As I sit at work most days I sit and ponder things about the car, the engine, and what I could do and what needs to be done and this and that. Well today, I came to something that still frustrates me to this day. There is no "direct" replacement for the CA18's turbo outlet pipe to connect to an aftermarket downpipe while using the stock manifold. Yes I've come to terms with it, and have even had my downpipe hacked and welded to solve the issue. But now after I've changed some thing and replacement my motors mounts the engine sits differently and in turn, the exhaust sits differently, which has put my wideband O2 sensor in a position where I would have to lower the exhaust to remove it because of clearance issues with the transmission cross member.

To sum things up, I'm thinking of embarking on the journey to make my own turbo outlet. Before I start really considering it I do one question.

How much power is really being gained from a larger outlet pipe from the stock? To me it seems as though only so much exhaust can pass through the turbo at one time as it is. Plus, the angle the downpipe was cut and welded at to allow for the exhaust to bolt up (not to mention how difficult it is to tighten the bolts now) it seems it would just be so much easier to have the flange rotated to fit rather at this point. So I may be in the market for an OEM outlet if someone still has one around and I can't find mine.

Input is greatly appreciated.

Thanks!

I've been eyeing this for a while, but here ya go.
http://www.rhdjapan.com/hpi-outlet-pipe ... 18det.html

Oh, I forgot to mention, beware JDM parts. I was considering that O2 pipe but I've never heard anyone who has ran it, along with that, JDM parts are notorious for coming close to the steering shaft (turbos, O2 elbows, exhaust manifolds).

I did some searching on HPI's website and that O2 housing actually is listed for the SR20DET...

Remember that what causes the movement of gasses through the engine is pressure differentials. Lowering backpressure after the turbine helps with spool and power by increasing the pressure differential across said turbine, which raises the flow rate.

The effect is more relevant at higher power levels and with bigger turbos, but it will pay dividends for your setup so long as the rest of the exhaust isn't acting as a bottleneck.

Tomei has some data on their elbows that illustrates what I'm talking about:


It's for an RB25, but you get the idea. http://www.tomeiusa.com/_2003web-catalo ... pe-en.html

sjbsuperman1425 wrote:I did some searching on HPI's website and that O2 housing actually is listed for the SR20DET...

Good catch, I thought the listing was accurate. Usually I check for those kinds of things since everyone seems to think all SR stuff works for CA.

So the consensus forever ago was that if you used an SR O2 pipe, you had to use an SR downpipe, but that as long as you used both, they fit just fine. Back when I was running a stock placement turbo, I was fortunate enough to find a CA specific, one piece, turbo outlet to cat inlet pipe. It fit perfectly, but the company went out of business. In hindsight, I wish I hadn't sold it. That being said, getting a T25 outlet flanges is easy enough as well as 2 bolt flanges for the cat inlet. Once you have those, and exhaust shop should be able to make what you're wanting.

float_6969 wrote:So the consensus forever ago was that if you used an SR O2 pipe, you had to use an SR downpipe, but that as long as you used both, they fit just fine. Back when I was running a stock placement turbo, I was fortunate enough to find a CA specific, one piece, turbo outlet to cat inlet pipe. It fit perfectly, but the company went out of business. In hindsight, I wish I hadn't sold it. That being said, getting a T25 outlet flanges is easy enough as well as 2 bolt flanges for the cat inlet. Once you have those, and exhaust shop should be able to make what you're wanting.

I had a shop cut the downpipe, weld in a flex section, O2 bung for my wideband, and alter it to fit the location of the outlet while using the stock manifold. I always check on eBay Australia and eBay throughout Europe to try and find O2 pipes that are CA specific (seeing as it was offered in these locations for a longer time) but there really isn't one.

Anyone have an OEM one for sale if I can't find mine that I may have thrown out?

I was always jealous of the Invidia DP on my friend's WRX, as it went from a big bell-mouth turbo outlet down to a 3" round pipe seamlessly. Looked much less restrictive than even the Tomei or similar Nissan t25/28 turbo outlet pipes. This one, for reference: https://www.rallysportdirect.com/part/d ... -bellmouth

So I bought this and had my own fabricated up. Its awesome, I got to put the O2 bung wherever I wanted, and its about as unrestrictive as it gets.

http://drivenperformance.co.nz/products ... et-single/

Mighty Car Mods did an episode on making an exhaust for 2-sexy (their lancer track car project) and made one using the same method, but its not quite as involved as the one I had done. Its still a great visual though, if you need to picture kind of what I am talking about. https://www.youtube.com/watch?v=nv7CKpB42vk

If you have a welder, this is a really easy project. If you don't have a welder, a professional will do this for about the price of that questionable RHDJapan unit a few posts above this.