Header and Torque

John Soliday johnsoliday at msn.com
Fri May 28 19:53:05 PDT 2010

I took out the reed valves, otherwise I agree with your analysis.  So now
the exhaust pulses from cylinders 1/2 and 3/4 can see the entire exhaust
system, so you have a lower pressure that any one cylinder sees.  I can tell
you there is pulses going through my bypass system, as you can actually hear
it pretty clearly...sounds nice, louder than the header from my position on
the bike!

-----Original Message-----
From: gpzlist-bounces at micapeak.com [mailto:gpzlist-bounces at micapeak.com] On
Behalf Of Steve Northrop
Sent: Friday, May 28, 2010 2:23 PM
To: GPZ List
Subject: Re: Header and Torque

It's a passive system that does absolutely nothing performance wise whether 
(or how) it's blocked off or not. The reed valves under the plates act as 
one-way valves so air can  be drawn into the exhaust system. The reed valves

prevented exhaust reversion pulses from feeding back through the system and 
into the airbox. Better get your ass dyno recalibrated ;^)

Steve in Western NY
'96 GPZ1100
'08 KLR 650
'08 Tuono Factory
"You Can't Fix Stupid", Ron White
----- Original Message ----- 
From: "John Soliday" <johnsoliday at msn.com>
To: "'GPZ List'" <gpzlist at micapeak.com>
Sent: Friday, May 28, 2010 10:55 AM
Subject: Header and Torque

> So I've been riding the GPZ a lot since rejetting, air box mods and adding
> the Jardin header and thought I'd throw this out to the group.  I noticed,
> as would be expected that the low end grunt (torque) was reduced somewhat
> after these changes, but liked the sound, high end power, and much reduced
> weight.  Initially I put block off plates on the air injection ports but
> then started thinking (that's always dangerous!).  I took off the block 
> off
> plates and put the air injection hoses back on and connected the two sides
> together with a 1/2" piece of PVC to act as a crossover pipe like I have 
> on
> my '73 Nova SS, except on the car it's after the header collectors.  It
> "feels" like I gained back some or all of the low end power of the stock
> pipe!  Maybe I'm imagining things but I'm thinking it's working in a 
> similar
> way.  Thoughts???
> Happy Memorial Day, Remember our Veterans,
> John

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