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Megasquirt EFI (and EDIS) for the BMW 2002 - Part 1

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While there is quite a lot of information on EFI conversions for our cars (some of which I will directly reference here), my goal with this article is to help anyone embarking on this type of project with a modular approach, so that one may go at his own pace, and deviate for personal preferences at any point along the way.  My own project has been done on a 1975 base 2002 using Megasquirt 2, Ford EDIS, and B&G firmware, so this will be the basis referenced here.  All standard disclaimers apply, please be safe about working on your car, and I'm not responsible if you screw something up, but I hope this helps many people interested in pursuing various EFI conversions for their 2002!

Useful 2002 Megasquirt conversion blogs:







Intro - Some things to consider

If you're just contemplating this undertaking and wondering if it's a good project for you and your car, here's my brief personal advice on the subject.  But obviously do your research and decide if it's a project you think you'd like doing.


Reasons EFI is a good fit for your 2002:

 - You like tinkering with your car on a regular basis

 - You like to drive your car regularly, and thus value better driveabiltiy and reliability

 - You have and are irked by issues with chokes, cold starts, and warmup


Reasons EFI is NOT a good fit for your 2002:

 - You value originality (your car might end up as much E30 as 2002 by the end).

 - Your main goal is performance (there are easier, cheaper, and quicker paths to pure horsepower).

 - You prefer to have someone else work on your car (this can make the tuning process slow, cumbersome, and frustrating).

 - You want it done quickly or are worried about scope creep.  (You WILL find other side projects you'll want to do along the way; the project WILL grow and take more time and money as it goes along.  This isn't necessarily a bad thing, but you need to be prepared for all of the 'well, while I'm in here' offshoots).


First things first. . .

You may not yet have decided on all of the details for a project with such a large scope yet, but that's actually OK, because there are some basic upgrades that make sense to take care of first, and are basically necessary no matter what direction you end up going with your car.  We're going to start with a few upgrades to the coolant and electrical system.  These items can, and I would say even should, be made to 2002s regardless of EFI, but are certainly required for EFI, and therefore make a good starting point.  


Section I - Coolant System Preparation

We'll begin with the cooling system, for which two specific upgrades are needed:

First is an E30 coolant divider with three sensor ports.  Try to pick up a used one here on the FAQ, Ebay, or a junkyard, and ideally get one that has all of the E30 sensors already in it.  You'll replace one with the stock 2002 sender to keep your dash gauge working, use the stock E30 sensor to provide coolant temperature data to Megasquirt, and leave the third in as a plug or use it for other needs (such as a switch to drive an electric cooling fan).  The additional coolant sensor is critical for fuel injection, as it is the main input that adjust how much fuel is injected during a cold start and then during warmup until the car is up to operating temperature.  Conveniently, it can also be used as the input to have Megasquirt drive an electric radiator fan directly, which is really nice.  Here's what this coolant divider looks like in my car, with the 2002 sender up front, the temperature sensor for Megasquirt behind it, and the switch/plug on the left:


Next up, while the coolant system is open, will be the coolant bypass line and hose, also from an E30.  You'll need this for pretty much anything other than the stock coolant manifold, be it side draft carbs, ITBs, or the 318i intake. You can salvage one from an E30, or buy a brand new one (or as part of a complete set with all new coolant hoses) from Ireland engineering here: http://www.iemotorsport.com/bmw/2002-cooling/M10sddrfthrdwr.html

And here's what it looks like installed on my car, sans intake manifold:


On last thing that is worth mentioning here.  While you have the coolant drained for performing these upgrades, it makes this a convenient time to also take the radiator out.  I'll leave scope-creep items like radiator and fan upgrades for other articles/blogs, but the reason I mention it here is that IF you are planning to use a Ford EDIS ignition setup (which is my recommendation, but see the later ignition section for more details), you will need the radiator out so that you can remove the crank pulley and replace it with one with a trigger wheel.  The easiest route that I would recommend is to just purchase a brand new pulley with a trigger wheel and also the sensor mount from Tom at 02again (http://www.02again.com/?page_id=358).


