[JHolland]

Two squirts can give a more homogenous air fuel mixture at low speeds and low loads, by not dumping in all the fuel in one go. The initial squirt on the closed valve evaporates and is drawn in at the start of the intake stroke, the second pulse goes into the airstream later, into what would otherwise be raw air, reversion isn't an issue with mild cams and its always less of an issue with EFi than it was with carbs. The sequential systems that I have worked on all switch to two squirts (not batch injection!) rather than one long squirt, except during stating when you get four squirts.

[Relic]

OK. Sounds like we are talking at cross purposes regarding two squirt sequential vs batch injection.
The two squirt injection also enables smaller injectors with better fuel atomisation anyway.
While unsaturated air would be easier to vaporise fuel into.
So I can see that angle of giving you twice the time window.

As we have gone form carbs > single point > multipoint > GDI, and the considerable extra expense of GDI over MPFI, I dont see how OEM would cough up for GDI unless they had no choice. That choice is emissions standards via wasted badly burnt fuel. Thats what tumble/swirl/squish was also about to maximise fuel suspenion and eliminate drop out....and reburning fuel via EGR.

I also remember many of the words of David Vizard with condensation on metal walls and the need to create inlet port tumble to maximise economy, by keeping the fuel in the airstream and not allowing it to condense on those walls....ie not burn. Especially with fuel drop out at low gas speeds.

[Relic]

https://youtu.be/8WOeYFTN6UU?t=66

Note the golf ball style dimpled port work...for a reason ^^^

[jonbill]

Speeduino doesn't have config options for "batch", although you can abuse it for that. The paired injection design is for two timed injections per cycle.

[PSIG]

You seem to be trying to wrap your brain around this stuff, and that's cool. We all have, and still do. Much of it is not intuitive or is more complex than first appears. We (I) also do not claim to know everything, but guys like Vizard parallel most of our thoughts, if viewed in relative context. Notice, nobody is saying one or another is better or worse; just that they are options, and have shown certain capabilities, advantages or disadvantages.

An important point in all of this is that no single mode or type is "best", e.g., internet comments that (pick one - MAF, fog spray, ethanol, timing, etc) is the winner. They all have pros and cons that can be applied to any specific project and it's goals and requirements. With Speeduino and other DIY systems, we can blend many of these things in ways the factories never could.

OK. Sounds like we are talking at cross purposes regarding two squirt sequential vs batch injection.

Confusion is available for any topic. Sometimes it is a perception thing, more than technical. While we all know the common definition of "sequential", many consider it different than any form of batch. In-fact, 2-squirt paired batch is a form of sequential (always injecting at the same relative crank angle for each cylinder). That confuses people, but also why it is sometimes called semi or quasi-sequential. Easy to see why we don't call paired batch any form of sequential in the Wiki as effects and the pros and cons are different, and it just confuses yet more users.

The two squirt injection also enables smaller injectors with better fuel atomisation anyway.

Actually the opposite, due to injector latency (dead time) for each squirt. The latency is subtracted from available injection time for every squirt added per-cycle, reducing effective injector flow.

While unsaturated air would be easier to vaporise fuel into.

The air is never saturated at 12-16 times as much air as fuel, and double that (24-32:1) with first injection/cycle with 2-shot, while identical ratio to a single injection volume with both. If there is a benefit, it would likely be with multiple injections/cycle for the various reasons already stated.

So I can see that angle of giving you twice the time window.

Same window, different division of time in that window.

As we have gone form carbs > single point > multipoint > GDI, and the considerable extra expense of GDI over MPFI, I dont see how OEM would cough up for GDI unless they had no choice. That choice is emissions standards via wasted badly burnt fuel. Thats what tumble/swirl/squish was also about to maximise fuel suspenion and eliminate drop out....and reburning fuel via EGR.

IMO mostly true as goals and requirements are far different for OEMs than most of us. Small point; EGR is more about reducing detonation with cooling, CO octane, and reducing temperatures, plus increasing effective compression (cylinder stuffing) for better efficiency than just re-burning or additional burning of exhaust. EGR is more about efficiency than emissions. Tumble and swirl apply more-so to "wet" carb and TBI manifolds, and part of what the OEMs (and some of our projects) are trying to avoid with MPFI, DI, injecting closed-valve, etc.

I also remember many of the words of David Vizard with condensation on metal walls and the need to create inlet port tumble to maximise economy, by keeping the fuel in the airstream and not allowing it to condense on those walls....ie not burn. Especially with fuel drop out at low gas speeds.

Yep. But again, more to do with wet manifolds than MPFI, although there is some overlap such as wall-wetting. That doesn't mean MPFI is always better, as there are many down-sides to it as well, balanced against the benefits of avoiding some wet manifold issues, among other things. Best of all we can use almost any of the many options, and use data to determine how to test effectiveness, tune it well, determine what's better for this project, etc. Fun stuff!

[JHolland]

In-fact, 2-squirt paired batch is a form of sequential (always injecting at the same relative crank angle for each cylinder). That confuses people, but also why it is sometimes called semi or quasi-sequential.

On early Japanese vehicles this is also referred to as Synchronous Injection which some people confuse with sequential. The first Japanese ECUs used the feedback from the spark event (the so called Ignition Fail Safe signal) to trigger the injection event. The injection angle moved with timing but this kept the processor interrupts apart foe maximum CPU performance.

[PSIG]

The first Japanese ECUs used the feedback from the spark event (the so called Ignition Fail Safe signal) to trigger the injection event.

IIRC, that was the coil discharge called the "IGf" signal by Toyota for example, yes? Effectively, just the coil(-) signal spike pulled from a point just before the driver transistor at firing (transistor-off), conditioned to a square wave, as I recall.




Sorry for the OT squirrel-chasing.

[JHolland]

The first Japanese ECUs used the feedback from the spark event (the so called Ignition Fail Safe signal) to trigger the injection event.

IIRC, that was the coil discharge called the "IGf" signal by Toyota for example, yes? Effectively, just the coil(-) signal spike pulled from a point just before the driver transistor at firing (transistor-off), conditioned to a square wave, as I recall.




Sorry for the OT squirrel-chasing.

Yes that's the one, IFS or IGf, probably a few other names too. The processor also counts the pulses and if there is no spark for a full (rolling) cycle it cuts the fuel pump.