Tachometer relationship with TPS

[Zed Head]

Looks like someone has done more than the usual messing around with your AFM, not right for 1978. Looks like your counterweight is completely missing. Was there a number on the cover? Maybe someone installed a ZX or even a BMW, or other brand AFM. Maybe it came with the Bosch injector. You might have the balance right from your calibration, but the potentiometer trace or aerodynamics of the air flow path might be totally wrong for the engine. You have a new puzzle piece.

Here's a link to the atlanticz site, probably Blue's work, for a comparison picture - http://atlanticz.ca/zclub/techtips/afm/index.html All of mine (4 so far) have looked like the atlanticz pictures.

The injectors look correct for a 280Z, one's a Bosch (the same number that I have on mine, that I've seen on several local Z cars in the salvage yard, no confirmation on the cross-reference though), the other is a stock Nissan or their supplier (I think that's tan color under the black grime).

[johnny haywire]

I was curious as to why mine didn't have one and all the Atlantic Z photos did. I was hoping that they changed it from '76 to '78 and maybe that was the reason? But perhaps it's just plain removed. Always something, eh?

Here's a shot of the cover - it appears to be for a 280Z, I cross-checked the numbers on the MSA site. What year cars did the AFMs you've had come out of?

Thanks for the input on the injectors. I changed the plugs recently and they all seem to be pretty uniform, so I'm guessing they are alright. I do plan on putting an inline fuel pressure gauge to make sure I'm not overloading them.

Edited July 13, 2012 by johnny haywire

[Zed Head]

Min came out of either 76 or 78 cars. They have the same number as yours, that cover looks like a typical 76-78 AFM cover number, maybe even 75.

I assume that it's possible that someone removed the counter weight, maybe with some misguided idea that it would increase throttle response. Or maybe it just fell off and they ran it anyway. It's main purpose is as a damper for pulses on the vane, if I remember right. Or they took the cover off of the 1978 model and stuck it on a different AFM. The design is a Bosch design and common, you'll see them on BMWs, Audis, Volvos, Alfa Romeos, etc.

No idea what you should now. If you could borrow an intact AFM, that might tell you something.

[johnny haywire]

Ha-ha, yeah, that last owner (or maybe the last two) were butchers. When I got the car, there were mismatched spark plugs, no battery hold-down, the fuel rail and injector lines were done up with hose that had "NOT FOR FUEL INJECTION" clearly printed on it, and the battery in the car (on the list to replace) is a tiny little thing. Luckily, after owning the car for a year, I think I've pretty much found all the bits that were messed with, and there aren't too many, but enough to keep me busy...

Do you know how the counterweight is affixed? If it's a bolt-on piece, I may try placing a want ad in the classifieds, maybe someone has a junker/parts AFM kicking around. The unit itself seems to be working, the resistance tested out fine, and the voltage output seemed to decrease smoothly as I moved the flap with the tester connected, so...hopefully it's salvageable.

Thanks again for all your help!

[grantf]

I concur, You may be in search of another afm. Perhaps try the wrecking yards and find one that at least is intact and ether calibrate it yourself or use as a core for a replacement. Looking at your pictures does not at all look like mine (1977).

note: this picture was taken when I found someone had molested my AFM, then sloppy glue blobs are not what you should see in a stock AFM, they should just be small dabs of glue.

Edited July 14, 2012 by grantf

[johnny haywire]

Thanks for the tips and the photo, Grant, much appreciated. Do you recall how the counterweight was affixed to the mechanism?

I'm going to look at the car today and see if I can get the numbers from the circuit board to make sure that my AFM is even correct for the car. The cover numbers indicate so, but...

I'll ring a few wrecking yards and see what I can come up with.

[grantf]

Sorry I have never taken the wiper assembly apart before. I am not sure but perhaps you may still be able to calibrate it to work properly. It sure does look messed with though.

[johnny haywire]

It definitely runs better since I recalibrated it according to the Atlantic Z method (Blue?), but the counterweight must have some effect on its operation, so...not knowing how it really should act is going to get the best of me. The hunt for another AFM is on. Anyone have any spares for sale?

[Zed Head]

For future readers. Might be a turbo AFM. I posted the same link in your other thread -

http://forums.hybridz.org/index.php/topic/108020-afm-does-this-look-right/page__pid__1010448#entry1010448

[johnny haywire]

Great eye, man! Thanks for sharing!