technine

I am about to get one and need to know if anyone here is running one and if they have any issues. Filetofit seems to be a straight up guy so I just wanna know about the product. Any probs with it? I know it supposed to work like the AFC and the SMC, but does it really perform like that (people who actually used it).

TIA

asianspeed

I've got it, but I haven't installed it yet. I read one post from a user that was satisfied, and I think filetofit know's his shhit. I'm still waiting for an update on his map limiting/timing retard circuit. But I'll let you know how his map limiter works for me in about 3 weeks when I get everything installed. Good luck.

technine

That is a good suggestion. I'm gonna be looking for one that I can mount in my glove box for in cabin tuning. Hope they make one that is just a display and not a multimeter kinda device.

Thanks for the reply afropuff, he's making me one as we speak.

zip

I don't think filetofit's circuit works like the SMC, or VAFC(SAFC) since fuel delivery isn't based on rpm. It mainly cuts the MAP voltage and keeps it clamped below 3.0V

filetofit

Correct, the circuit is not RPM based it's vacuum/boost based. It knocks down the MAP voltage that the ECU "sees" just like the SMC or AFC hack does. However unlike the SMC or AFC the knock down factor is not based on RPM, it is based on the vacuum/pressure in the manifold.

For those used to seeing 3-D fuel maps think of it this way. Manifold pressure is on the x axis, RPM is on the y axis, and fuel injector pulsewidth is the dependent variable, on the z axis. The SMC and AFC apply a unique scale factor along the entire x axis (MAP voltage) for a particular y (RPM) value. My circuit board applies a unique scale factor along the entire y axis (RPM) for a particular x value (MAP voltage).

A side effect of the circuitboard's construction is that the voltage is limited to around 3.0 -3.1 volts which puts you at or under the CEL threshold.

The net effect is the same, since to a pretty good first order approximation, engine fuel demand is a linear function of RPM and MAP.

technine

So cutting out the RPM adjustment really doesn't matter, right? All that really matters is what the MAP signal is doing, right? So you don't adjust by RPM, you adjust by manifold pressure, wouldn't this be better to do because it seems like everyone just adjusts a certain -% across the board anyway form all the replies I heard about the SMC and the AFC hack.

filetofit

To tell the truth since most people apply a constant across the board cut of about 35% the same thing could be accomplished with a single $2 potentiometer from radioshack. But having some adjustability at different points is desireable since idle can be a little pesky to get right.

1.8T_EG

filetofit : any word on when this will be done?

technine

In the pic that someone posted of the circuit, you have 3 potentiometers and I guess it's an eprom chip or something. I remember you telling me their was idle adjustment and I think WOT adjustment, is the other for part throttle adjustment?

filetofit

Actually the latest ones I've been making only have two adjustments, idle and WOT. The third one was kind of an overall amplification adjustment which I eliminated.

zip

Tuning for fuel is always based on the MAP signal and rpm on any factory ECU or standalone. Check out the fuel table below.



So, for both the SMC and VAFC you'd have the same columns and rows essentially expanding the fuel delivery scale for boosted conditions. Both the SMC and VAFC can behave similar to filetofit's if you set the correction the same throughout the rpm regions.

The rows add the rpm regions which is the key factor in tuning. The SMC has more flexibility in terms of being both applicable to turbo and sc applications. Superchargers, especially Jackson Racing, do not need the same amount of fuel across the board. Leaning out the mixture at high rpm is key to getting good power since they aren't intercooled or compressor efficient, compared to a turbo setup w/ a intercooler. The percentage cut maybe the same for similar setups (i.e. 6-8psi, intercooled, and DSM 450cc injectors). With some other setups I've experienced, such as 550cc and 10-12psi; the idle, mid, and high rpm fuel enrichment is not the same. With a one dimensional voltage divider circuit it's impossible to differentiate fuel delivery at various rpm regions especially with volumetric efficient high rpm Honda engines.

The SMC also has added features such as reverse/surge voltage protected circuitry for long-term reliability, internal voltage clamp to prevent CEL for the MAP sensor, logic circuitry to prevent the barometric CEL common in some VAFC setups, one touch EEPROM programming for great dependability, on-the-fly tuneablility, enclosed package, and much more.

My two cents.

1.8T_EG

do you have an updated schematic for this new one?...

filetofit

Naah, I never bothered to post a new schematic. Functionally it does the same thing, it's just one less pot so it's a little easier to build and tune.

For those of you keeping score at home I've been toying with the idea of adding a third point of adjustability so that at boost onset you can change the slope of the MAP output versus input curve in a non-linear sort of way but I haven't got around to building it. I know how to do it but laying out the board is a PITA.