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#166 |
Join Date: Mar 2022
Posts: 255
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Is that an expansion chamber, or cat?
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2022 X-Pro Templar X 250 “Rocinante” 2022 X-Pro Bolt 125cc “Dapple” 2022 Royal Enfield Interceptor 650 “Traveller” 2023 Royal Enfield Classic 350 “Trigger” |
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#167 |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,536
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An expansion chamber can be found on 2stroke engines. It might be a catalytic converter
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#168 |
Join Date: Apr 2008
Location: Somerset, KY
Posts: 686
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They also run expansion chambers on 4-Strokes, they are different than the 2-Stroke one, but the bigger section on the header is an expansion chamber, all the performance 4-Stokes systems have them, and the Templar has one on the stock system.... It smooths out the pulses, allowing the exhaust to flow smoother
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Huck 2013 Honda NC700X 2013 Moto Guzzi V7 Stone 2016 AJP PR4 2022 Templar X 250 2021 Sondors Metacycle AMA Life Member |
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#169 | |
Join Date: Mar 2022
Posts: 255
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2022 X-Pro Templar X 250 “Rocinante” 2022 X-Pro Bolt 125cc “Dapple” 2022 Royal Enfield Interceptor 650 “Traveller” 2023 Royal Enfield Classic 350 “Trigger” |
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#170 |
Join Date: Apr 2021
Location: Louisiana
Posts: 48
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I agree, the exhaust gives me supermoto vibes when riding from the sound of it, from idle to heavy throttle, odd that it does I know, but it really makes me want to invest in a set of 17's for really bad. I did figure at the same time doing this would be a good opportunity of going down on that rear sprocket a little for the top end gear expansion. Looks like I have a little researching and homework to do!
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2022 X-Pro Templar X 250 |
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#171 | |
Join Date: Mar 2022
Posts: 255
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when time permits (lol, ok) I need to run my inspection camera into the exhaust and check it out. it looks ok from the outside but I have to wonder what sort of restrictions it has inside. I probably won't be going that until I have a nibbi carb and new intake though...and the I don't have 2 kids under 2 years old anymore lol ![]()
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2022 X-Pro Templar X 250 “Rocinante” 2022 X-Pro Bolt 125cc “Dapple” 2022 Royal Enfield Interceptor 650 “Traveller” 2023 Royal Enfield Classic 350 “Trigger” |
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#172 |
Join Date: Mar 2022
Posts: 107
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I'm going to test out a 42T and a 38T. The 38T I suspect it going to be to high but some RBX 250 owners say it a good fit.. Amazon says they will have them to me by Friday. Should be fun to test out.
JT Sprockets JTR897.38 38T Steel Rear Sprocket https://www.amazon.com/dp/B001AVONLU...MCG20BD0H4HFR2 |
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#173 | |
Join Date: Mar 2022
Posts: 107
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#174 | |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,536
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No. An expansion chamber on a 2-stroke is a reduction in back pressure implemented with an expanding diameter into a chamber to baffle the impact of explosions from the exhaust port. The chamber reduces in inner diameter to a rat tail with or without a muffler. The expansion chamber reduces intake pressure, and increases power output of the engine. It is very effective in a 2-stroke application. It is an obvious feature on 2-stroke bikes. And I can tell you from experience, it works! But I believe the evidence too! In a 4 stroke bike, the expansion chamber is a megaphone at the tip of the exhaust (the muffler). There is no expansion "chamber" on a 4 stroke bike. There can be a "collector" which is a broadened but extremely short section of pipe ~2x or 4x the diameter of each individual headpipe in a multicylinder engine (2 cylinder or 4 cylinder), which goes into the muffler segment (which can be a megaphone). On a single cylinder bike, the "expansion chamber" is the muffler (or megaphone). |
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#175 | |
Join Date: Mar 2022
Posts: 255
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Would be cool to see some before and after numbers: 0-60, top speed in each gear, etc.
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2022 X-Pro Templar X 250 “Rocinante” 2022 X-Pro Bolt 125cc “Dapple” 2022 Royal Enfield Interceptor 650 “Traveller” 2023 Royal Enfield Classic 350 “Trigger” |
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#176 | |
Join Date: Apr 2021
Location: Louisiana
Posts: 48
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Oh and I used a Nibbi PE30, I also kept the choke lever in tact, very simple to unscrew it and put it on the new one, even though I no longer need it, as it fires up immediately and runs smooth on idle from a dead cold start!
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2022 X-Pro Templar X 250 Last edited by scbindisbihhh; 05-11-2022 at 10:17 AM. |
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#177 | |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,536
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This is what they say. FMF doesn't call it an expansion chamber. They mention sound reduction and power increase, but without calling it an expansion chamber. But all of the 2-stroke pipes have integrated full expansion chambers. Maybe this is semantics, but a 4 cycle engine can't benefit from the classic expansion chamber, or they would make pipes with them for 4 stroke bikes. An expansion chamber is different: "The basic idea behind an expansion chamber is to use the momentum and pressure of the exhaust gases to create a pump that squeezes more air and fuel into the cylinder during the intake stroke. It does the same sort of thing that a turbocharger does, but it does it without moving parts." A collector in a multi-cylinder 4-sroke exhaust system is related. The collector is at the union of the headpipes, but before the muffler (which can be a megaphone, which IS in fact an expansion chamber of sorts). Pulses are "tuned" at the collector to create a vacuum following each pulse. This creates an extraction effect, sucking more gases out of the cylinder during the exhaust stroke, and allowing more gases in on the intake stroke. It is also NOT an expansion chamber. Last edited by Thumper; 07-20-2022 at 09:39 PM. |
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#178 |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,536
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OK. Maybe it isn't an expansion chamber per se. But FMF uses the design. Did I create a power bomb when I did my cat delete? Seems more powerful. I also drill the exhaust. I posted this in the photos and videos section.
Seems like a power bomb ![]() Last edited by Thumper; 07-20-2022 at 09:39 PM. |
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#179 | |
Join Date: Mar 2022
Posts: 255
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Which effectively has no effect other than changing exhaust note. That makes sense.
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2022 X-Pro Templar X 250 “Rocinante” 2022 X-Pro Bolt 125cc “Dapple” 2022 Royal Enfield Interceptor 650 “Traveller” 2023 Royal Enfield Classic 350 “Trigger” |
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#180 |
Join Date: Feb 2021
Location: Kansas City
Posts: 2,536
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I wonder if that is a catalytic converter rather than an expansion chamber (or resonator)? Is that it behind the heat shield on the headpipe by the cylinder?
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