DaytonaRs4 wrote:carbon clean done and few more vac issues found....
i think this the N335 variable intake manifold change over valve that feeds tumble flaps?
few more bits to replace then car going straight to exhaust shop tomorrow....
Yes that looks like the part.
I'm not sure as I haven't tested or gone into detail however I suspect the ECU only checks the flap position once.
So something like
- engine below 3k rpm, no vac to manifold flaps so actual position = requested position (0%)
- engine goes above 3k rpm, ECU issues signal to solenoid to open causing the vacuum to be supplied to the actuators.
- actuators move as required vacuum is less than the amount available so actual position = requested position (100%)
- ECU goes "manifold ok" and never bothers to re-read the sensor.
- now the vacuum line is "active" it starts to bleed vacuum and it drops. Under full throttle vacuum is at its minimal level so it's likely the vacuum drops causing the flaps to close after the ECU has issued it's little check. Doesn't help that at 4.5k the exhaust flaps will (possibly) open along with the airbox valve at 5.5k. Every time a soloid / actuator engage a small amount of vacuum is lost.
- Engine is effectively starved of air but about 50%, the cam profile / timing and fueling is all wrong so power drops like a stone.
-rpms drop below 3.5 k, ecu cuts the vacuum to the flaps and then re-reads the position. All is well as actual position = requested position (0%).
This is purely my guesswork as I've not been able to log but it would be easy to rig up a test
