Author Topic: exhaust lengths differences in performance etc.  (Read 1705 times)

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Sectorsteve

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on: July 23, 2013, 04:36:42 am
it appears ive gone and bought the wrong exhaust - or not the one i intended to buy.
The one i bought was a 26 inch alloy end decibel from classic bike shop. THe one i intended to buy was the short megaphone. The one i bought is 67 cm, the short megaphone is 44cm. My question is. Will the 67cm one work ok on the C5?


Arizoni

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Reply #1 on: July 23, 2013, 05:02:30 am
I haven't seen any data that ties the silencer lengths to performance gains for the RE's fuel injected engines.

IMO, when you take into account the somewhat restrictive header pipe plus the O2 sensor that is blocking some of the exhaust I doubt the silencer length has much effect.

The bikes computer maps are set up to give high amounts of torque at low rpm plus good fuel economy so unless the silencer is overly restrictive because of some convoluted baffling it probably won't matter very much.
In the case of the Harley Sportster silencer I put on my RE G5, it was restrictive, so up until I drilled some holes thru its centrally located plug, it did reduce low end torque.

I think your longer silencer may have a better chance of giving the bike a nice deep tone than the shorter one.  I haven't heard the short silencer you thought you were getting but sometimes they can be pretty raspy sounding.
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary


Sectorsteve

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Reply #2 on: July 23, 2013, 05:44:04 am
Thanks Arizoni. Thats a relief. heres a link of the megaphone silencer. this is the reason i wanted it. More punch and better sound.  the one i have may be better as it might not be so loud. it was 30 quid more expensive so hopefully she will work ok.

http://www.youtube.com/watch?v=0-2YfY-cqJk


barenekd

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Reply #3 on: July 23, 2013, 05:59:30 pm
If anything the longer silencer will give you slightly better bottom end, but not knowing what's in it makes the point rather moot.
By comparison a longer straight pipe will tune to a lower RPM range than a short pipe or megaphone. FI you were running a race bike, you could, a low power engine like the Enfield Idoubt that you would see much of a difference.
Everybody acts like all these pipes on the market are going to vary a lot in performance. The only one I saw affect performance much on an Enfield was the full Goldstar exhaust with the full 1-3/4" exhaust pipe. the stock pipe is sleeved down. the Goldie pipe robbed the engine of a lot of bottom end power. It improved it toward the upper end where nobody rides the engine anyway. If you wanted a race bike, and modified the engine for the extra RPM,it would be the way to go, but on the stock engine, it was a letdown. As for the other silencers, most are better than stock to some varying degree, but nothing to get your panties in a bunch about! The thing you're really buying is the sound you want.
Bare
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Arizoni

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Reply #4 on: July 23, 2013, 08:33:06 pm
Quote
...The thing you're really buying is the sound you want.

I agree but I'll add another benifit of changing out the factory silencer for a aftermarket one.  Weight!

That factory bazooka must weigh all of 15 pounds or more!
With the 5 pound or so replacement it reduces the bikes weight over 10 pounds. :)
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary


Craig McClure

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Reply #5 on: July 23, 2013, 09:05:32 pm
I SPOT ONE DIFFICULTY... REPEAT AFTER ME; "UP SWEPT, UP SWEPT, UP SWEPT"! I would Drag that Low Fat Megaphone.
   With a piece of chrome extension pipe & extra clamp, you can snug that Megaphone right under your passenger peg, before it gets Scratched or Dented.  see photo, THIS WILL NOT DRAG ON HARD RIGHT TURNS.
Best Wishes, Craig McClure


barenekd

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Reply #6 on: July 23, 2013, 10:17:24 pm
Quote
That factory bazooka must weigh all of 15 pounds or more!

The torpedo, 11 lbs. The heat shield 20 oz. NFG EFI Muffler 4 lb 3 oz with mounting brace
Bare
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Sectorsteve

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Reply #7 on: July 23, 2013, 10:26:17 pm
good point craig. Im often bottom out , hitting the center stand. The silencer could very well be the lowest point after installation


wildbill

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Reply #8 on: July 24, 2013, 12:03:28 am
now if you go up swept with the muffler-you'll have half a norton commando.
the bike i always wanted -the mk3 850 cc
in those days it was $1750 new - $1599 for the honda 750 -4 and $1350 for the suziki 750 water bottle.
ended up getting the water bottle. what a difference $400 would have made ::)


ace.cafe

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Reply #9 on: July 24, 2013, 02:25:18 am
For all intents and purposes, any exhaust wave tuning going on in that pipe ends at the transition of the header to the muffler(unless you have an open unbaffled muffler or megaphone). So, unless you change the header length, then I don't expect to see any real power curve changes from different lengths of mufflers.

However, the differences in dead weight can be a factor.
Home of the Fireball 535 !


mkcharlie

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Reply #10 on: July 24, 2013, 02:48:06 am
I just changed from a shortish upswept raspy, loud muffler (D & D) to a Dunstall that is some 6 inches longer. The immediate benefit was a duplication of the great sound I remember from my singles of the 60s. The second benefit surprised me but not the tuner who suggested the change. With the shorter muffler, 40 mph felt too slow for 5th gear-always felt I should downshift. Now the bike pulls MUCH better. The tuner explained that the longer unit more efficiently scavenges the head, thus more power. The bike is still too new for me to rev it up to high RPM to see if top end is improved, but the "where I live mostly" is remarkably better.
Charlie