Cheap Electronic FCD - Revised

vrg3 · Post by **vrg3** » Wed Nov 28, 2007 6:47 pm

Long overdue, but...

If you want to lower the threshold of the FCD, replace the 10K resistor with a higher resistance. If you have an already-built FCD of this type, an easy way to do it would be to just wire a resistor in series with the wire that goes to +5v.

So, you're at 2600 feet... so barometric pressure is somewhere around 13 psia? Assuming the overboost threshold is still about 13 psig, that'd mean we'd want to clamp below 26 psia. Plugging that into the sensor transfer function says we'd want to clamp below about 4.1 volts. We'd want a little wiggle room too though...

So. If you haven't built your FCD yet, or can modify it, use a 15K resistor instead of the 10K resistor. That'll clamp at about 3.8 volts, or about 24 psia.

If your FCD is already built and you don't want to (or can't) modify it, try putting a 4.7K resistor in series with the +5v wire for the same effect.

ciper · Post by **ciper** » Thu Dec 06, 2007 1:32 am

Would anyone be interested in prebuilt FCD of a similar (though slightly better) design?

I had a bunch made YEARS ago with the intention to sell them to you's guys but then my life got flipped turned upside down.

beatersubi · Post by **beatersubi** » Thu Dec 06, 2007 8:13 am

ciper wrote:Would anyone be interested in prebuilt FCD of a similar (though slightly better) design?

Yes.

ciper · Post by **ciper** » Thu Dec 06, 2007 9:52 am

I will try to track down the details and then dig them out of my friends storage shed. I outsourced them to India and they came back looking great

edit: Dang! Although the design is pretty different the function and installation is nearly exactly the same as VRG3 LOL. I guess a price war is in order with Chris Paiano

SubaruNation · Post by **SubaruNation** » Sat Mar 15, 2008 9:27 pm

ciper wrote:I will try to track down the details and then dig them out of my friends storage shed. I outsourced them to India and they came back looking great

edit: Dang! Although the design is pretty different the function and installation is nearly exactly the same as VRG3 LOL. I guess a price war is in order with Chris Paiano

i need one

All_talk · Post by **All_talk** » Mon Mar 24, 2008 9:46 pm

Just FYI, I built one of these this weekend... Works great!

Gary

SubaruNation · Post by **SubaruNation** » Mon Mar 24, 2008 11:19 pm

All_talk wrote:Just FYI, I built one of these this weekend... Works great!

Gary

you mind sharing with me/ the class how you did it?

All_talk · Post by **All_talk** » Tue Mar 25, 2008 12:19 am

Well I just followed the schematic, I used that Radio Shack universal IC board and they didn’t have a 20K trim pot so I subbed in a 10K. By my math that gives me 3.5V to 5V adjustability. I bench set the reference voltage to 4.1, then road tuned it up to fuel cut, then back 1 turn (about 1 to 1 1/2 turns above the bench setting). I didn’t take any pictures, but I sure wouldn’t wanna show off my soldering skills, its been years since I did any board work and its not so pretty. Front side looks real nice though. Its wired and mounted under the hood at the MAP sensor. I put it in a “sealed” package (super ghetto), if I can figure out a way to keep the adjusting screw open (not that I really need it now) I might pot it in some epoxy. I can take a pic of the finished install if ya like.

Gary

SubaruNation · Post by **SubaruNation** » Tue Mar 25, 2008 3:43 am

that sounds way too intense for me...

i mean i installed my own fog lights but... I'm kinda worried about this one.

could somebody build on of these for me and i'll send them reasonable fundage? please?

All_talk · Post by **All_talk** » Tue Mar 25, 2008 4:40 am

Here's a couple of pics, the "packaging" is the plastic lid from a can of turttle food, the board is isolated with foam on both sides, then the whole mess wrapped in tape. If fuel cut is what ails ya, this big black pill is the cure.

Gary

asc_up · Post by **asc_up** » Tue Mar 25, 2008 5:06 am

Any chance you could make some of those 'big black pills' and sell them?

