Chiburbian

iTrader: (1)

I installed the flyback mod on my idle and on my VVT. I installed the diode in the factory wiring. Bridging the positive to negative anywhere along the pair should be ok right? I can post a pic later if this doesn't make sense...

Anyhow, Idle has been great, VVT has yet to work.

I unplugged both the idle and the vvt solenoids and metered the two pins to ground. On the idle, only one of the wires shows connectivity to ground with the diode in place.

On the VVT, both pins read 12v to ground.

Are one of my two diodes backwards? I am strongly leaning towards my Idle being correct and VVT backwards.

Since it is a PWM solenoid, is there a polarity to be concerned about or can I just reverse the pigtail without deconstructing the whole thing?

Thanks!

Joe Perez

iTrader: (8)

I'm not entirely certain that I'm interpreting everything you have written correctly, but...

The diode shall always be installed across the two wires leading to any solenoid. Schematically, this places the diode between +12 (the supply to the solenoid) and the ECU wire which provides a switched ground for it.

The diode MUST be placed such that the striped side is connected to the wire which supplies +12 to the solenoid. In general, this is a white/red wire in most Miata applications.

HOWEVER,

The '01 and later engines, oddly, supply +12 directly from the ECU on dedicated wires for the IAC and VVT control (OCV) valves in particular. For these specific applications:

IAC + is the Orange wire at ECU 2P
IAC - is the Violet / Red wire at ECU 2Q

OCV + is the Yellow wire at 4D
OCV - is the Violet / Yellow wire at 4R


NOTE: You should verify that the wiring of your ECU matches the above, by unplugging the solenoid, switching the ECU on, and checking for +12 at the indicated wires (relative to ground) without the diode installed. (eg: the wiring inside the ECU / ECU harness may be reversed relative to the OEM configuration.)

If the diode is installed backwards, it may explode. That's a good indication that you have reversed the polarity. Damage to the ECU is also possible, as the diode is essentially supplying an unlimited amount of current to the ECU driver.

(In theory, the ECU drivers should always be internally current-limited, which would prevent both ECU damage and exploding diodes, however this is not a universal truth. In this context, it would depend upon what specific output circuits you are using.)


The fact that you are measuring +12 on both legs of the VVT wire suggests that you may have have installed the diode backwards on that line. I suggest removing the diode and then re-checking both wires for +12 relative to ground with the solenoid disconnected.

Chiburbian

iTrader: (1)

Yellow is hot to ground direct from ecu. The other is verified to not be hot from the ecu.

I am using Nitrous2 to drive the OCV but VVT is disabled in software currently. More in a sec.

Chiburbian

iTrader: (1)

So here is what I did: like I explained above, I created a pigtail that featured a diode wired as described in the VVT flyback directions.

I then proceeded to solder splice the wires backwards.

Yep. I did that. And forced the stock ecu to try and run VVT for months before installing the MS3. Diode checks fine, no smoked circuits on the expander that I can find.

I dodged a bullet.

Thx for help.