Section II - Electrical System Preparation

So, with the main items for the coolant system in process and/or already taken care of, we will next move to the primary electrical system upgrades needed for EFI.  The first involves relocating the battery from the original location in the engine bay to *somewhere* else in the car.  The most popular new homes are either in the trunk or under the rear seat, but you can put it pretty much wherever you want to, as long as you get it the heck out of the way up front. I didn't like the idea of losing trunk space and drilling into the rust-prone rear shock towers, so I chose to follow Zeebucks lead and installed two Hawker Odyssey batteries under the back seat, and will link to his complete instructions for this here:


The only deviations I made from his method were to route the cable through the interior and through the drivers side firewall instead of underneath the car, and I then brought the positive terminal into a sealed junction box on the inside of the front drivers side fender just underneath the relay bracket.  Here's a great picture I nabbed while I happened to have the engine out:


I'm pretty sure I picked this up at a local Lowes or Home Depot, but I haven't been able to find it again. So at least here's a link to something similar that I did find on Amazon:



I further followed in Zeebuck's footsteps and installed the larger 80-amp alternator from a 318i, in order to have enough overhead to power all of the additional electronic components for EFI and engine management systems I'd be adding. Again, his guide for this is already complete and excellent, so I'll point you to that write up here:



Lastly, I added a small additional blade fuse box (picked it up either from Autozone or Amazon: https://www.amazon.com/OLS-6-Way-Blade-Indicator-Protection/dp/B00QMTAZ1W) up in the front of the car to provide the fused terminals for the forthcoming additional electronics.  The +12V supply for this fuse box is provided from a relay which is switched by the ignition.  The stock 2002 ignition switch actually powers a LOT of things directly and needs to handle fairly high current.  This isn't exactly desirable, and you certainly don't want to any more load to this poor 40 year old switch, so please heed this advice and use a relay for this job, and do NOT power any additional electronics directly from the ignition switch.  On square-light vehicles, you'll be looking for a solid green wire from the ignition switch to run the coil (terminal 85 or 86) on the relay.  You can find this wire several places; it supplies fuses #4 and #12, powers the stock ignition coil, and runs to the lights and turn signals.




Something else I should add here is that the stock wiring for the headlights is not that great, as the headlight switch must switch the full load for the headlights, some 20 amps!  Although there are relays in the circuit, they aren't used as relays should be.  As such, I took the opportunity to rewire the entire relay area and put in a new relay box to house everything.  I mention this not because it's necessary for EFI, but because it's what you'll see in all of my pictures and wiring diagrams, so you need to know what you're looking at.  Here's my full wiring schematic and final product, for those interested:




One final note in this section, and that's regarding electrical connections.  You can continue to use plain old spade terminals for just about everything, but as this project involves a lot more wires and connections than the original system, I found it easier to buy a kit full of Weatherpack connectors to make multi-wired connections.  My new fuse box for example uses two 5-wire connectors (white in the photo) to hook up the 10 wires coming from the relays to the wiring harness. (I think I ran the ground wire individually).  If you want to take a similar route, here's a good Weatherpack starter kit on Amazon:



Section III - Wideband O2 sensor

This is the final stand-alone part that is key to running EFI, but also equally useful for tuning a carburetor-equipped car.  There are two basic types of O2 sensors, narrow- and wide-band.  Narrow band sensors check if there is any un-burnt oxygen in the exhaust stream and report that back as either a rich or lean condition. Wideband sensors on the other hand are a little more sophisticated and report back just how much rich or lean the engine is running.  The target here is an air/fuel ratio in the range of 12~15 (depending on exact conditions) which represents the point at which both all fuel and all oxygen are burned. For either a carb or EFI, this feedback lets you see under which operating conditions you should change the amount of fuel flow to your engine to try to maintain this perfect balance all the time.  With EFI, it's as easy as adjusting the numbers in the tuning software, and for a carb it means trying out some different jets.  It can also be used in EFI for closed-loop feedback, where the engine management system will automatically make fueling adjustments on the fly based on what the oxygen sensor is seeing.


I installed the fairly common LC-1 wideband kit from Innovate:


There are many others, some probably better and some worse, but I chose this one as it was not hideously expensive and because it provides two analog outputs, one of which goes to Megasquirt and the other which can drive the gauge in the cockpit. The important points to remember for installing an Oxygen sensor are:

 - Mount the O2 sensor in the upper half of the exhaust pipe, at a point AFTER the exhaust streams from all 4 cylinders have come together. Here's what mine looks like right by the front of the transmission:


 - Make sure to program BOTH of the two analog outputs for 0-5V.  As received one of the two outputs is programmed to function like a narrow band instead of a wideband.