SubaruNation · Post by **SubaruNation** » Tue Mar 25, 2008 5:10 am

asc_up wrote:Any chance you could make some of those 'big black pills' and sell them?

PLEEEEEEEEEEASE!!!!!!!!

All_talk · Post by **All_talk** » Tue Mar 25, 2008 6:15 am

Isn't Chris selling them here?

http://fcd.chrispaiano.com/

SubaruNation · Post by **SubaruNation** » Tue Mar 25, 2008 9:57 pm

i was hoping to get one cheaper than that

i will look into it though, thanks for the link

asc_up · Post by **asc_up** » Tue Mar 25, 2008 10:22 pm

Are those still available?

I just don't want to send money and find out later that he went out of business or something...

SubaruNation · Post by **SubaruNation** » Wed Mar 26, 2008 9:18 pm

and better yet, +1 i'd like to know

farfrumwork · Post by **farfrumwork** » Fri Jun 20, 2008 5:51 pm

I had the VRG FCD (like version 1 or something) that I bought used here and when I installed it I still had the dreaded cut (around 13-14psi)

I removed it and installed a mechanical valve (releases at 10psi), and that worked ok..... but it would still hit cut when cold, and I was unsure of the effect it had on the MAP sensors ability to monitor boost.

So enter Vikash and his recommendation for modifying the FCD for altitude (I live at 5500ft ASL). I soldered a 4.7kohm resistor in series with the +5v wire as described above and resintalled the unit. So far (1 week) I have no fuel cut, the car runs smoother, and I'm getting better mileage (not sure if this is the FCD, but it makes sense if the mechanical unit was messing with the MAP sensor readings).

So thanks again Vikash!!

-Chad

Boostedballs · Post by **Boostedballs** » Fri Jun 20, 2008 10:17 pm

Would it be better to just install the GM 2.5bar MAP I have laying around? What would that do for me?

Post by **Legacy777** » Tue Jun 24, 2008 7:12 pm

It wouldn't do anything for you since the ECU isn't calibrated to use it.

Boostedballs · Post by **Boostedballs** » Sun Aug 31, 2008 3:05 am

All of the schematic links are dead!

I have my car running great now and I want to up the boost a touch.

I even bought the components to build it and I deleted the schematic from my work computer (because I'm quitting on Tuesday) because I assumed I could just download it at home. OOOPS!

please help!

corsair · Post by **corsair** » Sun Aug 31, 2008 4:05 am

I posed you a link to the schematic in your other thread balls.

here it is for anyone else interested
http://www.monasdivas.com/tmp/FCD/fcdsch.pdf

Post by **Legacy777** » Wed Sep 03, 2008 5:41 pm

I'll try and get to putting the files I pulled down from the internet archive.

Grayguy · Post by **Grayguy** » Sun Feb 08, 2009 6:54 pm

IS there a parts list somewhere for building this, short of paying the $25 to get one? I kinda thought there should be since Vgr3 posted this up as free info to begin with...

magicmike · Post by **magicmike** » Sun Feb 08, 2009 7:35 pm

Grayguy wrote:IS there a parts list somewhere for building this, short of paying the $25 to get one? I kinda thought there should be since Vgr3 posted this up as free info to begin with...

I don't think there is access anymore to any of his stuff. The guy is a genius and created/invented new techniques or circuits on many different occasions only to have his hard work stolen or used without even giving credit to him which I think is what hurt him the most. The fact that some people proffited from his designs and offerend no monitary payback makes me ill, you know who you are and shame on you.

94legacy2.2 · Post by **94legacy2.2** » Tue Feb 17, 2009 3:43 am

so just wondering on this FCD

Ive made them before for a dodge. Its a 3 wire electronic module. Much easier then above.

So the one I have or have built needs the 5volts in, ground and signal.
Would this work for the subie aswell?
If so All I need to hook up on the Subie wires are the red, white and black wires
Red= 5volts
White= Signal wire
Black= ground

Ill post a diagram of it here in a few

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Cheap Electronic FCD - Revised