Edit: 11/4/10 -- I'm now running turbocharged! Minor edits throughout, with Turbo install tweaks at bottom of page.

I am using MegaSquirt for engine management on my '96 Rav4. I didn't have to change any wiring for the initial install, the MS unit plugs into the existing harness and the only change under the hood was to disconnect the vacuum hose running to the stock MAP sensor and run a hose to the MAP sensor built into the MegaSquirt unit.

So, it's about a close to "Plug N Play" as you can get.

After running normally aspirated for a short time, I installed a low-boost turbo setup on my stock 3sfe engine. MS is helping me manage fuel and timing so I don't blow up the motor (fingers crossed!). This is my second MegaSquirt/Turbo project. I installed a turbo system on an '87 MR2 in late 2004. I sold the Mr2 a couple years ago, but talked with the owner  recently and it's still running fine. My hope is to repeat that success with the Rav4.

For this project, I'm using a DIYPNP MegaSquirt unit from DIYAutotune. This particular version of MS comes with connectors that plug into the stock Toyota harness -- you just unplug the stock ECU and plug in the MegaSquirt.

The key to making it work on the RAV4 was figuring out the ignition system. My '96 model has a distributor with a cam angle sensor built in and a crank angle sensor mounted on the crankshaft. In the end, I ignored the cam sensor and just used the signal from the crank sensor. Once I figured out the right settings, the car fired on the first try.

Toyota Crank Trigger Wheel

The crank trigger wheel on my '96 Rav4 has space for 36 teeth, but there is a block at one point that takes up the space of 3 teeth. The crank angle VR sensor sees that block as one tooth followed by two missing teeth. So, MegaSquirt sees 34 teeth and two missing.

Here's a drawing of the trigger wheel. If your Toyota has this same setup, you should be able to use an MS2 or PNP kit to control ignition, whether your car has a distributor or not.

DIY PNP Kit

The DIYPNP kit I used is short for "do it yourself, plug n play" -- Well, some assembly is required for the version I purchased. The kit consists of a MicroSquirt board, an expansion board that includes space for a lot of interesting functions, and the connector board that allows you to plug into your car's harness.

MicroSquirt is a scaled down version of the larger MegaSquirt and comes pre-assembled on a credit-card sized board. When mounted on the expansion board in the PNP kit, you've got all the functionality you could ever want, including boost control, knock control and lots of user selectable input/output options.

The picture is my assembled unit. It took about two hours of hands-on work to get to this stage. The orange wires connect the expansion board to the harness connector. On the edge of the expansion board you have a series of output holes that are clearly labeled: Ignition, injectors, coolant sensor, throttle position, etc. You just have to wire those to the appropriate pins on the connector board.

It helped that I had a complete schematic for my Rav4 that I downloaded from the Toyota Information Center. Included was a page showing the terminals of the ECM and which pins do what. That made the wiring straight-forward.

Anyone can do this with patience and a willingness to learn, even if you've never soldered anything before. But, it's not for the faint of heart. I understand you can get these kits pre-assembled if you want to pay the extra $$$. Even then the cost would be less than a third of most engine management systems. The DIYPNP kits are a product offered by www.diyautotune.com. The kit that has the right harness plugs for the Rav4 is the DIYPNP Nippon Denso 76pin Unassembled Kit [DIYPNPN76-K].

To save some money, you could go with the MegaSquirtII kit with the v3 board: [MS230-K] MegaSquirt-II Engine Management System w/PCB3 - UnAssembled Kit. The only drawback there is you have to hardwire it into your harness or build your own harness adapter. In my last project I cut up a spare ECU from the junk yard to get the female harness plugs to make my own. The MSII kit doesn't have all the flexibility offered by the PNP kit, but you can add adapter boards if you need some special function.

The software you need is MS2-Extra. Complete documentation, running to hundreds of pages, can be found here: http://www.msextra.com/doc/index.html. Be sure to scroll down to the MS2 information.

Here are the pinouts for my Rav4

 

1996 RAV4

ECU                       MegaSquirt             Notes

+B (E6-12)               12v                        Switched 12 v

VC (E5-1)                Vref                        5 volt reference for sensors

VTA (E5 11)            TPS signal              Throttle Position

THA (E5-3)              IAT                         Intake Air Sensor

THW (E5-4)             CLT                        Coolant Sensor

#10 (E4-12)             INJ 1                       Injectors 1-2 paired

#20 (E4-11)             Inj 2

#30 (E4-25)             Inj 3                        Injectors 3-4 paired

#40 (E4-24)             Inj 4

IGT (E4-20)              Igt                          Ignition out

NE+  (E4-4)             VR-                         VR sensor signal in

NE – (E4-17)           VR +                       VR sensor in (Backward of what seems right.  I had to swap them to make it work)

FC (E6-14)              Fuel                        Fuel Pump Control

ISCC (E4-9)             IAC Close               Idle air control closed            

ISCO  (E4-10)          IAC Open                Idle air control open

OX1 (E5-6               O2 sensor

OX2 (E5-5)              O2 sensor               second 02 sensor is optional

KNK (E5-10)            Knock                     Rav4 has a knock sensor. Optional.