 - I mounted the control unit on the passenger side of the engine bay just in front of the firewall. You can see it in this picture zip tied to the lip just above the distributor area:



Section IV - Ignition

(NOTE: If you are only interested in ignition control and want to keep your car carbureted, there is a system called Megajolt which is similar to Megasquirt but only for ignition control without EFI:



Ok, now we have reached the first major decision point in the project.  It's time to decide what type of ignition system you'd like to run.  I'm going to assume that you want SOME type of electronically controlled ignition, as this project would pretty much be a waste otherwise. Here are the three main options that I know of to choose from:


1.) 123/TUNE - https://www.123ignitionshop.com/gb/tune-bmw/106-123tune4rvbmw.html

This option has the advantage of being stand-alone, you could install this straight away on a stock car and be done if you wanted and not bother with EFI.  It also very stock looking, and works wonderfully with a Bosch blue coil.  If you looking for something quick and turnkey, this is what I would probably recommend.  However, if you plan to continue on with a Megasquirt EFI installation, I would instead recommend going with one of the next next two options.


1.) Megasquirt direct coil control - This is basically the same as the 123Tune setup, with the only differences being you will instead use your stock distributor (it's only purpose here is to direct the spark to the correct plug), and you will program the timing through Megasquirt, which will then directly control the firing of the ignition coil.

NOTE: you will need to make sure your Megasquirt control board is built properly to support this.  Here's the link to the direct coil control section in the MegaManual:



3.) Ford EDIS - Don't let the Ford brand name dissuade you, this is a truly elegant and awesome ignition system!  It is a distributor-less system that works in a wasted-spark configuration, so the only inputs it needs are crank position and RPM, and it can be easily driven by Megasquirt with whatever advance curve you desire. If you're going EFI, and especially if you're using Megasquirt, this is the way to go.  The parts are readily available, usually quite cheap, and it integrates perfectly in with MS.  I will detail out its parts and installation below.

NOTE: you will need to make sure your Megasquirt control board is built properly to support this.  Here's the link to the EDIS section of the MegaManual:



4.) Coil on Plug (COP) - You may by all means pursue and COP system and drive it with Megasquirt, and I think several 2002 owners have done so.  But my advice on this one is frankly don't bother and just stick with the Ford EDIS.  I won't dissuade you if COP is what you want, but I feel there's basically no advantages for using it in a 2002, and here are my reasons.  COP is mainstream today because it offers several advantages on MODERN cars.  These include things like no HT wires (which interfere with AM radio reception), longer dwell times to make a more powerful spark, and the ability to control the ignition on each individual cylinder, including things like multiple ignition events.  But in order to control just one cylinder at a time, we need to know which one of the two paired cylinders (2 or 3 and 1 or 4) is on it's compression stroke vs. exhaust stroke.  This generally requires a camshaft position sensor (as far as I know impossible to install on a 2002), or requires the signal from the distributor (to identify which cylinder should be firing), but to me that's just hokey to still have the distributor as part of a distributor-less ignition setup.  The way around this, and how the Ford EDIS works, is to utilize what is known as a wasted-spark configuration, where the spark is fired for both paired cylinders (based just on crankshaft position), and the spark for the cylinder on its exhaust stroke is therefore 'wasted.'  COP can be set up in a wasted spark configuration also, but now the advantages of longer dwell time and individual cylinder control are negated, and it's really no different than the Ford EDIS setup, just more complicated.  Unless of course, you strongly value AM radio.

