I'm glad Max and Chris came in to bring a few thing's to our attention. Factor's such as elevation and abient air temps, quality of fuel delivery, and cooling, all of which play major roles. My point was that while yes buying a Walbro will increase the flow of fuel, without an S-AFC you can't optimize the fuel delivery. For me and where I live, my money is best optimized, by using a S-AFC to utilize my stock system so it runs more effectively, efficiently, and safely. What had me bothered as of late reading this forum was all the doom and gloom talk about running anything over stock boost without major fuel mods.
Once again for where I live, raising boost to the level of 10-11psi can be done safely on the stock system if a S-AFC is put into action and tuned correctly.

 

I have been thinking of getting the AFC, but have a few ?s. It just has rpm range and throttle high/low adjustments right. It would seem like that could be hard to tune on our cars since our fuel requirements are BOOST dependent, not RPM. Do you just tune it by RPM for max boost on the high throttle map and then choose to tune the low end rich or the mid range leanish for the low throttle position? It would seem like there would be many transitionary moments that would suffer (well, yes still much better than just a rich running Walbro, but $300 could land a remapped ECU.)
Does anyone produce a air/fuel adjuster with a boost reference line?

 

The first generation of the S-AFC was RPM dependant entirely I believe. I am not sure if the new digital version uses RPM or not, I do however remember Chris Ng saying something about how his is wired to be boost dependant, not sure if this is a feature of the device or if Chris has done some mods to make it this way.

 

The first generation s-afc was completely RPM dependent.. it had one set fuel map to use..It kept things simple and made tuning quite simple as well.. so long as you were driving around at WOT most of the time..

the second gen digital s-afc changed things by basically giving you 3 diffrent fuel maps to work with .. a low throttle setting fuel map, a high throttle fuel map and a somwhere inbetween fuel map..baically you adjusted what percentage of throttle input would be concidered low throttle and what would be concidered as high throttle.. you would then change fuel correction for low and high throttle.. any throttle input between the low and high throttle settings would give you a fuel correction that was interpolated between the 2 "user changeable" maps..
This offered users a little more flexability in tuning their cars for driveability and fuel consumption..however there was a drawback.. series 4 T2's (87-88) used a narrow range TPS, while the series 5 (89-92) used a full range..
peopel with the narrow range TPS would find that they would hit 100% throttle at about 1/4 throttle..it was basically an on-off switch to tell the ecu if you were at idle or not.. while the s-afc could still be tuned for this type of tps, it made it a bit harder to do.. if you were crusing in 4th gear for example, and wanted to accelerate a little bit, if you passed 1/4 throttle you were put into your high throttle map.. however you're at low revs and low boost .. you end up with an over rich situation that either makes your car accelerate slower then it should, waste more gas, and/or even bog or stutter.. not fun
People with full throttle tps's didn't have to really worry about this..

To overcome this limitation with my 10AE (narrow range TPS), rather then hooking the s-afc to sense throttle position, I have hooked it up to sense boost pressure.. I now tune my car to not care about how much I'm on the accelerator, but how much boost I'm actually running.. this might seem like a more elegant way of doing things, however you do have to tune things a little diffrently, taking into account how the FCD plays around with your boost sensor, what happens in low rpm, high throttle situations etc..

okay okay.. once again I'm rambling.. somethign i find myself doing alot these days.. anyways, you get the gist of how the s-afc works I hope..

 

Thanks Chris for the info on setting S-AFC up on the boost sensor instead of TPS, that was a sweet idea! I think I want to do this on my '87 TII, so if you could share any of the finer points that would be great. So, for full throttle map I guess one would tune from full boost sensor output,duh; but since my car runs full stock boost from below 2000rpm do you just dial in alot more fuel at rpms boost is likely above stock fuel cut? for low throttle map do you tune it for 0 boost and let it extrapolate? Thanks.

 

Feel free to ramble all you want, I'm just trying to take it all in.

 

Easy mod that not only performs better, but cleans up they bay a little. I like it for less than twenty bucks.

 

Okay.. umm this might end up being a little mish mashed, but I'll attempt to explain it as clearly as possible..

