Fuel injection on the V12 engine

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abowie
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#21 Re: Fuel injection on the V12 engine

Post by abowie » Sun Feb 09, 2020 7:17 am

At the moment I'm having a look at the software from the different manufacturers.

Any chance I could borrow some ecu map files to have a play with?
Andrew.
881824, 1E21538. 889457..oops. Jezza the V12 XJS race car.
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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#22 Re: Fuel injection on the V12 engine

Post by jagwit » Sun Feb 09, 2020 8:31 am

lowact wrote:
Sun Feb 09, 2020 4:00 am
With my 12.5:1 CR engine, I want to try closed loop (knock sensor) and adaptive control of sequential ignition timing.
I have reservations about this idea. This approach simply aims to chase the maximum advance whilst limiting detonation. This is based on the assumption that max EFFICIENCY is always found at max advance. I understand that this is often the case but not always.

What I have found is that barometric changes has the biggest effect on detonation. More so in my case where I tune my engines at high altitude (1450m) and then drive to higher and lower altitudes. Sadly, although MS does do FULL TIME barometric based fuelling compensation (using a dedicated barometric pressure sensor), it does not do so for timing. I tried very hard to convince the devs to add baro timing correction but failed to get them to see the merits.

Thereafter comes fuel quality and octane (most likely not an issue in Aus or NZ)
Thereafter comes intake air temps.

Thankfully MS can be built to have a manual switch with which to select an alternative timing map (with much retarded timing) which I use when any of the above factors result in detonation.

I prefer to tune my engines for open loop running and then use the oxygen sensor for that last little bit of correction limited to a max of 3%). This way, even if the sensor fail (and they do), the engine still runs "perfectly".

Coming back to knock detection, I also understand that the knock sensor listens for a frequency that is highly dependent on the combustion chamber geometry. This means one can not just take any sensor and use it since it may not be tuned for the frequency generated by the V12. Then, with the V12 being so long, I wonder if one sensor per bank would suffice.

But, if you are bored, with nothing better to do, go for it! :bouncyyellow:

Using injectors that are excessively large is just a bad idea, very bad idea. This was one of the contributory factors why the "pre-HE" horsetrack V12s were so thirsty. Using such large injectors forces the tuner to tune for very small injector pulsewidths. This then amplifies the DIFFERENCES in flow rates (the injectors are not EXACTLY 280cc/min) as well as DIFFERENCES in opening times and closing times. You then end up with injectors flowing vastly different amounts of fuel at small pulsewidths such as at idle and lean cruise, which again forces the tuner to increase the pulsewidths to ensure than no misfires result, but then some cylinders are running richer or overly rich under those circumstances. Injectors should be chosen just large enough for the amount of HP the engine will deliver (per cyl).
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#23 Re: Fuel injection on the V12 engine

Post by jagwit » Sun Feb 09, 2020 8:38 am

Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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MarekH
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#24 Re: Fuel injection on the V12 engine

Post by MarekH » Sun Feb 09, 2020 10:16 am

The 190cc/min is for the 5.3litre HE engine.
Once you have a part number, you can look up these things on the web.

Individual injectors do indeed behave in a non-ideal way. For example, one may have the same deadtime as another but flow 20% less fuel below a certain pulsewidth than another. (Deadtime = injector opening time minus injector closing time.)

I'm not convinced a knock sensor is needed day to day. From my understanding, these engines seem to have a relatively flat curve as to the optimal amount of advance at any particular point, so thinking it doesn't run well if it isn't the exact isn't everything. Having said that, if you run a race car, then you may think otherwise. I seem to remember Roger Bywater writing that the v12 distributors weren't all that accurate anyway, so simply having a distributorless ignition with a map not a curve will be a huge gain in itself.

The old j-l website photo albums are still accessible as thumbnails. Some of my posts have pictures here and there.

Choosing which ECU to go for does affect support. Only a new manufacturer can support a new ECU, whereas a Jaguar solution has the most (hopefully knowledgeable) people behind it. An established aftermarket ECU sits somewhere in the middle. Plotted against that, the old ECU has fewest features whilst the newest have the most. For example, I can see in real time when I am running on eleven cylinders and why because I can have laptop open (with a second custom dashboard) as I drive. That has never been an option with a 16CU or to the general public before OBD1/2 came in. I have no problem with a new ECU being used, but the tech setting it up may not appreciate something as simple a running an idle valve with enough spare capacity to provide air at 0'c if he puts a system together at 15'c - it works now, but isn't physically spec'd right for sub-zero temperatures, or it works at sea level, but not at altitude, where he has never been, or a component always overheats or misreads when in a certain position "under the hood".