Here's a link to the best thread I've come across on this topic, should you decide you'd like to research the topic further:



Installing MS-controlled EDIS in the 2002

If you'll take my recommendation, this is the way to go, and here's how you accomplish this:


1.) Read and understand the EDIS section in the MegaManual:



2.) Trigger wheel - As I mentioned in the coolant section, the easiest way to do this is to buy the correct crank pulley with the trigger wheel already on it from 02Again (http://www.02again.com/?page_id=358). Sadly, this option was not available to me when I started my project, so instead I had a local shop turn a collar for me to mount a scavenged Ford trigger wheel to a stock E30 crank pulley.  But I can tell you the next time that I have the radiator out of the car for some reason, I'm going seize the opportunity to upgrade to the 02again pulley/wheel! Anyway, here's how mine looks like currently:


If you look closely in the picture, you can see a small white arrow on the wheel where one tooth is missing, and this is lined up with the #1 cylinder TDC mark on the crankshaft.  This missing tooth tells the EDIS brain where TDC is, and then it 'counts' each tooth as it moves past the sensor so that it always knows what position the engine is in, and can decide when to fire the spark accordingly.  The sensor

should be mounted so that is lined up with the 5th tooth AHEAD of the gap when the missing tooth is at TDC.  There's a 'trigger offset' parameter in the Megasquirt software to adjust this if it's not perfect, but it's wise to still try to get it pretty close, so that the EDIS will function correctly in 'limp home' mode.  This is a built-in backup where, if for some reason there is no signal from Megasquirt as to what timing is desired, the EDIS will default to simply firing consistently at a static 10deg BTDC. This means the car will still be able to run on just EDIS alone, albeit not very well at higher revs and at a loss of power, but it's great for testing to make sure everything is working and just in case something should go wrong.

NOTE: If you have or desire air conditioning in your car, that complicates matters as the compressor pulley is right were we want to mount the trigger wheel.  I think this is still possible, but will likely require a different trigger wheel and some extra ingenuity and custom work on your part.


3.) Crank position sensor - Should be pretty obvious by this point, this is the VR sensor that senses the teeth on the crank trigger wheel and sends the signal back to the EDIS brain.  There's a link to the right sensor on the above mentioned 02again website, and the right connector I know can be sourced here:


The only two things to remember here are to make sure that the sensor wires are shielded to prevent electrical noise in the signal, and to set gap between the sensor and the wheel teeth to about 1mm.


4.) EDIS module, coil pack, and wires - Honestly your best bet for the module these days is probably Ebay, although if you have a local salvage yard that you like to frequent, look for an early 90s Ford Escort/Mercury Tracer to liberate these parts from.  You'll want the EDIS-4 module, connector, and coil pack connector (don't bother with the donor coil pack or plug wires themselves, see below).  Should look like this:


The original Ford coil pack and wires are ludicrously difficult to mount, but fortunately more user-friendly brand new options are available for cheap, such as this coil pack from Amazon for just $20:


To install this coil pack, I *think* I purchased this wonderful mount from 02Again, but I don't see it listed on the website, so you might need to inquire.  It mounts in the stock distributor location, nicely plugging the hole for the now unnecessary distributor while maintaining a stock-ish look:


For plug wires, the *RIGHT* set to look for is a 2001-2003 Ford Taurus 3.0L V6 with 24V/DOHC.  This will fit both that coil and the 2002 cylinder head.  Do NOT get wires from the very similar 3.0L SOHC V6 from the same vintage Tauruses!!! Here's what I bought:


Here's how my wires look installed, note the use of the E30 exhaust manifold gasket with the extra exhaust heat shield:


5.) Wiring - This is pretty straight forward, just follow the diagram below.  EDIS pins 1 and 3 to Megasquirt pins 24 and 36,  VR sensor goes to EDIS pins 5 and 6, both paired shields go to pin 7, pin 8 gets +12V (from the new fuse panel), 9 is ground, and 10 and 12 go to the coils:


NOTE: This is important to keep your tachometer working!  The Megamanual presents a schematic using some diodes to tie the output of the two coils together to drive the tachometer, but I worked for months on this and could never get it to work properly.  I think the flyback voltage that the stock tach wants to see is higher than what makes it through the diodes.  What DID work for me in the end is actually much simpler.  EDIS pin #11 (CTO) is the tach signal output.  This with a big NON-POLARIZED capacitor (I used 0.068uF) in the line directly drives my tachometer perfectly throughout the whole rev range!  In this picture, you can see where I mounted the EDIS module to the firewall and you can even see the orange capacitor dangling down just below the module on the yellow wire, before it plugs into the original factory tachometer wiring:



