benefit to running 3.5" downpipe?
#3
Rotary Motoring
iTrader: (9)
On my TII I tried a couple aftermarket exhaust configurations with the same motor and turbo (stock hybrid w/ 60mm external WG) configuration.
First 3.5" turbo back single with one muffler- JIC Spec 90.
Very loud at all rpms with in the low frequency (boomy) with a bad resonance right around 70mph cruise rpm on the freeway.
Full boost @ 3,400rpm in 4th.
Switched to Racing Beat Rev TII 3" turbo back with pre-silencer to dual mufflers.
Fairly quiet at idle/cruise, really quiet under load until WG opened- Psssh noise like air trying to escape my exhaust tips.
Full boost @ 4,000rpm and much less power tooling around off idle.
3.5" downpipe and mid pipe section to Racing Beat Rev TII 3" "catback section".
Fairly quiet compared to JIC Spec 90 at idle- much less boomy, but more exhaust noise than full RB system by far. Pretty loud and raspy sounding at full load even before the WG opened.
Full boost @ 3,400rpm in 4th- no noticeable performance difference over full 3.5" exhaust at any rpm.
Back to full 3.5" turbo back with a Vibrant Streetpower muffler instead of original cannister style.
Surprisingly quiet at idle compared to original JIC Spec 90 cannister style muffler, but still louder than with RB cat back and very boomy. Very loud under full load, but boomy not raspy until WG opened. Surprisingly quiet at cruise with no booming resonances.
Full boost @ 3,400rpm- no noticeable performance difference over 3.5" downpipe/midpipe and 3" "catback" section. No noticeable difference on dyno either.
I preferred the deep tone of the single rear section though over the chainsaw rasp of the Racing Beat duals, others maybe didn't prefer the overall louder exhaust.
I watched some out of car videos of both single and dual rear section, but all you can tell is idle/free rev sound or open wastegate sound because its at the drags.
Well- might as well post.
3.5" downpipe/midpipe to RB 3" dual-
3.5" turbo back single with Vibrant street series muffler. This vid is an aftermarket turbo with slightly smaller exhaust side and dual 44mm WG- but sounded really close to same as stock hybrid with bigger P-trim exhaust and single 60mm WG.
First 3.5" turbo back single with one muffler- JIC Spec 90.
Very loud at all rpms with in the low frequency (boomy) with a bad resonance right around 70mph cruise rpm on the freeway.
Full boost @ 3,400rpm in 4th.
Switched to Racing Beat Rev TII 3" turbo back with pre-silencer to dual mufflers.
Fairly quiet at idle/cruise, really quiet under load until WG opened- Psssh noise like air trying to escape my exhaust tips.
Full boost @ 4,000rpm and much less power tooling around off idle.
3.5" downpipe and mid pipe section to Racing Beat Rev TII 3" "catback section".
Fairly quiet compared to JIC Spec 90 at idle- much less boomy, but more exhaust noise than full RB system by far. Pretty loud and raspy sounding at full load even before the WG opened.
Full boost @ 3,400rpm in 4th- no noticeable performance difference over full 3.5" exhaust at any rpm.
Back to full 3.5" turbo back with a Vibrant Streetpower muffler instead of original cannister style.
Surprisingly quiet at idle compared to original JIC Spec 90 cannister style muffler, but still louder than with RB cat back and very boomy. Very loud under full load, but boomy not raspy until WG opened. Surprisingly quiet at cruise with no booming resonances.
Full boost @ 3,400rpm- no noticeable performance difference over 3.5" downpipe/midpipe and 3" "catback" section. No noticeable difference on dyno either.
I preferred the deep tone of the single rear section though over the chainsaw rasp of the Racing Beat duals, others maybe didn't prefer the overall louder exhaust.
I watched some out of car videos of both single and dual rear section, but all you can tell is idle/free rev sound or open wastegate sound because its at the drags.
Well- might as well post.
3.5" downpipe/midpipe to RB 3" dual-
3.5" turbo back single with Vibrant street series muffler. This vid is an aftermarket turbo with slightly smaller exhaust side and dual 44mm WG- but sounded really close to same as stock hybrid with bigger P-trim exhaust and single 60mm WG.
Last edited by BLUE TII; 09-10-15 at 09:04 PM.
#4
On my TII I tried a couple aftermarket exhaust configurations with the same motor and turbo (stock hybrid w/ 60mm external WG) configuration.
First 3.5" turbo back single with one muffler- JIC Spec 90.
Very loud at all rpms with in the low frequency (boomy) with a bad resonance right around 70mph cruise rpm on the freeway.
Full boost @ 3,400rpm in 4th.
Switched to Racing Beat Rev TII 3" turbo back with pre-silencer to dual mufflers.
Fairly quiet at idle/cruise, really quiet under load until WG opened- Psssh noise like air trying to escape my exhaust tips.
Full boost @ 4,000rpm and much less power tooling around off idle.
3.5" downpipe and mid pipe section to Racing Beat Rev TII 3" "catback section".
Fairly quiet compared to JIC Spec 90 at idle- much less boomy, but more exhaust noise than full RB system by far. Pretty loud and raspy sounding at full load even before the WG opened.
Full boost @ 3,400rpm in 4th- no noticeable performance difference over full 3.5" exhaust at any rpm.