What such a project does do is give you a ringside seat into how the car works. For example, during startup you'll see how quickly the car fires up under different parameters and you quickly see that the exact amount of advance isn't critical but that the amount of fuel is. From log files, I can see that mine sometimes starts on about the third cylinder to receive a pulse - that's a total rotation of the engine of just 180'! - compare that to the tortuous starting procedure (hot or cold) of a v12 where the the wrong amount of poorly atomised fuel must be going everywhere except where it is needed. From this you can also deduce that these high torque geared starter motors do nothing for you, except save a bit of electrical energy which you'll need because you're fueling it wrongly which is why it won't start.... until you eventually flog the battery and rob the ignition of spark. (OK so the engine turns over at 160rpm instead of 120rpm but so what? Charlie Chaplin started engines with a hand crank and no OBD2 or knock sensors...)

kind regards
Marek

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#25 Re: Fuel injection on the V12 engine

Post by MLBS3V12 » Sun Feb 09, 2020 11:27 am

If you are using the original ECU you maybe have no option but to use the original injectors? The high impedance injector you are proposing has flowrate 280 cc/min compared to the original injectors 190 cc/min, also will have different open/close characteristic. So, with the original ECU these injectors would be squirting ~50% more fuel than required? You would need an aftermarket ECU with the pulse width adjusted.
You re right! I ve kept the original ones. I just wanted to share this information for those who wants to use MS with high impédance injectors which look like original ones.
Michel
Le chemin sera long!...

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#26 Re: Fuel injection on the V12 engine

Post by abowie » Sun Feb 09, 2020 10:04 pm

jagwit wrote:
Sun Feb 02, 2020 10:11 am

The MS2 can be built with 1 ignition output that will already give you good control of ignition timing albeit still using the dissy. This would be an uncomplicated ignition solution.
This seems a good starting point.

How does the MS2 handle 12 injectors?
Andrew.
881824, 1E21538. 889457..oops. Jezza the V12 XJS race car.
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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#27 Re: Fuel injection on the V12 engine

Post by jagwit » Mon Feb 10, 2020 5:39 am

abowie wrote:
Sun Feb 09, 2020 10:04 pm
How does the MS2 handle 12 injectors?
I will presume your question to be:

"How does the MS2 handle 12 LOW IMPEDANCE injectors?"

The short answer is: Comfortably.

The medium answer is: 6 injectors per each of the two injector outputs using PWM and active flyback control to minimise current drawn by the injectors yet ensure they remain open of the duration of the injector pulse.

The comprehensive answer (without going into the electronic circuits):

The MS2 has two injector outputs. Typically one would connect an output to each bank of 6 injectors. Each injector output circuit has two main parts:
- The "main injector switch" and
- the "active flyback switch"

The main injector switch is simply a substantial transistor that switches the injectors on (provides an earth so current can flow from the 12V supply through the injectors), through this main injector switch to ground. It has an active current limiter that can be used as a safety backup in case something goes wrong.

For high impedance injectors, this main injector switch will simply switch on at the start of the injector pulse (firing all the injectors connected to it) and switch off when the commanded pulse duration expires.

For low impedance injectors, this main injector switch will switch on at the start of the injector pulse, and then, once the "opening time" (typ just under 1ms) of the injectors expires (the injector is now open and squirting fuel), it will that start a rapid sequence of switching off and on, off and on, etc, just to hold it open, until the the commanded injector pulse duration expires, when it will finally switch off - until the next injector pulse comes along. This rapid series of switching off and on is called Pulse Width Modulation. Its purpose is to minimise the amount of current flowing through the low impedance injectors to prevent the current going too high and damage the injectors, yet ensure that enough current is maintained for them to remain open for the duration of the injector pulse. The "opening time" and PWM duty cycle (ratio between off and on) and PWM frequency is software configurable.

However...

Each injector has an inductance which (IIRC) is in the same ballpark as an ignition coil primary winding. Now, in the case of the Jag V12, we will have SIX of them connected in parallel!! Each capable of producing that same +-350V kickback spike when they are switched off!! This is where the active flyback switch comes in. At the same time, when the main injector switch switches off, the active flyback switch switches on providing a "dead short" from the injectors back to 12V (NOT ground) to rapidly "kill" that flyback pulse and to limit the electromagnetic noise that may result. Likewise the active flyback switch will switch off, each time, just before the main injector switch switches on again.

With all the above the MS2 (which has a surprisingly small heat sink for all these transistors) only becomes luke warm after a long drive (2 hours plus) which confirms how efficient it is at controlling 12 low impedance injectors!! I once proved a point by connecting all 12 injectors to one MS2 injector output and it was all fine.

