Good day all,
We're working on a 912ULS equipped with a 914 turbo and are having problems with temperature and power delivery. The motor is installed on a highwing, with wing fuel tanks + a header tank and 2 auxiliary electrical fuel pumps in addition to the mechanical. One of the electrical fuel pumps is always on, while the other is on a switch.
We've installed an Air/Fuel Ratio sensor in the exhaust to ensure we setup the mixture correctly.
The motor runs pretty well and smooth- with carbs balanced. We've taken it for a flight and noted the following:
On takeoff, the motor does make a decent amount of power, and reaches a Manifold Pressure of 41inches. On throttling back to 35 inches however (constant speed prop set at 5400rpm) , the power delivery seems weak, and it is a challenge maintaining altitude even at a low speed.
Immediately evident as well are very high EGTs. The hottest EGT (left) approaches 900degrees C, with the right being about 850degrees C (a 50C delta). This is well above the max allowable...
Shortly after takeoff, Water temps also shoot up, and necesitated a quick decend and landing (approaching 105-110C after <3 min; <500ft AGL)
A challenge has been adjusting the mixture to run optimally throught the rev range. At low and high RPM, A/FR is at about 12:1; and midrange at 14:1; which should be pretty good. This stays the same while in flight. To achieve this, we've adjusted needles to pretty rich and tried richening the hot cylinder, without any real effect.
Starting the 2nd electric pump also did not yield any difference..
Pretty large radiator, oil cooler and Intercoolers are installed - about the same used on the 915.. Decent ducting is also in place to allow flow through the coolers (this was where we started trying to solve the problem).
I would be very grateful for some advise on where to look for solutions here.. High EGT's tell me it must be running lean, but AFR says something else, and exhaust burns dark..
This is from an altitude of 4500ft, ambient temp ~ 24degrees C.
Thanks
Jean
