ROSHX7

Ok, let me decode that. When I floor the car, I wanna know if for sure the AIR FLOW meter flapper is opening all the way. How to check that?

The Ace

Ermmmm, tell a very technicallly inclined friend of your to WOT, while you are over the engine, looking at the AFM ????

well, worked for my Honda, should work for the Rex....

HAILERS

Piece of cake. Patch your meter into pin 2E of the ECU and a ground. Turn the key on. Should be approx 4v. Have someone push the flapper door by hand to full open. Write down the voltage. Put the air flow meter and filter back on and go for a ride with the meter still hooked up to pin 2E. Stomp on the pedal. Does the meter read close to what it read when your buddy held it open earlier? Never done this myself, but it seems like that it should work. I'll try it out sometime this week. If you look at the 88 manual at http://www.iluvmyrx7.com and look at section 4B, pages 4B-32 and also page 4B-60 you'll see that pin 2E is the wiper on the pot in or on the afm door. Voltage should decrease as the door opens.

RETed

That will not really work - the flapper airflow meter signal fluctuates from 0 to 5k-ohm several times till full open.&nbsp It is not linear.&nbsp The only thing I know of that can translate that signal easily is the new A'PEXi S-AFC.




-Ted

HAILERS

Well darn. Won't work. I'll think of something else. In the mean time remove the air filter and have your buddy strapped to the fender staring at the flapper door and go for a ride(humor, don't do it please). Wonder how much the Apexi AFC cost? Gonna have to go look.

RETed

Yeah, I just read that thread - gotta give the guy credit on thinking up an idea like that.&nbsp Hell, just jump the airflow meter plug with a 5k-ohm resistor and the fuel pump cut-out switch built into it and chuck the damn thing altogether!

S-AFC's go for $400-$500 typically new from authorized dealers.




-Ted

Scott 89t2

they are around $300 I think. but they only read around 66% when the door is all the way open.

HAILERS

This *will not really work* has been bothering me all day, so I went home and took off my K AND N. Tapped into the 2e wire at the ECU. Put a meter on it. Turned the key on. Read 3.9volts. Pushed the flapper from one end to the other. At full open it read .40 volts. Voltage went progressively from 3.9 to .40 and back. Went for a ride. Fourth gear stomped. At about 6000 it read .42 volts. Repeated several times. There's no(make that *not much*) doubt in my mind that you can tell if the door is opening fully by monitoring a volt meter while driving. My story and I'm sticking with it until someone explains how the .40v figure does not represent a fully open door. I don't have a closed mind, it just seems that way at times. Maybe I misunderstood the question. The car I did this on is a 87N/A. Stock ECU.

Henrik

Hailers has got it right, the voltage will decrease monotonically as the flapper door opens. RETed is also correct that if you measure the resistance of the door on a bench situation, it will fluctuate several times. Why the difference - the only reason I can think of is that the meter is not properly loading the AFM output and hence reading false. I'm sure the ECU draws considerably more current through the AFM than the meter. Makes it real tough to test an AFM at the junkers.

I have also tested it on my TII, and have similar results to Hailers.

Henrik
87TII

Keith

I'll third that. The voltage is definitely linear. There is some kind of electronic circuitry with multiple input "pads" at work here - hence the funny resistance readings. But, by gosh, it comes out linear, though!

Irv, Keith's dad

HAILERS

I should have done a resistance check, and then I would have understood why the confusion better. Probably do it tomorrow just to see what the ***** is . Anyway it was still a fun thing to do and 'ole ROSH7 can now find out if his door fully opens. I'm still biased towards taking the hood off and tying a fellow to the fender and having him look at the flapper door. There's several guys at work that I'd like to volenteer(sp)that job. Maybe do a sixty to zero brake check while we're at it.

ROSHX7

Man, I really made you guys *THINK* about this ONE! Keep the suggestions coming, I really wanna know the PROPER and MOST ACCURATE way to check the damn thing...

HAILERS

I'm biased. That is the best way, picking the signal from the ECU on pin 2E. You can buy some of those *wire taps* from Radio Shack* and tap in just down from the plug and use one of the bolts that hold the ECU down as a ground point for your meter. I think you'll have a lot of confidence in this method if you do the above and watch you meter while you open and close the flapper door from full open back to close. Just make sure you do it with the key to the on position and the meter to DC volts. Wire taps cost maybe 70 cents and some wire for a buck or two. Don't wanna here how I'm compromising my wiring harness using a wire tap. I've got about nine taps right now and no problems. (humor)

Henrik

You can also pick up the signal at the AFM (forget the pin - check the wiring diagram) as its easier to get at than pulling up the carpet and ECU cover.

Henrik
87TII

HAILERS

Its the green wire with the blue stripe. Second from the end(don't ask which end please). That makes for a long piece of wire though. Talking 86-88 only. You know, the good models.