Clear as mud? :bigrin:

For more technical information:
http://www.megamanual.com/v22manual/minj.htm#pwm
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#28 Re: Fuel injection on the V12 engine

Post by abowie » Tue Feb 11, 2020 7:50 am

My brain hurts...
Andrew.
881824, 1E21538. 889457..oops. Jezza the V12 XJS race car.
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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#29 Re: Fuel injection on the V12 engine

Post by jagwit » Tue Feb 11, 2020 8:11 am

abowie wrote:
Tue Feb 11, 2020 7:50 am
My brain hurts...

Welcome to EFI....

EFI wil make your brain hurt if you attempt it yourself.

Some ECUs will just make it hurt more than others.

It is a fantastic learning experience though - if you are willing /keen to learn. Having excellent documentation and support is a prerequisite.
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#30 Re: Fuel injection on the V12 engine

Post by AussieEtype » Tue Feb 11, 2020 8:17 am

abowie wrote:
Tue Feb 11, 2020 7:50 am
My brain hurts...
Megasquirt and its atrocious documentation will do that to you.

Garry
1971 Series 3 E-type OTS

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#31 Re: Fuel injection on the V12 engine

Post by jagwit » Wed Feb 12, 2020 3:11 pm

AussieEtype wrote:
Tue Feb 11, 2020 8:17 am

Megasquirt and its atrocious documentation will do that to you.
Perhaps you mean "comprehensive" rather?

I believe the MS documentation is astonishing! Amazingly comprehensive. But I concede that many "squirters" find it hard to find the info they are looking for because there is SO MUCH INFO on the various MS sites.
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#32 Re: Fuel injection on the V12 engine

Post by abowie » Wed Feb 12, 2020 11:07 pm

jagwit wrote:
Mon Feb 10, 2020 5:39 am

Clear as mud? :bigrin:

For more technical information:
http://www.megamanual.com/v22manual/minj.htm#pwm
So how does one output control 6 individual injectors connected in parallel? Surely this just opens all 6 each time it fires?
Andrew.
881824, 1E21538. 889457..oops. Jezza the V12 XJS race car.
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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#33 Re: Fuel injection on the V12 engine

Post by MarekH » Thu Feb 13, 2020 8:26 am

Yes that's right - it's called "batch fired" and it works reasonably well. The AJ16 ECU only has four drivers, so this is also batch fired in four groups of three.

kind regards
Marek

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#34 Re: Fuel injection on the V12 engine

Post by jagwit » Thu Feb 13, 2020 8:36 am

abowie wrote:
Wed Feb 12, 2020 11:07 pm
jagwit wrote:
Mon Feb 10, 2020 5:39 am

Clear as mud? :bigrin:

For more technical information:
http://www.megamanual.com/v22manual/minj.htm#pwm
So how does one output control 6 individual injectors connected in parallel? Surely this just opens all 6 each time it fires?
Correct. You can then choose to fire the banks alternating between between them every 180degs or every 360 degs (or all 12 simultaneously every 180 degs or 360 degs or 720degs.)

I found best results alternating and firing every 180degs.
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#35 Re: Fuel injection on the V12 engine

Post by MarekH » Thu Feb 13, 2020 9:04 am

Let's help put Garry's comments into context.

Megasquirt has been in existence and in continuous development, both software and hardware, for about fifteen years or more. Any documentation or user comments on the forums have not been deleted, but will often now be behind the times. It was conceived as a self built, cheap way to introduce EFI, electronic ignition and the control of peripherals where no such product existed at less than the price of an arm and a leg.

Since it has had continuous upgrades added (how does your Adaptatronic talk to the CAN network on your car?), that means the newest features will need to be tested by the userbase and only then are they fully documented as a release item. This means you'd be expected to actually read the manuals, read the forums, ask questions and eventually contribute something back to the community.

Simply saying something is atrocious is not going to help the developers make the code better, improve documentation, or help less experienced people with their problems. Neither does this help anyone else with EFI, purchased from any vendor or to any other end user for that matter.

Not all Megasquirts are equal. Some have removed the self build option and are supported by their vendors rather than the user forums, whilt at the cutting edge, development code and source code are made available to those who want to rewrite the firmware that runs the engine to make their own custom units. The truth is, if you apply yourself, think about what is written down and do your homework first, then you'd realise it is mostly your own frustration at what you don't know and can't grasp which are limiting your successful implementation of what is provided.

