FreeEMS firmware feature wishlist! (out of date)

[AbeFM]

Staged fuel injection has always been near and dear to my heart, the ability (though with peak-and-hold its less of an issue) to run huge injectors (or effective flow rates) while having smooth idle is nice. I could take a car like mine with port injectors.... Downsize them 50% for excellent control, then have secondary injectors 4 times the size of stock and not pay any penalty.

The other thing I've seen which I really like is the ability to run two different fuel supplies. You can put race gas at $$$$$/gallon in a second, smaller tank, and when you cross some threshold you can run a mix of the two fuels or even switch over entirely (ideally over a range so there's no harsh transition).

People complain that a set up like this doubles the chances for failure, running low on race gas, etc - but with more inputs a second pressure sensor in the fuel line would be great.

This lets you run the lowest octane, cheapest gas you can find without worry, and get race gas performance all the time when you lay into it.


Also, add to the list a fuel injection pulse width modifier based on fuel pressure. I want to ask for a delivered amount of fuel, not have to base it on what the pressure *should* be under certain circumstances. Tied to that can be the "oh shit where's my fuel" emergancy handling.

[Fred]

Thanks for the staging suggestion. I'll add that in now. I've intended it to be in there, but somehow it slipped through the net :-)

Staged fuel injection has always been near and dear to my heart, the ability (though with peak-and-hold its less of an issue) to run huge injectors (or effective flow rates) while having smooth idle is nice. I could take a car like mine with port injectors.... Downsize them 50% for excellent control, then have secondary injectors 4 times the size of stock and not pay any penalty.

My experience is that even with 1cc of injector per 1cc of cylinder you have a good idle etc with MS2 as it is. Enter sequential control with the same accuracy and I think you will find that running 700 - 1000 cc on a 2.0 will be doable with a decent idle and throttle response. Reality is that with huge injectors you can't have what you need. You need one timed pulse per cylinder per engine cycle, you need it to be at the right time, and you need ONLY one. With MS you can have 4/engine cycle on a 4 pot, and you get the nice idle IF your injectors are small enough, or you have 1 per cycle if they are not and you get a bodgy idle, not because of difficulty controlling them, but because of the timing of the shots.

People complain that a set up like this doubles the chances for failure, running low on race gas, etc - but with more inputs a second pressure sensor in the fuel line would be great.

I've thought about this too as my engine is 10:1 compression pushing 17+ psi above 5k rpm. The thing is though, that even with a pressure sensor like that, it only takes one cycle with the wrong afr to split a piston in two at high boost. I certainly wouldn't trust the system to not fail at the most important time. Plus the extra complexity and cost of the dual fuel setup would be significant.

Also, add to the list a fuel injection pulse width modifier based on fuel pressure. I want to ask for a delivered amount of fuel, not have to base it on what the pressure *should* be under certain circumstances. Tied to that can be the "oh shit where's my fuel" emergancy handling.

Unless I'm mistaken, this is already on that list somewhere.

Fred.

[AbeFM]

Sure sure, you wouldn't want to discover you're out of fuel at high boost. A much more, plain jane solution would be to monitor a fuel level sender in the second tank, maybe in series with a pressure sensor so it cuts off if you lose pressure.

Anyway, just posting it as a note here:
For low strung, high boosted motors, they don't need any real fuel at low rpm/low boost. As boost increases you need more octane. I'd like to run full on race gas on the street all the time, but 90% of what $8/gal race gas will be doing the job that $3/gal 87 octane gas could do just as well.

So, purely as a feature suggestion, it would be nice not so much to have staged injection for idle (which, as you said is pretty unnecessary), but to actually have a cross over, turn off the primary injectors as boost rises and fill in with the high octane secondaries, with a slope you could define in software.
You'd pick the start and stop max percent delivered by the primaries. Something like that.

I'd imagine it would be a very simple job indeed then to make this into fully functioning multi-dimensional water injector with the same code. You start cutting fuel and adding water, keeping them in some ratio you decide based on boost/etc.

[Fred]

Nice ideas :-)

[AbeFM]

It's been suggested to automate the process of a rev limit based on coolant settings. I;m sure if one was careful not to make it too agressive it would be a Good Thing. Maybe a time after start, too? So your motor doesn't rev to the moon on cold start.

