I just don't like the rasp and the drone that goes with it.

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I recently replaced my stock mufflers with M2 Performance axlebacks. My planned "completion" of the exhaust upgrades is removing the center sub-cat, which is generally described as the most restrictive element of the SC400's system, and replacing it with a 2.5" straight pipe. I figured it would be a good introductory question on the Lextreme forums, but the Exhaust System sub-forum seems to be dead...

Several people have said to also replace the second Y-pipe prior to the resonators. Is that really necessary for performance, or is it more for aesthetics? It's a super simple replacement if I can just do a straight pipe and keep both Y's, but if keeping the second one compromises performance, then it's not worth the trouble replacing the sub-cat and leaving it in.

Columbia River Mandrel-Bending has the best options I've found if replacing it, with splayed 2.5" inlet and dual 2.25" outlets that would somewhat follow the stock Y-pipe's exit angle (unlike Magnaflow's #10758) and require less downstream modification to mate up. They have it in stainless steel (#MCL2S-2025-SS, $68), 6061 aluminum (#MCL2S-22525-AL, $68), and mild steel (#MCL2S-22525-MS, $58). How much difference does the material choice make if it's being mated up to stock mild steel downstream? Weight reduction would be the main difference, right?

Are there any better options out there to consider?

 

4inch stainless turbo back no muffler

 

Bump... Any thoughts on the best approach?

I took a closer look under the car and the second Y-pipe does look like some pretty small outlet pipes. I can see why that's considered one of the restrictive points in the system.

I noticed that Columba River Mandrel-Bending's stainless model is only 2" or 2.13" outlets, not the desired 2.25". I haven't called them yet to see if they have it in the right size, just unlisted. Also, I think I was wrong about the stock system being mild steel. It's actually unpolished stainless steel, I believe?

Edit: I'm also thinking the Magnaflow 10733 is worth a try. It's 2.5" for both inlet and dual outlet, so it would need a reducer to the 2.25" downstream pipes. It looks like a good match for the stock layout, though, and seems like it should be a very smooth transition. There wouldn't be any negative to adding reducers to it instead of having the proper 2.25" outlets to start with, would there?

 

Post sound / videos!!

 

OEM exhaust systems are typically made from T409 stainless. It's considered stainless, but it's chromium and nickle content is much lower than the T304 SS we all think of when we say SS, thus it does eventually start to oxidize and rust.

 

Makes sense, thanks. A lot of pipes and Y's I've seen are T409, and I've read that's the lowest rating considered adequate for long-term exhaust usage.

 

Yep, I mean look at OEM exhaust systems. They last a long time, but still eventually succumb to corrosion. It's cheaper so if you're looking to pinch every penny then it's not a bad option. I still prefer T304 as it will pretty much never rust.

 

Perhaps I should have started a second thread for this, but someone surely would have said to merge it into the SC Exhaust Thread... I found a new possible fit for the downstream Y-pipe: the Wesdon WES-U4-3 on Amazon for $38. It's 2.5" inlet to dual 2.25" outlets and long enough on the outlets that the straight part could be cut off, leaving the angled part as a fairly good match for the stock pipe layout. With a little luck, that could be tied in with minimal bending.

Looking on eBay, it appears Wesdon is just the seller of what is actually the Jones Exhaust U4-3, which can be had for as little as $20. The only downsides I see are: 1) it's aluminized mild steel, which probably isn't going to be quite as good long-term as stainless, and 2) the craftsmanship is a bit shy of artistic. It looks like an efficient splitter design, at least.

 

The issue with the oem set up on the sc400 is that the cats are directly at the end of the manifold, which halts the scavenger effect from the cylinders, also they are huge so that there is a huge differential in airflow due to the air being dumped into a big open space, this is great for the 300 as turbos need this but for a normally aspirated engine as the 400 we need to encourage a scavenger effect, I feel that the best is to place the cat at the end of the engine pipe in a single form but use a free flowing 3 inch, and run a 2.5 inch pipe from the headers back to the join to the three inch then go to dual for the tail pipes to enhance the scavenger effect, remember that WOT is not everyones goal especially on a normally aspirated engine.

 

Here you go; $60 at local muffler shop.
Cut out center section before Y, and after Y, weld in 2" pipe sections with a crossover at exactly the same place where the first Y was.
No drone, sporty rasp at full throttle on slightly ported 4.0.
The stock mufflers are straight thru just like aftermarket ones, so why would you make more of a project out of it, it's an exhaust?

 

Gutted cats with stock resonators and straight pipes

 

Has anyone ever put a Tubi style exhaust on their SC?
Would love to hear one of the M5 ones retrofitted on the SC300

 

I know this is like a year later but, I tried searching for these "tops speed pro-1's" and i wasnt able to find them. where'd you get them? are they just axel backs? did you delete resonators?

thanks in advanced.

 

custom made 2.5" midpipe/x-pipe, stock cats, and tanabe medallion mufflers. I really like the sound, it doesn't drone and the in-cabin noise is barely noticeable unless I hit the go button.







Final Product..