The beginnings of a Megasquirt how-to guide

[BRZCory]

Originally Posted by BackWoodsBob

Why not buy the diy bob and make your ecu 100% plug and play so you can jusst swap them back and forth as you sort **** out and still drive to work?

Because the wiring is different. I'd need to add wires to the stock harness for the IAT, and some more wires for the ignition. A second harness is the way to go.

And they're friggin $90. Eff that noise. For that much, I'll just hack up my spare stock ECU and use the connector from it like they do for the "DIY megasquirt inside stock ECU case" threads.

[BackWoodsBob]

pretty sure due to it having 2 electromagnets it's able to act as a stepper motor, by energizing one coil more than the other it can turn in small increments. Or it can hold a position.

Not sure why it isn't a spring/always closed or always open then controlled to idle the car as that would be less complex. Then again, subaru did a lot of things in a complicated way such as the window regulator system haha.

[BackWoodsBob]

Originally Posted by BRZCory

Because the wiring is different. I'd need to add wires to the stock harness for the IAT, and some more wires for the ignition. A second harness is the way to go.

And they're friggin $90. Eff that noise. For that much, I'll just hack up my spare stock ECU and use the connector from it like they do for the "DIY megasquirt inside stock ECU case" threads.

Wait, you can't use the stock harness/plug to work with the IAT? Doesn't the MAF send the reading through one of the 4/5 wires?

[SilverSpear]

My friend suggests that you carefully check post 117, where the IACV is carefully described in detail, and note that:-

Only a single inductor is involved, fitted with dual windings, one in reverse of the other. In this way two voltages of the same polarity enable open and closed operation.

There is no return spring. The use of a permanent solenoid magnet retains a rotary solenoid in a mean central rest position and enables two variable voltages to move, position and hold the solenoid valve at any desired point, towards open or closed. This arrangement also insurers no voltage, fail safe operation.

A balanced pair of NPN and PNP transistors within the TCU, allow a single control voltage, to swing the supply voltage, towards either of the open or closed solenoid windings, via their ground circuits.

[oab_au]

Originally Posted by SilverSpear

My friend Trevor suggests that you carefully check post 117, where the IACV is carefully described in detail, and note that:-

Only a single inductor is involved, fitted with dual windings, one in reverse of the other. In this way two voltages of the same polarity enable open and closed operation.

There is no return spring. The use of a permanent solenoid magnet retains a rotary solenoid in a mean central rest position and enables two variable voltages to move, position and hold the solenoid valve at any desired point, towards open or closed. This arrangement also insurers no voltage, fail safe operation.

A balanced pair of NPN and PNP transistors within the TCU, allow a single control voltage, to swing the supply voltage, towards either of the open or closed solenoid windings, via their ground circuits.

He was wrong then and is still wrong.

Harvey.

[BRZCory]

Picked up a spare motor with an engine wiring harness today, which means I get to bench test And that I've got a spare IACV to test.

Obligatory funny picture (Click for fullsize, or use Firefox/chrome with the Thumbnail zoom/Hoverzoom add-on because it will change the way you internet):

[BackWoodsBob]

where'd you snag that brute from?

I need an engine stand

[SilverSpear]

Originally Posted by oab_au

He was wrong then and is still wrong.

Harvey.

Hello Harvey, I am simply a messenger, and you are ALL my friends without differentiation.

Trevor sends this message: "The accused invites those who are interested in facts to make contact by email. ---

ralphmedway@gmail/.com"

Play it nice, we look up to you guys!

[icingdeath88]

Originally Posted by BackWoodsBob

Wait, you can't use the stock harness/plug to work with the IAT? Doesn't the MAF send the reading through one of the 4/5 wires?

You can hijack one of the MAF wires to run the signal from the IAT, but you will have to cut off the MAF plug to get at the wire. Not for a PNP setup.

[BackWoodsBob]

Why would you have to do that, why not tap into the signal wire instead? I did it as my 'map' reference wire to my phase 2 4eat transmission. Works like a charm.

[icingdeath88]

You mean use the signal from the MAF as the IAT sensor? I'm not understanding what you mean.

[BackWoodsBob]

Exactly, doesn't the MAF measure 2 things. Air flow AND air temp? Can't you use the air temp sensor's output and jack into it for the MS?

[icingdeath88]

Originally Posted by BackWoodsBob

Exactly, doesn't the MAF measure 2 things. Air flow AND air temp? Can't you use the air temp sensor's output and jack into it for the MS?

I don't think it works like that. If you had the MAF voltage/airflow calibration curve for our MAF, you could use the MAF directly instead of the MAP/IAT sensors with the Megasquirt. (At least with the MS3X I know it can be done, not sure about the MS2, but I'd be surprised if not.) But I don't think you can get air temp data from the MAF like that.

What I was trying to say you could do with the wiring is splice a connector for an IAT sensor. (I used the GM one.) To save the trouble of running new wiring all the way up there and being able use a pin on the stock ECU plug.

[BRZCory]

The MS2/Extra does have MAF options. I don't remember off the top of my head but I know one is MAF/MAP, and possibly a MAF all by itself.

That being said, a hot-wire MAF works on temperature to measure flow. It heats the wire to a known temperature, then measures how much energy it takes to keep that wire at that temperature. The air goes past the wire, which cools it. The MAF heats up the wire again, and that voltage is DIRECTLY related to how much air went past the element. This is how a MAF works.

It does not have an air temp sensor like you think it does. (Or at least I haven't seen one).

[BackWoodsBob]

Hm, there are 2 sensors on our maf's, I thought one was ambient air temp sensor. Maybe I'm wrong.