Megasquirt guidance, questions and opinions

As it gets colder here in WI I'm really starting to gear up to spend as much time as possible in the garage. As some of you know my '11 Challenge car is going to be a Festiva with drivetrain from a Mercury Capri XR2 which uses a Mazda B6T motor.

I'm at a crossroads as whether to add Megasquirt or not. My main hang up is that my experience with stand alone FI is nil and I have never tuned a car from a bare bones map. I have done a lot of reading of the MegaManual and Matt and Jerry's book will hopefully be under my Christmas tree this year but I still having some doubts as to my capabilities. I've read a couple of build threads on other sites where people have started a Megasquirt install only to give up and never see the car run (I might be confusing my build threads but I believe that's how the Phostiva started out). I really don't want to go that route.

Other problems is that while there is a couple of wiring write-ups using the stock ECU and a fuel injected Festiva, mine is carbureted which uses a different body harness. That brings another set of challenges as I won't have any type of reference to check against.

So my pointed questions are:

How hard is it really to accomplish a MS install?

Is it possible to make the MS ECU run independently from the body harness? That would simplify my wiring if I could keep the body harness for the lights only. My plans include to remove the key ignition lock and go to a switch panel to control engine on/start/fuel pump functions. I'm also thinking aftermarket mechanical gauges might simplify things too with wiring.

What version would be best for my build? My goals are simple, simple, and simple. I want the motor to be bare bones wiring. Stock a B6T uses a distributor and AFM. Switching to MS allows me to eliminate the AFM if I install a IAT sensor correct? Also will it be easier tune if I switch to a Cam Angle Sensor and coil from a Miata? Will MS also allow me to lose the stock boost pressure sensor?

Is a wideband needed for the MS ECU to run? I know that I will need one in order to tune, but once it's tuned can it be removed? The reason for that question is I would like to free up the extra $200 from my budget by not leaving it in.

Thanks for indulging my questions, I'm sure I'll have more when I think of them. This will be a large part of my budget to do this and I want to make sure I'm making the right choice here.

P.S. I also thought just emailing Matt directly but I'm hoping that asking here it will be easier for others MS'ing a B6T to find answers via Google.

Marty! wrote: What version would be best for my build? My goals are simple, simple, and simple. I want the motor to be bare bones wiring. Stock a B6T uses a distributor and AFM. Switching to MS allows me to eliminate the AFM if I install a IAT sensor correct? Also will it be easier tune if I switch to a Cam Angle Sensor and coil from a Miata? Will MS also allow me to lose the stock boost pressure sensor?

IIRC you have to add the IAT sensor, but the AFM is actually being replaced by the MS's built-in MAP sensor.

Marty! wrote: Is a wideband needed for the MS ECU to run? I know that I will need one in order to tune, but once it's tuned can it be removed? The reason for that question is I would like to free up the extra $200 from my budget by not leaving it in.

IIRC you can use a narrow band one if/when it's tuned; you might get more power out of it with a wideband, though.

Get rid of the AFM and use a MAP. You'll need an IAT as well, but you need the MAP for load. The MAP will work for the boost sensor for the MS. I recommend the Map Daddy dual MAP. I assume this is a boosted motor then. I think that on a boosted motor, you should go wide band. I'm planning on that with my next one. You will need a Cam Angle Sensor or a Crank Angle Sensor. If this is already an injected motor, the install is fairly straight forward and all the sensors should be there. Get the DIYAutoTune.com harness with all the stuff printed on the wires. Pick up a wire, read where it goes, run it to the sensor, pick up another wire.

You really sound like a noobie here, but that's OK. I have 3 MS'ed vehicles, and we all have to start somewhere. I use a 3.0 board with MS1 and Squirt n Spark code on 2 of them and a custom version 1 based board with SnS code on the other.

