while it is still fresh, here are some pointers and answers to questions i had when installing/tuning this marvelous fuel controller. first, here is the yahoo group for the vpc:
DO NOT follow everything here. each car is different, and some of the settings are way different on my car.
the chip inside is a mofo to get out. i think the basic head unit is all the same, just the chip tells it what car it is set for. there are mount knobs on each side, loosen/remove these, and gently pry off the top half of the head unit. the harness is really long. it can probably make it to the trunk. the temp sensor mount is arguable. i have it in the intake, most put it in front of the t/bdy. several posts i have read imply it is better in the intake.
if you drill and tap the intake, there will be shavings up the butt. what i did was remove the throttle body, and get a vacuum cleaner. take an old secion of radiator hose, and cut part of it lenthwise about in half, you will have a "trough" to catch the shavings, and the other end goes on the vacuum cleaner hose. turn that sucker on and it will suck up all the shavings. the temp sensor has a "sleeve" it screws in to, this fitting is 1/8 pipe thread, and it is the part that the intake is tapped for.
the map sensor needs to be mounted with the vacuum port pointing down, and above the level of the t/bdy, keeping the vacuum/boost hose as short as possible. the little filter is a restriction, i removed it, and so have several others.
the head unit dont have to be adjusted a lot, so it doesnt have to be out in the open. i just put it in the glovebox, along with the miles of extra harness. if you get the adapter harness, that plugs into the ecu, then the rest plugs into the head unit, you have to really stuff it in there.
there are 4 knobs, they rotate 360 deg, and do NOT stop. 12 o'clock is the base settings, i am not sure if 6 o'clock is max or min. the knobs lite up, but the names on top of the knobs dont. really dumb. from left to right, response, gain, idle, and op out. the op out is not used, unless you have another hks controller, i think f-con.
response-this controls tip-in. like accelerator pump jets, it adds fuel when the throttle is initially opened. i dont yet know if that means the t/bdy has to be completely closed(which then would be useless) or, rather, when you are just cruising, then step on it. it seems to have some effect on cruise/step on it. you should initially set this at 3 o'clock, from all i have seen it will eventually end up between 3 and 6.
gain-this is explained as lean/rich, in 2% increments. it should initially be set at 9, i have it backed off further to about 7. so, this is in the minus side, if it is set too rich, you will get hesitation a lot like fuel cut, ESPECIALLY at part throttle. i think it has way more effect on part throttle than a mash-it-wot.
idle-this sucker is wacky. it is way on the minus(6 to 9) side, and affects idle below 1300 rpm. i notice overall fuel trims low like to be at 81, and barely cycling. there, it is really smooth, but i still have a hot start problem with it dying. i dont know how much influence the map sensor has on hot start, but i think there is just not enough vacuum. anyway, you will play with this till the cows come home. it will idle smooth, but fuel trims will be confusing.
i have my afc wired in after the vpc. low side i have at 1k, 1.5k, 2k, 3k, etc. here the settings are really wacky. 1k -7, 1.5k 0, 2k -4, 3k -1.
lo and med fuel trims like to be at 81. i am thinking the vpc tries to correct lo and mid fuel to 81, and will fight with the ecu to do this.
i welcome any comments/corrections. this is really a good unit, and now they seem to be affordable. jeff o has chips for them, too.
after living with this thing for a few weeks, i am also seeing-and it is almost unbelievable-a slight INCREASE in fuel economy. 1-2 mpg. even with all the mad boosting being done, because it just pulls so well. the only problem still seems to be a hot start, it really surges a lot. once it is going, it goes away, and it is just at idle.