What worries me about this is you pull away from your house, it's 47* F out and just as you get on the main street a school bus decides he wants to become one with your rear bumper. You step on the gas and... hit your 2200 rpm rev limit.

So, I suggest that above some setable throttle, the extra rev limit is removed. So you're cruising along and the car gently refuses to push itself, but in an emergancy, you can floor it (say, 90% or more throttle) and the motor will say "Damn the torpedoes!" and get you the power you need right away.

There might be some drivability issues with it coming in and out of rev limit as you modulate the throttle (a timer, or just ending the rev limit till the next restart?), but in an emergancy, Road&Track reviewer driving impressions are not important.

[Fred]

Good idea!

In my experience fuel cut limiters come back smoothly and straight away in OEM applications at least, and in my ute too actually.

I've always thought that such a coolant limiter would be a great asset to ring life, but at the same time the "bus factor" has always bothered me. This method seems to capture the best of both worlds.

As my old man often says "good thinking mannering", I have no idea what that means at all, but let it be here as a tribute to his strange existence anyway :-)

Fred.

[AbeFM]

This may sound dumb (it may BE dumb) but one thing I find sorely lacking in my current EMS solution... The ability to just set a variable. When working on my idle, I hate running around to 5 or 10 grid locations (I guess 4 or 9 would be more correct) tyring to "box in" what I want to set it in real time. I want a FLAT VE table, as a place to start. What I really want is to set VE to some known number, and let it stay there, independant of the table. For timing, you can say use fixed value, turning the table off. But not for fuel. Not in general.

The other issue I sometimes have is not knowing what a variable really is. This might be getting into non-freeEMS specifics, but my WideBand often has points in the log that are way out of range. Where did it come from? If 0V is 10 afr, how do I get a value of 2.35 afr in the log? Is it noise? Is it software or a logging bug? If I saw "-11 volts" then ... Well, it'd be more information than I have now.

[Fred]

That's an interesting idea. Certainly it would be very easy to implement, in fact, the first time FreeEMS runs an engine, its likely to have pulse width controlled directly via a pot on my JimStim such that we can crank and just wind in fuel until it starts :-)

Having said that, I'm not certain that it would be all that much help except in initial tuning where you just have a flat map and tweak the master fuel trim until it runs in a similar fashion.

As for logs showing impossible values, I swear I have seen that myself! Bizzare. Glad that I haven't lost my mind. MS1 passed out O2 values as raw ADC converted in MT because it was unused inside. At least at first, that will be the same for us too. Later when/if we do closed loop AFR control during low load etc both variables should be passed out such that they can be compared. That way the algorithm can be verified from the logs too.

Fred.

[AbeFM]

Uh huh. The flat value is just for basic tuning. I have a sense it would help fine tune injector open times, too - something that drives me batty on other EMS systems.

In general it's a little too hard to tell what's going on in the ECU. Ok for OEM, silly for something you built yourself a week ago.

Well, really what would be nice is a large paintbrush for the maps - to turn every value within a square of YxZ up/down by the same value or percent, etc. It would make it so much easier to do those or rows or whatever, instead of banging shift-up/up/shift-up/right/shift-up/down/shift-up/right/shift-up...etc etc. But, it's a bit far off....

I keep thinking there has to be ways to autotune injector characteristics - by adding 10% to pulse width and looking for a 10% change in AFRs... If you see a smaller change then it means your open times are wrong.

A friend and I have both noticed a drop in fuel economy since switching to peak-and-hold injectors and wonder if that's why.

[Fred]

Well, really what would be nice is a large paintbrush for the maps - to turn every value within a square of YxZ up/down by the same value or percent, etc. It would make it so much easier to do those or rows or whatever, instead of banging shift-up/up/shift-up/right/shift-up/down/shift-up/right/shift-up...etc etc. But, it's a bit far off....

Sounds to me like you are using MT, download and have a play with MTX, then post a hows MS2 support progress coming along dave question somewhere appropriate :-) MT is teh suck for table adjustment of bulk areas, MTX is nice :-)

I keep thinking there has to be ways to autotune injector characteristics - by adding 10% to pulse width and looking for a 10% change in AFRs... If you see a smaller change then it means your open times are wrong.

You need perfectly steady state operation for that to work, so it's best done manually. There is nothing to stop you doing exactly that. Also, nothing to stop you (on your existing setup) changing up and down "squirt" count and ensuring its the same AFR at the same load point.