Does this MS3 look right?
#5
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.
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.
#7
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.
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.
Last edited by engdahl; 12-28-2011 at 03:31 AM.
#10
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.
Code:
37 pin harness conn ECU MS description color ====== === ====== ============================ ========== 1 gnd 2 gnd 3 spr1 spare 4 spr2 spare 5 spr3 spare 6 spr4 spare 7 2A gnd engine ground blk 8 2A gnd engine ground blk 9 2A gnd engine ground blk 10 2C gnd O2 ground blk/lt grn 11 2D gnd sensor ground blk/blu 12 gnd 13 gnd 14 gnd 15 gnd 16 gnd 17 2B gnd engine ground blk 18 2B gnd engine ground blk 19 2B gnd engine ground blk 20 2P mat intake air temperature (new wire) 21 2Q clt coolant temperature blu/wht 22 2M tps throttle position sensor red/blk 23 2N O2 oxygen sensor red/blu 24 2E tachin tach, crank angle sensor CKP wht 25 2G iac1a crank angle CMP (TDC index) yel/blu 26 vref +5 reference for sensors (not used) 27 iac1b turbo boost control (new wire) 28 1B 12 raw 12 volts from main relay wht/red 29 1L iac2a fan relay blk/grn 30 idl idle air control (not used) 31 1H iac2b ignition coils 2&3 brn 32 2U inj1 injector 1 yel 33 2Y inj1 injector 3 grn/wht 34 2Z inj2 injector 4 grn 35 2V inj2 injector 2 yel/blk 36 1G ign ignition coils 1&4 brn/yel 37 2T fp1 fuel pump relay lt grn
#12
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.
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.
#13
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.
#14
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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.
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.
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.
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