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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
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10-29-2021, 01:30 AM | #29 |
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The Following User Says Thank You to Dirty Harry For This Useful Post: | CrowsFeast (10-29-2021) |
10-29-2021, 11:15 AM | #30 |
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10-29-2021, 12:54 PM | #31 |
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Whoa whoa whoa. Let's back this train up... The reason that in a few rare cases a smaller diameter exhaust pipe can make more power than a larger one is NOT due to higher exhaust velocity, it is due to exhaust scavenging. Let's unpack the science behind this.
Firstly, we need to understand that fluid dynamics IS pressure diffentials. The lower you can reduce the exhaust backpressure, you will create a higher pressure differential which will increase the volume of flow. This results in an overall increase in cylinder volumetric efficiency. Secondly, I believe the phenomenon you are actually referring to is exhaust scavenging, not velocity. See, as exhausts waves created by the combustion events over through the exhaust into a collector, a wave is sent backwards through the runner. The more exhaust valve overlap you have, the more important this effect becomes. If timed correctly, you can use the low pressure zone created by the pulsation to your advantage which again, results in increased volumetric efficiency. So, to conclude, we have two different ways that exhausts can be tuned to produce a more efficient (and more powerful) engine. The reality is more complex though. While less backpressure is always beneficial, a properly tuned (!!!) exhaust that matches the intake, exhaust and cylinder heads correctly could produce higher numbers in rare cases. The problem is to do this you need an advanced combustion analysis system that literally costs OE's tens of thousands of dollars including custom machining cylinder heads to take in-cylinder dynamic pressure traces. Sorry, no aftermarket company is doing that realistically. TLDR: -You are incorrect about exhaust velocity -You are correct about exhaust scavenging potentially producing higher results in rare cases -In reality, if an aftermarket company claims to be doing this, they probably just got lucky -Just get an exhaust with less backpressure and thank me later
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The Following 6 Users Say Thank You to Goingnowherefast For This Useful Post: | BigTuna (10-29-2021), DarkPira7e (11-04-2021), Jdmjunkie (10-29-2021), NoHaveMSG (10-29-2021), PulsarBeeerz (10-29-2021), Ultramaroon (10-29-2021) |
10-29-2021, 12:57 PM | #32 |
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Yes, I realize this is a bit dense for internet car forum lol. Let me know (anyone) if you have any questions .
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2022 Hyundai Elantra N 6MT SCCA TT S3//Will be back in an 86 eventually
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10-29-2021, 01:16 PM | #33 |
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Crushing dreams. How dare you!
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10-29-2021, 01:55 PM | #34 |
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The Following User Says Thank You to PulsarBeeerz For This Useful Post: | Ultramaroon (10-29-2021) |
10-29-2021, 01:56 PM | #35 |
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10-29-2021, 01:58 PM | #36 | |
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Quote:
https://www.vividracing.com/sti-stai...150749122.html |
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10-29-2021, 02:10 PM | #37 |
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I remember reading books on exhaust scavenging 20 years ago thinking I could build my own 2 stroke exhaust but math is hard.
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10-29-2021, 02:13 PM | #38 | |
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Quote:
Sent from my ONEPLUS A5010 using Tapatalk |
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10-29-2021, 02:16 PM | #39 | |
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Quote:
https://www.dundonmotorsports.com/pr...-crack-pretzel
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10-29-2021, 02:19 PM | #40 |
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10-29-2021, 02:21 PM | #41 |
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Oh, FFS... money>brainz
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The Following User Says Thank You to Ultramaroon For This Useful Post: | NoHaveMSG (10-29-2021) |
10-29-2021, 02:24 PM | #42 |
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You could almost buy a new GR86 for what a full exhaust cost from Dundon.
The Dundon guys are really cool though. Sometimes they bring their support trailer out to the Ridge and will help anyone out.
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The Following User Says Thank You to NoHaveMSG For This Useful Post: | Ultramaroon (10-29-2021) |
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