Section V - Megasquirt controller

This will be a pretty short section, as you only have two major decisions to make here: Which version of Megasquirt and do you want to buy: a turnkey pre-assembled module or the kit and build/solder your own?  I built my own; mostly for the fun of it, but it was also a bit cheaper.  But if you don't like soldering or are in a hurry, it's probably worth the extra $200 to buy the pre-assembled version.  There may be other sources, but the main one that I know of and would recommend for all Megasquirt kits is www.DIYautotune.com.  Here's a short list of the options and my thoughts on each of them:


Megasquirt I - This is the cheapest option at only around $200 for the kit, and it does in fact have all the capability necessary to run a naturally aspirated 2002 withEFI and spark via EDIS, making this a perfectly acceptable route for a budget build.  I would however in general recommend stepping up to MS2 for most people, primarily because the MS2 community is larger and therefore it's easier to find answers than for MS1. I also think the MS1 processor is now obsolete and no longer supported.

MS1 DIY kit: https://www.diyautotune.com/product/megasquirt-i-programmable-efi-system-pcb3-0-kit-w-black-case/

MS1 assembled: https://www.diyautotune.com/product/megasquirt-i-programmable-efi-system-pcb3-0-assembled-unit/


Megasquirt II - This was my pick because it's far cheaper than MS3, has all the capability you could ever need for a 2002 (including forced induction, etc), and a nice large support community.  As far as assembly time, I think it took me about a month working about an hour or so at a time several evenings a week.  It's definitely time consuming, but an absolutely tremendous learning experience for both the principals of EFI/engine control as well as electronics in general, which is what made it worth it for me.  I feel that the knowledge gained here makes the tuning process vastly easier to tackle when that time comes.

MS2 DIY kit: https://www.diyautotune.com/product/megasquirt-ii-programmable-efi-system-pcb3-0-kit-w-black-case/

MS2 assembled: https://www.diyautotune.com/product/megasquirt-ii-ems-system-smd-pcb3-57-assembled-ecu


Microsquirt - This is basically the same thing as a pre-assembled MS2 but in a smaller package and slightly cheaper.  I think the one drawback is that it needs and additional module to support idle control with a stepper motor.  Since I've already had the fun and learning of building one MS2 setup, I would give Microsquirt some serious consideration if I were ever to do a second car.

Microsquirt: https://www.diyautotune.com/product/microsquirt-engine-management-system-w-8-39-wiring-harness/


Megasquirt III - While the capabilities of MS3 are truly awesome, I think it's really hard to justify the additional cost for use on an M10 engine.  Features like 8-cylinder sequential injector control, 4-bank wankel control, water injection, nitrous, CAN-bus support, etc. are just, well, unnecessary for a 2002. But if for some reason you are interested in going this route, here's a link.

MS3 assembled: https://www.diyautotune.com/product/megasquirt-iii-ems-system-v3-57-assembled-unit-w-black-case/


The last main thing you'll need is the MS wiring harness, which I STRONGLY recommend you just buy instead of make.  For $80, you get the right connector complete with 10 feet of high quality, different colored and labeled wires.  You just can't beat that!



Once you've sourced or built your Megasquirt board, don't forget that before sealing it up in it's enclosure that you'll need to load some firmware on it.  There are two main types of firmware:

1.) 'Stock' firmware (use MegaTune software for tuning)

2.) MS/Extra firmware (use TunerStudio software for tuning)

I used the stock code and MegaTune and now that I'm used to it and have the car running great I'm not going to bother changing, but for new builds I would recommend using the MS/Extra code and TunerStudio.  It recent years it seems to have 'won out' in the mainstream and for all intents and purposes, it's just better.

Instructions and source for stock firmware: http://www.megamanual.com/ms2/install.htm

Instructions and source for MS/Extra firmware:



Optionally, you might find it useful to also pick up the Stimulator.  This neat little doodad runs on a 9V battery and plugs into the Megasquirt controller and simulates all of the various engine systems (e.g. RPM, MAP, temperature, AFR, etc.) This allows you to fully bench-test and program your Megasquirt so that you know it basically works BEFORE you start hacking into your actual car.  Below is a picture of my just-completed MS2 on it's first test run using the Stimulator.  Boy, I can still remember bouncing off the walls with happiness that evening!




