseveredveganx

I wonder if we sent an OEM s-pipe to a place that does mandrel bending, if they could make that part for a decent price. It's worth emailing about.

ScionFred

iTrader: (1)

If you can find the right exhaust shop they should be able to make a new s-pipe for about the cost of the W-R pipe. I'm pretty sure that MBS could do it but they'd need your car for a few hours.

TrevorS

iTrader: (1)

Yes, that could be interesting!

Just checked the W-R web site and their 'S'-Pipe is the right size (2.5"), but not the right price ($215 + ship).

http://www.weapon-r.com/products/626...ader-25-s-pipe

I would need to get significantly lower to justify not going Weapon-R, plus I'd need to go much lower still to justify the purchase to begin with ! The eBay CXR 3" is $125 shipped -- same as the header I just installed, however, looking at the photos, I've the suspicion it won't work with the scuba. I'll see what CXR has to say.

xseveredveganx

Turns out there's a place that does mandrel bending here. I'll have to talk to the owner, but the person I spoke to said that the owner likes taking up some little one-offs from time to time. So I'll have to see what can be had.

TrevorS

iTrader: (1)

Given an attractive price, I'd be in for a 2.5". Stainless Steel would be preferred since mild steel might rust at the lowest point -- though perhaps it's hot enough there to stay free of interior condensation.

ScionFred

iTrader: (1)

About a year ago I ordered a W-R S-pipe but after a few days was informed that it was backordered for several months. If you can get one, it's a nice piece. I'm 99% sure that the CXR pipe won't bolt up to the scuba without some cutting and welding. Even if it did you'd have an abrupt 3" to 2" reduction sure to create a lot of turbulence and flow restriction.

TrevorS

iTrader: (1)

Yeah, I had to mate an oversize down-pipe (2.5") to my Eclipse cat a couple years ago since the OE had rusted through at the flexible mesh coupling. I understood the stock size was 2.25", but it turned out to be 2" -- 2.25" would have worked. I ended up making a steel adapter and installing a gasket on each side.




The car seems happy enough with it, very noticable difference in exhaust sound and noticable exhaust breathing improvement, but it needs 2.5" right through. Now, that's just a .5" miss, the CXR would be around 1". You're right, not nice !

TrevorS

iTrader: (1)

Well, thinking about it further, I realize the header only cost $125 shipped because it was made in China and the nearest other pipe is the 3" CXR which is also $125 and probably also made in China. To get one hand built in the US with good fit & finish is logically going to cost a fair bit more (as Fred suggested). So, I decided if I'm serious about a 2.5" 'S'-Pipe, I should hunt for a good price for the Weapon-R. I did, and came across $182 shipped, which is equivalent to $157 + $25 ship from Ebay -- ~60% more than the CXR. So, I decided to go with it -- unless there's a better price somewhere, looks to me like the only game in town. (Lordy -- is that ever a splurge !)

ScionFred

iTrader: (1)

When I first went to MBS they quoted me $500 to fab a complete exhaust system from downpipe back using 2.5" or 3" 409 SS. I decided to try the CXR exhaust instead since it was 304 SS and I was able to buy a used one for only $150. My current exhaust system cost me $1000 because I spent $500 on the TRD axle-back and CXR exhaust. If I could start over I would definitely skip TRD and CXR and have MBS make me a full custom exhaust instead. In the future all of my exhaust work will be done by them but I have no idea how common a shop like this is in other areas of the country.

It sounds like your exhaust is too far along to go this route now as all you seem to need is a new s-pipe but there are still advantages to going custom. If you could find a shop like MBS and they made you a new s-pipe for ~$200, that would also include installation and guaranteed fitment. The key word there being "if". Obviously a trip to Pasadena MD is easaier for me than you so you'd want to find a local shop that can do the same work for the same price.

Anyway, I haven't heard any complaints about the WR s-pipe so it's probably your best option at this point. OTOH the CXR s-pipe doesn't fit very well and the guy I bought mine from had to have it modded so it didn't hit the chassis cross-member. As for 304 vs 409 SS, they both last as long but 304 can be polished and looks prettier as long as you polish it regularly. I'd definitely want 304 for a header but prefer 409 for the rest of the exhaust. It's not as brittle and much easier to cut and form.

Good luck either way.

TrevorS

iTrader: (1)

Thanks !

Thinking about the "scuba" entrance and exit pipes --

The exit area of a 1.75" ID pipe is 2.4sq-in and the entrance area of a 2" ID pipe is 3.1sq-in, for a in-to-out reduction of 33% I don't know how much exhaust gas temperature drop occurs while it passes through the "scuba", but I wouldn't be surprised if it's 33% or even greater. Given the inverse relationship between temperature and volume for gas, it's quite possible the 1.75" exit has little impact on 'S'-Pipe flow. That may also explain why my Eclipse responded very well to the upgrade from a 2" to 2.5" down-pipe. The ratio there is 3.1sq-in to 4.9sq-in, for a reduction of 37%. The temperature drop over the cat is probably serving to mate the flow to the OE 2" exhaust -- kind of a temperature activated adapter, if you will !

