Fuel cut controller differences
 

is there a difference between the s4 and the s5 fuel controllers? Mazdatrix has two part numbers.

The reason why i ask, i bought a fuel cut controller off ebay... but it doesnt specify what year it is.
Thanks
-Ross

I remembered this from a while back:
https://www.rx7club.com/forum/showth...hreadid=133288

The S5 clamps at a higher voltage, because fuel cut is like 2 psi higher on the s5 then s4, i think.

And the wiring at the sensor is different. They don't work if mixed and matched, and they can fry your ECU.

Ok... so how do i ensure that I have the right one? Which wires are supposed to go where?
Thanks
-Ross

FUCK FUCK FUCK!!! It's the wrong one. If anyone is interested in buying a Mazdatrix 11570 FCD, I have one for sale, or will trade for a 11571 FCD.
Thanks
-Ross

How much

Dunno, make me an offer. i paid around $50 USD for it.

Now you gurus... is there any way to modify my Mazdatrix S4 FCD to work in my s5 t2?
Thanks

If it plugs in, and the wiring is the same, it should be able to be modified to set the clamping voltage higher...

No, the wiring is different.

dr0x, you're next in line if i can't find someone that's willing to trade for my series :)
Thanks!

personally i would open up the mazdatrix FCD, and start snooping around.

All FCDs are designed the same way, it is just a basic clamping circuit, there will always be a POT or poteniohmeter to adjust the clamp.

i would feed 5V to the V ref wire, 12 V for the supply, have another POT wired in to adjust the input voltage to the input wire, along with a voltmeter at the input and ground.

and borrow another voltmeter to measure the output and ground.

Adjust the pot so that it clamps at a higher voltage.

Paul stokes used 7.9 psi or 3.65 V. i can't remember what S5 TII fuel cut PSI was.

Anyhow here is the equation u need to determine the voltage if u find out hte fuel cut PSI for S5 TII

Out(V) = 0.169V/psi*P(psi) + 2.318V

so just adjust hte pot in the FCD to the caculated voltage.

for wiring, you will notice there are 5 leads on the FCD.
Vref (5V)
12 Volts
Ground
Input
Ouput

the S5 TII wiring is different because the boost sensor plug does not have a 12 V supply.

So what you do then is find a wire in the engine bay that is 12 V switched when IG is ON.

cut the corresponding wire on the FCD harness and solder the new 12V wire u tapped into onto the wire on the FCD u cut. Remember to heat shrink it too.

there... done... it works now.

Cheers, can i just send it to you and you modify it for me for money? LOL :)

Cheers,
Are you sure that'll work? Why doesn't the RB S5 FCD need an outside 12v source?

i havne't done it myself... but i did build paul stokes FCD and it worked perfect on the LAB bench...

too bad i left the stupd thing in my apt in kingston and i'm in mississauga now.... basically the thing is 3 hour drive away.

i will have a look at the schematics again tonight when i get home from work, to double check everything.

Fingers, If i do figure things out, iwont charge you anything... u just have to pay for postage.


Actually i'm waiting for HAILERS or Scot89T2 or RETED to chime in... with their knowledge and experience.

I have been building Paul's S4 FCD design for over a year, and I'd like to start doing the S5's. I know the wiring is different to the S5 boost sensor, and I'm guessing that something in the circuitry of the FCD is different as well.

Cheers, Thanks a TON! Let me know how it goes :) You have an s5 t2 as well, i see?

yup, with teh bling bling factory mesh wheels too!

spifftacular :D

You're gonna try the fcd out on your car first, arent ya!??! :) hahah