Another way to mod 912 for sequential question.

[olrowdy01]

I have come up with another way to do the 912 uP daughter board modification for sequential injection (and perhaps it has been done before) that allows me to use the original two MS2 injector drivers to drive injectors C & D (inj3 & inj4). The drive voltages for injectors A & B still appear on R23 & R36 as the original two wire jumper modification does. I don't use the two jumper wires installed for the original modification. They can be left in place if you've already added them but they aren't used in my mod.

My question:
Are there any plans to use U2a & U2b on the 912 uP daughter board in the near future? (I use U2a,b with my modification.)
____________________________________________________________________
[edit 1/7/10]
I have posted schematics, instructions, etc how to do the modification on my website at

http://dmr-architect.com/~locouki/o2-ms ... ation.html

There is also a schematic for a way to drive non logic level FETs with a logic (5V) drive signal. There are links to other articles on the site at the bottom of the home page.
-- Enjoy --

[jsmcortina]

I don't think there are any plans for those unconnected NAND gates, but likewise you don't need to do any board mods - MS3 already has sequential fuel outputs for 8 cylinders on the MS3X pin headers.
See http://www.msextra.com/doc/ms3/hardware.html#headers

James

[olrowdy01]

I don't think there are any plans for those unconnected NAND gates, but likewise you don't need to do any board mods - MS3 already has sequential fuel outputs for 8 cylinders on the MS3X pin headers.
See http://www.msextra.com/doc/ms3/hardware.html#headers

James

I didn't know about the MS3. In any case I'm still playing around getting my MS2-V3 set up between my other chores.

OK on the non-plans for U2 on the daughter board. I use U2 for my mod and I was concerned that some future firmware might use U2 for some other purpose.

[jsmcortina]

Oh, I kind of assumed that you knew about MS3 as you posted in the MS3 section.
Read more at http://www.ms3efi.com

James

[olrowdy01]

Oh, I kind of assumed that you knew about MS3 as you posted in the MS3 section.
Read more at http://www.ms3efi.com

James

I'm still slightly (or maybe even more so) confused by all the names for the Extra firmware that's out there. I got V3 and Extra3 mushed together. So thanks for answering even if I'm in the wrong pew.

I bought four Hi-Z injectors at the junk yard for testing. I squirted a little oil in them to lubricate the guts. This morning I had them on the bench running with the MS2. I never realized how noisy those things are when they are running (especially at 12,000 RPM!).

For some reason even though I have "Notify me when a reply is posted" at the bottom of the Post a Reply page I do NOT get notified. I also have the Notify me checked in my User Control Panel. Is that another forum feature that has been disabled?

[jsmcortina]

Not-to scale pictures.

Megasquirt-1 is this:


Megasquirt-2 is this:


Megasquirt-3 is this:


I added these pictures to the MSEXTRA manual index to hopefully help reduce the confusion.

James

[Keithg]

I have come up with another way to do the 912 uP daughter board modification for sequential injection (and perhaps it has been done before) that allows me to use the original two MS2 injector drivers to drive injectors C & D (inj3 & inj4). The drive voltages for injectors A & B still appear on R23 & R36 as the original two wire jumper modification does. I don't use the two jumper wires installed for the original modification. They can be left in place if you've already added them but they aren't used in my mod.

My question:
Are there any plans to use U2a & U2b on the 912 uP daughter board in the near future? (I use U2a,b with my modification.)

Sounds like you have found a nice way of using the FETs on board for 2 of the outputs in a 4 output setting. Please post this in the MS2 section with "V3" or "sequential" in the title.

I would recommend using identical drive circuits for all 4 outputs. So, in this case, you would build an inverting FET driver with the 2 Z34 fets. Use this as a pattern:[url]http://www.megamanual.com/ms2/v3pcb_4.gif/url]
As the note says, you do not need Q9, Q10, Q12, Q13, Q14, Q15. I would use the TIP42s as flyback for the other 2 circuits, though, with a jumper from your circuit for channels C&D. This would be an alternate to Jean's sequential board. Total components would be U4, Q1, Q5, D17, D18, C13, C14, D21, R14, R15, R17, R20 to have 2 more channels.

