S-AFC THR wire...pressure sensor or Throttle wire?
 

Alright....right now my afc is hooked up with the thr (gray) wire from the afc tapping into the throttle wire coming out of the ecu. Well, when you sweep the throttle, it hits 100% at like 1/4 pedal..maybe less than that. So, i've been talking with SureShot in pm's and he told me to hook the thr wire from the afc to the pressure signal...instead of the throttle wire coming off the ecu.

My question is...where exactly do I tap this in at? Which pressure signal? Is the pressure sensor the same as the boost sensor (the one in the engine bay...or is it the pressure sensor that is in the passenger side kickpanel?

I have an fcd on the car as well, which according to SureShot will come into play as well when wiring this up.

Sooo...long story short...i need somebody to super simplify this for me....where exactly do I tap the THR (gray) wire from the afc to?

The MAP sensor, i.e. manifold pressure sensor. Disconnect the S-AFC's grey wire from the TPS signal wire and connect it to the MAP sensor signal wire instead.

https://www.rx7club.com/attachment.p...hmentid=136350

If you have an FCD connected at the MAP sensor you won't get a "throttle" reading over ~75%. Just make sure you set your "Hi-throttle" set-point below that.

Go to the boost sensor. Splice into where the output wire is on the plug. That wire used to be brown/red. It is NOT brown/red now because you have a FCD harness plug there now.

To determine which wire, look at the factory boost sensor plug and how it once attaced to the boost sensor. You now know which wire on the FCD harness to splice into.

Do not splice into the brown/red wire. Make sense? Yes. You should get a full reading like that.

now that diagram, is that looking at the back of the plug (side with the wires coming out...or is that with the plug out looking into the connector? Do you know the color of that map wire by chance just to double check myself? This is an 88 TII btw...with an n333 ecu.

Are you talking about the sensor in the bay on the passenger shock tower?
I've never installed an fcd, it was on the car when I got it...but I understand what you're saying, just have to find exactly what sensor I'm looking at, and where it is.

i believe thats looking at the harness as if they are plugged... i switched mine like this and it seemed to help quite a bit... i got the throttle points at lo-45 high-99.
sureshot also helped me..he is a great person and very helpful.

yea, he's been really helpful...now I just have to figure out where i'm tapping this wire...if it's at the ecu...or at the boost sensor in the bay.

There's no point running a wire all the way to the MAP sensor when you can make the connection at the ECU. The FCD is a non-issue because the Hi-throttle set-point should be well below the FCD clamp point anyway.

Yep, that's what it says... ;)

The MAP sensor signal wire is brown/red. FSM Wiring Diagrams page 50-25 (middle of the page towards the bottom) and 50-26 (plug EM-31).

alright...now can i swap this with just the ignition on...or does the car have to be running...or under load? I'm asking all this so I won't have to tomorrow when I go change the wiring..

You mean swap the wire?! When you work on the ECU you turn the ignition OFF!

I'm misunderstanding this whole post/threaq/answers.

If you intecept the output of the boost sensor before it enters the FCD, then you have full range on the SAFC and there is no *clamping* on THAT wire/signal going to the SAFC. It'll read the output of the boost sensor thru its full range.

Where is your FCD located right now? If not in the engine compartment.

LOL...i just read my post again...and I can honestly say...I have no idea why I typed that. The question was suppose to be...can I sweep the throttle with just the ignition on...or does the car need to be idling to sweep through the range, or will it only go above 0% under boost?

swap was suppose to = sweep...sorry...ha

sorry...my whole misunderstanding was coming from the fact that some people say boost sensor, some say pressure sensor...and then I think there is another pressure sensor inside in the passenger kick panel. I just wasn't sure exactly where I'm supose to hook up the THR wire from the afc.

I think i understand it now...It needs to be hooked up to the boost sensor wire. Now, you are saying it needs to go right after the sensor, before the fcd..correct?
Hailers is saying it just needs to tap into the wire at the ecu. Who's right? haha

My other question was...after I hook up this wire to the boost sensor, can I do a sweep with the ignition on...or does the car have to be idling, or under boost to see a change in the thr reading on the afc?

The Boost sensor/pressure sensor/MAP sensor(all the same item), is in the engine bay near the right front strut tower. It has a plug. One wire is brown/red, one black/white, one brown/white, one either pure black or brown/black.

The brown/red is the output from the boost sensor to the ECU pin 2B (series four car).

You would not want to splice into that wire to feed the SAFC IF you have a FCD in the car. Because if you splice directly to that wire, the SAFC will not see the full range of the boost sensor.

Some people mount the FCD in the engine bay. It has two connectors. One goes to the boost sensor and the other to the harness plug that used to go to the boost sensor.