The digital S-afc has the ability to adjust itself to what the full voltage reading a sensor it's tied into gives it.. The boost sensor on the T2 has a 5 volt refrence voltage given to it.. at any given boost or vacume, the sensor outputs a voltage to the ecu between 0-5 volts.. the more vacume, the less voltage, the more boost the higher the voltage reading.. okay, so far so good..
Now the boost sensor is actually able to see more then 8.5psi boost.. infact the ecu gets the full 5v's signal at aprox 1 bar.. however the ecu is programmed for fuel cut once it gets a signal voltage that corresponds to more then 8.5psi.. following so far?
So what we do to defeat the fuel cut is to install an FCD into the system.. what the FCD does (At least the RB FCD.. I belive the HKS units are a little diffrent) is clamps the voltage at about 8.0 psi .. what this means is that the ECU will only ever get a max signal voltage that corresponds to 8.0psi and therefor will not initiate fuel cut.. This is where the S-AFC does a little magic.. After hooking up the s-afc for boost signal input, and then hitting fullboost a few times, it realizes that the voltage the boost sensor gives out at 8.0psi is the max voltage it will ever see, and so it sets itself to hit 100% throttle (Boost sensor tied into throttle input, so it's going to read the voltages as throttle %) at about 8 psi(come to think about it, I belive voltage clamp comes on a little bit sooner then 8 psi, perhaps 7.5 psi.. but all this applies anyways).. After driving around a little bit and watching your guages, you'll soon find that at the transition between vac and boost (0psi) the s-afc reads a boost(throttle) of about 50%..
super.. now you know your baselines .. the following is how I have my car setup at the moment (These are coming off the top of my head, so don't hold me to the correction values)

I have the s-afc to switch over to the low throttle map at anything under 35% boost reading.. this is aprox -5 inches of vacume... I have my HI throttle setting at anything beyond 60% of boost readings (aprox 5psi).. everything between 36%-59% is given the interpolated fuel map between low and high throttle maps..

I'm running a rewired FD fuel pump along with 720cc injectors.. I'm running quite rich everywhere when I'm off boost, and so most of my RPM settings in the low throttle maps are at about -8% correction.. I have a bit more correction at 4000rpm - 6000 rpm because of the secondaries coming online..

On my high throttle map, I make sure that I am adding some +% correction at low rpms (1000-3500 rpm) not alot.. 1 or 2% betwwen 1000-2500 rpm, 3% at 3500rpm.. this is to add a little safety in the situation that I findmyself cruising along at low rpms, but in high gear (3rd-5th).. it is very possible to hit high boost if you get on the accelerator hard while at low rpm's.. so I make sure I have extra fuel when that happens.. I start leaning things out between 4000-6000rpm.. this is the point when the secondarie kick in, and need to be tuned down.. I start adding more fuel after 6000 rpm to redline..

But this setup is specific to my car and the area (elevation, temperature etc) I live in.. you're car could behave quite diffrently, so please take my settings with a grain of salt..

So there you go.. a quick overview of running the S-afc as a boost/rpm dependent controller.. have fun tuning your car, jsut take some time and try conservative settings at first.. find out what works best for you..

 

I almost forgot to mention another step you guys can do while you are doing the TID mod.... I don't know if you can see it in the pics or not, but the fuel resistor/relay pack that sits in front of the filter is no longer there...

During operation of the car this unit heats up a hell of alot.. (trust me.. it's quite hot) Don't belive me? go for a spirited drive and come home.. open your hood and put your hand on the resistor/relay unit... chances are you'll burn yourself...

Now the problem with this is that it's basically heating up the air in front of your filter.. even if you made yourself a cold air box, you've gotten rid of hot air radiated by the motor, however you havn't gotten rid of the hot air the resistor/relay unit is heating up..

easy fix.. unbolt the unit from the car.. you'll find that it's actually 2 peices bolted onto a metal bracket that it uses as a heatsink.. unbolt the relay and the resistor back and throw away the heatsink/bracket ... now I'm sure you'll be able to relocate these 2 items somewhere else away from your filter.. I've got my relay attached to a bold near the bottom of the radiator and the resistor pack behind and below the airflow meter bolted at a location that used to bolt down a plastic harness for wireing.. I'd run outside and take some pictures.. but I'm too damn lazy right now...

There you go.. the last part of my TID mod..

 

i'll do that!!!

 

Thanks for that info Chris! That tidbit about max pressure sensor voltage exceeding the voltage the ECU uses as reference for fuel cut is interesting. So mabye a good reprorammed ECU really could be good up to a Bar w/ added maps? I have been weary of trying one, lest it be some superchips like rip off.