Where to Properly Tee in your Boost Controller
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From: San Diego, Ca
Where to Properly Tee in your Boost Controller
in my time reading this board i have noticed a large variance in what Gearheads,Tuners & Part Manufacturers will tell you into to feed your signal line to the Boost Controller's input
while quite a few posters on the board seem to have an opinion on this matter, nobody seems willing to discuss the matter logically, just "This is how "X" Tuner/gearhead/Manufacturer said to do it so it must be correct!"
im not saying my method is the end all correct way, so if you have something positive to add/discuss feel free to chime in
to start you must properly understant how the turbo operates & how it is affected by changes in the engine caused by the Throttle Body
when your "Mashing It" the throttle body is wide open, recieving boost from the Turbo & there is no pressure diffrential Pre/Post Throttle body.
but when you close that throttle body by say shifting, or just letting off the gas to decelerate. the area between the T/B & engine (post- T/B) goes into vacum. & the area from the turbo up until the T/B (Pre- T/B)has all this air with no place to escape, hence the Bpv/Bov to relieve pressure or youd see one heck of a boost spike when you let off the gas @ WOT
the turbo is powered by the exhaust & limited/ controlled by the wastegate, which operates on pressure (Stock W/G spring in the evo seems to be 7-8 psi)
so if you were to tee a line directly from the wastegate to the turbo, you would be able to hold 7-8 psi before your W/G opened & allowed the exhaust to escape
now, knowing that your turbo is limited/controlled by the very boost it produces, what would happen if you cut off the wastegates feed line & ability to control boost? you would boost as high as your turbine would phisically allow the turbo assembly to spin (probably 30+ psi) FYI- thats not good =p
so if you tap your boost control solenoid/MBC from say, your BOV/Bpv line which recieves its boost/vacum signal from a Post Throttle body scource, when you let off the gas, your MBC/Solenoid is recieving zero boost to control the turbo @ a time when your off the gas & want that turbo to spin down. granted the turbos power to spin comes from the engine & will naturally come down on its own rather quickly. but there is still a split second where you may be relying completly on your BOV/Bpv for Boost control, slowing down the process of allowing the turbo to spin down so as to not get a pressure surge
"but i watch my boost guage & im not getting any spikes!"
well, where is your Boost guage Teed into? most likely a Post T/B vac scource & thus you would never see them as they are happening on the other side of the T/B
----tired of typing, will update/finish in a bit
while quite a few posters on the board seem to have an opinion on this matter, nobody seems willing to discuss the matter logically, just "This is how "X" Tuner/gearhead/Manufacturer said to do it so it must be correct!"
im not saying my method is the end all correct way, so if you have something positive to add/discuss feel free to chime in
to start you must properly understant how the turbo operates & how it is affected by changes in the engine caused by the Throttle Body
when your "Mashing It" the throttle body is wide open, recieving boost from the Turbo & there is no pressure diffrential Pre/Post Throttle body.
but when you close that throttle body by say shifting, or just letting off the gas to decelerate. the area between the T/B & engine (post- T/B) goes into vacum. & the area from the turbo up until the T/B (Pre- T/B)has all this air with no place to escape, hence the Bpv/Bov to relieve pressure or youd see one heck of a boost spike when you let off the gas @ WOT
the turbo is powered by the exhaust & limited/ controlled by the wastegate, which operates on pressure (Stock W/G spring in the evo seems to be 7-8 psi)
so if you were to tee a line directly from the wastegate to the turbo, you would be able to hold 7-8 psi before your W/G opened & allowed the exhaust to escape
now, knowing that your turbo is limited/controlled by the very boost it produces, what would happen if you cut off the wastegates feed line & ability to control boost? you would boost as high as your turbine would phisically allow the turbo assembly to spin (probably 30+ psi) FYI- thats not good =p
so if you tap your boost control solenoid/MBC from say, your BOV/Bpv line which recieves its boost/vacum signal from a Post Throttle body scource, when you let off the gas, your MBC/Solenoid is recieving zero boost to control the turbo @ a time when your off the gas & want that turbo to spin down. granted the turbos power to spin comes from the engine & will naturally come down on its own rather quickly. but there is still a split second where you may be relying completly on your BOV/Bpv for Boost control, slowing down the process of allowing the turbo to spin down so as to not get a pressure surge
"but i watch my boost guage & im not getting any spikes!"
well, where is your Boost guage Teed into? most likely a Post T/B vac scource & thus you would never see them as they are happening on the other side of the T/B
----tired of typing, will update/finish in a bit