Megasquirt for the Mirage

[Loren]

Didn't want to clutter up an already meandering existing thread, so I thought I'd start a new one.

Caveat: I'm not planning to do this, at least not anytime soon. If I ever decide to follow through with a supercharger installation, then maybe. But, that's something that's barely on my long range sensors, not quite on the radar yet. I'll likely opt out of the car before I get that crazy, but who knows?

Just posting this discussion to maybe inspire someone. If you're thinking about forced induction, your best bet would be to do this FIRST. Get control of the engine with an aftermarket ECU, and get comfortable with tuning... then when you go FI, it's a simple matter of retuning. Please don't take what I'm saying here as gospel. I have a bit of experience, but I do tend to forget things. DO YOUR HOMEWORK. Study up on the MS, and how it works. Dig up your stock wiring diagrams. Get on the MS forum and post up your ideas and have those who have gone before verify that you're on the right path. (but, do your homework first to cut down on the dumb questions) There's LOTS of help out there. If you're doing something new like a Mirage, don't be afraid to ask for help. You don't have to go it alone! (and the folks at DIY Autotune are VERY helpful)

Bottom line: If you're a (very) technically minded person, you're not afraid of wiring and maybe a little bit of custom fabrication (which you can hire out to someone else), don't be afraid of Megasquirt. Dig into it. Start as simply as you can. Learn as you go. Do more as you go.

The question has been asked: Can we use a Megasquirt (aftermarket ECU) on the Mirage to make it fully tunable either with stock hardware (for a little more power/responsiveness or even for more economy)? This thread isn't about the philosophy of "should we", so please don't go there. It's just "can we", for those who have their reasons for wanting to do so. And the answer is "yes, absolutely"... it just depends on how bad you want it at this point. It's easy... ish.

A Megasquirt 3x (Google it) is capable of running fully sequential spark and fuel (that means an individual output for each fuel injector and each spark plug), handling the VVT, and cooling fans, switching the AC compressor on/off, and has several spare outputs to handle other things. I can totally handle running the ENGINE and everything associated with it. (you CVT guys are on your own, I'm not going there)

What it won't do is all of the OTHER functions of the factory ECU (and secondary computers, I really haven't looked at the electrical system of this car... I know there's a lot to it). So, what you'd want to do, unless you're building a pure race car and don't care about the other stuff, is do a "parallel" or "piggyback" installation. Sounds complicated, right?

Well, I happen to have done exactly that with my S10. I didn't use an MS3, I used a much cheaper (and less capable, but adequate for the truck) Microsquirt. The fundamentals are the same. And it's NOT that difficult.

I'll describe the process in the next post...

[Loren]

Piggyback or Parallel Installation:

What you're doing with a piggyback installation is SHARING as many sensors as you can to give the MS the inputs that it needs, and then HIJACKING the outputs that you want to control. The factory ECU is still there, it's still seeing all of its inputs, and it THINKS that it is still running the engine... but, it's not. This means that all of your gauges work, all of the other stuff in the car works. You might possibly get a CEL because the factory ECU is going to detect that "the engine isn't responding exactly to my commands". You'd have to just deal with that. But, you'd have full control of the engine, and that's what you're after.

Sensors can generally be shared quite easily, just splice into the wiring, and run that wire to the MS. The sensors that CAN'T be shared are those that are variable resistance sensors. That's going to be Coolant Temp (CLT) and Intake Air Temp (IAT). You'll need to install separate sensors for CLT and IAT to go to the MS. Not a huge deal. You'll tap into the stock MAP sensor (if there isn't one, you can easily add a MAP sensor to the intake manifold), the stock crankshaft position sensor (or add a custom toothed crank pulley and sensor at the front of the engine), the stock cam position sensor, and that's it. That's all of the inputs required by the MS.

(On the truck, I just teed into the stock CLT, added a second sensor. And I hijacked the stock IAT rather than share it. Was able to use all of the other sensors without issue. There was quite the handful of wiring involved, but mechanically it was a very simple installation.)

Note: While those are the only absolutely REQUIRED inputs, for tuning (unless you want to go old school and sniff the tailpipe for richness, and learn to read sparkplugs) you're going to want a Wideband O2 sensor. I'm not sure if any of the stock sensors are wideband or not, probably best to just buy and install a known good Wideband sensor. A Megasquirt using the associated Tuner Studio software has an absolutely brilliant "auto tune" feature that you can use if you have a WBO2, the thing pretty much tunes itself.

