Turbo Charging

Hi Jeff B,

Certainly the photos of the two aftermarket conversions show what looks to be mechanical wastegate control systems😈

I had hoped that one or more of our Gurus would have joined this discussing - why does a 914 need a computer controlled wastegate?😈

Sean,

The TCU allows for turbo pressure mapping for specific boost profiles based on throttle position (via the throttle position sensor). This allows for specific and programmable mapping for multi-modal operation.  

The 914 has two specific boost profiles (modes):  normal operation (maximum continuous power), and maximum performance take-off, which is restricted to 5 minutes.  The normal operation happens in throttle positions 0-100% and the max takeoff power is from 108-115%. The throttle lever has a specific detent at the 100% position so it’s obvious when you push past it into the max power area, which is limited to 5 minutes. 

The transition between the modes is non-linear, with boost pressure and power rising quickly as the max power throttle position is selected.  This bi-modal operation would be very difficult to create without the TCU, and its associated mapping based on throttle positions.  

Hi Jeff,

Sorry not convinced.

Sounds like an unnecessarily complex system, that may only be delivering a small advantage, over a mechanical wastegate, at significant cost in dollars. 

I accept that the combination of turbo charging & fuel injection, has the potential to deliver significant performance gains, when computer controlled BUT the 914 is a carburetted engine.

😈

Hi Sean,

I did not say it was necessarily better, just that electronics are an easy way to get the two distinct turbo modes that Rotax provides.  It also allow as them to send updates that may fine tune the boost mapping. From a complexity point of view, it’s a very light weight control solution, just the throttle position sensor and the TCU. I maintain a 914 aircraft for a close friend, and the TCU has been very reliable.