Grounds:

E4-14                      Main ground

E5-9                       Sensor Ground

E4-13                      Injector ground

 

Idle Air Control Valve

Warning: I'm not 100% happy with this idle setup. It does okay most of the time, but occasionally struggles under load. Use at your own risk

The ’96 Rav4 has a three-wire Idle Air Control (IAC) valve that opens and closes to bypass air around the throttle and control the idle. To make it work with the DIYPNP kit, you need to add the circuit pictured below. This was the most complex wiring task of the entire project. All the components below were sourced at my local Radio Shack and looked to be fairly standard components they keep on hand. They also may be purchased online through Electronic Supply houses.

The PNK kit includes a couple open areas on the board for building add-on circuits like this. I understand some of the kit suppliers offer this circuit pre-mounted on a add-on board for use with the standard MegaSquirt.

By tracking engine temp and other sensors, the MS kit provides an IAC output. You run a wire from that output port to the control circuit.  It splits that signal into an Open and Close signal that the Toyota IAC understands. Make sure you get the open and close order correct. I wired it up backwards the first time around and the car would NOT idle. On the ’96 Rav4 harness, the pins are marked ISCC (valve closed) and ISCO (valve open).

“This circuit uses a pair of TIP120s to drive the opening and closing coils of a 3 wire idle air control valve. Some cars that use the N76 board (particularly Toyota and Subaru products) use versions of the 3 wire IAC valve. This circuit takes the IAC signal and splits it into two opposite signals. The IAC_Open output is grounded when the input is grounded, and the IAC_Close output is grounded when the input is not grounded.” –Source, DIY AutoTune.

 

Idle Software Setup

The MS-Extra software includes several strategies for controlling Idle. The one that works for my Rav4 was PWM Closed Loop. (PWM stands for pulse width modulation). In very basic terms it uses the open and close signals to “modulate” or move the valve back and forth to maintain idle.

Note: I'm using TunerStudio MS Lite v0.999.7

For PWM idle settings, I set valve mode to Normal, 0%=off and the PWM idle port to local. Valve frequency was 300hz. For cold starts, I added timing using the Cold Ignition Advance Offset function. This function lets you add timing to increase idle rpm when cold. I'm still fine tuning this, but right now I start with 6 degrees of extra timing below an air temperature of 60 degrees F and taper down as the engine warms.

Rather than go into further detail on the idle setup, here are some screen shots. My car idled fine on these settings throughout warmup and during stop-n-go driving.  You can find an in-depth discussion on idle setup here: http://www.msextra.com/doc/ms3/tmp/2Idle_Control.html

 

 

Other Software Settings

Here are some various screenshots from my setup, including engine constants and ignition. My Rav4 uses injectors rated at 250cc per minute and the 3sfe is 2000 cc:

Turbo Install:

For the turbo install, I did make some minor wiring changes in the engine compartment. I  replaced the stock Toyota air intake temperature sensor with an open element unit from a GM car. The open element sensor has a faster reaction time to air temperature changes you might see with a turbo. Both sensors use two wires, so I just snipped off the Toyota sensor and solder on the GM sensor using the same two wires. The harness connects to MegaSquirt the same way.

I also installed a wideband O2 sensor. The Toyota narrowband O2 sensor was a two wire unit, with one wire going to ground and the other a signal wire going to the ECU. The Innovate Lc-1 I'm using has several wires -- signal, power and four grounds. I used the stock signal wire and ganged the four grounds onto the main engine ground, which also serves as the ground for the MegaSquirt unit. You want to avoid ground offset issues with the Lc-1, so that seemed like the best solution.  I sourced power from a nearby sensor that has 12v switched power -- meaning power is supplied only when the key is turned on.  Since I'm using the stock O2 signal wire, the harness plug at MS was not affected. 

With both sensor changes, I had to update the MS software settings to match the new sensors. To provide the extra fuel needed for the added boost, I installed upgraded fuel injectors. I selected injectors from a 90-92, MX6/626/Probe, Turbo, gray top, PN 195500-2150. They are rated at 326cc for their stock application, but flow 350cc at 43.5 psi, which I believe to be the Rav4 fuel pressure. Their connectors are the same as the stock Toyota units, so they were plug n play.

Of course, the new injectors and added boost also require new fuel maps and tuning. I'm in the process of fine tuning now. I'm using a TD04 turbo from a 2005 WRX. I've set a boost cut of just over 8 psi.

Conclusion (for now)
The balance of the settings for MegaSquirt should be configured for your specific car. I encourage you to work carefully through the setup instructions, which can be found on the MS-Extra Documentation Page, here: http://www.msextra.com/doc/index.html.