The other thing that isn't "required", but makes it a lot easier to tune things like idle control and acceleration enrichment is a Throttle Position Sensor. TPS is going to be another resistance based sensor, so if you use the stock sensor on the throttle body (yes, it has one) you'd have to hijack it rather than share it. (edit: I'm not 100% sure about that... while it is a resistance based sensor, the output is actually a voltage... you'd possibly be okay to share it) You CAN get by without it. (Seeing 0% TPS just confirms that "the engine is idling" for idle control instead of guessing based on RPM and MAP readings. And you can do throttle enrichment with either TPS or MAP... MAP is just VERY touchy, TPS is more stable and is a more definite indication of "demand".) I've tuned without TPS before. The MS is very flexible.

Outputs, you're controlling 3 fuel injectors, 3 spark plugs, one VVT actuator, one cooling fan, and one AC compressor. You could also take over the idle control valve, or add an idle control valve if needed. Idle control is sort of secondary to getting things up and running. Worst case, you can set the idle at like 900 rpm and forgo any variable idle control at all. (because race car) You can always go in and add idle control later.

(On the truck, it uses "batch" injection, so only one injector output per cylinder bank, total of two. And spark goes through a distributor from a single coil... so only one spark output. I'm controlling the fan. But, I left the idle control and AC compressor controlled by the stock ECU. I'm not sure exactly how well the idle control is going to work, but it DOES seem to be working. The stock ECU is controlling the airflow through the idle valve to determine idle speed... and the MS is just delivering fuel based on the airflow into the engine. Should work okay in theory... and the same method could possibly be used on the Mirage.)

That's basically it. You give the MS inputs. You connect the outputs. You configure the software correctly, and it will run the engine and allow you to tune it.

Next Post: Mirage Peculiarities

[Loren]

Mirage Peculiarities:

What's weird about the Mirage? Well, here's what we know so far...

Hurdle #1: Crankshaft Position Sensor
The toothed wheel for the crankshaft sensor is located INSIDE the engine, and it's a non-standard configuration. That means that the MS software doesn't have a "decoder" among its many options to read it simply because nobody has ever done it before.

There are several ways around this. You could pay the MS gurus to write a custom decoder for you and get it working. Or, if you're a serious programmer type, YOU could write a decoder... MS is all open-source, and it's not THAT complicated. If you're that guy... you could write it, and contribute it to the project, and then everyone would be able to hook up to the stock 3A9 crankshaft sensor. If that's not your bag, or it's too pricey, you could brute-force it... just replace the crankshaft pulley, or bolt/weld a ring to the crankshaft pulley that has 36 teeth with one tooth missing. (I did this on my Spitfire, which was my first MS project, it's not as hard as it sounds... I used a 36-tooth motorcycle sprocket, filed off one tooth, and had it welded to the crank pulley) Then make a bracket to mount the sensor, and your set.

Hurdle #2: DBW Throttle
I really have NO information about this, but the engine does use a drive-by-wire throttle. And last I heard (and this was at least 2-3 years ago... could have changed by now, the MS world is constantly evolving) the MS was not reliably known to handle an electronic throttle.

There are several ways around this. The most obvious would be to simply replace the DBW throttle body with a standard throttle body... but, you'd also have to run a throttle cable and fit a mechanical pedal. Not a show-stopper, but definitely "a thing". But, I'd start by looking into whether anyone has formally introduced the DBW feature to the MS and tested it. If so, then this wouldn't be a problem at all. Another possibility might be to just let the stock ECU keep controlling the throttle if it will. The MS doesn't care, it just sees the results of the throttle being open... the change in pressure at the intake manifold. If that would work, it would be an absolute no-brainer. (and I'm doing essentially the same thing for idle control on my truck... stock ECU is controlling the air, MS is controlling everything else)

I think that's it. Everything else about piggybacking a MS onto the Mirage would be just a matter of wiring, settings and tuning.

[Loren]

Plug & Play Installation

If you're pondering doing this on your street car, I'd highly recommend doing it in a "Plug & Play" fashion. By that, I mean do it so that you can easily switch back to the stock ECU within 5-10 minutes by just switching some connectors around. This is one of those things that you might be very glad you did as you're learning to tune the MS. If you get your tune so borked up that the engine won't idle when it's cold, or just won't run right, and you need to get to work in the morning... switch it back to stock and go about your business.

