Poor man FCD

[morgie]

that's what you have to do when you're poor and want more boost ...

(in fact, that's just a temp setup for this weekend.. a valve that exaust in the atmo. )


HiRez : http://images3.fotki.com/v25/free/2845/ ... img-or.jpg

[-K-]

That will do it
vrg3 drew up a cheap electronic fcd that I plan to build and test, I hope it will even work with the factory boost controler, but we'll see.
If it works I'll let you know.

[vrg3]

-K-, that wasn't ready for production! :)

I haven't had time to try to build it yet, but I did run it past one of my friend's who's also an electronics geek like me and he seemed to agree that it ought to work. We did come up with a couple revisions though.

The 1K resistors (both of them) are probably a bit too small; I'd replace them with 10K resistors probably. And you might want to run the output of the whole circuit through another voltage follower just to make sure the output impedance is high enough.

You can get a pair of LM324 chips from Radio Shack, but if it works, I'd suggest replacing them with LM124 or LM224s which are more rugged and rated below 0 and above 70 degrees celsius. Power the op amps off the ECU's control system ground and power supply lines (which gives them 12 to 14 volts), but use the TPS or MAP sensor power line for the 5 volts needed for the threshold setting pot. That way all signal voltages are within the op amps' common mode input range and output swing but the reference voltage for the threshold is well regulated.

I was planning on trying to build it and then starting a new thread if it worked. If you do build it and it works, you should probably do the same, so we don't end up hijacking two threads.

Funnily enough, my friend might build the exact same circuit to use as a chip to give his Volkswagen TDI more power by modifying the fuel injection feedback signal, tricking the ECU into fueling more.

[morgie]

K : My home made Boost Controler & Blablabla in corporates an FCD... that cheap one was just temporari.. in fact that doesn't work, i would need a one way valve. (as soon as i get vaccuum, Ecu enters in error mode for the map, and as soon as you get 2-3psi, fuel cuts) .

:\

[-K-]

morgie, I know the box you'r making has a fcd. But is it this cool? I've seen what most fcd's do to the signal and this would be far better.
vrg3 don't worry, I have a buddy who has a regulated voltage output to test it on. He has done a lot of work in elctronics but not making up curcits so we thought it might be fun. So I'm not going to blow my ECU or anything. Now what I need is the voltage for positive pressure and for 8.7 psi. My haynes only gives me the readings for N/A cars

[NICO]

morgie ur set up looks very intresting but is this how everyone is doing it. why dont u just plug the vacume line go to the factory FCD. its the other line that goes down to the black box from the brown sensor get pliers sqweez the line & stick a nail in it so it hold s the vacum. u might leen out cuz that brown sensor controls gas & ecu readings.

[vrg3]

K - Off the top of my head, I think atmospheric was something like 2.7 volts or something maybe? And 6psi was around 3.3 volts... This is fuzzy recollection from like a year ago though. You should hook a voltmeter up to your pressure sensor and have a friend see what it reads as he watches your boost gauge while you drive; it's not that hard.

[morgie]

2.6v atmo on the MAP ..


actually, my Cheap FCD doesn't work in that configuration, i would need a one-way valve after the adjustable valve (or no adjustable valve at all)... nyway, i drop this cuzz tomorrow, i'll try to plug my controler, and.. THIS TIME, that little M***** Fu*** will WORK !!!!!!!!!! grrrrrrr

[-K-]

Yeah... and let us know how it goes.