B3 Megasquirt II diagram

[fujioko]

Hi 'ya folks,

Here are some pictures and schematics on my recent B3 MegaSquirt install.

I built an adapter to mate the Megasquirt DB37 to a Festiva harness.

The adapter was made by cutting off the main connector (header) off of a Miata ECU and wiring it to the DB37. The Festiva and the Miata use the same ECU connector and Miata ones are a dime a dozen.



ECU DB37 DESCRIPTION

B........28........Main relay, hot in run
G........36........To ignitor
N........22........TPS signal
2A......8..........ground
2B......9..........ground
2C......10,11....ground
2D......19........signal return from TPS
2E......24........ignition signal from distributor (jump to pin 26 with 1K resistor for ign pullup)
2L......26........5V reference for TPS. (also jump to pin 24 with 1K resistor for ign pullup)
2N......23........O2 sensor. Use a wideband for infinite tuning.
2P.......20.......Manifold air temp (MAT)
2Q......21.......engine coolant temperature (ECT)
2U......32-33...injector 1&3
2V......34-35...injector 2&4
2W*.....30*........PWM Idle solenoid. DO NOT CONNECT without modifying Megasquirt first. You will destroy the ECU.

Actually the PWM idle solenoid is not required and the B3 will idle fine without it. You have to manually adjust the idle screw on the throttlebody for idle. Cold idle is handled by the coolant flowing through the idle valve.

pin 30 on the DB37 goes to the fuel pump relay.


In my instillation I eliminated the mass air meter and used the MAP sensor built into the megasquirt. Eliminating the mass air meter also eliminates the manifold air temp sensor (MAT)... so you will need to supply a new MAT sensor.



This is the adapter


It is recommended that you also use a wideband O2 controller. A narrowband will work but it is pointless to use a narrowband with Megasquirt. I used a LC-1 from Innovative Motor Sports.


Unfortunately I don't own a Festiva. This install was on a Miata that was electrically modified to be identical to a Festiva. I have no idea how the megasquirt will perform on a Festiva, but it works great on my B3 powered Miata.

Jim

[fujioko]

I used a TPS from a 1999 Hyundai Accent. It is a perfect fit to the 93 Festiva throttle body shaft, however I had to fabricate an adapter plate to mount the TPS to the throttle body.

Automatic festivas have a real TPS??




I moved the MAT to the intake tube. My intake tube is different because the B3 is installed in a Miata.

Jim

[KingFish]

You continue to do great work man. Any reason you did not get one of the PnP units for a Protege or Escort GT and do a custom burn? I am not literate with MS, so if my question makes zero sense I am sorry.

[KingFish]

OH yea, any new pics if the engine bay?

[fujioko]

You continue to do great work man. Any reason you did not get one of the PnP units for a Protege or Escort GT and do a custom burn? I am not literate with MS, so if my question makes zero sense I am sorry.

Hi 'ya KingFish,

I didn't do a PNP MS mostly because I wanted a universal ECU to experiment with on other cars.



The B3 in a Miata. Looks like it was built that way.

[festyfreak39]

i always wondered if the b3 would offer worse fuel economy then a well bulit b6. All my friends with swapped hondas got better fuel economy then with their stock d series. more hp/tq = less throttle to get the car up a hill etc.

Regardless this is very valuable info and should be stickied.

[KingFish]

I would be interested in the diagram for the waste spark chip. I have no intentions of using a B3 for a RWD project, bit would love to build one for experience.

[fujioko]

I would be interested in the diagram for the waste spark chip. I have no intentions of using a B3 for a RWD project, bit would love to build one for experience.

Hi 'ya kingFish,

The coilpack ignition is a cool upgrade. I'll start a new thread on that one. Lots of pictures!

jim

[KingFish]

Excellent, I look forward to it.

[festyfreak39]

i definatly look forward to that!!!! that is an upgrade we need.

[festyfreak39]

wait, i just realized what happened there.

This is genius!

I can now run a cheaper megasquirt instead of buying a pnp unit. WIN!!!!!!!!

Just a quick question if thats ok:
-How did you calibrate the hyundai tps sensor to the megasquirt?
-How did you configure and wire the coils instead of a distributor? And what coils did u use?
-and why do you still run a maf box? and what IAT did you use?

[fujioko]

wait, i just realized what happened there.

This is genius!

I can now run a cheaper megasquirt instead of buying a pnp unit. WIN!!!!!!!!

Just a quick question if thats ok:
-How did you calibrate the hyundai tps sensor to the megasquirt?
-How did you configure and wire the coils instead of a distributor? And what coils did u use?
-and why do you still run a maf box? and what IAT did you use?

TunerStudio has a built in utility that calibrates the Hyundai TPS. Basically you click on Calibrate TPS and a window appears. The window will show the current TPS readings. Click on current readings for the closed throttle and then press on accelerator (engine off) for wide open throttle. Click on current readings and the TPS is calibrated.

The megasquirt should will work fine with the Festiva distributor. My schematic is arranged for the Festiva distributor or the custom coilpack. They both are wired the same as far as megasquirt is concerned. Info on how to build the custom coilpack ignition is in another thread I just started.

The picture of the engine is older and the MAF was still present. I removed the MAF and used the MAP sensor that is built into megasquirt. The air temp sensor is something I pulled off a car at the scrapyard and I don't recall what it is from.

You will need to develop a temperature/resistance profile for the air temp sensor and the engine coolant sensor. I put both sensors in a pot with water and ice cubes. I let the temperature stabilize and then measured the resistance of the sensors. for example, the engine coolant sensor measured 5200 ohms at 32 degrees F. Turn on the stove and grab another reading at about 140 degrees F and then grab another reading at 212 degrees F. This is your profile, input your values into tuner studio and Megasquirt will be able to measure the engine temp accurately.

Jim

[eurotiva]

I have the same adapter. Mine came from Stratified a long time ago