Robtune with stock catback/axleback

Headers, cats, uppipes, downpipes, midpipes and mufflers.

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James614
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Robtune with stock catback/axleback

Post by James614 » Thu Nov 30, 2017 12:09 am

Just wondering what peoples' thoughts were on running the Robtune with a catless bellmouth downpipe, but mated to a factory catback or axleback exhaust. Since the SS/TW have 2.5" all the way through the muffler, I'd imagine any loss would only be at the very top end, if any at all.

My goal is to get back to a stock-ish sound since noise and power are not necessarily correllated (OMG I've officially become old man!). I've looked at adding a resonator, however from what Ive read and videos Ive watched they improve tone and can reduce cabin intrusion but don't actually make it that much more quiet at the tip.

That leaves me with chambered mufflers, of which ones designed to fit Subies are slim. I've looked at the Bosal/SPT unit, but even those are louder than stock. However they are 3" and far quieter than the perforated core fart cannons so if there's a bonafide performance benefit between that and stock, I just might go that route.
93 Touring Wagon (EJ20G 5spd Swap) -- Finally back and running strong as ever!

05 Outback 2.5XT 5spd -- Now the wife can have her SUV and get in on the turbo Legacy goodness at the same time.

Pntaste4evr99
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Re: Robtune with stock catback/axleback

Post by Pntaste4evr99 » Thu Nov 30, 2017 2:40 am

Just grab a used stock sti muffler and cat back and call it a day....
94 Winestone SS 5MT Rob 550 20g. (Pickle)
Original WA car with 460k miles and climbing

James614
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Re: Robtune with stock catback/axleback

Post by James614 » Thu Nov 30, 2017 2:16 pm

The appeal of the SS/TW system is that it is a direct fit, and I don't have access to welding tools anymore. So if our system flows as well as the STI's (and I believe I remember reading that it does or likely does) I'd much rather go that route.

If the stock STI system does flow better than ours, then I'd be willing to get the work done to install it. But direct fit > making it fit if performance is about equal.
93 Touring Wagon (EJ20G 5spd Swap) -- Finally back and running strong as ever!

05 Outback 2.5XT 5spd -- Now the wife can have her SUV and get in on the turbo Legacy goodness at the same time.

mike-tracy
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Re: Robtune with stock catback/axleback

Post by mike-tracy » Thu Nov 30, 2017 6:05 pm

I think the STI muffler flows better than stock, but the rest of the system is the same size. I can confirm that the Robtune works with the stock exhaust. It really kills the top end power, but it's still fun.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

James614
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Joined: Sun Jun 10, 2007 4:35 am
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Re: Robtune with stock catback/axleback

Post by James614 » Thu Nov 30, 2017 7:12 pm

Mike, are you able to elaborate more on "really kills the top end"? I'd expect maybe a minor power loss, however I'm not looking to make the car markedly slower. Also, was that with a stock downpipe/cats? I'm thinking that keeping my catless downpipe and possibly midpipe that I'd alleviate the worst of the restrictions in the stock system.
93 Touring Wagon (EJ20G 5spd Swap) -- Finally back and running strong as ever!

05 Outback 2.5XT 5spd -- Now the wife can have her SUV and get in on the turbo Legacy goodness at the same time.

mike-tracy
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Re: Robtune with stock catback/axleback

Post by mike-tracy » Thu Nov 30, 2017 7:25 pm

Yeah I tried it with full stock exhaust, from the turbo on back. That was also with my ej20g and a td05, so that engine only really shines in the mid to top end of the power band anyways. It killed the top end for me, as in, the push you get from running the td05 at 18psi just wasn't there.

I feel like with a stock exhaust and an STI axleback welded to fit, you'd be better off while still having a quiet car.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

mike-tracy
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Re: Robtune with stock catback/axleback

Post by mike-tracy » Thu Nov 30, 2017 7:29 pm

I currently have a custom catless full 3" exhaust with an 18" resonator, and the SPT muffler (previous owner had a 3" pipe welded to said muffler) and it's really quite loud. Not annoyingly droney on the freeway, but it certainly gets attention. I'd really like to get a borla hush axleback and run that.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

James614
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Joined: Sun Jun 10, 2007 4:35 am
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Re: Robtune with stock catback/axleback

Post by James614 » Fri Dec 01, 2017 4:37 am

That feedback helps a lot. I've got the EJ20G/TD05 so it definitely sounds like I'll loose some power going as quiet as I want to cheaply.

I've looked at the Hushback, but man it's expensive. I guess having a subtle tone and good flow costs money.

I think I might try grabbing a used STI axleback since they can be had for pretty cheap and throw that on first, and go from there on sound vs. power.
93 Touring Wagon (EJ20G 5spd Swap) -- Finally back and running strong as ever!

05 Outback 2.5XT 5spd -- Now the wife can have her SUV and get in on the turbo Legacy goodness at the same time.

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