I bought a rolling chassis and a jspec engine which isn't in yet. The question is, i don't have the MAF Mass Air Flow Senor. Is all the MAF the same on a 86-88 turbo and N/A or do I need to find a one exactly for a turbo? I can get a MAF off a 87 N/A and i just need to know if it would work. Thanks in advance Mike

 

Technically, it will allow the car to run but the turbo model has a specific AFM. If you use the NA AFM, it will run either rich or lean, I forget which one.

 

Oh yeah, the S4 TII model AFM # is N318.

 

A Turbo AFM on an NA will cause a lean mixture. An NA AFM on a Turbo will cause a rich mixture.

 

What do you base that on?? I'm gonna have to check that out.

 

i heard that they're basically the same other than a different spring or something?

 

Yeah, I've heard of some people who change out the spring for the flapper door.

 

Actually NZ is right. I put a turboii afm on my 86 non-turbo this morning and the afr ran generally about .5 afr leaner under full throttle....from 2000 to 7000 rpm. Uphill runs. Actually the 86 na seems a touch happier like that. No SAFC involved in this swap. Just pure RX-7 stuff.

And just to get NZ's attention with this post, a little info for you about the switch in the afm that makes the fuel pump relays circuit.......It ain't that hard to adjust/clean off/bend a touch/you name it. Get a exacto knife and cut that clear RTV around the black cover and pry it off gingerly and you'll see what I mean. Maybe while your there get some contact cleaner and spray it on the carbon track. Maybe that'll clear up your mid range hesitation. Maybe it won't.

 

Simple deduction and a few assumptions .

The Turbo breathes a lot more air than the NA, so it makes sense that the springs are calibrated to match that airflow. If you used the same spring in both AFM's, depending on the stiffness of the spring either the Turbo AFM would reach full deflection too early or the NA AFM would be using only a small part of the flap's swing at full load.

So you put a stiffer sping in the Turbo AFM so it doesn't max out early, and a weaker spring in the NA AFM so it uses more of the flap's swing at full load.

Thus a Turbo engine will pull a NA AFM open futher for the same airflow and run rich, while an NA engine won't pull a Turbo AFM open as far as it should and run lean.
Phew...
Could it be you've you just discovered the latest must-have NA mod?

Note than anyone who thinks a NA AFM is a cheap and easy way to get richer mixtures on a Turbo should be aware that it'll be richer all the time at low load and probably max out the AFM early at high load, causing a lean mixtures. Bad idea all round.
That's good to know. It sure beats having to replace the whole thing. Good work man.

 

i was wondering the same thing i think myn is bad on my turbo 2 and i have a good na one so mabe just stifen the pring a bit and it would be goood to go but if it runs rich crank up the boost

 

The spring tension is easily changed. Just loosen a little set screw that holds the device (can't think of the right word right now) that secures the gear in place. Prior to doing any change you NEED, I repeat NEED to make a mark on the gear opposite the cog (???) keeper(???) so you can return to the original setting when you've found out you've botched things up royaly.

The little screw should only be loosened after you've made you mark on the gear opposite where the cog is holding it in place. Then you only need to loosen, not remove the screw. Pry back the holding cog and rotate the gear which ever way you want. Clockwise to make the spring stiffer, anti-clockwise to lessen the tension.

I don't think there is any need to change the spring at all. There's really more to the afm than the above.

I think I might have started this little writeup to cause some mischief. Sorry, couldn't help myself.

 

Yeah but I think there's more to it than that. The resistance values in the FSM are different too, so the whole calibration is obviously different beween the two.

 

Without a doubt. Been there, seen that. Just up to mischief here.