How do we accomplish this? Buy some quality connectors. I used a set of 12-pin connectors on the S10. I wired them like so:

Connector #1: Shared Inputs
This is all the stuff that I can plug into the MS that's NOT going to affect the stock ECU in any way. Power, Ground, and all of the sharable sensors. This connector can be left unplugged when using the stock ECU. When JUST this connector is plugged in, the MS should operate in a "monitor" mode. It will read all the sensors, and you can look at things, and verify that your setup is correct. (if you get proper RPM, IAT, CLT and MAP... you're golden)

Connector #2: Hijacked Outputs
You'll need one male (to the engine) and two female (one to each ECU) connectors for this. First, determine what outputs you are going to hijack. Simply CUT those wires, and insert the connector in there. Now you can connect/disconnect outputs from the stock ECU. Then take the third connector and wire those outputs to the MS. Now you can switch that plug to go from the stock ECU controlling the engine to the MS controlling the engine.

Connector #3: Extra stuff
Stuff like your wideband O2 sensor, anything else you want to add... like a boost controller, whatever.

[Loren]

Curiosity freshly piqued, I took a quick look into the status of DBW and MS.

It's still in a slow development process. But, with so many newer cars having DBW throttles, I think it's just a matter of time before it becomes a standard feature of the MS software. (Getting technical, MS already has throttle position, so it would just need a spare input to pick up pedal position, and a spare output to drive the throttle, everything else is just "logic" in the software... the big problem is that nobody wants to be responsible for it! It's a liability thing.)

But, it seems that using the stock ECU to control the throttle is not an uncommon approach.

And if you really HAD to ditch the stock ECU, there is/was at least one stand-alone DBW throttle controller that would do the job of translating pedal position to the throttle body. But, for $500... I'd think seriously about a $20 salvage yard standard throttle body, and fitting a mechanical pedal! (the only problem there is that it's not "plug & play")

Meanwhile, as soon as I get my truck back from my friend who's doing some work on it for me... I get to play with tuning!

[Qrush]

(rubs hands together expectantly)

[Daox]

Very nice write up!

How much do the different versions of megasquirt cost?

[Loren]

My favorite source can answer those questions:
https://www.diyautotune.com/

I haven't priced this stuff in a while, and the prices do vary. Typically, the prices do come down though, so that's good. These are just rough prices based on my feeble memory.

Megasquirt Flavors that I'm aware of from the costliest to the cheapest:

MS Pro - This is their high-dollar fully-sealed, "race car" level product. It's expensive. I think it's based on the MS3x, but it's been a while since it came out... and that's the only time I bothered to read anything about it. Out of my league.

MS PnP - $900ish? These are available for a handful of cars. More than just "cars", they're available in several "ECU Styles". For example, the "Miata" PnP is compatible with a lot of 90-97ish Mazdas and Mazda-based Fords, and probably some other cars. They plug directly into the stock connectors, no mods to the car or the ECU required. Just set it up, plug it in, and start tuning. They're good, but they are based on the MS2. (actually, they physically have the Microsquirt board inside them) And they're not gonna have anything available for our Mirage. They're pretty great if you have a compatible car and are looking for "quick and easy".

MS3x - $750ish? The MS3x is an MS3 with the 3x expansion board. That expansion board is the ****! It handles all of it inputs and outputs and is all kinds of software configurable to work with damn near anything without requiring any hardware modifications. Just wire it, set it up, plug it in and start tuning! This is, by far, my favorite Megasquirt. And it's what you'd want for a Mirage because it handles VVT, an has plent of spare inputs and outputs to handle whatever you want. It is the goodness. Get it with the DIYBOB, even better!

MS1 ($150), MS2 ($300) and MS3 ($500) - Best discussed together. In the beginning there was the MS1. Specifically, the MS1 on the "version 2.2" board. That's what started it all. It did basic spark and ignition, and not much else. It required hardware modifications to work with YOUR specific car. (Mainly, what kind of ignition system do you have? You have to modify the input and output circuits to work with that.) MS1 is still good for a "dirt cheap" and "simple" project, like building a LeMons race car on a budget where you just need basic control of some random engine, but you don't need all the bells and whistles.

In time, they revised and improved the board with the "version 3.0", which is still in use. The MS2 is an MS1 board (V.2.2 or V3.0) with an add-on MS2 "daughter card" that gives is a more powerful processor and some additional i/o capability. You still have to do hardware mods to suit your car, but it's a lot more capable. MS2 is my second favorite Megasquirt. If you're trying to get something done, you want or need "some" of the bells and whistles, but you're still on a tight budget... MS2 is good.

