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Will a Larger Header Pipe Reduce Low RPM Torque? (Read 64 times)

d3adrock

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Will a Larger Header Pipe Reduce Low RPM Torque?
08/09/21 at 07:51:44

I'm thinking about getting a custom header pipe built for my Savage that would follow Lancers recommendations of 1.65 ID pipe (1.75" OD).

My bike has a stage 3 cam, 10.5 piston, mikuni VM carb, and a delkevic muffler (which I wish was a but quieter)

My main concern is that the shop I'm working with said it would destroy my low RPM torque, which is exactly my favorite kind of torque!

So, does anyone know if that is true or is it baloney?

Thanks for any advice!

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Gary_in_NJ Serious Thumper Offline LS650 Cafe Racer Posts: 2626 Amongst the Twisty Roads	Re: Will a Larger Header Pipe Reduce Low RPM Torqu Reply #1 - 08/09/21 at 09:21:32 That is true in theory. I think DragBikeMike has actually done some testing if you look at his performance threads. Have you done any porting to the head? You'll get more bang for the buck with that effort. If the exhaust port hasn't been derestricted, then header pipe diameter wont matter anyway.
Back to top	A life-time student of motorcycling. LS650 Cafe, DRZ400SM, FZ6N, SV650S, CB900C, Ducati ST2, CB550F-SS My LS650=> http://suzukisavage.com/yabb2.2/Attachments/Left.JPG IP Logged

d3adrock Full Member Offline Posts: 111	Re: Will a Larger Header Pipe Reduce Low RPM Torqu Reply #2 - 08/09/21 at 09:23:40 supposedly the shop did. Although I'd have to take it apart to look. if they didn't I would port it myself anyways. Would you happen to know where dragbikemike did that comparison? I looked for a bit but couldn't find it.
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Fast 650 Senior Member Offline SuzukiSavage.com Rocks! Posts: 393 Valrico, FL Gender:	Re: Will a Larger Header Pipe Reduce Low RPM Torqu Reply #3 - 08/09/21 at 11:07:19 Look in his evolution of a hotrod thread. He tested a larger 2 inch MAC pipe with a 1.79 inch ID against the stock pipe. Low rpm torque loss even with that huge pipe was so small that it isn't really noticeable . These engines respond well to port work along with a bigger pipe and less restrictive muffler.
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d3adrock Full Member Offline Posts: 111	Re: Will a Larger Header Pipe Reduce Low RPM Torqu Reply #4 - 08/09/21 at 11:33:42 I must be the worst forum searcher ever, because I looked there and I still couldn't find it.
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Ruttly Serious Thumper Offline Thumpers Rule Posts: 4997 Manteca , CA Gender:	Re: Will a Larger Header Pipe Reduce Low RPM Torqu Reply #5 - 08/09/21 at 11:56:16 You have already changed the dynamics of your engine by changing cam , piston , carb & muffler. Now it needs the larger header. It will have a different powerband and torque curve. Don’t worry you will like it !
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d3adrock Full Member Offline Posts: 111	Re: Will a Larger Header Pipe Reduce Low RPM Torqu Reply #6 - 08/09/21 at 11:59:10 I guess I just have to find someone to bend one for me, which is easier said than done.
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DragBikeMike

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Re: Will a Larger Header Pipe Reduce Low RPM Torqu
Reply #7 - 08/09/21 at 15:17:50

D3, you will find that the stock header works amazingly good for as small as it is, but a larger header works great too. There really isn't any appreciable impact on low speed performance with the BIG header (nothing you will feel with your butt dyno). The bigger headers have a significant impact on top end performance.

I did tests comparing the stock header (1.3" ID) to a Mac header (1.79" ID). Those tests were extensive, comparing the effect of the header when installed on a stock head, ported head, hotter cam, larger carb. In every instance, the two headers performed very close to each other. You can find all the specifics in Parts 3, 4, 5 & 7 of the Evolution of a HotRod series. I have included the links below.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1623048749

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1625732492

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1626391255

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1627891507

Please tell us more about your setup. That 10.5:1 piston, is it the new Wiseco flat-top piston. Did you experience any problems with installation regarding valve-to-piston interference? Do you like how it runs?

Knowledge is power.

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d3adrock

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Re: Will a Larger Header Pipe Reduce Low RPM Torqu
Reply #8 - 08/09/21 at 16:11:49

Holy cow, a response from the man himself. I'm honored. Thanks for those links. I will definitely do a deep read of those.

Yes, I installed the flat top 10.5 wiseco in 95mm for a grand total of 666cc (I'm tickled silly by that and I will never stop telling people)

I actually did end up with my valves slamming into my piston. Cost me a pretty penny to fix.

Pretty sure it was the mechanics fault for the initial install, but I've already paid so whatchagonnado?

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