Several days ago when test flying my 4 the EI popped its circuit breaker so reverted to running on the mag. The immediate effect was a loss of power and EGTs went about 100 degrees higher. The EI is normally running some advance at the RPM range I use but what happened surprised me. Long story short after checking the fuel/ switching tanks and various other checks while making my way back to land, I only realised what the problem was when safely back on the ground. However, I decided that the mag would have to go because it was very inefficient in terms of getting best power and for LOP operations. The problem with the EI was nothing more than a loose connection.
In researching my options for a second EI the EF11 web page actually made me engage my brain..... thats difficult to do these days because I am getting older. Anyway they pointed out the inefficiency of running a mag with EI. Sometimes the mag will spar first sometimes the EI, the only time the engine will be optimum is when the EI is advanced of the 25 degree mag timing.
My brain had still not taken in all the implications of this when I tried to balance the prop the other day. I was not able to get it better than .3 ips despite being at it all day...... I was running on both the EI and mag.
Yesterday I managed to do the 2 hour flight which is required before a full flight permit is issued in the UK. So, I decided to experiment and switched off the mag and just ran on the EI, there was no drop in performance but there was a reduction in vibration from the engine. I switched of the advance on the EI and this had the same effect as running on the mag alone, a drop in power and higher EGT's. So I continued the flight just running on the EI with advance on and she ran smoothly for the 2 hour flight. Of course if there was a problem with the EI I could revert to the mag so the mag did still provide for redundancy in the system although very inefficient compared with the EI.
So, the reason for posting..... well firstly if you prop balance with an EI and mag switch off the mag because it adds to vibration by giving a secondary ignition source out of sync with the EI. Secondly, so you can consider the options with knowledge of the full implications.
I will at some stage replace the mag with a second EI and I think the only time my mag will be switched on will be for take off and landing until I do that.
Running the diesel in my RV 9 was much easier!!
In researching my options for a second EI the EF11 web page actually made me engage my brain..... thats difficult to do these days because I am getting older. Anyway they pointed out the inefficiency of running a mag with EI. Sometimes the mag will spar first sometimes the EI, the only time the engine will be optimum is when the EI is advanced of the 25 degree mag timing.
My brain had still not taken in all the implications of this when I tried to balance the prop the other day. I was not able to get it better than .3 ips despite being at it all day...... I was running on both the EI and mag.
Yesterday I managed to do the 2 hour flight which is required before a full flight permit is issued in the UK. So, I decided to experiment and switched off the mag and just ran on the EI, there was no drop in performance but there was a reduction in vibration from the engine. I switched of the advance on the EI and this had the same effect as running on the mag alone, a drop in power and higher EGT's. So I continued the flight just running on the EI with advance on and she ran smoothly for the 2 hour flight. Of course if there was a problem with the EI I could revert to the mag so the mag did still provide for redundancy in the system although very inefficient compared with the EI.
So, the reason for posting..... well firstly if you prop balance with an EI and mag switch off the mag because it adds to vibration by giving a secondary ignition source out of sync with the EI. Secondly, so you can consider the options with knowledge of the full implications.
I will at some stage replace the mag with a second EI and I think the only time my mag will be switched on will be for take off and landing until I do that.
Running the diesel in my RV 9 was much easier!!
