Secondary Butterflies

[The Stranger:Me]

Why would one remove or disable the secondary butterflies on your fuel injection system?

What are the pros and cons of this modification?

Why does the manufacturer see fit to install them if many people remove them?

[Cajun]

This helps with low down throttle response i believe, which on smaller bikes with not much down low it helps, but larger bikes does not,

but on the upside removing them on larger cc bikes gives more you power zx10rs been known to give a good 5-6hp+

Would be handy to do if you know you are about to go on a dyno, to pull them off.

[BarBender]

Cant speak for other bikes but with the butterflies out on the ZX14 you get more go-go down low....
Very common for ZX14 owners to do it because power curve drops at 3K and doesnt pick up again until about 5k. With the secondaries out the power comes in early and goes straight to the top...A pre-requisite if you run the bike at the drags.

The cons? Increased fuel consumption. My bike drinks anyway but its dropped almost 2 ks/per litre. Its also trickier to ride through the twisties with the throttle response being a tad more sensitive.

[Gremlin]

Its also trickier to ride through the twisties with the throttle response being a tad more sensitive.

this would be an understatement... Leant right over exiting a corner, you try to open the throttle a leeeetle, and it cracks open.

Funnily enough, I hated the really delayed response with secondaries in, now I struggle without the secondaries As others have said, more down low, and possibly better breathing, depending on bike, pipe, restrictions the pipe might have etc.

Can often see on dyno graphs a fluctuation in the curves around where the secondaries become fully open...