Others have the boost sensor located in the car near the ECU and splice the wires of the FCD to the ECU wires.

I've no idea where your FCD is located.

Personally, when I had a FCD, I connected it to the boost sensor. I then ran a wire from the SAFC to the output wire of the boost sensor. Remember now, it no longer has the original harness plug on it, it has one of the FCD plugs on it. I remeber not the color of that wire.

If you connect it like I did, then when you turn on the SAFC (key on), you will read the percentage the throttle (now the boost sensor output) is open or you can go to the SAFC page that says Sensor Test /Ck????? and you'll read the output of the boost sensor in volts dc.

You will NOT be able to read the full sweep as you put it. You'd need to connect a MittyVac or similar tool to the boost sensors input vacuum line and apply pressure to the boost sensor in order to see it's max output

Or go for a ride and watch the SAFC while your in full boost going up a steep hill. Then it should go to 100% or close to 100%

If you have a FCD and connect the SAFC throttle wire to the brown/red wire at the ECU brown/red wire, then you'll probably never see 100 percent on the SACF......because the FCD is going to clamp the output of the Boost sensor at approx 3.65 vdc or so.

ah ok...i think i'm with ya now. I'm pretty sure my fcd is up by the boost sensor. So I'll trace that back to the factory plug, to find the right wire to tap into on the fcd harness coming out of the sensor.

What would be the major downside of not seeing the full voltage (if I wired it in at the ecu after the fcd)?

If you have a S5, like your profile says.................then you should run the wire to the Full Range throttle sensor wire at the ECU, not the Low Range wire.

But why would it matter if it didn't? The signal is just for the Lo-Throttle and Hi-Throttle points, and both of these setting should be well below the FCD's clamp point. It won't make any difference to how the S-AFC operates if it's connected at the ECU, it'll just save running yet another wire through the engine bay.

The FSM calls it a "pressure sensor" in the Turbo chapter and (incorrectly) a "boost sensor" in the NA chapter. The industry term is MAP (manifold absolute pressure) sensor. The atmospheric pressure sensor in the cabin is something else, and nothing to do with all this.

The FCD should be right next to the MAP sensor. They only have very short wires.

No downside.

Damn, why are we having this discussion for an S5?! :confused:

it's an s4 tII...i sold the s5 awhile back...but i don't ever update my info here...ha

One more question on this guys...I switched the wire over to the boost sensor output. I hooked it up in the bay. Not saying you're wrong NZ....just better safe than sorry I guess, and it only took me like 10 minutes extra to run the wire to the bay.

Anyway, again, talking with SureShot...he suggested setting the lo-throttle point to about 40%...and the Hi-throttle to 99%. He then said to hit each Ne point in neutral and lean the mixture down to about 15:1. This is done...I had to leave the 1000 rpm setting a bit richer. Leaning it to 15:1, the car wouldn't idle.

Anyway, now that the lo-throttle is set. Is there anyway to test to make sure that my
new connection is working BEFORE boosting?...I don't want to go boosting, if I made some stupid mistake (which I don't believe I did...but I'm extremely paranoid with rotaries and blowing up...haha). Is there a way on the afc to make sure the THR wire is getting a correct signal from the pressure sensor without boosting...or to at least let me know it's getting some kind of a reading?

interesting...so you just revved it in neutral at each point and leaned it out?? will this be safe if your at 3K and in 3rd gear at say 60MPH...????say your getting ready to pass and you down shifted to this situation...will the settings be ok???
i never thought of adjusting mine this way....

It isn't any safer.

He obviously has an NA and doesn't realise you have Turbo. This is why this mod is not such a good idea if you don't fully understand what you're doing.

The S-AFC's throttle reading now corresponds to manifold presusre, where 0% is ~30inHg vac (i.e. impossible), 50% is close to atmospheric and 100% is ~15psi boost. Your Hi-Throttle point should be set well under 99%, more like 60% (2-3psi boost).

He knows I have a turbo...his is turbo as well...he mentioned also, that about 40% was close to atmospheric...and 100% would be ~15psi, but he says to set the hi-throttle point to 99%...dunno if that was a typo or what...but I know most of what I've seen, everybody's hi-throttle is set from like 97% to 99%. I don't know sensor they're using for their THR reading, but 99% seems to be what everobody sets for hi-throttle....anybody else with a turbo car set up this way? What hi-lo points are you using?

im using lo-40 HI-99 but now im not sure...it makes sense that you would want it lower since if your not at full throttle and you will still see boost...

Can you tell me what readings you get with the ignition on (engine not running)?
What THR, AFL, PRS, etc readings you get?

sure...when i get a chance i will check it out for ya... it might be a couple of days though...