KeithG

[olrowdy01]

I have come up with another way to do the 912 uP daughter board modification for sequential injection (and perhaps it has been done before) that allows me to use the original two MS2 injector drivers to drive injectors C & D (inj3 & inj4). ...............

Sounds like you have found a nice way of using the FETs on board for 2 of the outputs in a 4 output setting. Please post this in the MS2 section with "V3" or "sequential" in the title.

I would recommend using identical drive circuits for all 4 outputs. So, in this case, you would build an inverting FET driver with the 2 Z34 fets. Use this as a pattern:[url]http://www.megamanual.com/ms2/v3pcb_4.gif/url]
KeithG

I have to draw the changes on a schematic since it would be too hard to explain without seeing it. I'll post the changes as you suggested as soon as I can finish up some details and post it on my (non-commercial http://dmr-architect.com/~locouki/) website about my converting my car to Megasquirt.

I'm using a pair of Motorola MLP2N06CL FETs as the extra drivers. They are now obsolete but I see that there are people selling them but at an inflated price of ~$18 each. Each FET has complete protection circuitry built into it and the price might not be that bad when you consider the extra components you have to add to do the same thing. Having the extra lead for the current sensing was popular years ago. I haven't kept up to see if there are companies still using it (I suspect there are though.) So it might be possible to find something in production.

This link will get you a data sheet: http://doc.chipfind.ru/search.htm?s=MLP2N06C&t=part

I don't see any delay or other differences when driving injectors on the bench (even at 12,000 RPM) on a dual trace scope except for the different spike peak voltages due to the different limiting characteristics of the two different pairs of FETs. (Disclaimer: I haven't installed the MS in the car yet.)

Do you know if there would be any objection (by the author of the original schematic) to me posting my version of the schematic that you referenced? I will have to draw it in my schematic program and then screen copy that to post it. Perhaps other people have already posted changes to the schematics?

[jsmcortina]

As Keith says, all four driver circuits should be identical or it is likely that the opening and closing time of the injectors will be different and result in weird fuelling problems.

James

[olrowdy01]

As Keith says, all four driver circuits should be identical or it is likely that the opening and closing time of the injectors will be different and result in weird fuelling problems.

James

OK, I'll do some tests on the initial current wave forms etc while driving my bench injectors and if I see any differences I can replace the original two drivers with 2 MLPs if necessary. There is a difference in the Rds (ON) (and the peak spike limiting voltage) between the pairs but I think the resistance difference could even occur in the wiring harness/connectors etc of the car.

[olrowdy01]

I have come up with another way to do the 912 uP daughter board modification for sequential injection that allows me to use the original two MS2 injector drivers to drive injectors C & D (inj3 & inj4). The drive voltages for injectors A & B still appear on R23 & R36 as the original two wire jumper modification does. I don't use the two jumper wires installed for the original modification. They can be left in place if you've already added them but they aren't used in my mod.

I have posted schematics, instructions, etc how to do the modification on my website at

http://dmr-architect.com/~locouki/o2-ms ... ation.html

There is also a schematic for a way to drive non logic level FETs with a logic (5V) drive signal. There are links to other articles on the site at the bottom of the home page.
-- Enjoy --

[racingmini_mtl]

While your modification will work and can use the on-board drivers, I would just like to point out that there are a couple of things to consider. First, you need to unsolder SMD pins and jumper which is not something for everyone and you can destroy the MS2 card if you're not careful. And second, that modification means you can't go back to the using the MS2 in it's original configuration (unless you undo the modification which is an additional risk).

With the modification I have done and presented (and recommend), you can use the MS2 card in it's original configuration with the original injector drivers in a non-sequential mode by simply changing the configuration in the tuning software and by connecting the injectors to the original drivers. You can run the additional injector drivers in parallel with the original drivers without any issue as long as you connect the injectors to only one set of drivers.

Another point to mention is that the on-board drivers are completely overkill for use in a sequential setup. First they can drive many times more current than is needed and the entire flyback damping circuit is not needed sine there is no PWM (actually the active flyback circuit is not needed either since the IRFIZ34N is fully avalanche rated and can therefore handle the flyback of a single injector and the current limiting circuit is also not needed because the current from a single injector is much lower than the limit).

