1 From: "Ryan Douthit" <ryan@midnightcafe.com>
Though I want one, I would have to personally vote for close to factory-but better.
SINGLE
2) From: Ryan Lalonde <dc-burnout@rogers.com>
I want an exhaust done that will give me maximum HP gain; with total EVERY DAY drivability...I also don't want to drown out my cool Boxer engine sounds.
DUAL
3) From: "Josh Colombo" <josh@surrealmirage.com>
I've been doin some research......temp/heat is one of the main driving factors in a turbo.....so I'll agree that a 4" pipe before turbo isn't a good idea. For the most part, velocity and volumetric expansion is what drives the turbo. So I guess I would choose a size before the turbo that would maintain exhaust gas velocities, but not choke the engine. As for that size.....I'm really not sure.....but if I had to guess....probably somewhere between 2-2.5" Or somewhere in that range......
NOT SPECIFIED
Remember Josh, this is all after the turbo, we're not buying headers, that's another story
4) From: "abs526" <andrew.b.smith@umit.maine.edu>
I really like the compatibility with the stock exhaust idea. I'd like to see 3 inch (or 80 mm) exhaust piping, no cats, small nonrestrictive pre-silencer, then the glass pack straight through muffler perforated design so air flows smoothly. I'd like to see a canister muffler, like what all performance exhausts come with. None of that louvered crap I've seen. Mainly, the idea is to keep the exhaust velocity up, and things sticking in its way to a minimum. Now I've seen a lot of downpipes that offer a splitter off the wastegate, and I've never heard anyone gaining anything from it. It seems like a good idea, but in the real world it doesn't do anything but drive up cost. That is my main concern. Lets try and keep the cost down here.
SINGLE
Andy, there is a performance improvement with the splitter off the wastegate, but you're right about the cost tradeoff. To the racers it's probably worth it, to the daily drivers, maybe not. I think we need a price differential, before most can decide.
>From Josh Colombo" <josh@surrealmirage.com>
I would recommend you keeping the cat. Firstly you can get into some serious trouble Secondly if you get a high flow cat performance really is not hampered that much. The O2 sensor is not merely for emissions it helps fine tune your car's a/f mixture. You will most definitely want to keep that puppy in there.
5) From: "Ian Shastko" <smotocon@hotmail.com>
When are we going to see some prices? I'm interested in the downpipe with no cat and a 02 sensor bung that will fit in place with my stock system. It would be cheaper and easier to put a high flow cat on the mid pipe anyway
NOT SPECIFIED
From: "Josh Colombo" <josh@surrealmirage.com>
Like I said earlier.....you don't need the cat to have your O2 sensor
6) From: Brian White <eastbaysubaru@yahoo.com>
I would like to see a high-flow cat in the stock location. A cat would be a good thing, and shouldn't inhibit performance at all.
NOT SPECIFIED
7) From Zak Malbin "laser158754" <laser158754@yahoo.com>
I would prefer a cheap stockish-looking twin outlet. BUT, #1 preference is to reduce backpressure, so nothing less then the equivalent of 3" going out.
DUAL
But cheap stockish-looking twin outlet is a contradiction Zak. The twin outlet is neither stockish-looking or cheap
From: "scott_christopher_nelson" <scott_christopher_nelson@yahoo.com>I want a system that:
1. I or my mechanic can bolt-on out of the box.
2. Of course, I'm looking for performance improvement.
3. Will pass emissions or can be removed and the OEM system reinstalled, therefore:
4. I don't want to reuse parts of existing exhaust as part of the replacement. The O2 sensor is one exception.
5. I lean toward a quieter exhaust note
NOT SPECIFIED
So there it is. Eight responses. About half the original group of interested parties. I am copying everybody from the original group that is not represented here.
Two seemed like they wanted the dual outlet, two seemed like they wanted the single outlet, and four I just couldn't tell one way or the other.
I think we need to revisit the upside and downside of the dual outlet vs the single outlet and weigh that against the probable price differential. In the meantime, Russ Kappelman has provided an excellent of the ups and downs of DUAL vs SINGLE; (I have taken some liberties with our original communication to clarify where the DUAL and SINGLE are referenced)
The advantage of DUAL is that it offers the most flow. It is also the most difficult to build (and expensive) due to the fact that there would be two tubes and the turbo flange area would have to be partitioned so that there would be no cross contamination of gasses in the turbine housing. There would be the option of including a converter in the SINGLE tube construction but I don't see any practical way of offering a converter with the DUAL downpipe.
>From Corky Bell's Maximum Boost Russ quotes;
"Exhaust gas return from the wastegate to the tailpipe after the turbine should receive the same forethought as gas entering the wastegate. The principle here is to avoid interfering with exhaust gas flow exiting the turbine. Interference will raise exhaust back pressure, thus reducing power. An integral wastegate will usually channel bypassed exhaust back into the system immediately aft of the turbine wheel. This is acceptable for economic reasons but is not in the best interest of power. A few integral wasegate designs, like some models of Japanese IHI, have provided a separate exhaust pipe for the bypasses gases. When this separate pipe is available, it should be taken advantage of and routed some distance down the tailpipe before being dumped back into the main exhaust system. A minimum distance would be 18 inches."
And Russ explains further;
My intention with the DUAL system would be to merge wastegate exhaust gasses back into the main pipe once the pipe diameter has been reduced (from four inches coming off the turbine) to three inches. The reason for this is higher velocity gasses (gasses in the smaller section of pipe will be traveling at a rate of speed greater than those in the larger section before) have less pressure than lower velocity gasses. I do not want the wastegate gasses to have any trouble rejoining the main flow. The 18-24 inch specification is in line with the above recommendation, so should prove to offer the best performance possible with this type of system. I believe that 3 inches for the system overall is appropriate given available materials to build from. The diameter of the section immediately after the turbine is still up in the air though I am leaning toward 4 inches.
The SINGLE dump style proposition would be similarly priced to the EA82T pipe though it would be a bit more, because the larger 3 inch elbows and tubing cost a bit more. In short, the labor would be the same pretty much since they are so similar. The DUAL pipe proposition would be more expensive because of all of the fabrication involved.
So there's something to chew on over the weekend.
Larry Witherspoon
Torrance (Los Angeles), CA 90504
ssspoon@aol.com
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