Aerovee timing with turbo

[Waiex 176]

I've finally finished with my turbo upgrade. Today I started my engine for the first time and tried to get my timing set. The engine will run on the primary ignition very well, but no matter where I set my secondary, I get a 250 rpm drop and it runs rough on the secondary ignition alone. I've double checked everything and I can't find anything wrong. It seems like an ignition problem. How did you turbo pioneers approach your timing. I started with the secondary set a per the manual and it was rough from the beginning. No matter which way I turn the trigger cap it doesn't seem to make a difference. Thoughts? Suggestions?
Thanks
John

[Gripdana]

I am going through the same thing without turbo. It was running rough intermittently. So I did the ignition service bulletin and discovered my ignition modules are bad and I can also no longer shut down the engine with the primary switch. And the secondary off. The switch is functioning correctly. I have removed the magnatron and sent it back to Sonex. My RPM difference is about 150.

[wlarson861]

My first start showed about 250 rpm drop after the manual setup. I moved the magnet a little clockwise and it improved to 150/175 drop. A little more and it was 50 to 60. Thats where I left it. I had retarded the ignition further clockwise when normally aspirated so went about 10 to 15 degrees further to get the rpm drop close.
After 7 hours I developed an ignition problem with the right coil or trigger. I ordered a new coil but haven't installed it yet. The question to ponder is whether the turbo heat had anything to do with the coil or if it was coincidental.

[MichaelFarley56]

Hi John,

I have a little over 10 hours on my turbo AeroVee now and had the same issues as you did. When flying on the secondary ignition alone I would loose several hundred RPM and it just didn't run well. Ultimately I followed other people's practices and reset my secondary ignition to around 24 BTC. It runs much happier there and flipping between primary and secondary ignition keeps the engine running pretty much the same.

With the primary ignition running at such an advanced setting, I really don't see why setting the secondary so far off would make that much of a difference. Unless both ignitions could be reset I don't see any reason not to keep them around the same setting.

Please bear in mind that this is simply what works for me and before you make any changes from the plans, I suggest you contact the factory for their thoughts and approval.

[MichaelFarley56]

After 7 hours I developed an ignition problem with the right coil or trigger. I ordered a new coil but haven't installed it yet. The question to ponder is whether the turbo heat had anything to do with the coil or if it was coincidental.

I had to replace my right ignition coil last summer but that was way before the turbo. It just went out. I'd be tempted to say it's coincidental for you at this point, especially since (knock on wood) I haven't had any of these issues with mine.

[Gripdana]

How do you test the coils? I don't think I have a secondary problem. I just want to educate myself.

[wlarson861]

The engine was extremely rough when only running on the electronic ignition on run up. I pulled the plug wires for the left coil and attempted to start the engine. Fired up but still failed the mag check. Reversed the set up for other coil and engine would not start. One of two problems, bad coil or bad trigger. Coil is most likely so I'll start there.

[MichaelFarley56]

How do you test the coils? I don't think I have a secondary problem. I just want to educate myself.

I wish I remember what the exact values are Dana, but you can check the coil with a volt meter. You check the resistance in Ohms between the two threaded points on top of the coil where our trigger wires connect, and then you check the resistance between the two points where the plug wires plug into the coil. I honestly don't remember the resistance values right off hand but if you check either of those two sets of points and you find 0 resistance, it would indicate a bad coil. I'll try to look up those actual numbers and post accordingly.

[Waiex 176]

Thanks for the input. I sent an inquiry to Sonex and they think from my description that I have either a bad plug or plug wire. Since there is a difference in timing, they say there will be a noticeable change in rpm going from one ignition to the other, but they engine should run well on either ignition. They suggested that I run the engine on the secondary ignition alone for a few minutes and watch the EGT's. The cold cylinder is the problem. I have already replaced my plugs in my diagnosis, and know the engine will run on each coil as described in an earlier post. I purchased some cheap wires at the auto parts store to use until I can get replacements. Tomorrow I will spend some more time and let you know. I did have to relocate my coils in the upgrade, maybe I damaged a wire somewhere. I believe it's an intermittent failure because the engine will run on two cylinders when I isolate the coils and turn off the primary ignition. Hopefully this will solve my problem.
John

[Onex107]

This may not apply, but, I just had a bad cylinder in the Onex after 60 hours.. Check the simple things first. I lost one cylinder when running on the secondary. The EGT nailed it down to #3. The secondary is the bottom plugs and I had just changed them all, so it had to be the wire. And it was. The OHMS ckeck was open. The end of the wire that I made up was bad. I had not been carefull enough when stripping the wire originally. The small inner core is covered with a black sheath and you have to be very carefull to not remove it when you strip the white insulation, and, the end of the wire must be located up to the hole in the crimped end so it is near or contats the end of the plug. When pulling the wire off the plug you can move the crimped end away from it's original position. Simple, but frustrating.