So, for these reasons, I would not recommend this method since there is more risk and I'm not sure the advantage of using the on-board drivers overcomes this. I don't want to discourage people from proposing alternatives but I want to make sure people know what they're getting in. By the way, the warning on your web page is a good idea.

Jean

[olrowdy01]

Jean, your points are well taken and I don't mean to be confrontational in this post. But I do want to respond to them.

While your modification will work and can use the on-board drivers, I would just like to point out that there are a couple of things to consider. First, you need to unsolder SMD pins and jumper which is not something for everyone and you can destroy the MS2 card if you're not careful.

Any mod involving soldering IC pins or the pads they connect to shouldn't be done by someone who isn't familar with doing it. If one has that skill then it is a simple mod. I feel the greater danger is bending the pins up too high which could break them off.

Actually if you place the tip of the soldering iron only on the PCB pad the IC lead comes loose very easily and can be lifted with the dental pick with no problem. I was going to suggest that slipping a piece of paper under the lifted pin should help it not reconnecting it to the pad while jumping it to the adjacent pin. But hopefully anyone doing these mods (yours or mine) would understand the risks involved. Checking the circuitry with a low voltage ohm meter after modifying any circuit is highly recommended.

And second, that modification means you can't go back to the using the MS2 in it's original configuration (unless you undo the modification which is an additional risk).

We have to keep in mind that Microsquirt ECUs are designed to be a "one size fits all" with various modifications, additions, jumpers etc. My mod is just one more mod with that in mind.

Additionally, you would have to undo most mods (jumpers etc) to go back to the original configuration. My mod is basically intended to use sequential injection, not one that was given a lot of thought to flipping it back and forth.

If flipping is really desired a pair of 3 pin SIPs could be connected at the 74HC00 so two jumpers could be easily moved to simulate a DPDT switch.

With the modification I have done and presented (and recommend), you can use the MS2 card in it's original configuration with the original injector drivers in a non-sequential mode by simply changing the configuration in the tuning software and by connecting the injectors to the original drivers.

No doubt that is an advantage if one really wants to flip back and forth. But my mod gives you the advantage of using the two original drivers. So if we ignore the ham fisted solder person each mod has its own advantages.

You can run the additional injector drivers in parallel with the original drivers without any issue as long as you connect the injectors to only one set of drivers.

Another point to mention is that the on-board drivers are completely overkill for use in a sequential setup. First they can drive many times more current than is needed and the entire flyback damping circuit is not needed sine there is no PWM (actually the active flyback circuit is not needed either since the IRFIZ34N is fully avalanche rated and can therefore handle the flyback of a single injector and the current limiting circuit is also not needed because the current from a single injector is much lower than the limit).

I agree, the IDZI404 could just about drive Hi-Z injectors without the FETs. But that is part of the original design. For simplicity I just utilized the drive circuitry that was already there.

Disconnecting D5 & D7 would allow the Z34s to fly up to their full potential. I've found in my experiments that if I place a 1N4004 diode across my Hi-Z injectors to eliminate the fly back voltage the injector gets very erratic at speeds above ~10,000 RPM. So it seems that it is better to let the voltage spike fairly high as long as it doesn't cause interference.

So, for these reasons, I would not recommend this method since there is more risk and I'm not sure the advantage of using the on-board drivers overcomes this. I don't want to discourage people from proposing alternatives but I want to make sure people know what they're getting in. By the way, the warning on your web page is a good idea.

Jean

I will make the warning a little more specific as to the dangers of soldering directly on IC pins although I can't remember ever loosing a solid state device by soldering directly to the pins. We used to solder on all the pins of outboard RAM to increase the capacity of the old Color Computers.

I usually destroy solid state parts by forgetting to discharge electrolytic caps when temporarily touching the leads from one part to another. (Another reason to use sockets on all ICs.)

[olrowdy01]

Jean,

I have a question about using either sequential mod as is for bank injection. i.e. leave the sequential mod and tune as it is for sequential and do the following;

Connect 2 injectors to FET drain "A" and the other 2 injectors to FET drain "C". Or use "B" & "D". The unused FETs will still receive gate drive but the drains wouldn't be connected to any injectors.

