General Category > General waffle in here

Secondary flies / servo valve

(1/2) > >>

lukebolger:
Hi guys,

I have been trawling the internet looking for answers.

Are these two things power enhancing or emissions and noise control?

But I get told yes to both by different people.

Does anyone have any actual proof IE Dyno charts with and without to say for sure?

Thanks

Matt83:
What other mods have you done to the bike? Unless you're going balls out I wouldn't bother with the hassle. Bit more intake noise and throttle response, very little power gain

HammyUK:
OK - servo valve serves two purposes.
1. yes it does help with emissions/noise. Back pressure affects scavenging and in addition to the clean air system reburns gases. The valve closing at "certain" rpm's lowers the noise output for homologation. With the wheels turning it doesn't do this - the ecu has a different setting.

2.The secondary butterflies help with low down torque and cold starting.
They were only removed on race bikes as above 8.5k they are fully open regardless.
The amount of work involved doesn't justify removing them - the increase is very, very minimal. You WILL lose torque. Fact. You have to decide if you want maximum power OR the best driveability - you can't have both.

Simple 60s experiment at RJS one day - full power run.
Everything connected.
174.9bhp 83.2ftlb

Servo disconnected.
175.2bhp 74ftlb

A gen 3 on the same day with a race system did 176.8 and 81ftlb then with the throttle bodies swapped for modified ones it did 178 and 79.8ftlb
When they put them back on along with the servo valve and mappped it it produced 177.5 and 84ftlb.

Not everything is there because of the EU crap.

lukebolger:
I don't see how those numbers add up hammy. The servo valve is full open past six thousand rpm, so how can it add ten ft lb of torque at max pull on a dyno run when it's not operating

michael4012:
The secondary butterflies start to close at the top as part of the restriction process, unless there flashed to stay open they severely reduce power right at the top.Hence why people used to remove, but with tools like "wollich" flashing g the best of both worlds can be had by flashing the secondary butterflies.

Navigation

[0] Message Index

[#] Next page