Section VI - EFI Hardware

Here's where things start to get fun, installing the major components needed for EFI, but this is also sort of a point of no return, so make sure you have your Megasquirt controller working, all of the parts ready, and enough down time lined up before you pull the trigger.  We'll start with the list of parts/hardware needed, and then go into the details of each:

1.) Intake manifolds

2.) Throttle bodies

3.) Individual throttle bodies (ITBs)

4.) Fuel rail & injectors

5.) Fuel pump

6.) Additional sensors

7.) Idle control

8.) Megasquirt controller and wiring harness

9.) Miscellaneous

NOTE: Plan out and source everything before installing anything, and then start with the wiring (step 8.) first!


1a.) Plenum intake manifolds - For a more tii look, I think it's possible to use an E21 320i intake manifold or even a 2002tii manifold, but I'm not going to recommend that as I have no idea how to get the right fuel rail or injectors for it, but I think it has been done before.  For 95% of us, the E30 318i intake is the way to go.  It's basically plug-n-play, and is fantastically engineered by those Bavarians for off-the-chart fantastic mid-range performance.  I'd guess less than $50 on ebay or from junkyards.  Just one personal request, please take the time to clean up and paint your manifold.  It's easy to do before installing it, and makes it everything look so much better!



2.) Throttle body - If you pick up a manifold with the 318i throttle body already on it, then great! For a stock to mildly-modified engine this will work just fine.  Megamanual calculator says this should be fine up to 116 horsepower.  If you plan for your engine to go above that however, you'll probably want a slightly larger one from either the 325e or 325is.  Here's a link to a detailed run down of each and, as always, there's a wonderful adapter plate available at 02again.com!




While you're shopping on 02again there are some other accessories that you'll probably want to order as well, including the IAC adapter (for idle control), the throttle position sensor mount, and again though this isn't on the website I think I sourced this nice set of aluminum plugs from there for plugging up all of the various unused ports on the TB. One note, I did need to backfill some of the openings with epoxy, as the plugged holes would whistle something fierce at certain throttle positions!


3.) - ITBs - For those that desire more top end horsepower than mid-rage torque, there are several ITB options for EFI out there.  Having previously loved dual DCOEs, I've often toyed with this idea, but for me I think it will need to be done on a different car.  There simply isn't enough room in the 2002 engine bay to get long enough runners on ITBs to match the mid-range performance of the impeccably designed 318 manifold, so in my opinion ITBs are a better match for an engine build that's designed for a >4000 RPM power band.  But if you have high compression pistons (10.0:1 or greater), a rather aggressive cam (292 or greater), and some porting, this will likely be the route you want to pursue.  I know of two vendors (formerly TWM, now Borla, and Dbilas) that market EFI throttle bodies with mounting geometry that matches DCOE carburetors, so if you already happen to have a manifold for dual sidedrafts, this becomes rather straight forward.


The TWM/Borla parts are found here: http://www.borlainduction.com/2900-series.html and are probably the way to go if you already have a sidedraft manifold.

If you don't already have a manifold, then I would probably go for the Dbilas kit, as it comes with everything including the throttle bodies: http://www.dbilas-shop.com/Products/Throttle-body-kit/Street/BMW/M10/Mutli-throttle-intake-system-for-1602-1802-2002-316-318-518-520-E21-E30-1-5-2-0-8V-M10::10351.html

Lastly, I have also toyed with the idea of running just one of these throttle bodies on the Lynx single-sidedraft manifold that I have. I've done some calculations and think it should work, but would take some pretty specific selection of injectors and fuel control setup.  If you want to experiment with this, contact me directly for the specifics as I don't want to bore everybody with the math here, but in case this peaks your interest, here's the link to the manifold:



I won't go into much more detail on ITBs here as there is already a good writeup on this from Johnup, so see here for further reading on the subject:



4a.) Fuel Rails - Unfortunately I can't offer much help with fuel rails for E21 or tii manifold setups, but the others are easy; the ITB vendors all supply their own rails and the 318 intake uses the stock 318 rail including fuel pressure regulator.  Again you can clean up and use the one from a donor vehicle or buy new parts.  Here are links to the right parts from ECS, but I think local dealer pricing is also decent on these parts, with the added bonus of offering a CCA discount:

Fuel rail: https://www.ecstuning.com/b-genuine-bmw-parts/fuel-rail/13531707731/

Fuel pressure regulator: https://www.ecstuning.com/b-bosch-parts/30-bar-fuel-pressure-regulator/13531722040~bos/

Injector retainer clips: https://www.ecstuning.com/b-genuine-bmw-parts/fuel-injector-clip-priced-each/13531274729/

(DON'T FORGET THESE CLIPS, otherwise the rail can pop off of the injectors, dumping high pressure fuel into you engine bay, ask me how I know!)


