Rotrex exhaust/muffler selection
02-27-2018, 10:26 AM
#1
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Rotrex exhaust/muffler selection
Yeah, I know, Rotrex is lame. I also know that the MT consensus for turbo cars is using the Magnaflow 12589. I am a bit skeptic as it regards using it in a Rotrex car as I will not have the muffling action of the turbo. What would be your suggestions for a low-tone, burbling but not droning system?
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02-28-2018, 11:08 AM
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I am going to be fabricating my own 3 inch exhaust from stainless and as many resonators as I can fit. Fortunately I have lots of scrap from working at a BMW dealership. I am looking for quiet 3 inch muffler suggestions in addition to the resonators. I'll be sure to post sound clips, hopefully within a couple weeks. 1.8 bp4w with c30-94
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02-28-2018, 03:03 PM
#9
I've seen some old posts about modifying the standard RB header to merge to 3" and do a full 3" exhaust but that is about it. Too expensive to dyno test that sort of thing, for 95% of builds off the shelf RB bits will get the job done. You are splitting hairs compared to a 2.5 inch set up when the RB is 2.375 diameter.
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02-28-2018, 03:15 PM
#10
I've seen some old posts about modifying the standard RB header to merge to 3" and do a full 3" exhaust but that is about it. Too expensive to dyno test that sort of thing, for 95% of builds off the shelf RB bits will get the job done. You are splitting hairs compared to a 2.5 inch set up when the RB is 2.375 diameter.
You can watch this YT which does a 2.5" vs 3" on a v8 that makes more HP than a rotrex miata.
Last edited by Girz0r; 02-28-2018 at 03:45 PM.
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02-28-2018, 04:04 PM
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The diameter matters way more on a turbo car. On something with an SC you can run a smaller exhaust and still make good power. I'm running a raceland header, test pipe and RB catback (resonated midpipe) and it sounds great, with absolutely no drone. I'm making 234 whp at 4500ft on a 1.6 with that exhaust.
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02-28-2018, 07:15 PM
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The channel "The Driver's Perspective" on Youtube actually has a clip of a launch with the racing beat, and a launch with the roadstersport from similar distances/angles. AFAIK he started with the RB, moved to the roadstersport and then switched back. His videos are why I ended up with the RB setup.
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03-01-2018, 11:18 AM
#15
The channel "The Driver's Perspective" on Youtube actually has a clip of a launch with the racing beat, and a launch with the roadstersport from similar distances/angles. AFAIK he started with the RB, moved to the roadstersport and then switched back. His videos are why I ended up with the RB setup.
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03-01-2018, 12:00 PM
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Thanks for the thread Brain:
This matches everything I have read as well. The RB exhaust still seems like the easy button for Rotrex setups until you start making really big power.
Turbo cars are much more sensitive to the exhaust size because the turbine acts as a backpressure multiplier.
The considerations for a SC car are different and more like doing the exhaust for an NA car (taking into consideration some additional flow). Things like sizing the pipe diameter and length to promote scavenging become important. Bottom line, on an SC car run a good header and an exhaust system matched to the header. That will likely be smaller than a 3".
The considerations for a SC car are different and more like doing the exhaust for an NA car (taking into consideration some additional flow). Things like sizing the pipe diameter and length to promote scavenging become important. Bottom line, on an SC car run a good header and an exhaust system matched to the header. That will likely be smaller than a 3".
^^ This. Everything I've read backs this up. The only person with an SC setup that I've seen that is running anything bigger is TrackDayHooky. At one point he was running one of the discontinued 949Racing 2.75" exhausts on a 400+HP C38 Rotrex build. No clue what that car has on it now.
Ok, back to the trubo stuff. Who has more apples to apples comparison data for exhaust upgrades?
Ok, back to the trubo stuff. Who has more apples to apples comparison data for exhaust upgrades?
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03-02-2018, 06:31 AM
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Thanks guys, much appreciated. Original question was mostly related to sound, diameter will most likely be 2.25" or 2.5". The RB exhaust is sweet, however being located in Europe, it will be a bit more difficult to get one. Most probably gonna get a large Maglaflow backbox plus a smaller one as a midpipe resonator.
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03-02-2018, 02:08 PM
#19
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I ran a 2.5" system before my RB (old muffler core broke, was cheap) and it had a nice deep tone. It did drone a bit, but the muffler was pretty minimal. I'd think that a big back box and resonator(s) should help with that.
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