The MS3 just replaces the MS2 daughterboard with an even more powerful processor. It's very, very good. But, personally, I don't think it's worth running an MS3 without the 3x. It's not that much better than an MS2. But, with the 3x... it's just amazing and easy to configure and use. So, I guess you could run a base MS3. I just wouldn't bother.

Microsquirt - $350ish. This is an MS2, but completely redesigned using surface mount technology. It's VERY small. It does everything an MS2 can do, it's just smaller and lighter, and not as "expandable". It does have some limitations, mainly not a lot of outputs, but it's good for a lot of things. This is what is currently running my S10. It was designed for like motorcycles and snowmobiles and such. But, it's just an MS2... as such, it will run damn near any basic engine. The Mirage with it's VVT and all, isn't quite "basic". (you probably could actually run the Mirage on the Microsquirt if you either ignored the VVT, or used an external VVT controller... which was a very common thing to do before they integrated VVT into the 3x)

So, that's the various Megasquirts in a nutshell. As mentioned, the MS3x would be the best setup for the Mirage.

Other thoughts:

You can buy a kit and build most of these yourself. (not the Microsquirt or MSPro) Prices have come down a lot, though... I'm an electronics guy, and can solder stuff together with my eyes closed... and it's gotten to the point where the difference in price between the kit and fully assembled and tested ECU just isn't worth it to me! But, you can save some money, and gain some fun experience, and be able to say "I built this from a pile of parts!" by buying and assembling a MS kit. DIY's kits are VERY thorough with VERY good instructions, and VERY easy to build (if you can solder and read and aren't stupid). Bonus: If you're doing a 3x... the 3x board takes over SO MANY of the basic functions that you really only have to put about 1/3 of the components on the main board! There are instructions out on the webz that tell you exactly what you need to bother with, and what you can ignore. This makes an MS3x build a lot quicker... if you were going to DIY.

There's a thing called a DIYBOB. That's DIY Breakout Box. It's just a box with a very cool little "patchboard" circuit board in it that allows you to very easily configure and REconfigure your wiring without having to splice into your factory wiring. They have them for several common ECU styles. If you get the proper DIYBOB, you can essentially build your own "plug and play" ECU. It's highly unlikely that they have a DIYBOB with the Mirage connectors... though it is possible, and I haven't looked.

Without a DIYBOB, you could still build your own "adapter cable" if you can find the appropriate ECU connector. (worst case, you can buy a cheap used ECU and cannibalize the connector out of it) It would be sort of like the DIYBOB, but instead of a neat and tidy circuit board to make it easy and clean to connect this to that, and be able to move this from here to there, and add a diode on this circuit, and a resistor to ground on that circuit and so on... instead of that, you'd just have a bundle of wires. But, you could still make it PnP with the car, which is always cool.

And, of course, you could directly wire it to the car. Either cutting out the stock ECU connector, or building your own wiring harness. The sky is the limit. You can literally do anything if you're crazy enough to do it!

For the Mirage, as mentioned in previous posts, your best bet would be to do a parallel installation and keep the stock ECU running pretty much everything other than the ignition and injectors.

Oh, and you can get a wiring harness for any of the MS kits that includes either 30 inches or 8 feet of wire. The beauty of these kits is that you get all of the different TYPES of wire that you need (like shielded wires for the sensitive cam and crank inputs, higher gauge wires for power and ground, etc), and all MFR grade automotive wire, AND each wire is color coded and very well marked with specifically what it's for! So, you have a TPS wire that's a particular color and marked "TPS" (also marked with what pin it goes to on the MS end, which is VERY convenient), and each injector wire is marked appropriately, and so on. The DIYTune wiring harnesses are very much worth the $50 or whatever it is that they cost. I shudder at the thought of doing this with just a couple spools of generic wire!

[WEXX]

What about Haltech? Do they have a trigger pattern for the 3A92? or any other triple? What I would love to see is a 3B40TC engine from Mitsubishi. The 4B40TC in my Eclipse Cross is based off of the 4A92 engine, just with a turbo and direct injection and I love the power it has for 1500cc.

[Loren]

Taking a giant leap off-topic in several directions, eh?

This topic isn't about Haltech or specific engine swaps.

If you had a Megasquirt in the car, it would likely support any 4 cylinder engine.

Here's the thing about MS: it requires you to do research. Want to know if MS can run a particular engine? Start searching! That's just the tip of the iceberg. If you're not into researching answers and reading and understating LOTS, then you shouldn't even consider it.