I have the whole top part of my sc300 apart for the first time (replacing valve cover gaskets, plugs, wires, throttle body cleaning, replacing vacuum hoses before winter rolls around). I noticed a butterfly valve inside my plenum. Did a lil research but there isn't much on it, supposedly I lose some torque if I remove it? I'm wondering if anyone has any direct knowledge on it, and whether or not I should remove it. Seems like it restricts airflow when it is closed. I know toyota had a reason behind adding this and I am just wondering what type of effects removing it would cause (throttle response, lower end torque, power that sort of thing). Engine is completely stock with auto trans. I'm experiencing 2 secs of rattle when I start the engine up which may have been due to my valve cover bolts being somewhat loose, possibly this butterfly? Idk. Also wondering if I should look into deleting my egr. Any help/knowledge is greatly appreciated!! Thank you!

Also looking to buy a radiator fan shroud shipped to 98198 or I can pick up anywhere around the seattle/tacoma area! Thanks again!

 

hey man, im assuming you're coming from the 240sx world. the butterfly is the same setup as the butterfly system in the s13 ka24de. when you remove the butterfly valves in the 240, you loose a little bit of lower end power. Basically the butterfly valves open and close with vacuum pressure to "swirl" the air properly to help it into the head better. it goes something like that. anywho, removing it for no reason doesnt make sense to me. it is all your decision though. just my .02

 

Keep the butterfly in! It remains closed to improve low end torque until a set RPM point and then opens in high RPM to maximize airflow up top. This design maximizes torque, removing it will result in a loss of low end torque response.

I'm currently NA-T, and have deleted the Vacuum Canister below the intake, and I have the butterfly actuator plumbed straight from a vacuum line, no VSV or vacuum tank. This results in a closed butterfly at idle, pre boost conditions and opens as boost comes on which is roughly 3500-4000 rpm.