how do u use an safc with a map sensor instead of the tps sensor ? i know there isnt any map sensor in there but i understand Dale Clark used a map sensor instead of the tps sensor

 

He used the boost sensor instead of the TPS. You are right we do not have MAP sensors in stock FCs.

James

 

whats the difference between the boost sensor and tps sensor ? whats the boost sensor do and whats he advantage using the boost sensor instead of tps ?

 

You are both wrong, FC's do have MAP sensors. MAP stands for Manifold Absolute Pressure. You should be able to work the rest out yourself...

 

i thought fc's had mass air flow sensors. i thought thats what my s5 had, the plunger type on the intake. and s4's had some kind of honey comb flapper type? dont quote me, im a newb

 

the reason that you would want/need to use the boost sensor instead of the tps (at least on s4) is that the tps is narrow band. meaning that the tps signal maxs out at about 1/2 open throttle. the boost sensor would then be used to adjust the fuel curve realitive to boost instead of throttle. you need to tap the output wire on the boost sensor (consult factory service manual) instead of the tps. then you can use the throttle % setting on the safc to pick how much boost it needs to switch from low to high fuel curves. if all of this is too complex for you, you need to find some help from someone locally that is experienced with this.

 

n e one knows the thread on how to hook safc to pressure sensor??

 

It all wires up the same as it normally does, except the wire that goes to the TPS goes to the preasure sensor output. If you have a FCD, it is recomended that you run the wire into the engine bay and tap the TPS BEFORE the FCD. you get a larger range of signal that way. On my racing bead FCD, I think it is the red wire.

 

i know everthing else is the same.....and the only wire different is that instead of tps you use the pressure sensor....and i do have fcd...i will check the wire colour...(in s4 it is only 4 wire connector)

thanks

 

interesting... i had never heard of this...

so using the MAP sensor would be more reflectant to engine load rather then TPS right?

will the AFC II go retarded when the MAP is reading vacuume (like negative TPS % on the output)

when ur boosting beyond stock boost.. does the MAP sensor keep rising too? like is there a cap where the MAP sensor is no longer accurate? say 15psi for example?

 

bump.....good question

 

Hrng. RTFM, chaps.

Answering a few of the questions I see:

No, the AFC will not see "negative TPS" in vacuum. For an (ideal) pressure sensor capable of reporting 1ATM of boost, you'll see 0v at full vacuum, 2.5v at atmospheric, and 5v at 1ATM of boost. So it won't confuse the AFC.

A MAP sensor is rated for a given pressure. It will "peg out" at that pressure, and won't be of any use beyond that. So, if you have a NA pressure sensor, it won't read much into boost. If you have a pressure sensor rated for 1 ATM of boost, and try getting it to read 25lbs of boost, you're not going to get anything meaningful past 14-17psi.

-=Russ=-

 

You have to look deeper...


TPS's have a 0-5v output. So does the stock FC boost sensor - the range will ALWAYS be between 0-5v. That's what originally gave me the idea to tap into the boost sensor instead of the TPS.

The 86-88 FC's have a narrow-range TPS that shows full open at about 25% throttle. That's pretty useless when it comes to tuning. Using the boost sensor you can get a full range input - vacuum to atmospheric on an NA, vacuum to boost on a TII.

Some DSM guys found that they could tune the car in better and get smoother driveability using a MAP sensor instead of the TPS, BTW.

Oh, "MAP" and "boost sensor" are totally interchangeable terms. "Boost sensor" is just Mazda's name for the part, but it's fundamentally a MAP sensor. The stock ECU uses it in lieu of a vacuum advance on a distributor - since the ignition system is totally electronic, it needs a manifold reference for determining the proper ignition timing. That's why NA's have the boost sensor as well. The boost sensor does NOT affect fuel at ALL - that's why we have airflow meters, the AFM gives the ECU all the input it needs for providing fuel.

Dale

 

That makes perfect sense. Nosing around the displays with my setup (S4 NA, tied into the boost sensor (turbos have a pressure sensor... go figure)), I hit 100% manifold pressure VERY early in the throttle application at low RPM - literally 70% of the pedal travel is useless. This makes sense when thinking about how an engine works, but it means that at low RPM, the high throttle map is coming in too late.

-=Russ=-

 

Dale Clark....can you PLEASE post the thread link about the write up you did on how to wire SAFC to "map" sensor (i search for it and cant find it)

thank you and be appreciated by all newbee here (including me)