Back to full 3.5" turbo back with a Vibrant Streetpower muffler instead of original cannister style.
Surprisingly quiet at idle compared to original JIC Spec 90 cannister style muffler, but still louder than with RB cat back and very boomy. Very loud under full load, but boomy not raspy until WG opened. Surprisingly quiet at cruise with no booming resonances.
Full boost @ 3,400rpm- no noticeable performance difference over 3.5" downpipe/midpipe and 3" "catback" section. No noticeable difference on dyno either.
I preferred the deep tone of the single rear section though over the chainsaw rasp of the Racing Beat duals, others maybe didn't prefer the overall louder exhaust.
First 3.5" turbo back single with one muffler- JIC Spec 90.
Very loud at all rpms with in the low frequency (boomy) with a bad resonance right around 70mph cruise rpm on the freeway.
Full boost @ 3,400rpm in 4th.
Switched to Racing Beat Rev TII 3" turbo back with pre-silencer to dual mufflers.
Fairly quiet at idle/cruise, really quiet under load until WG opened- Psssh noise like air trying to escape my exhaust tips.
Full boost @ 4,000rpm and much less power tooling around off idle.
3.5" downpipe and mid pipe section to Racing Beat Rev TII 3" "catback section".
Fairly quiet compared to JIC Spec 90 at idle- much less boomy, but more exhaust noise than full RB system by far. Pretty loud and raspy sounding at full load even before the WG opened.
Full boost @ 3,400rpm in 4th- no noticeable performance difference over full 3.5" exhaust at any rpm.
Back to full 3.5" turbo back with a Vibrant Streetpower muffler instead of original cannister style.
Surprisingly quiet at idle compared to original JIC Spec 90 cannister style muffler, but still louder than with RB cat back and very boomy. Very loud under full load, but boomy not raspy until WG opened. Surprisingly quiet at cruise with no booming resonances.
Full boost @ 3,400rpm- no noticeable performance difference over 3.5" downpipe/midpipe and 3" "catback" section. No noticeable difference on dyno either.
I preferred the deep tone of the single rear section though over the chainsaw rasp of the Racing Beat duals, others maybe didn't prefer the overall louder exhaust.
I was reading on the BW efr iwg turbos, and I saw people saying a full 3.5" exhaust were causing boost spikes.
#7
Old [Sch|F]ool
An ideal exhaust system would be a gently tapering cone.
Through experiments (on an N/A car) I found power increases going up to a 2.5" exhaust system at the header. I also found no power decreases when putting a 1.75" ID restrictor in the exhaust tip. The only decrease was exhaust drone on the highway.
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#10
Old [Sch|F]ool
Funny story: Drove out to Tulsa with a friend in his GC, which had Super Drager or something exhaust. (Not parts store crap) He put an oil filter in the exhaust. Literally, a used ol filter that he cut the top off of, put in the exhaust like a silencer, and held in with a couple screws. He didn't even gut it first, said it smoked for DAYS when he first put it in
No difference in power. But the car was annoyingly quiet, it was driving me crazy that all you could hear was a little wind whistle, so I took it out for the drive home
I guess this isn't an uncommon thing to do in the Subaru world. I'd search for oil filter silencer but the ATF has gotten wise to the "cleaning kits" for threading oil filters onto the end of your pistol for use as an untaxed/unregistered (therefore unlegal) silencer and I don't know how deep they care about it. (Which is another rant, because IMO silencers should be compulsory instead of discouraged... hearing loss is a bitch)
No difference in power. But the car was annoyingly quiet, it was driving me crazy that all you could hear was a little wind whistle, so I took it out for the drive home
I guess this isn't an uncommon thing to do in the Subaru world. I'd search for oil filter silencer but the ATF has gotten wise to the "cleaning kits" for threading oil filters onto the end of your pistol for use as an untaxed/unregistered (therefore unlegal) silencer and I don't know how deep they care about it. (Which is another rant, because IMO silencers should be compulsory instead of discouraged... hearing loss is a bitch)
Last edited by peejay; 09-13-15 at 05:05 AM.
#11
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the noise comes from the exhaust pulses, if you drew a graph of exhaust pressure, you'd get a sine wave, and the height and steepness of the wave = noise. the turbo works because it chops up the wave a little, and then the small tips work, because its a little restrictive and it turns the wave into a smoother flow.
the other way would be a dual pass muffler, where the waves can cancel each other, but its complex.
its also why a v8 is quiet, even though the cylinders are about the same size as a chamber in a 13B, there are more of them, and there is much less going on in each one, so the peaks are shorter, and its easier to bunch them together
the other way would be a dual pass muffler, where the waves can cancel each other, but its complex.
its also why a v8 is quiet, even though the cylinders are about the same size as a chamber in a 13B, there are more of them, and there is much less going on in each one, so the peaks are shorter, and its easier to bunch them together
#12
Rotary Motoring
iTrader: (9)
On my original 3.5" turbo back JIC Spec 90 exhaust it came with a "tip silencer" which I basically had to run all the time because otherwise it was instant arrest loud.
Funny thing, like others are saying above- even with this tip silencer with one tiny 1.75" opening the power felt about the same.
Funny thing, like others are saying above- even with this tip silencer with one tiny 1.75" opening the power felt about the same.
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