Low Imp Injectors

[JAM]

thanks. Count me on the list, i will buy when they are ready. will there be a case for this board?

Can you comment on my opening time question above?

[racingmini_mtl]

Yes there will be a case.

And the problem is that it is difficult to generalize because not all low Z injectors react the same. However, the p&h drivers will give more consistent results under all conditions simply because of the current sensing and the fact that you have a lower hold current. With resistors, you have to choose a resistance value that is a compromise between opening the injector under most battery voltage conditions and that keep current low and closing time reasonably short.

Jean

[JAM]

Yes there will be a case.

And the problem is that it is difficult to generalize because not all low Z injectors react the same. However, the p&h drivers will give more consistent results under all conditions simply because of the current sensing and the fact that you have a lower hold current. With resistors, you have to choose a resistance value that is a compromise between opening the injector under most battery voltage conditions and that keep current low and closing time reasonably short.

Jean

Thanks Jean, that is how I understood it. Thanks for the verification. For my application I believe it is the best method.

[Fabio421]

Thanks for your advice. First, let me say that electronics aren't my strong suite. I have a few more questions. When batch firing the injectors, is it necessary to use a resistor for each injector or can you use one resistor for each bank? If I were to use the P&H board from racingmini, how do I mount this? From what I can tell from reading the site, I would need two boards to run 8 injectors. Am I correct that these two boards will not fit inside the MS3x box? Would I have to build a seperate box for these? Is this available somewhere commercially?

Regarding someones earlier post that I should switch to high Z injectors. The car is a 1982 Porsche 928s that I have turbo charged. I plan on using high Z injectors later on in the build but I'd like to adapt to the stock fuel system first. The stock fuel injection on this car uses low Z and I have found and fitted some larger than stock low Z injectors. This car has Bosch L-Jet which uses low Z, barb style injectors. These are very rare birds. They use a small hose between the fuel rail and the injector. I've just finished machining some custom rails and hold downs that will utilize the high Z injectors but I have more to do. I still have to build and route all of the fuel hoses, regulators, dampners, hard lines, etc. I thought that it would be nice to go ahead and temporarily use the stock fuel system and adapt the MS3x to it to allow tuning. Later on, I would pull off the stock system because my plan is to use E85 ethanol and these 29LB injectors don't flow enough to support that. The L-Jet fuel system w/ MS3x controller will then be fitted to an older Porsche 928 that I have that currently has mechanical CIS fuel injection.

I appologize for all the noob questions. I'm just getting into this so I'm learning as I go. I appreciate all of your help.

[racingmini_mtl]

With an MS3/MS3X, the simplest solution for p&h drivers is to use the external box version. This is the one I have at this time: http://jbperf.com/p&h_board/v2_0.html#Buy. And you will need 2 of them since they only have 4 drivers per box.

Jean

[Peter Florance]

With an MS3/MS3X, the simplest solution for p&h drivers is to use the external box version. This is the one I have at this time: http://jbperf.com/p&h_board/v2_0.html#Buy. And you will need 2 of them since they only have 4 drivers per box.

Jean

Is that a straight interface to the MS3X injector output?

[racingmini_mtl]

Is that a straight interface to the MS3X injector output?

Yes it is.

Jean

[billr]

If you can machine fuel rails, you might consider doing what I did. I made a special finned heat-sink with a pocket on the back side in which my two V1.1 boards mount. That unit then is screwed on to the top MS cover and makes a fairly protected and compact package. It adds 1" to the height of the standard MS case, but I'm pretty sure I have much more fin than I need, the extra height could probably be reduced to 1/2". I joined the two V1.1 boards on the edges where each has a single-row header such that I connect from the MS3 with a single cable and double-row connector. No, of course I don't have any pictures handy, but I'll attach a .pdf of the heat-sink.

ms heatsink.pdf

[racingmini_mtl]

If you ever take pictures, I'd be interested in seeing them.