MS is a great option for running (largely) independent of the main body harness. that's how we did the jeep setup essentially. we used a FSM but any good electrical diagram should work and simply removed the wiring unnecessary for MS from the ECU chunk and used the extra wire to build whatever harness we needed to give it power/ground or relocate it.

not sure about whats easiest for you to get it running on, but there is a lot of documentation on MS'ing a miata. you'll need a compatible TPS, IAT, CTS, vacuum port, and something to give it RPM. we were able to use the hall effect switch in a jeep distributor, but theyre not all that easy.

you can remove the wideband so long as you're comfortable that your tune is good enough to not need feedback correction. we had so little tune time on the jeep that we budgeted for the wideband and let MS correct for itself, but next year we'll have a solid tune and remove it to free up that money.

One major question to ask yourself is what you'll gain from running megasquirt. If you can just put the stock wiring harness and ecu from the Capri in the car and don't have any radical engine modifications this might be the best way to go.
We regretted not sticking with the stock management for the 1UZ on the Wreck Racing miata for the first few years because we didn't really need a standalone system for what we were doing and megasqurit makes up a huge part of our budget even though we build our own ecu from the kit.

^ ^ ^ this x2

like i mentioned the jeep was MS'd but we ran out of time to complete the turbo part which we felt required the tunability of MS, and ended up running the autocross portion on a largely untuned otherwise stock engine. we would have been better off with the stock computer until we turbocharged it. a lot cheaper on a challenge budget too like JohnyHachi6 said, if you can run it that way.

Thanks for the responses so far, you're right Hess I am definitely a noob when it comes to this.

What I would like to gain with MS is simplification of the wiring, control of the boost (otherwise I'm stuck with stock ECU settings), elimination of the rats nest of vacuum hoses for emission controls, and just a cleaner looking engine bay.

I would also like some wiggle room for future upgrades also, but I don't want too get ahead of myself yet.

Sounds like you're a good candidate and are ahead of the game by starting by asking questions first! Definitely give Jerry and Matts book a read, it'll give you a good overview of 'everything' without getting into the scary details. Then read the Megamanual.. and then if your head isn't spinning check out the docs section of msextra.. more information then you ever need! Honestly, anymore wading through the what you need to know, what to know, and what you don't want to know is the hardest part!

Most installs that I do use little of the stock engine harness, and with just a few quick hookups to the fuseblock (power, ground, sometimes the fuel pump relay trigger) it's all separate. Other cars are more involved if you want to use some of the existing stock relays, but that's very vehicle specific.

924s Megasquirt project.

Doing it on my 924s you can follow my trial and tribulations here. The applications are different but you will get an idea of the process. I am re using the stock wiring so it is a tad more complicated.

Marty! wrote: So my pointed questions are: How hard is it really to accomplish a MS install?

The wiring itself is normally pretty straightforward. Often the toughest part can be getting a starting point for fueling, but you could probably borrow a turbo Miata map and tweak it for your ignition. (Or put the Miata ignition on your B6T if you prefer.)

Is it possible to make the MS ECU run independently from the body harness? That would simplify my wiring if I could keep the body harness for the lights only. My plans include to remove the key ignition lock and go to a switch panel to control engine on/start/fuel pump functions. I'm also thinking aftermarket mechanical gauges might simplify things too with wiring.

Yes, and this is normally the easy way to do that. Most of our MS installations on cars that aren't factory fuel injected use a separate harness from the MS. The only connection to the factory harness is for 12 volt power.

What version would be best for my build? My goals are simple, simple, and simple. I want the motor to be bare bones wiring. Stock a B6T uses a distributor and AFM. Switching to MS allows me to eliminate the AFM if I install a IAT sensor correct? Also will it be easier tune if I switch to a Cam Angle Sensor and coil from a Miata? Will MS also allow me to lose the stock boost pressure sensor?

The MS would have its own boost pressure sensor (MAP sensor) and allow removing the AFM. We've seen a fairly noticable power gain from removing the vane air flow meters. You won't be able to tune spark with the stock distributor - it's a mechanical / vacuum advance setup - but you can use either a Miata or later 323 optical distributor.

You could use a MS1 for this - at Challenge prices, you might even consider a V2.2.

