Good morning Carpenter547! Welcome to Fordification.
I think you've asked some great questions here. Before I respond to them, know that I'm a beginner--most of the other guys here know a lot more than I do on these topics!
Solid state ignition is beneficial because there's nothing to adjust, and as far as I know, once installed it works at least as well as the old points/condenser style ignition system. Solid state ignition systems, compared with the old style ignition, rarely fail. So they probably make the vehicle more reliable.
Another benefit offered by some solid state ignition systems, like the MSD ignition systems, is that instead of firing the spark plug only once each time it's trying to ignite the mixture, it fires it multiple times. Their claim is that a single fire of the spark plug doesn't always ignite all of the mixture, and that with multiple sparks, they burn the mixture more completely. Note that they're only able to do this at low RPMs, since as the engine speed increases, the window of opportunity for spark plug firing decreases.
I've read reports of some guys who say that this multiple spark ignition system makes their older vehicles produce less of that funky, rotten egg smell when they start them up in the morning, or when they're idling, presumably because of more complete combustion. They supposedly pass less unburned gasoline in to the exhaust system.
One more benefit of the solid state ignition system is that many of them come with built-in RPM limiters. I think those are really cool, because as you probably know, they prevent the engine from spinning too fast for its own good. And as you also probably know, if an engine runs too fast, its valves can stop sealing properly (since they don't have enough time to completely open and close), also known as "floating." It's my understanding that this "floating" can cause very bad things to happen, perhaps like significant amounts of mixture being dumped out the exhaust ports, or burning, high pressure mixture shooting backwards through the intake ports.
I gather that as engine compression increases, these things become increasingly true:
- The engine becomes more efficient, doing more work with the same amount of fuel.
- The engine becomes more difficult to start, since it gets harder to crank over.
- The engine provides increased compression braking (also known as engine braking), which is handy for mountain driving.
- The engine requires a fuel type that's formulated to burn, instead of exploding, at higher compression levels. And for street gas engines, this means octane.
- The engine runs less smoothly and becomes generally "difficult." I know that this is an ultra general statement that could probably be proven inaccurate!
- The engine requires more expensive internals to cope with the additional stress of the high compression.
The upper limit for compression for an engine that's going to be driven on the street seems to be dictated by the fuel that's available. I gather that the highest quality pump gas can usually run without detonation (exploding in the cylinders) in engines up to around 10:1 compression. Engines with still higher compression may need expensive additives to the gas at each fill-up (I'm pretty sure these additives consist of octane, in the main), which makes these vehicles less convenient to drive.
The compression ratios of the engines that originally came in our trucks were relatively low (8:1 or thereabouts), which made them quite resilient to inferior gas, and trouble-free across a wide range of situations (like pulling an overloaded truck up a steep grade at low RPMs). It also made them easier to start (I think).
To address the specific comparison that you've made, between adding displacement versus adding compression: it's my understanding that both have the potential to increase power. The engine with additional displacement will tend to drink more gas and be more trouble-free, while the engine with increased compression will tend to drink less gas and be more trouble-prone.
Even these statements are highly generalized though. As you know, engine design is highly technical and specific to each instance. Adding displacement to an engine, for instance, won't increase the engine's performance if the engine's already hitting a different bottleneck, such as the flow rate through the heads.
Carpenter547, thanks for your great questions, and remember that this reply comes from a beginner!
Robroy
