Toyota Vane-type AFM

[JustCallMeOrlando]

Hey all,

There was a couple of things that lead to me creating this thread. First of which was me plugging in my Jaycar DFA. I had an AFM out, and I measured the output voltage of it. Fully closed the AFM put out ~4.5V, fully open it put out ~0.4V (or close enough, those were the figures from memory). As such, when I calibrated the DFA, I did it for a 0-5V range.

Now when I plugged it in, in passthrough mode, the car would go nuts as soon as it got a whiff of boost. This lead me to whipping out my multimeter and sticking it on the output of the AFM, before and after the DFA. the voltages appeared the same, but that wasn't the interesting bit.

As soon as the car hit boost, the AFM voltage went to basically fully open voltage. It stayed that way, regardless of boost. This got me thinking, and is why I created this thread.

How exactly is the ECU catering for this, when it doesn't seem to distinguish voltage wise at least, the different airflow? Does anyone know a bit more about how they work? Is my AFM stuffed (although I doubt it, because someone else explained that this happened)?

Cheers,
Nathan

[stradlater]

I might be pulling at the hair strings here, BUT,

Wouldn't it work with the TPS to know how far the throttle is depressed for more information?

Equally, is there not some sort of boost reading into the 1g ECU? Because don't they have a "BOOST" light output from the ECU?

But, the question your asking Is, How does it differentiate between 4psi and 11 psi given that the AFM will be fully open either way, right?

[gearb0x]

I got a feeling it doesnt differentiate, it just senses full load and gives it all shes got. So if u were over fueling at say 4psi, u might be slightly lean at 11psi. ive read AFM 4AGZEs do the same thing (flap snaps open at any hint of boost), and as such its pretty much useless using a DFA on them.

Autospeed did an article on this trying to tune a 4AGZE with a sender bender

[ViPeR_NiPPleX]

probably just chucks in a maximum value of fuel based on revs when its on boost? unless there is a map sensor hiding somewhere, but i doubt it, doesnt make sense to have both :?

[JustCallMeOrlando]

Exactly right Strad. I'm thinking it just uses the TPS and revs to work out, but it still doesn't explain how it boost cuts.

It has no pressure sensor to speak of, so I'm not entirely sure how it detects boost, perhaps thats based on when it james itself open

[myne]

I'd be guessing that it simply wasnt sprung to cope with that much flow.
Since the flap internal dimensions are a known size, and they work at a known 15psi absolute pressure, the AFM and ECU are both told that fully open = XXX CFM, fuel is added to suit that amount of air.

All I can think is to try a bigger one off a 7MGTE or something. You're simply sucking more air than the AFM was designed to flow.

[ViPeR_NiPPleX]

if it's like the ma7x, they have a seperate map sensor for a digital guage in the dash, it is located near the pass. side strut tower....

otherwise its entirely possible its an output on the ecu and its based on the afm exceeding a certain voltage.

[ViPeR_NiPPleX]

7mgte is karmen vortex.... 7mge is still vane and might be pin for pin compatible...

[JustCallMeOrlando]

The 7MGE one is pin for pin compatible.

myne,
Thought about that theory, problem is it happens at lower than stock boost too.

[The Witzl]

all 7-pin vane type Toyota AFMs have the same pinonuts.....


Nathan.... you have me intrigued, I am now going to be measuring the AFM output on my 18RGEU for interests sake, but i'll use an analog Voltage meter for quick response and easy visualisation.

[myne]

Broken/worn spring?

[ViPeR_NiPPleX]

hmms, i can't remember now, but i think when i swapped the 5me to 5mge for the first time the 5m-e afm didn't work although it plugged in ok... but that could've been because i hadnt wired up the fuel pump switch to the new loom :S.....

[JustCallMeOrlando]

Nathan.... you have me intrigued, I am now going to be measuring the AFM output on my 18RGEU for interests sake, but i'll use an analog Voltage meter for quick response and easy visualisation.

Someone I was speaking to in Perth had told me about it before, but I pretty much wrote it off because I couldn't see how it would work. Then I looked at it myself and was quite weird. My old analog multimeter bit it a month or two ago. Lemme know how you go.