914 TCU bypass.

by terry sharp in 912 / 914 Technical Questions 9 years ago

Looking for more info how the switch works, when to use it and when engaged are you just flying an 80 hp Rotex?

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Re: 914 TCU bypass.

by Rob Seaton » 9 years ago

Rob Seaton

3 1.32k 240

The switch just cuts power to the wastegate servo motor, whatever position the wastegate is in, there it stays until you turn the switch back on.
It is used if you get bootstrapping or any loss of control over the turbo.
Is it a 912 with the switch off? No, the 914 will make more power as, even with the wastegate fully open, it is making some boost.

Thank you said by: terry sharp

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Re: 914 TCU bypass.

by Mark BETTIOL » 9 years ago

Mark BETTIOL

9 17 5

HI ALL I HAVE OFTEN WONDERED THE SAME THING REGARDING THE SWITCH AND HOW IT WORKS AND WHEN I WOULD EVER NEED TO USE IT IS THERE ANY INFORMATION ON THIS AND WHERE WOULD WE ALL GO TO FIND IT I WOULD LIKE TO READ UP MORE ABOUT IT I HOPE I DONT COME ACROSS AS STUPID BUT I HAVE ASKED MANY PEOPLE WITH MANY DIFFRENT ANSWERS

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Re: 914 TCU bypass.

by terry sharp » 9 years ago

terry sharp

1 5 0

I experienced a series of power surges on climb out which stopped after reducing power below ambient pressure. The switch never crossed my mind although it had been pointed out during my checkout. I'm sure it's a TCU issue and that's the reason for the disconnect. Hope this helps someone in the future.

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Re: 914 TCU bypass.

by Rob Seaton » 9 years ago

Rob Seaton

3 1.32k 240

Are you sure you are having a "surge" ?
A true surge is an increase in MAP as well as a decrease.
It is more likely you are experiencing a power loss followed by a recovery. That would most likely be a boost leak in the float bowl seal area.
-Make sure the float bowls are not distorted from over-torque (the float pins will be bent outwards and the bowl will be dished slightly at the contact surface of the big screw.
-Upgrade to the new o-ring type screw.
-Use a new gasket and pre-soak it for an hour before installing
-Torque is only 49 inch pounds

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Re: 914 TCU bypass.

by terry sharp » 9 years ago

terry sharp

1 5 0

I believe you are right. I few it yesterday after some adjustments were made to the throttle position sensor problems started shortly after takeoff servo discount made no difference engine was literally shutting down. Power reduction to 4900 rpm resolved things. I'm sure now that it's running out of fuel, thanks for the tips.

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914 TCU bypass.

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