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Home > A-Series EFI / Injection > My Journey into EFI

rhcp4life

6 Posts
Member #: 11809
Junior Member

I am looking into converting my Mini 1275gt from Carb to EFI. The end goal is to do forced induction. I will start with converting to EFI on a 1275 engine that is currently running a SU 1.5" Carb.

This is my first time doing converting to EFI or even tuning a car. I have always worked on cars but mostly basic things. The goal is to achive around 90hp as a nat-asp car.

List of things i think need. Please correct me if I am wrong
ECU: MegaSquirt II Extra PCB V3.57 (with Siamese code) I need to do a lot more research on this.
Injectors: Im thinking 2 800cc, port injection, Not sure what dis/advantages there are to High/Low impedance
Injector bungs: I would like to get a couple weld in style and cut into the carb intake
Throttle Body: No idea. leaning towards something around 50mm. Whats a good option for this?.
Fuel Pump: No idea . Is a return line required?
Fuel Rail: likely something custom based on location of injectors
Mechanical Fuel Pump block off plate. Not sure if this can be purchased or made.
Ignition Coil: diyautotunehas a IGN 4 tower coil pack with 2 inputs for around 72 USD. I will likely do wasted spark.
Crank Position Sensor: 36-1, I see a few sites offer these specific to the A series motor, not sure if i can just use a generic one from diyautotune and make my own bracket.
Cam Phase Sensor: Already hacked up an old distributor to convert to a slotted optical switch (picture attached). I need to shorten the shaft but i am waiting on me choosing a switch and how it will mount.


Fuse Box: wont need much. but need to plan this out still.
Wideband Sensor: Im thinking i might need 2 of these.
Coolant temp Sensor: Do i need a buy this aftermarket or can i use the original mini sensor.
Intake Air Temperature Sensor: Do i need one?

I know i have a lot of questions in here, but im still learning a lot and have already learned a bunch from this forum. Thanks for everything!


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Rod S

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5839 Posts
Member #: 2024
Formally Retired

Rural Suffolk

First thing I would say is get registered on the MS-Extra forums and use the link at the top to download and read the manuals, both for the v3.0 board and the V3.57.

Second thing I would say (because Paul will say it if I don't) is the newer MS-3 is also an option, or any other ECU that allows individual injection timing, if you want to get around the charge robbing buy sending a single slug of fuel down the port during the window between the inner valve opening and the outer closing and timing it such that slightly more fuel goes through the outer valve. This is a perfectly valid alternative and proven to work. However, only the MS-2 has the code to allow for timed individual pulses through individual valves and/or the single pulse through both valves. Personally I prefer the MS-2 individual pulses although I do currently have mine switching over to a single pulse above 3K RPM (which I found a lot harder to time right than the individual pulses).
The MEMS ECU used by Rover in the MPI Mini was configured to use both methods - individual pulses at low RPM, single pulse at higher RPM - as I'm currently doing.

But you do have choices.


Answers are attached as a pdf as the text is too large to fit on this page.


EDIT - typo


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Edited by Rod S on 7th Oct, 2018.

Schrödinger's cat - so which one am I ???


jbelanger

1239 Posts
Member #: 831
Post Whore

Montreal, Canada

Rod has given a very good and complete reply but I'd like to add something. You don't mention if you're comfortable soldering your own ECU board and make modifications and additions. If that's not something you're comfortable with and/or not something you want to deal with then you need to go with the MS3/MS3X if you go with a Megasquirt solution as the MS2 does require quite a bit of DIY modifications and soldering.

But you also need to consider the MS3/MS3X limitations such as you can only use high Z injectors and logic level ignition coils (and not all of those can be driven directly by the on-board drivers). Both of these limitations can be overcome by external boxes but at a cost.

http://www.jbperf.com/


rhcp4life

6 Posts
Member #: 11809
Junior Member

Rod, Thank you for your detailed write up. Yes i'm on the wrong side of the pond... Located in the corn fields of Iowa

JB, I am pretty good with a soldering iron. I work as a Automation systems engineer and i do a lot of troubleshooting with electrical systems.

I am leaning more toward MS2 not sure i can get the board 3.57 without being assembled. So i may go with the 3.0 board especially if its been proven by people here.

I like the idea of low Impd. (z) injectors. I am now looking at 750cc as they seem more available and about $65USD each. I will keep investigating.


rhcp4life

6 Posts
Member #: 11809
Junior Member

So the MS2 has 1 high current ignition output. Can i Drive all 4 spark plugs with this? or is it recommended to only drive 2 with this?


Rod S

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5839 Posts
Member #: 2024
Formally Retired

Rural Suffolk

On 7th Oct, 2018 rhcp4life said:
So the MS2 has 1 high current ignition output. Can i Drive all 4 spark plugs with this? or is it recommended to only drive 2 with this?


No, not unless you revert back to a single coil and distributor which really is a retrograde step. You could still have the MS control the timing but you would be relying on the mechanical advance being similar so the rotor arm was close enough to the right terminal in the cap to send the spark to the plug or you would have to lock out the mechanical advance such that the rotor arm would always be close enough to the terminal whatever the advance was which isn't always possible unless the rotor arm has a very wide contact area.

Once you select wasted spark in TunerStudio the code will send the spark signal out of two different CPU pins alternately so it needs two "ignitors" (or logic level buffers) for the two individual coils inside the wasted spark coilpack.

Adding a second "ignitor" transistor to the MS-2 to run wasted spark is one of the easiest mods - apart from lack of space on the heatsink bar if all the standard injector driver components are installed, which is another good reason to decide up front how you are going to approach forced induction later if you go down that route.

And totally off topic, as soon as you said "the cornfields of Iowa" the first thing I thought of was Bay City, Tx - I saw "Field of Dreams" when it first came out in the cinema in Bay City (I was living/working in the USA at the time....)

Schrödinger's cat - so which one am I ???

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