For the Eclipse, custom will be the only way practical for me to upgrade the exhaust piping (an Apexi N1 exhaust is way to expensive for me), but I think the xB2 is pretty much where it's going to be. I just keep scratching my head on the 'S'-Pipe trying to evaluate what's really going on, but at least I have the example of the Eclipse and its down-pipe upgrade. On the surface, one wouldn't have expected much without changing everything after it, but that wasn't the case (I actually found a review of that down-pipe that shared my result). I think it's delta-T over the cat that provides the explanation -- in which case, the xB2 should benefit as well. The area reduction from 2.5" to 1.75" is 51%, though with a 2" "scuba" input restriction. However, that restriction probably quickly opens again due to diffusion in the "scuba".

PS. Guess I should note that the pressure is going to be less after the "scuba" than before, and that allows the gases to expand, so there are two opposite effects at work. My money is on temperature drop being the heavier hitter !

ScionFred

iTrader: (1)

I don't have the necessary tools or knowledge to construct an optimal N/A 2AZ-FE exhaust system but AFAIK the basics still apply. The seemingly over-sized 3" CXR exhaust has been shown to produce optimal peak hp and tq. I can only guess that the oem reduction in exhaust pipe diameter from 2.25" to 1.75" causes unwanted restriction in a performance oriented application. I would think that increasing those pipe diameters should help. Likewise, it seems that lessoning exhaust restriction in one part of the system helps to reduce overall restriction even when not optimally sized to acheive overall exhaust efficiency. Leaving the scuba intact will always represent a compromise solution.

bosnik

$500 for a TRD exhaust????? I bought mine for $50 from a salvage yard

ScionFred

iTrader: (1)

No, $500 for the TRD and the CXR exhaust. TRD is like $350 new.

TrevorS

iTrader: (1)

Yeah, 3" makes sense for a turbo application, would make sense for my Eclipse as well if I wanted to upgrade the 14b turbo and build more power. But 2.5" is fine for my turbo aspirations (the down-pipe's a start ). I figure 2.5" is gonzo plenty for an N/A xB2 and 2" is probably adequate. Still, I do have some confidence in my cat "pipe adapter" theory because it actually is based on physical science and it does help explain my Eclipse down-pipe upgrade result. It could be the purpose of the "scuba" exit ID reduction is to help maintain enough back pressure (given the temp related exhaust gas volume reduction) to support good torque at lower rpm -- thinking N/A again, not F/I.

Still, I've decided to try playing the temperature card and will paint the 'S'-Pipe for max heat delivery to the "scuba" (the Eclipse down-pipe is also painted). Think I may also remove the "scuba" to try porting the pipe entrance for a smoother match. Can't be sure of a tangible result, but that's OK -- I figure every little bit should help . I'm expecting the pipe to arrive tomorrow, so that'll kick off another project !

================================LATER==================================

Shucks! Just learned the pipe shipped from San Pablo CA instead of PA -- so much for Thursday !

ScionFred

iTrader: (1)

My memory sucks! I remembered a thread where someone dyno tested the CXR exhaust on their XB and gained 10whp from it. I looked it up today and saw that he also had a CAI installed. The CAI alone could have added the 10whp. I was thinking it was all from the exhaust. Oh well, getting old sucks but still beats the alternative.

Anyway, I agree with you that 3" is over-kill for N/A or even ~300hp boosted apps. My current exhaust is a hodge-podge because I had it done a piece at a time. 2.5" DP, 3" S-pipe, 3" resonator, 3-2.5" tapered reducer, and 2.5" mid-pipe and axle-back. The turbo still spools very quickly and I'm sure I could easily make 350BHP with this exhaust.

As for the typical oem exhaust diameter reduction, my understanding is that it's done to maintain gas velocity as the temp decreases. Although it has the effect of adding back-pressure, that's not the goal. I think you're on the right track but believe you'll be leaving some hp/tq on the table by keeping the scuba. Ideally I believe you would want to increase all of the oem pipe diameters by 1/4" to 1/2" but I'm sure you'll still gain some power even with the scuba still in there.

Good luck with the new project! I look forward to reading about it.

TrevorS

iTrader: (1)

Yeah, my memory is a whole lot worse than I like to think too -- what can you do, time goes by !

According to the recognized impacts of my Eclipse mods, it's in the neighborhood of 300HP now, which I feel is a respectable and adequate bump over the 195 OE -- I'm satisfied ! I've been advised to go for a 3" exhaust, but there's just no point, that is, not for me.

Matched velocity at the "scuba" outlet would make sense in terms of reduced gas volume, just another way of looking at it -- the "transformer"/"adapter" effect . I pulled the "scuba" and there is definitely an opportunity for a little porting. Turns out my exterior pipe measurement was wrong since a bench inside measurement gives me aprox 2.25". That makes complete sense when you're under the car looking at the two pipes where they meet, the "scuba" pipe appearing easily larger than the rear of the OE 'S'-Pipe, so I'm disappointed I obviously blew my measurement of the "scuba" pipe OD -- still, that was a long reach for my caliper, perhaps that was the problem. In any case, the step from 2.5" to 2.25" is nicely less, though there remains plenty of Dremel time to smooth it out ! Think I need to pick up a new grinding stone.

In any case, thanks for the interest and as far as the "scuba", I'm comfortable with it being a likely limitation in what I can accomplish. For me, it's fun to have additional performance on tap, but mostly, I don't use it -- besides, it is an xB2, performance not being an inherent forte'. I get "challenged" occasionally as it is, why make it official ? 'Course, your turbo xB2 could answer that in spades !