914F3 turbo

A starting poin might be to make sure the adjusting nuts on the wategate arm are tight.  See Rotax MML, Section 12-20-00, 8); and Rotax MMH, Section 78-00-00, 3.6.3).  Note wording: "Adjust Bowden cable with M6 hex. nuts (15) so that no clearance is perceptible on wastegate lever."

Mike Montefusco wrote:

A starting poin might be to make sure the adjusting nuts on the wategate arm are tight.  See Rotax MML, Section 12-20-00, 8); and Rotax MMH, Section 78-00-00, 3.6.3).  Note wording: "Adjust Bowden cable with M6 hex. nuts (15) so that no clearance is perceptible on wastegate lever."

Hi thank´s for replying

We adjusted the waste gate wire according to the video instruction and the gate closes tightly, when throttle is in idle position.

“Adjust Bowden cable with M6 hex. nuts (15) so that no clearance is perceptible on wastegate lever. With this adjustment set, pre-tension the pressure spring by 1 to 2 mm (0.04 - 0.08 in.) at straightened cable with the adjustment screw at support”

Sandberg,

In the TCU Log you posted the max RPM of 5800 is being exceeded, so the engine is making its full rated power.  The stated boost pressure of 39.5 is nominal.  As per the 914 operating manual, the TCU will adjust the boost pressure to protect the motor from over-speeding or over-temperature of the airbox. The higher boost pressure you have seen before may be under different ambient conditions. You should limit your RPM at takeoff to 5800, manually or by adjusting the prop pitch. 

From page 7-12 of the operator manual:

Besides the throttle position, overspeeding of the engine and too high intake air temperature have an effect on the nominal boost pressure. If one of the stated factors exceeds the specified limits, the boost pressure is automatically reduced, thus protecting the engine against overload.

If the wastegate and servo are operating correctly and as they should, check the rubber hose that is connecting the turbo assembly to the airbox. If that is leaking air (it has two clamps at each end) you might be loosing boost pressure. And just to be sure ,have you done any recent maintenance on the carbs? 

Jeff Blakeslee wrote:

Sandberg,

In the TCU Log you posted the max RPM of 5800 is being exceeded, so the engine is making its full rated power.  The stated boost pressure of 39.5 is nominal.  As per the 914 operating manual, the TCU will adjust the boost pressure to protect the motor from over-speeding or over-temperature of the airbox. The higher boost pressure you have seen before may be under different ambient conditions. You should limit your RPM at takeoff to 5800, manually or by adjusting the prop pitch. 

From page 7-12 of the operator manual:

Besides the throttle position, overspeeding of the engine and too high intake air temperature have an effect on the nominal boost pressure. If one of the stated factors exceeds the specified limits, the boost pressure is automatically reduced, thus protecting the engine against overload.

Hi 

You are absolutely right and we are aware of that. Once we have towed we have lowered the rpm:s manually. This is how we have got full boost pressure. Now we adjusted the governor to 5800rpm, but still the pressure doesn’t rise anymore even though the flap is completely closed.

Another observation was that when the turbo starts to warm up, the flap closes completely, but the pressure no longer rises. What i want to say is that, there has now been a change in the turbo because so far s has produced full pressure.

There is also not much clearance in the turbo shaft anymore, so I suspect there is already soot in the bearings. Turbo has running now near 1900h.