[Podunk]

Hello all, when i was doing my oil pan gasket and baffle install, i had a good opportunity to check my turbos for the dreaded N54 rattle.. and yes, they both have worn out flapper bushings/rods giving side to side play.

now, i've had a B16G powered 1str gen DSM with over 100K miles
and i've had an SRT4 with over 260K miles. and neither of those two turbo cars had flapper issues.

SO why does BMW seem to have this issue? cause factory turbo's even tuned ( both my SRT and DSM where "tuned", SRT Diablo sport, DSM was DSMLink)
should last the life of the car, if not longer.

is it the angle the arm is actuated from causing the failure? cause i noticed that the arm starting angle on boost controlled internal wastegates are closer to a straight up and down, instead of about 30 degree angle off center away from the vacuum/boost valve that closes it.

What are your thoughts? those of you that did a flapper replacement and re-adjust, did you change the angle and rod length and have better results for longevity compared to mimmicking factory arm angle?

[jadams161]

BMW doesn't make the turbos. It's just an early design flaw by Mitsubishi

[lookalikehuuh]

it's not unique to BMW, almost all manufacturers nowadays have issues with wastegates wear/rattle.

I have seen Ford Ecoboosts, Kia/Hyundais, VW/Audi with wastegate issues. It seems like a lot of turbo MFGs are using similar designs to what Mitsubishi used in the N54 wastegates.

[Rob@RB]

It's the difference between vacuum and pressure controlled actuators. The vacuum style actuators hang the flapper hardware "open" in normal operation, only to close when directed by ECU controls. So as they are mostly always "hanging open" they are subjected to constant turbulence in the exhaust stream, which causes wear over time. This contrasts with pressure controlled actuators as the flapper hardware is "closed" in normal operation, only to open when directed by Pressure/ECU controls, which means that there is much less exposure to turbulence in the exhaust stream to cause such wear.

It is worth noting that the benefit of the vacuum arrangements is safety, if the ECU controls or actuation components fail there is no chance of overboost (as the flapper stays open and exhaust bypasses the turbine); whereas if you have that happen with the Pressure controlled actuation then you will be full boost and risk serious engine damages.

[Podunk]

Originally Posted by Rob@RB

It's the difference between vacuum and pressure controlled actuators. The vacuum style actuators hang the flapper hardware "open" in normal operation, only to close when directed by ECU controls. So as they are mostly always "hanging open" they are subjected to constant turbulence in the exhaust stream, which causes wear over time. This contrasts with pressure controlled actuators as the flapper hardware is "closed" in normal operation, only to open when directed by Pressure/ECU controls, which means that there is much less exposure to turbulence in the exhaust stream to cause such wear.

It is worth noting that the benefit of the vacuum arrangements is safety, if the ECU controls or actuation components fail there is no chance of overboost (as the flapper stays open and exhaust bypasses the turbine); whereas if you have that happen with the Pressure controlled actuation then you will be full boost and risk serious engine damages.

Thanks for the explanation this actually makes sense as the 4G63 B16G and the SRT4 where boost actuated and not vacuum.