Is a wideband needed for the MS ECU to run? I know that I will need one in order to tune, but once it's tuned can it be removed? The reason for that question is I would like to free up the extra $200 from my budget by not leaving it in.

Correct, it doesn't have to be in full time for it to run.

Putting an MS in a formerly carbed car is going to require rewiring the car.

I'd got stock if you can do that. Just take the wiring harness out of the Capri and transplant the parts you need into the Festiva. If you were going to turn up the boost then I'd say a MS would work for you. But remember that you'll need a wideband to tune. I know Hess has tuned with a narrowband. I have no idea how he's done it as I would be lost in the woods trying his method. You'll also need a GM Intake Air Temp sensor (IAT). Since you're boosting you'll also need to source a Manifold Air Pressure sensor (MAP) to track boost and vacuum levels.

The costs quickly mount as you can tell.

Once you've got the thing physically in place then you begin tuning. With the new TunerStudio..it's cake man. The car tunes itself while you drive. That assuming you get it started. I don't see a problem getting it started as you could most likely use a stock Miata map to get it turned over and then tune from there.

Xceler8x wrote: Putting an MS in a formerly carbed car is going to require rewiring the car.

It's just putting wires where there were no wires before. Honestly in some ways doing a carb car is easier as you don't have the option to tie into some factory efi wiring.

Normally I come down on the side of EFI, but since this is a Challange car and money is a big deal, I agree that a carb has a LOT going for it in this case - if a manifold can be found along with someone to tune it.

kb58 wrote: Normally I come down on the side of EFI, but since this is a Challange car and money is a big deal, I agree that a carb has a LOT going for it in this case - if a manifold can be found along with someone to tune it.

A carb does not have anything going for it on a Mazda B6T if we care about.. well anything I can think of actually.

But in this context a carb may save a lot of money and time.

kb58 wrote: But in *this* context a carb may save a lot of money and time.

In what context? OP is talking about a 1.6 liter turbocharged four cylinder engine. How are you hoping to cheaply hang a carb off that again?

pres589 wrote:

kb58 wrote: But in *this* context a carb may save a lot of money and time.

In what context? OP is talking about a 1.6 liter turbocharged four cylinder engine. How are you hoping to cheaply hang a carb off that again?

Sheet metal intake?

I think you could bolt a carb to that if you were going that route. I'd rather stay injected meself.

suck through small 4bbl but I don't think it'd be fun to make run right....

Sorry, no carbs here.

The whole point is to ditch a anemic 58hp SOHC carbed motor for a turbocharged DOHC engine that will hopefully be in the 180hp range.

Now I'm off to look at the DIY site some more..........

I think the stock turbo is not going to flow enough air to get you to 180hp. Stock transmission may not like life at 180hp either.

I found a VJ11 turbo at the local pick 'n pull, I just gotta get there to pull it. If it turns out to be good a VJ11/VJ14 hybrid will be happening.

I will also be using the G-series trans/axles from the Capri also.

Isn't there a PNP setup for that motor from DIYautotune? Matt, maybe you can weigh in?

Marty, would YOU be interested in a strange VJ hybrid involving a VJ11 exhaust housing, Garrett 50trim compressor housing, and a T4S wheel?

Is a 1.6 going to huff & puff enough exhaust through that Thomas Knight to be worth bolting on?

93celicaGT2 wrote: Isn't there a PNP setup for that motor from DIYautotune? Matt, maybe you can weigh in?

Not quite - it's not exactly Challenge price, and intended for the Miata wiring harness. The factory B6T harness (at least as used in the Capri and other US market cars) has a totally different connector and ignition system. Its electronics are closer to the naturally aspirated first generation MX-6 than the Miata's.

If you're worried about wiring, I would suggest getting the MS Relay Board. Then you pretty much run everything through it, giving it power and ground, and you're done.

Well, it's never that simple, but it can make it a lot easier on a carb-EFI upgrade.

My $0.02.

PS, isn't it amazing? Matt is like Elvis. He's everywhere!

Cheers, Brady