S-AFC idea

[cjthor]

Can you swap a DOHC TPS onto your SOHC throttle body?

[maldo]

You could swap it but the plugs are completely different. Ours is a 3 wire TPS (if my memory serves me), yours is a 4 wire. It has been done, essentially using the MAF voltage to signal the TPS. It doesn't work that well though, the guy who did it later switched to using a MAP sensor to trigger the S-AFC and found it much more responsive.

[Marlon]

what if we use the auto tps(it's a 4 wire), could we just not connect to out stock ecu, just the safc and run it, the ecu will never go into wot (might get a cel)

[maldo]

If you figure out how to wire it up.

[Marlon]

you know where i could find out which wire dose what on the auto and 5speed tps
i have auto tps(came with my engine) so i might try something

[maldo]

I printed off the discussion of the non-variable to variable voltage TPS from the Miata.net forum plus the MAP sensor conversion for the S-AFC. I will try to dig them up and see what it says (tomorrow though as I really need to do some school work).

[BATTOSAI]

And why not to install an accesory TPS only for the S/afc?

[Marlon]

Originally posted by BATTOSAI:
And why not to install an accesory TPS only for the S/afc?

where? on a 2nd tb

[BATTOSAI]

No man! on the same axle of the throttlebody! quite tricky to do but not impossible!

[maldo]

Ok, Here is what I have from a post on Miataforum.com dating back to 2001. A user by the name turbo95EGT wired his S-AFC up with a 2 bar MAP sensor in order to control 460cc RX7 injectors. Idle was set close to -50%, under boost he was at -25% running 13.5 psi and EGTs of 1525-1550F (which is dead on). The MAP sensor he was using was from a 1988 Dodge Shadow turbo. He tapped the 5v VREF line at the VAF sensor. He did install the 4 wire TPS found on the auto Miata but found that he was experiencing harsh backfiring. He switched to the MAP sensor, tapping into the VAF sensor which has a 4.5-5v closed to near 0v at open. Just a comment to wiring the 4 wire to our cars, if it is like the 1.6l miata, the ecu is only programmed to see on/off readings and nothing in between so this will pose a problem. His solution was to tap the 5v VREF for the VAF and ran that to the 4 wire TPS and a WOT micro switch. This allowed him to have a variable signal for the S-AFC and a on/off for the ecu.

That is a quick run down as the topic is 15 pages long. If you want to read it for yourself, go here: "Why isn't anyone using the Apexi S-AFC?" If the link doesn't work, do a search on the site.