SteyrTMP

We're about done. Anyone see anything that looks wrong? I realize the photos suck, they are from my crappy phone.

Front:



Here's the back side:

Matt Cramer

Er, yeah, you should have used better lighting instead of resorting to the flash.

As for the ECU itself, nothing wrong jumps out at me.

Ben

iTrader: (33)

I'm curious what's going on with your ignition outputs.
What kind of car is this for, a Miata or something like a fwd BP (distributor ignition)?

Braineack

iTrader: (62)

looks like it would work for a miata, but the ignition ouputs look wrong.

Looks like a combo of Joe's spark output mod (possible incorrectly done) and a BIP output on one of the channels.

SteyrTMP

This is for a turbocharged Miata motor in a Lotus 7. The build is in the Build Log section.

I am still confused about the ignition wiring. Some MS3 and MS2 builds have them crossed, while others do not. I've been told to cross them and not to, but I haven't been given an explaination why. So far, the oscilloscope hasn't shown any signs of the Jimstim operating out of order... I will try to get some better pictures.

Ben

iTrader: (33)

Ignition output wiring seems very wrong. What coils? Wasted spark or COP? What's going on with the BIP? What is JS11 doing?

engdahl

I (Nathan's dad) built the MS board pictured above. Nathan built the rest of the Lotus 7 starting with a load of steel tubing, a scrap Miata from the police impound lot, and a welder. The Lotus has a '94 1.8L Miata engine in it. Right now the engine is pretty much stock, except for the turbo. The engine runs fine with the stock ECU, and the turbo isn't doing anything at the moment. The next thing we will try is to get the engine running with the Megasquirt using the stock coils and injectors.

I built the board according to the megamanual, then modified it using the Megasquirt 2 assembly instructions at miataturbo.wikidot.com. CMP comes in on JS10, CKP on XG1, and OptoIn is connected to VCC. I put the boost control FET at Q16, driven by JS11, and it's output is wired to IAC1B. Q7 was replaced with a 2N2222 and is wired to IAC2A for fan control. We used Joe Perez's ignition inverters driven by the D14 and D16 drivers. The board talks to TunerStudio and has been tested with a JimStim and a scope. I am now in the process of designing the wiring harness modifications prior to installing the Megasquirt in the car. This will be a standalone installation.

I became confused when some instructions showed the ignition signals crossed and others not crossed. I decided to not cross the ignition, so D14 inverted goes to IGN which will drive coils 1&4, and D16 inverted goes to IAC2B which will drive coils 2&3. Assuming the falling edge of CKP that occurs during CMP high indicates cylinder 1 TDC, then we appear to be getting the correct firing pulses.

When I started to consider the various injector wiring diagrams I could find on the web, seeing INJ1 driving injectors 1&3 and INJ2 driving 2&4 initially appeared to be an error. I even found one harness drawing that shows INJ1 driving 2&3 and INJ2 driving 1&4, same grouping as the ignition. I spent several evenings trying to figure out what the MS is doing with the injectors, and why. It appears that the default setup (batch injection) is to fire each bank once per cycle, not necessarily synchronized to anything, which reminds me of the CIS injection on my '74 Audi Fox. In this case it may not make a lot of difference how the injectors are wired up.

I'm still experimenting with the JimStim and the scope. I tried setting the MS up to do semi-sequential injection. What it appears to be doing now is firing injectors 2&4 during the exhaust stroke of 1, and injectors 1&3 during the compression stroke of 1. Here is a drawing (using Excel) of what I'm seeing on the scope:



Here is the same data as a polar plot. Each quadrant of the circle is one stroke. The upper right quadrant is the power stroke of cylinder 1.



Here is a chart of what is happening in each cylinder on each stroke. Red is when the injector is squirting, orange is the fuel just sitting around in the manifold, yellow is when the intake value is open and the fuel is pulled into the cylinder. Red and yellow stripes is when the injector is squirting into an open intake. Asterisk indicates plug firing.



This is with the engine loafing at 1500 RPM, BTW. I realize the squirts will get longer (start earlier?) at higher loads.

if I swap the injector wires, then injectors 1&3 squirt during the exhaust stroke of 1, and injectors 2&4 during the compression stroke of 1, and I get this sequence:



This setup seems more symmetrical. Whether it is better, I can't say. From what I've read, the engine will run either way, and we can experiment and see if one arrangement works better. Maybe we should use barrel connectors in the injector wires so we can swap them more easily.

One thing we would like to find is a plain vanilla msq file for an unmodified Miata engine. We have an MS3 CPU daughterboard, and most of the example msq files we found are for earlier boards and can't be loaded into the MS3. The only example I could find that would load into our board was for a modified engine, and I'm not sure how appropriate it is for a stock engine.

Braineack

iTrader: (62)

Okay, boost driver where the BIP normally sits -- that's what was confusing us.

So far as I can tell it looks good to go.

engdahl

Here are some better pictures of our megasquirt, with the mods annotated:

engdahl

And here is the preliminary list of connections to the car:

Since a Lotus 7 does not have AC, remote mirrors, heated windows, (or windows for that matter), the Miata harness has already been greatly reduced.

Braineack

iTrader: (62)

this thread is confusing, why was it asked if anything was wrong with it? it looks perfect and well done.

engdahl

Here is how I installed the boost control, somewhat following the Miata MS2 mods page at http://miataturbo.wikidot.com/ms2-m, but using more of the preexisting parts and wiring on the board.



I have one question regarding the boost control: should the 1N4002 catch diode get mounted on the solenoid, as implied by the schematic, or should it be mounted on the megasquirt, as shown here: http://boostedmiata.com/MS/built/lea...e/CIMG1761.jpg? I noticed from the datasheet that the IRLZ44 already has a built-in catch diode.

engdahl

Insecurity, I guess. *I* think I know what I'm doing, but Nathan wanted a second opinion before the smoke test. I'm very slow and methodical about things like this -- I've been mumbling on the harness for maybe 3-4 weeks now in my spare time. Nathan wants to get rolling. However, I think we're finally ready to start snipping the harness.

Ben

iTrader: (33)

Everything looks great in your new pics. The only thing I would have done differently is I would have set up the tach input circuits following the MS3 directions instead of the MS2 directions (it would have been simpler), but it should work the way you've done it as well.

We've found that the boost control extra flyback diode is not required--there is no harm to adding it, but we've seen no benefit/detriment either way.

Techsalvager

so I can remove the diode on the boost control circuit and should be fine?

Braineack

iTrader: (62)

why remove it if it's there?

Techsalvager

Because its in my way.

Braineack

iTrader: (62)

okay.