Having said that, there are shortcomings:- the quality of the connectors provided on self build units of previous years is not good because computer connectors are not well suited to the soldering quality most amateur car mechanics can achieve; some of the components on the main v3.0 board are too closely spaced should a repair to the board be needed; such repairs are needed when the end user has under spec'd what they have soldered to the board as most amateur car mechanics don't understand electronics well enough to know how electricity behaves (or misbehaves). On the plus side, it'll be ten or twenty years before there is a userbase for Motronic, Adaptronic, Canems or Emeralds which rivals that of the Megasquirt community who are willing to help a new user with their installation.

Even if you don't have a Megasquirt, you can learn a lot from their forums and documentation - far more than you will from all of the others put together and that in itself is a resource well worth having.

kind regards
Marek

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#36 Re: Fuel injection on the V12 engine

Post by abowie » Thu Feb 13, 2020 9:09 am

Again pardon my ignorance but doesn't this waste a lot of fuel? And if it cant fire the injectors individually wouldn't it be better to have a single throttle body injector per manifold?
Andrew.
881824, 1E21538. 889457..oops. Jezza the V12 XJS race car.
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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#37 Re: Fuel injection on the V12 engine

Post by MarekH » Thu Feb 13, 2020 2:11 pm

Yes, but not as much as you'd think....

With sequential injection, the fuel is usually fired onto a closed (hot) input valve where it atomises and gets sucked into the relevant cylinder as the valve opens. Mistiming this simply means some fuel doesn't go to that particular cylinder but gets spread around some of the others, so the fueling is adjusted to compensate.

When under very heavy load, the injectors may be open for up to 80% of the whole 720' cycle, so the car is effectively batch fired anyway. The savings, or benefit, of sequential injection, come when the injector opening time is a tiny percentage of the 720' cycle and are progressively lost as the load gets heavier.

I'd estimate a carburettored engine, which sprays fuel anywhere and everywhere except into a cylinder, wastes some 20% and this is mainly because it only has one possible setting for any given load and little adjustment for anything else. By contrast, the fuel injected engine can be set to be richer or leaner not only by the load, but also by rpm, air temperature, coolant temperature to tune out flat spots, resonances and what have you and tailor the air fuel ratio to optimum.

For short journeys the carburettored car has to spray a huge amount of fuel all over cold manifolds and runners at startup and as it warms up and any sort of fuel injected engine massively outperforms its ancestor - injecting sequentially is just icing on the cake as a cold start is effectively almost a batch fired start due to the relatively long injector opening time.

You'll be able to get a handle on how big this effect is if you set up to run sequentially but then deliberately alter when during the 720' cycle the injections are made. If there is a relativley wide window where the measured lambda of the exhaust gases does not vary, then sequential injection gives little benefit over batch firing. In other words, you can measure this if you want to, rather than rely on some heresay from a bloke on the internet.

kind regards
Marek

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#38 Re: Fuel injection on the V12 engine

Post by MarekH » Thu Feb 13, 2020 2:17 pm

You may find it harder to get a good stable idle with throttle bodies, i.e. without a airbox. You also need a good stable source of vacuum for your brakes and you need to measure vacuum accurately to fuel the car properly. Not having a linked plenum may mean some cylinders have different vacuum from others if you are running the brakes from one, the crank case ventilation from another....

kind regards
Marek

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#39 Re: Fuel injection on the V12 engine

Post by jagwit » Thu Feb 13, 2020 3:06 pm

abowie wrote:
Thu Feb 13, 2020 9:09 am
Again pardon my ignorance but doesn't this waste a lot of fuel? And if it cant fire the injectors individually wouldn't it be better to have a single throttle body injector per manifold?
The "wastage" in fuel is of academic proportions. "All" fuel supplied goes through the engine and is combusted.

Remember that Bosch K-jetronic was CONTINUOUS fuel being squirted. Like a water tap, if more fuel was required, it just squirted harder (tap opened more). Electronic injectors are either open or closed, hence more fuel simply requires for them to stay open longer.

Single throttle bodies is most effective at providing more air, as in racing or high performance applications.
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#40 Re: Fuel injection on the V12 engine

Post by abowie » Thu Feb 13, 2020 10:07 pm

Very interesting. Thanks to both of you for the explanation.

I have bought a book on EFI and I'll read it; hopefully this will help pad out my knowledge.

WRT brake vacuum. My car currently has 6 IDA Webers fitted which means there are no inlet manifolds. The ingenious fellow who built it has installed a vacuum pump and reservoir in the boot of the car.
Andrew.
881824, 1E21538. 889457..oops. Jezza the V12 XJS race car.
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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