Quote:
Originally posted by cjoffe
Both 4-stroke inline 4 cylinder bikes. Yamaha R1 and Honda 929. There may be more by now, but those are the two I know of. I know that if you replace the exhaust and remove the valve, you lose torque but gain top-end HP. I know that when I removed the cats on my 928, I lost torque but gained top-end (and noise!).
CJ
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Hi CJ, Had a look at them, It's basicly the old Yamaha EXUP system.
This type of valve is mainly to help with the rideabilty of the bike, Not to increase the torque output of the engine.
These engines are designed to put out max torque at 7000 to 8000, so they have a few holes in the torque curve down around 2500 to 3500. They use a restrictor valve in the exhaust and the Honda's is also linked to a flap in the air box, to increase the velocity of the gas flow at these low rpm and to prevent inlet spillage due to the cam timing.
The SVX is 'mindmannered' compared to these engines, so we dont have that problem, yet.
Harvey.