Jean

[aarc240]

Jean, thanks for replying re the consistency question (I'm catching this thread occasionally between visits to the orthopaedic surgeons).
My testing concurs, high heat or freezing cold has very little effect on Hitachi injectors as used on a Datsun Z car or the higher capacity after market equivalent when driven from the P&H boards.
I wouldn't expect this to change much with other injectors provided they are in the impedance range the P&H driver boards are designed for.
This is not the case with OEM Datsun injectors and resistors where the injectors run extremely hot in high heat testing.
As always, the environment in which they are used is a significant factor and in my case that is summer shade temperatures of 43 degrees Celsius, engine bay temp often 60 degrees higher. Winter is the opposite, sub zero mornings being common.

Re the question whether OEM's used lo-Z because they were cheaper, no that wasn't the case.
Initially, there wasn't a choice between hi-Z and lo-Z injectors, all were lo-Z. Improved manufacturing methods made the hi-Z feasible and reliable (the wire gauge used in in hi-Z injectors is remarkably thin).
If there is a choice between the two, hi-Z may be the better option but that's not always possible without undesirable modifications to an existing engine.
Again, for an OEM this is a cost cutting exercise - no resistors means less components and zero failure rate from them. The devices to drive the injectors are cheaper too

[JAM]

Here is another way to do it with the earlier version of the board with the standard case and a small additional cover. i used 9 pin DB connectors, 1 for each bank and a 3 pin for each board (it was batch fire mode)

[Peter Florance]

Here is another way to do it with the earlier version of the board with the standard case and a small additional cover. i used 9 pin DB connectors, 1 for each bank and a 3 pin for each board (it was batch fire mode)

Nice work
BTW love the signature quote

[billr]

I'm going to have my unit out soon to add wiring for a fuel-pressure sensor; I'll take some pictures then.

[billr]

OK, here are some pix. I'm sure the heat-sinking is way too much, I could probably cut off the fins and have just a plate. I don't know if it really matters, but I like having the P&H boards pretty well shielded and isolated from the MS3 with the MS standard cover in between.

[billr]

And, the last picture...

[racingmini_mtl]

Bill,

That's a great setup. And while this is likely overkill for almost any condition, there's nothing wrong with it and just means that it's one aspect (heat) you will never have to worry about.

From what I can see, I imagine the small blue wire is to send 5V from one board to the other?

Jean

[billr]

Yes, the blue wire connects +5 on each P&H board, the ground traces on each are jumpered together at several places, on their adjacent edges, on the far-side. Each +5 pin connects to the proto area +5 supply on the V3.0 mainboard, and each ground pin connects to the MS3 injector header; plenty of redundancy on both. I have dots marking the connector that plugs into the header on the two P&H boards, but even if it was reversed there would be no damage; only effect would be injectors wouldn't be in proper sequence

[bytesandbolts]

Just come across this thread, have a couple questions of my in regards to running low impedance injectors with a MS3X Board.

According to the docs you are able to run the injectors using PWM from the two main injector pins from the MS3 board. However the docs also mention "Ensure your board and loom are wired for the injector flyback 12V return if using injector PWM". Would someone mind clarifying what this is for, as I'm a bit puzzled. Also not sure how the 12v return should be wired up, it appears to run from pin 6 on the DB37 from the images I have seen?

I only need to control a single injector and PWM seems like the best bet to get things running to me.

Dan

[Peter Florance]

Just come across this thread, have a couple questions of my in regards to running low impedance injectors with a MS3X Board.

According to the docs you are able to run the injectors using PWM from the two main injector pins from the MS3 board. However the docs also mention "Ensure your board and loom are wired for the injector flyback 12V return if using injector PWM". Would someone mind clarifying what this is for, as I'm a bit puzzled. Also not sure how the 12v return should be wired up, it appears to run from pin 6 on the DB37 from the images I have seen?

I only need to control a single injector and PWM seems like the best bet to get things running to me.

Dan

As long as your MegaSquirt Pin 28 is powered from same relay output as injector +12v, you should be fine. It will be important you follow MSExtra recommended grounding scheme.

http://www.msextra.com/doc/general/grounding.html

[bytesandbolts]

Hi Peter,

Yes my grounding is already setup the same to the diagram you mentioned.
I sourced a 4ohm resister in the end to get my injector working, all set up correctly now.

Thanks again