mark6

hi,just had a friend with a 89' mr2 turbo ask me how the boost is increased by re-mapping on an impreza,as on his car he was saying the only way to increase boost is by a manual boost controller,obviously the impreza is more advanced than his car and all i could say was that it's probably controlled electronically where as his maybe mechanically controlled,can anyone explain what exactly is controlled electronically to increase the boost?,it's not the boost solenoid is it??

VAL113R

having a guess, the ecu is changed which tells the car to run higher boost. I assume it has something to do with the boost soleniod and the wastegate?

if you want to run a higher boost then you need to either add a 3 port soleniod or whatever they are called or something like and Apexi AVCR which comes with its own soleniod.

tath

modern turbos have a vac hose to the ecu (or to a sensor then ecu) which basically tells the wastegate when to open - i.e. when correct boost is achieved.

some cars' ecus can open the wastegate later by remapping, some need the actuator adjusting and some need bleed valves which divert air from the ecu vac hose to "trick" the ecu into thinking that correct boost has not been achieved yet. many need a combination of these...

Midget

I always thought by your right foot !!

grahamfrary

I think it works like this. The wastegate is a mechanical device and will open at around 6 psi. The Boost Controller looks at the manifild pressure and compares it with atmospheric. It generates a voltage and tells the ECU what the boost is. The ECU decides what boost it wants by looking at the appropriate map and compares it with what it has got. The manifold is connected to the wastegate (with a restrictor in the pipe to iron out fluctuations) and to the Wastegate Actuator. The ECU tells the Wastegate Actuator to open and close (duty cycle) effectively controlling the pressure the wastegate 'sees'. The Wastegate opens as much as is required to hold the manifold pressure at what the ECU wants it to be.

Graham

mark6

cheers for that,i'll say its to do with the wastegate actuator cycle which is controlled by the ecu