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Discussion Starter · #1 ·
4-2-1 or 4-1 ?

I'm looking at systems for my 91 750. I'm thinking chrome or stainless, wieght is unimportant at skill level.. lol.
Whats the theory behind this whole 4-2-1, 4-1 thing...

Thanks - Chris
 

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The theory is as follows:

4-2-1 Bigger Midrange, Lesser Top End
4-1 Lesser Midrange, Bigger Top End

It all depends on the type of riding it is for,
if you are on the track and want maximum HP and
don't mind keeping the thing reving a 4-1 is for
you, but for general road use a 4-2-1 is more
ridable due to the better spread of HP in the
midrange where most of your riding will be.

Hope this helps.

Also consider a Hindle pipe, they
are a very good 4-2-1 stainless system,
light too.

Adrock.
 

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if you look at a dynograph of a 4 into 1 it has a dip at about 75% of the torque peak. this is due to the 4-1 being tuned for best exhaust scavenging in the upper rev range(little to no backpressure).
the 4-2-1 exhaust actually slows down exhaust flow to a certain extent creating backpressure, and using that backpressure to help pull in the intake charge. this boost effieciency in the mid range(due to better intake and exhaust port velocity), but will soften the top end a little(not as noticible as the midrange boost you will get).

for more info read "Sportbike Performance Handbook" by Kevin Cameron. it is very informative about stuff like this.
 

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Remember that the design isn't the only factor... I tried three different 4-2-1 systems on my bike. Header diameter and where the pipes join together are off a big influence.

...just to say that choosing between 4-1 and 4-2-1 is the easy bit ;-)

[ 07-30-2002, 04:11 AM: Message edited by: Mr.7/11 ]
 

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Discussion Starter · #6 ·
WOW, thanks for the replys.. I mostly lurk here, doing searches, and you ppl seem alright!

One more: What about removing the canister packing. Will this increase or decrease backpressure, and whats the effect on hp curve? Reason being now I'm running a yosh slip-on with the packing removed and its loud as hell. I'm not sure I want to do this to a new can/system...

Thanks
 

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Originally posted by gsxr-jeeper:
WOW, thanks for the replys.. I mostly lurk here, doing searches, and you ppl seem alright!

One more: What about removing the canister packing. Will this increase or decrease backpressure, and whats the effect on hp curve? Reason being now I'm running a yosh slip-on with the packing removed and its loud as hell. I'm not sure I want to do this to a new can/system...

Thanks
<font size="2" face="Verdana, Arial">leave the packing in. all it does is increase noise. a race can is not a street can without the packing.
I run a Hindle stealth Titanium can on my gixxer, and I ride much faster with a quieter can and have more fun.
 

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take it from me and everyone else who has a hindle, they are the best! (by the way, mine is a 4-2-1 design)
 
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