How do I make one? ERDT used to have a good writeup/how to make one. I find when im racing it takes too long to open, and I only get power for the last 1000 rpm's or so. Anyways let me know please, thanks...
Well, if I remember correctly, the VICS on the EGTs were operated through vacuum. However... there must have been a solenoid or a delay valve, otherwise it would have opened at WOT every time. I'm tempted to say that my 91EGT had a delay valve and my 95 used a solenoid, but I honestly don't know for sure.
I recently converted my dual barrel single pumper nikki carb to mechanical secondaries, which is the homologue to VICS. The thing used to barely climb hills... now I can hardly keep traction in 2nd gear. Although, I did do some significant re-jetting of the carbs, but having control over your induction really helps. The thing is fast as hell.
What you can do is basically emulate this on a fuel injected car, either mechanically or electronically.
Do you want to do it according to...?
The thing that most people don't realize is the dead spot you'd get in your A/F when you convert to mechanical/manual induction. If the ECU doesn't KNOW that you're doing it, it can't enrichen the mix and you'll lean out and get a dead spot in power.
-- For those of you saying I'm wrong, thinking that the MAS will "see" the secondaries open and enrichen the mix- you're wrong. The thing that ENRICHENS the fuel mix is the time deravative of the TPS position, NOT the MAS. For a really good enrichment system, you should really have a second TPS hooked up to the secondary butterflies... but ford wouldn't do that of course because it's one more cost, and since they know exactly what is happening at that rpm/throttle position, then can account for the enrichment. It's only when you change it that you run into problems. Anyway...
So if you touch it, you have to take this into account.
1. Doing it by throttle position would be pretty stupid. Don't do it this way, but it could be done.
2. Air flux- this would probably be the best way to do it. What you'll have to do is interpret a voltage/resistance sent from your MAS and rig up a relay circuit to open a solenoid valve to open your secondary butterflies. This requires some electrical knowledge, but you could completely customize when they opened.
3. RPM - this is another way to do it, similar to your air flux- since the volumetric efficiency of the engine is known since it isn't boosted, your results would likely be similar.
4. Vacuum - the only way you could really get it to work off vacuum (without electronics or complicated mechanics) would be a delay valve. It would be a crappy way to do it though. It wouldn't be as accurate as 2 and 3, but it would be significantly cheaper and easier.
Either way, by changing when the secondaries are opening you're going to lean out the mix unless you let the ECU know to enrichen the mixture. You CAN offset this dead spot by opening the valves gradually, though. Either way, you'd maximize your acceleration and smoothness of power substantially if you could somehow rig up a circuit to momentarily enrichen the fuel mix when you open the butterfly valves.
I allways use RPM's to open the secondaries. It's a Electric motor so there's no vacuume lines to worry about. Since are air meter's are a MAF, the can see any change or increase it air flow and correct is instantly.
You may get a CEL, since the ECU can see if there not opeing when it tells it to open.
Mind you that VICS/SPI/whatever is progressive, not boolean. What I mean by this is that it isn't on/off. At least not in my 3000GT... therefore operating it by a switch really doesn't make much sense.
It uses a switched ground to activate, so you would need to somehow splice in a switch to ground it but still allow the ECU to control it as well. Only thing I could think of is you could splice another grounded wire (with a switch/button in-line) to the switched ground lead on the SPI motor, and then when you pressed the button it would open.
I did this on mine for about a month or so then I riped it out. I put a switch on a relay so that at WOT the motor would open the secondaries.
Basically when the the switch was activated (by flooring the car) it sent 12 volts to a relay which then tripped the relay from the ECU's signal (Which I believe is normally 5v) to ground. It worked but I didn't really notice that much of a difference at the lower RPM (gas milage went down though).
It also throws a CEL and the CEL doesn't go off by itself after shuting the car down.
It was wired something like this:
When the relay isn't energized:
ECU SPI CONTROL SIGNAL -> RELAY -> SPI motor
When the relay is energized with a 12V signal from the WOT switch:
GND -> RELAY -> SPI MOTOR
Basically when the relay controls aren't energized it operates normally through the relay (from the ECU), when the relay gets 12V it floats the output from the ECU and forces a ground signal to the SPI motor. Viola, your secondarys are opened.
Again I don't believe this will help you much under 3000 RPM as I didn't notice much of a HP gain (I've heard you actually lose torque by doing this mod). I believe ford has set the opening point at 3K for a reason.
Jeff was saying something I believe at one time about a resistor needing to be in the circuit so that the SPI motor didn't get damaged? I forgot specifics on this.
I have experimented with opening the SPI secondaries at lower rpm's and it bogs really bad if you open it at anything below about 2750. Right now I have them opening at ~3500 and it is a smooth transition with no bogging or lag.
i just wired in a switch. stuft a wire into the plug, attached it to a switch, then grounded the other side...works fine for me.I've also put my IAT on a 10k ohm resistor activated by a switch and my ECT on a 5k ohm switch. ALL of them make a difference. IAT advances ignition timing, ECT gives slightly more fuel, and IMRC allows more air. The ECT switch can't be left on too long cause the O2 sensors will balance out the mixture, but I'm workin on that, I just need to know which wire from the upstream HO2S is the signal wire.