VWSam00Cleveland wrote: ↑Sat Aug 04, 2018 4:57 pmMain reason I wanted to go full sequential was purely to make the engine more efficient (thought process there was that you have 2 injectors providing the same fuel pulse twice per cycle rather than once, I get that the injector on time will probably be reduced to compensate but still fuel used overall with sequential - correct me if I am wrong? )
Sam, you caught me with a cup of coffee on a Sunday morning.
My responses below mostly center on the specific engine's dynamics, as each engine, fuel, and specific hardware respond differently to these dynamics. After extensive research, different OEMs use different methods to accomplish different goals. Some inject 1-per cycle at a specific point to capture the entire pulse while the valve is open. Some inject only on a closed valve, in order to allow the valve and engine heat to help vaporize the fuel before the valve opens. Still others inject twice per cycle, for a combination of effects, keeping in-mind the goals of an OEM system may be entirely different than yours.
Also keeping in-mind that the injection timing effects change dynamically with speed, load, temperature, charge velocity, etc., and therefore are most effective in a narrow operating range. Also realizing that the larger benefit in most cases is not sequential itself, but the ability to trim specific injectors at specific pulse widths for corrected flow, improving fueling under a much wider range of operation than just timing control. . . and so on.
Lab computers and books can be filled with this stuff (and have), but the point I am trying to make is that "sequential" does not mean the same thing or have the same effects or usefulness for any two engines or user goals. Sequential, fuel and ignition trims, and similar features are great to have if you can get to the point and do the work to make them most effective. For racing teams and OEMs, it's worth it for the relatively small gains it can give to use against the competition after extensive basic tuning is already razor-sharp; but for most Speeduino users that's all rather deep and distant work for an average percent or two of gain, making it a fairly low priority in the overall scheme of things.
VWSam00Cleveland wrote: ↑Sat Aug 04, 2018 4:57 pmI also didn't really like the idea of having non atomized fuel sitting in the other intake port ready to be sucked into the bore on the next intake stroke, washing bores, ETC - I know this is probably going to be minimal, perhaps I'm being anal but just a thought.
What is the fuel delivery scheme of your OEM design? Is it a wide-pattern fogging injector in a twisted port to carry the fuel into the cylinder while the valve is open? Or a thin stream injection to avoid fuel hitting port walls and making it directly to the closed hot valve for vaporization? I (just me) would not assume what scheme is used, for what purposes (emissions?), requiring what injector spray type, timing, pressure, etc in order to recover or improve on that scheme for
my purposes. Freely admitting there are too many factors and unknowns for me to know or anticipate; I could do extensive experimentation to stumble upon something that works better for what I want. I think that type of stuff can be fun — but I'm weird that way. I would not suggest it for most Speeduino goals, and why I don't rate it a high priority.
This is what I call "incremental" racing, where you squeeze every drop of performance (power
and economy) with all your basic functions and hardware, leaving you to incrementally nibble at relatively small gains that put you ahead of the other teams. A HP here, a TQ there, a pound of weight savings or a 0.001 drop in drag; it all adds-up for a winning combo. But, you have to work through the big numbers to that point in order to see those relatively little gains. That is the domain of some other systems and users, but not typically the goals of typical Speeduino users.
VWSam00Cleveland wrote: ↑Sat Aug 04, 2018 4:57 pmOn that note, does anybody have experience on fuel knock at an injected fuel quantity with batch vs. sequential injection ? - be interesting to see the differences
Sure, but as above it will be different with every engine and fuel type, design and dynamics. That said, imagine how sharply-tuned the setup would have to be in order to see that difference? Are you at that point? Can you imagine the larger difference other factors such as injector trims, ignition timing accuracy, or temperature corrections could have on that situation beyond simple batch vs sequential? I hope you see here that I'm not throwing a wet towel on all this by any means, but rather attempting to put it all into perspective. You have long vision, which is a great thing. Wire and fire your Speedy, tune it within an inch of its life, and let us know what you find it needs to make the next best gains in the real-world for your goals. That will help both Speeduino and its users the most.
David
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