Re: Back pressure

[Bill Hussey <vfrboy@home.net>]

Matt Zajac wrote:

> Hi Bill
> Thank you for explanation. The only thing that I don't really understand is why backpressure is impoortant for low end torque. From what I've heard so far is that too low backpressure will hurt low end torque. Perhaps you can help me with this.
> Thank you very much.
>
> Sincerely
> Matt Z.

    To tell you the truth I have no idea.  It doesn't necessarily have to do with the amount of torque, but rather the position of the power band.  My main machine is a 1997 Honda VFR750.  Stock the bike ran 88.3RWHP @ 9100 RPM.  After putting a little over 22K miles on the bike in the first year, I bought a Two Brother's full exhaust system, a Dyno Jet jet kit (carbs doncha know), and a K&N air filter.

    After 6 months, a dozen trips to the carbs, and one banzaii trip to Quebec on a weekend in early December, I finally got the jetting to what I consider perfect.  Of course, I'm putting out more power now, an official 100.2 RWHP, but interestingly, it peaks at 10,200 RPM now (and holds until the rev limiter kicks in at 12,500).  The very bottom-end of the power curve (below 3K rpm) has lost a little bit even though the rest of the rev range has gained.

Bill
'98 GLX