4b.) Injectors - You'll need to estimate your engines peak horsepower for this, but once you do that the rest is easy.  The important thing to remember is to get the SMALLEST injector that you can which still flows enough fuel at peak horsepower.  The reason not to oversize much on the injectors is because then the pulse width will get very very short at idle, making it both difficult to tune and not as smooth of an idle as is possible with the smaller sized injectors.  Here are my guidelines:

Up to 120HP get 19# Bosch yellow tops: https://www.fiveomotorsport.com/bosch-yellow-top-19lb-fuel-injector

120-140HP get 21# Bosch pink tops: https://www.fiveomotorsport.com/bmw-0280150440-pink-top-13641703819

140-160HP get 24# Bosch blue tops: https://www.fiveomotorsport.com/24lb-bosch-fuel-injector-0280150947-blue-top

Here's the correct EV1 connector for all of the above Bosch injectors: https://www.diyautotune.com/product/fuel-injector-pigtails-bosch-ev1/

And lastly here's the fuel injector in the MegaManual for more information:



5.) Fuel pump - We need to pause here and again give thanks to the old generation of Bavarian engineers, who developed stuff that just plain worked and then didn't feel the need to mess with things every few months just for the hell of it! It is because of this that we have the very great fortune of having a high pressure fuel injection pump available that drops straight into the 2002 fuel tank with no modifications whatsoever! Obviously the E30 is once again our benefactor, and ebay and junkyards are the best budget options.  The pump is available new and not too expensive from off-brand manufactures, but the sending unit for the fuel gauge (which ALSO works perfectly with the 2002 gauge, as hard as that is to believe) I only see listed as 'genuine BMW' for lots o' $$$.  Here's the link to ECS with the various options:


Note: there are two versions of the hanger, one with a return fitting and one without, so check to see if your tank has a return fitting on the tank itself.  If it does, here's the version with only the supply fitting:


You will need to install another relay to power the fuel pump (power for it can come from that nice new fuse panel), and this relay's negative coil will be controlled by Megasquirt.  I did something pretty clever with the wiring here: since my rear window defrost wires were all rotted and non-functioning, I used those existing defrost wires to run back to the fuel pump instead of trying to run a new set of wires back through the whole length of the car.  All installed, mine looks like this:


Other than a short priming pulse at start-up, MS will not run the pump unless there is an RPM signal >0.  While this is moderately safe, additional oil pressure and/or roll-over sensors can be added as further safety measures to cut off the fuel pump in the event of an accident.

And as always, here's the link the fueling section of the Megamanual:



IMPORTANT: You MUST run new fuel line rated for high pressure fuel injection for the supply line from the tank to the fuel rail! If you have a late-model Sqaurie, you can cheat a little by swapping things and using the steel RETURN line on the driver's side of the car for the supply, and then running the low pressure return through the plastic line the runs through the passenger side interior.  Be sure to run all new fuel injection rated rubber lines everywhere on the high pressure supply though, and certainly do NOT use the stock plastic line for the supply!


6.) Sensors - EFI requires a few extra sensors than what were normally included on cars in the 70s, so here's the list of additional input sensors that you'll need to plan on adding:

a.) Coolant temperature - See previous coolant section, use the E30 temp sensor in the coolant divider neck, and program the temperature curve in Megasquirt.

b.) Throttle position sensor - Use the TPS sensor from a late 80s Nissan 300Z with the adapter mount from 02again.com

c.) Oxygen sensor - See above, use and Innovate LC-1 or similar heated wideband O2 sensor with 0-5v analog output.

d.) Inlet air temperature sensor - Use this open element GM sensor somewhere in the intake track before the throttle body and program temperature curve in Megasquirt:



7.) Idle control - The two basic options for idle control are a fast idle solenoid and a stepper motor idle air control valve.  If you've got the 318i intake route, your job is again ridiculously easy as you can just get the adapter block from 02again.com (I told you at the beginning this was a great place for this project!) and the proper 90s Jeep stepper motor.  Wire it up according the the Megasquirt wiring diagram for a stepper IAC and here are the 02again installation instructions:


If you are not using the 318i manifold, then a fast idle solenoid is likely easier to install as it can be plumbed in with hoses, but this pretty much exhausts my knowledge of fast idle solenoids here, and I also unfortunately have no idea how to approach idle control with ITBs.

