Re the stroke the engine's on when the throttle is blipped: if the crank is turning 3600 rpm (for ease of calculation) then it's turning 60 times a second. Or at 1800 it's turning 30 times. Pretty hard to catch it on a given stroke.
I don’t believe that the AT fuel injection is sequential, I don’t see a high resolution tone ring in the parts diagrams.Well, my point was that in the time it takes for a shot of fuel to get into the cylinder, as in an old carbureted engine with an accelerator pump, the piston has done many complete cycles, and it won't make it through until the intake valve is open and engine is sucking, regardless. Fuel-injection ECUs won't shoot unless it's on the intake stroke in any case. Each cylinder has its own injector, BTW, so it doesn't matter how many cylinders there are.
It’s all about getting around the limitations of the camshaft isn’t it. I thought that we’d see a mass production cam-less engine someday, but everything is pointing to the direction of motors. You’re right about the muscle cars of the “old days”, they made all the right noises, odors, vibrations… but modern stuff is so much faster.Graves, I believe you're right about the non-sequential injection. I was getting used to thinking of automotive systems, which are not batch-fire much anymore.
Whenever the intake valve opens, there's going to be fuel with it. If the EFI is properly designed, there's just the right amount of fuel, squirted in at about 42PSI, and there's never a period where the intake valve is open without something to burn. It's not like a carb, where the act of air rushing past will draw the fuel into the port, and hopefully it's all sized properly to let it run without problems. Accelerator pumps were added to bike carbs in the early 80s because the idle mixtures were set very lean to meet emissions specs. Without them you have your scenario where there's a flow of air without enough fuel in it to combust. Cold starts are particularly hard, since the engine wants more fuel than warm running. Which is why there were chokes and enricheners, but the EFI does all those compensations now. So if inspection and analysis says that it's lean, either it's purposely set "on the edge", or there's a fault. Some designs are nearer the edge than others, and the engines need to be fairly well warmed up before they'll run right. Not getting into the "unintended consequences" scenario of end-user changes to the various systems.
Valve overlap has such a big impact on emissions that most engines are designed with as little as possible these days. We've all heard the rump-rump sound of muscle-car cams from the olden days, but that was a direct result of too much overlap. At low speeds, those engines ran like crap, and some of the intake charge was either going straight out the exhaust valve, or burnt gasses were getting pushed back up into the intake and diluting the next incoming fuel charge. On a big V8, this could be endured, but on a single or dual-cylinder engine, the idle speed would have to be set very high just to keep it running.
And just FYI, on my particular bike, in 12K miles over 3-1/2 years, I've heard it cough once (only at startup) about 3 times. So they don't all do it. I've not changed anything in the fuel/exhaust areas.
That’s what I meant by saying everything is pointing to the direction of motors. I know that motor and engine are often interchanged, but technically speaking motor refers to electric motor. Electrically controlled valves are more than a concept they exist, just not in mass production. Think of it, computer controlled valves, you could throttle through the valve train, control turbo boost eliminating the waste gate, control exhaust gas recirculating without a valve, drop cylinders, total control of engine braking… the possibilities are endless. But the focus these days is on improving electrical storage, so the internal combustion engine is taking a back seat, if the metal battery works out the engine is doomed.Graves, I think cam-less engines are an interesting concept but how much of a future will they have with the EV/and other alternative markets expanding and the beginning of bans on ICE, like the one in the EU banning all ICE by 2035. I don't think they will succeed with the ban as Italy is already seeking exceptions from the ban. Exceptions or not it is coming. Will 100% EV/alternative vehicles become the norm? Maybe, not totally in my lifetime, but definitely in my children and now G-children's lifetime.
Just to throw a wrench into the pot. Shadowjack, all very good points. There is a reason these engines miss and as a youngster, I was taught that if there is an engine not running right, the first place to look is the weakest part of the process, electrical. This could all come down to an ignition issue like a weak coil, worn plugs, incorrect plug temp, or plug gap. Just a thought.
I went for a 270 mile, mostly back/dirt/baby heads/rutted roads, ride yesterday and I had one miss. It is an intermitent issue for me and as long as it doesn't interfere at critical moments, like when stuck on a hill sideways, then I'll leave it as it is.
As I am thinking about this it seems the misses happen more at lower rpm like when a quick throttle is used to get the rev's up to pop the clutch to climb a hil
From what I’ve read the reason for two plugs per cylinder is to remedy an otherwise unsolvable problem. Modern era engines have a problem at low RPM, the problem is a lean combustion charge that becomes stagnant in the cylinder at the point of ignition. Ideally you would want the combustion charge to be mixing, or spinning, when the ignition sequence is initiated, so that the burn pattern remains predictable and complete. In modern engines with their relatively higher compression and lean combustion charge, gaps are created between the hydrocarbons of the combustion charge when the mixture stops mixing due to the compression by the piston just before ignition. When correctly timed, two plugs in the cylinder can help to mitigate the problem of incomplete charge combustion and prevent unburned hydrocarbons from leaving the cylinder through the exhaust. Two flame fronts as you suggest are not desired as they would tend to cause a knock. This “knock, ping, detonation…”, from whatever source, also creates an extraordinary amount of heat, heat that not only damages metal surfaces but also creates NOx (oxide of nitrogen), which is one of the components of photochemical smog. Side note: Do you know what the exhaust gas recirculation valves’ (EGR) function is in your automobile? It’s sole function is to introduce and inert gas back into the combustion charge to cool the combustion process to prevent the formation of NOx. The more I learn, the more I realize that a lot of the engineering involved in things is to work around the imperfect nature of things, everything is a compromise to reach a more desirable outcome. At least that’s how I understand it.You are correct, motor refers to, well motors not engines. Brain fart on my part.
Two plugs could be for several reasons:
Reliability if one fails with twin magneto. More of an aircraft thing than road vehicles.
A twin flame front for better and more complete ignition.
And better ignition. Instead of a single centerfire, that burns top-down from the center, with two on opposing sides of the cylinder, you have burn from the edges to the center helping to prevent hot spots and a more even distribution of pressure, which means more power.
My guess is Honda did this to have a better burn on a large bore to please the EPA numbers game.
Those plugs are expensive. Mine were replaced at 38K miles and I now have 46K