Andrewr
Loved the cartoon. It shows the very reason I'm often tardy with replies. All wives must be tarred with the same brush. They fail to realize what's REALLY important.
The reason IO520s with equal sized injector nozzles have such a disparity in mixture strengths between the 6 cylinders is partly due to the type of injector system used and even more due to the built in induction design fault.
At rich mixture settings uneven mixtures are not much of a problem IF each cylinder is receiving pretty equal quantities of air. When the oxygen is burnt in each cylinder it takes the fuel it needs and the unburnt surplus is wasted down the exhaust.
The power produced from each cylinder will be pretty even because the amount of fuel and oxygen burnt in each cylinder is equal. The engine doesn't care if unburnt fuel goes down the exhaust. This is only true if the air to each cylinder is equal.
If an engine has uneven mixtures it causes uneven power when leaning brings the cylinder with the weakest mixture to the point where there is an excess of oxygen. Power from there on is governed by mixture.
As leaning is continued that cylinder puts out less and less power. As the other cylinders reach peak EGT they too put out less power as the leaning continues. If there is a big gap between when the first cylinder peaks and the last one it is readily obvious the engine will be running pretty roughly with all the cylinders putting out different horse powers unlike the situation with uneven rich mixtures with cylinders having equal air supply.
Back to theIO520. It's injector system is known as constant flow system.
The best description I've heard for it that it has 6 hoses all the same size coming from a central distribution point . These hoses have a nozzles on the end and each nozzle, inside the inlet manifold, sprays fuel in the general direction of the inlet valve. It sprays at a constant rate (controlled elsewhere by the quantity of air flow) whether the cylinder head inlet valve is open or not. When the valve does open fuel and air are sucked into the cylinder, the valve closes and the fuel air build up continues.
What could go wrong?
Well it's this. There is a manifold tube down each side of the engine. Each one feeds air to 3 cylinders. The air makes it way from the air filter down this tube to the three cylinders . Each cylinder has a fuel hose making a fuel puddle or more likely a mini fuel and air vapor storm outside the inlet valve that spends most of it's time shut.
If the injector nozzles are all equal size and we assume the mixture is correct at the cylinder nearest air filter then the 2nd one from the filter will be richer and the third one richer again. The air rushing past the first cylinder steals a bit of fuel vapor as it goes past. So the second cylinder gets not just air but a bit of stolen fuel as well. It is even worse at the third cylinder because it has stolen fuel from both cylinders before it.
That's why GAMI has progressively smaller injector nozzles on the cylinders as they get further from the air filter. Who needs big nozzles if you can steal from somewhere else.
Without GAMI or similar balanced injectors IO520s are rough running LOP.
I hope Continental have lifted their game. 5 years ago I bought a factory exchange IO520 engine for the 210 They assured me that it had balanced injectors installed. It didn't. I now have GAMIs and it runs beautifully to way below peak EGT if I want it to.