It would seem that if the car was already tuned for sequential that the tune would be fairly close to work for bank injection since each injector would still be pulsed for the same amount of time. Only the order that they would be firing would be different (two at a time).

The tuner would still have the problem of selecting which injector to connect in parallel with another one and the point in the engine cycle to inject fuel.

Would this work?
If so then neither mod has to be changed to switch from one mode to the other.

[racingmini_mtl]

It would work the same way as non-sequential depending on which drivers you chose and which injectors are connected to the drivers. But you would get to chose the exact angle and you wouldn't be able to have more than 1 squirt per cycle.

But that's not the reason I think some people might want to go from one set of drivers to the other. The reason is that with the 4 drivers, you can't do PWM. If someone needs to go back to using PWM, then it might be more practical to be using the already present drivers and just switch to non-sequential (or semi-sequential). Your mods would not allow that since the MS2 card can't do PWM anymore unless you undo the NAND gate pin joining. With my mods, it's simply a question of connecting the injectors to the V3.0 drivers.

So, while it's nice to be able to do what you propose, I think there is very little advantage to it and potentially quite a few disadvantages to save installing 2 FETs and 4 resistors. And there is also the disadvantage of potentially being more confusing if there are many options to chose from instead of a single simple one. So while I won't be asking you to remove the information or not talk about it, I won't be presenting it either in the sequential code web page. Hopefully, you won't be offended by it and will understand the reasoning behind this.

Jean

[olrowdy01]

It would work the same way as non-sequential depending on which drivers you chose and which injectors are connected to the drivers. But you would get to chose the exact angle and you wouldn't be able to have more than 1 squirt per cycle.

But that's not the reason I think some people might want to go from one set of drivers to the other. The reason is that with the 4 drivers, you can't do PWM. If someone needs to go back to using PWM, then it might be more practical to be using the already present drivers and just switch to non-sequential (or semi-sequential). Your mods would not allow that since the MS2 card can't do PWM anymore unless you undo the NAND gate pin joining. With my mods, it's simply a question of connecting the injectors to the V3.0 drivers.

Yes, I agree with the above.

So, while it's nice to be able to do what you propose, I think there is very little advantage to it and potentially quite a few disadvantages to save installing 2 FETs and 4 resistors. And there is also the disadvantage of potentially being more confusing if there are many options to chose from instead of a single simple one. So while I won't be asking you to remove the information or not talk about it, I won't be presenting it either in the sequential code web page. Hopefully, you won't be offended by it and will understand the reasoning behind this.

Jean

No problem at all about not presenting it on the page. And I understand your point of view. My aim was to tailor the MS for my engine with Hi-Z injectors using as much of the original circuitry as possible. I have the info on my website and I reference this topic for people to see both sides of the discussion.
CUL

[olrowdy01]

Comparison of waveforms of two different type of FETs driving injectors.

Here is a picture I took off my Tek dual trace scope. It shows a comparison of the fall/rise time of two different type FET injector drivers. Two identical Hi-Z injectors are being driven. The upper trace is the stock MS2 Z34 FET running with my mod. The lower trace is a MPL2N06 FET with no external spike suppression.

The two waveforms appear to be the same, which means the injectors should inject the same amount of fuel.

I attached a pizo-electric transducer to the injector to check the glitches on the falling waveform. The glitch corresponds to the mechanical noise the injector makes. I believe the glitch is caused when the injector movable plunger mechanically hits the stop after ~1.56 mS. Of course fuel would already be spraying some time before the glitch.

Setup for test:
I connected the 13.8 Vdc supply through a .22 ohm resistor in series with each supply lead to the injectors. The scope leads were connected at the junction of the the resistor and the injector. The waveforms are showing the voltage drop (hence current) that each injector is experiencing.


The vertical scale is .5 V/div. The horizontal scale is 5 ms/div.

The smaller negative going voltage pulse on each trace is the supply voltage dropping slightly when the other injector is firing. I had a 50,000 mfd cap connected between the bat lead and ground at the time.