On a side note, if you use the stepper motor, Megasquirt allows you to configure your unused fast idle output for other purposes; I have mine set up to control my electric cooling fan!

Megamanual link to idle control:



8.) Megasquirt controller and wiring harness - Maybe I should have put this further up, because these are really the FIRST pieces of hardware that you'll want to install, on the other hand you need to already have planned out all of the above hardware and options before installing anything.  Anyway, once you know what hardware you're going to use, how everything will be plumbed, where all of the sensors will go, and so on; you should then start laying out the wiring harness.  It's easiest to do this with all of the old hardware out of the way so you can really work at tucking the wires back out of the way to keep things clean looking.  I recommend laying out all of the wires individually, and then wrapping them/sheathing them in conduit in sections. Obviously if you haven't already ridded your car of all of the obscene 70's emissions junk, then do this concurrently, as reuse those same wiring clips for the new stuff.  The Megasquirt controller needs to be mounted in the car's interior (it's not meant to survive in the engine bay environment), so this means making one big hole somewhere in the fire wall big enough to pull the whole wiring harness through.  The best spot I found for this was on the passenger's side high up in the foot well, just underneath where the brake lines come across (obviously be careful not to drill through your brake lines!) I also used a small bit of coolant hose as a grommet:


NOTE: Since you'll likely have purchased a wiring harness with the Megasquirt DB39 connector already on one end, this means you'll need to feed the whole length of the harness through the firewall from inside to outside, and this takes some patience!

Besides the harness, you also need to run a vacuum line through the firewall to get Megasquirt the MAP signal.  I was able to do this right along side the plastic fuel return line, thereby saving drilling an additional hole.


Once the whole harness is through the firewall, you can start routing all of the individual wires.  Once you have everything laid out, the next step is to install all of the proper connectors on the ends, and then finally wrap and tuck all of the various branches.  Here's how my finished wiring harness looked laid out in the engine bay before installing any of the hardware:


It's trickier than it sounds to layout wiring cleanly, so take your time with this process, make good soldered connections, cover them in heat-shrink tubing, and wrap/tape up conduit joints and ends, and you'll end up very pleased with how much cleaner the whole engine bay looks in the end! Here's a copy of the general Megasquirt wiring diagram (including EDIS) that's a good one to work from:



As I mentioned the MS controller box itself needs to be mounted in the interior of the car.  Many people choose to mount it inside the glove box which works just great, but I didn't want to give up that much real estate in my glove box so instead I chose to mount mine on top of the transmission tunnel behind the center console where, as long as the car has no A/C, affords a good bit of space.  I did later end up also installing an amp for my built-in Android tablet here and an RS232-to-Bluetooth adapter for wireless connectivity to Megasquirt (https://www.efianalytics.com/products/class1Bluetooth.html), at which point I moved the MS module up on to the face of the heater core box (having already had the heater box out once, that's not a job I plan to EVER do again on this car!)


9.) Miscellaneous - Probably the two most difficult parts of this installation, at least for me, were the intake plumbing to the throttle body and the throttle linkage.  The stock E30 intake boots/etc. obviously will fit, but I didn't have this so I managed to cobble together a decent setup using the generic bits of AEM intake piping/couplers/air filter/etc. found at my local auto parts store, routed up into the old battery area and supported by a rather primitive block of wood.  While this works fine, I'm sure there are plenty of better ways to get this done than what I achieved.


The throttle linkage is also quite tricky and you'll likely need to play around some to find something that works best for you.  I kept the original throttle rod and used it to pull a bell-crank which in turn pulls the throttle cable.  Again there's probably room for improvement here, but I spent enough hours on this by now I'm will to call it good enough and move on.

Please continue to the Megasquirt Tuning article for how to properly tune Megasquirt once it's all properly installed.



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