Can I disconnect the airbox on a 914?

Renz,

The problem with answering your question of "Will it hurt the engine" is that you have addressed the symptom without knowing the root cause of the problem.

Chances are that you will be just fine.  Then again, you may not.

Only you can make that call.

Proceed with caution.

Hi Pete,

Thanks for your answer. Yes I did, I also removed my fuelcap to eliminate this probable cause. 

I ordered a new solenoid that is gonna be send to me in Spain, just to rule out this too. 

Kind Regards, Renz

The solenoid enriches the mixture during full power operation thus reducing the risk of detonation. The engine, if the solenoid was inoperational, would still be able to deliver full take off power. If for some reason becomes blocked or partially blocked when operating at full power setting ( from ram air port to the carb bowls) the engine would deliver less power as the pressure at the bowls would be incorrect in relation to the airbox pressure. By directing the carb vent lines to the airbox, bypassing the solenoid valve, you could opearate the engine at full power. The only risk would be detonation, but if the inlet air temperature is not very high I believe that you do not have any serious problems.

Hi Bill and Spiros,

Thanks for your replies. 

In the meantime I discovered that the solenoid is good, I checked it with an Ohm meter and by connecting the solenoid to the battery. 

What I discovered is that the wastegate doesn’t respond to the throttle movement. When the TCU starts up, he makes it’s full test cycle but doesn’t respond after that on the throttle. 

I think that this is maybe the root cause of the problem. (Please correct me if I’m biased). 

So the next thing is the potential meter on the carb that could be faulty, right?

Yesterday, I started with the first leg of my journey back home, I flew with the TCU off and the wastegate fully open, all went reasonably well, except for the reduced thrust. 

During this flight of 3 hours all the temps & pressures were well within limits, but after roughly 1 hour of flying I started to feel that the engine was running more roughly, I adjusted the throttle a bit and it became better when I reduced the throttle, but the rpm’s were now around 4000 which is a little uncomfortable, but I managed to stay level and landed safely without troubles on my first destination. 

Today I wanted to continue, but only if I felt comfortable. 

But I didn’t, because I checked the sparks and all were quite white and that seems a too lean mixture. 

I swapped my TCU with another TCU on the spot (a mechanic had one for me to try ou), at first it seemed that the wastegate was responding something better, but again with full throttle  the engine started to surge again. 

Next step is that I will try to get another potential meter and a laptop that can read and program my TCU. 

Kind Regards, Renz

PROBLEM SOLVED!!!

Floats in the carb had gone deteriorating and left what appears coating in my bowls which clogged the jet (it seems). 

After cleaning and new floats all is fine again.