At this site.. http://www.teamfc3s.org/info/articles/fcd/diy_fcd.htm

a fellow named Paul Stoaks shows how to make a fuel cut defender. Cost...about fifteen bucks maximum.

The question: In the diagram of the fuel cut defenser I need confirmation that D1 and D2 are soldered butt to butt and connect to C1 at one end and +12V at the other.......and that the wire b/t R2 and the LM358 pin 3, IS NOT soldered b/t the D1 and the D2.

I'm 90% sure the the wire b/t R2 and LM358 pin 3 , is not soldered b/t D1 and D2........but there is 10% doubt.

Perhaps THE ICEMARK??? would know or one of you that has the knowledge.

 

WOW! this reads like a different language to me.... come now and amaze me rotor gods!

 

I built one using those same directions about 6 months ago, and I couldn't get it to work, I stuck it in my glove box and bought a RB one instead. I was going to take it all apart and start over, but a friend of mine needs an FCD so I gave it to him to fix.

 

sounds right to me. the part where the gate is (and,or,nor can't remember) i think it might also connect between the two diodes.

 

Holy crap I have to do this!

 

I followed those directions to the T. I even bench tested the fcd and was able to make it clamp at a specified voltage. Unfortunatly when I finally hooked it up in the car, I reversed the polarity and fried the IC.

If anyone wants a free diy fcd, talk to me. All you need is a new IC costing about 2 bux from Radio Shack or Mouser.com. Maybe a new diode as well, but I cant imagine anything else is bad on the thing. Hell, someone can use it for parts!!

It would have worked for me but I'm an idiot.

 

It's a bit tricky to make unless you're VERY familiar with electronics, and there ARE some bugs in the document. I built mine (with the help of an EE friend) YEARS ago, back when Paul was still around, and he sent me documents on updating the design.

You can pick up FCD's used fairly cheaply, and new ones aren't that bad - I'd recommend buying one instead of trying to make the circuit. Unless you're REALLY good with electronics and love to tinker (as Paul did), just buy one.

Dale

 

the wire b/t R2 and the LM358 pin 3, IS soldered b/t the D1 and the D2.

When looking at the schematic remember that a higher voltage will flow through the diodes in the direction of the arrow.

By soldering the input of the op-amp between those 2 doides you're ensuring that the voltage into the op-amp will never go above 12V or below 0V. (for the purists I know this is not quite true but close enough in this case)

Thanks for the link........do you have another for cheaply fooling the ECU to increase the duty cycle of the injectors???


zub

 

No it's there. Ignore the pin numbers and just get the schematic to the op amp you buy and follow the diagram. Some of that circuit is pretty wierd and I think you could do without (eg. D1), but just do it anyway.

Contrary to my sig, the FCD isn't on my car yet, I'm really lazy and only hitting 7psi max. However, I benchtested it. Schematics are easy to follow once you've got the basics. I'm in 4th year ECE and you'd be shocked at how bad I am at circuit analysis. For my 4th year project (sort of like a thesis) I'm builidng an AFC, anyone want to preorder?

 

ZUB.....you be THE MAN! After going to work and talking it over with a friend, we figured that it had to be soldered. Only way the diodes made any sense, especially when we read on the description of the diodes in the article.

DCFC3S.....I'm doing this absolutely **** backwards. I bought a fcd from ROTARY PERFORMANCE in DALLAS, TEXAS already, 90 bucks.

Its just something came over me. I've known about the PAUL STOAKS article for a couple of years now and I'm driven to make one. I ordered the parts from JAMECO monday. Cost is under ten bucks if you don't count shipping and the other parts I bought.

I hope it works. Paul Stoaks is one fine fellow. I read his article on bac's and the possibility of the transistor in the ECU being blown. I used his information to restore my spare ECU for turbo.

Its a shame someone can't go to that article that shows the diagram, and insert a dot where the two diodes should be soldered to the input to the op amplifier.

 

HAILERS....you been around in the 7 community for longer than me.

If you could get permission from teamfc3s we could modify the pic and send them a new one to put up. Wouldn't be too hard at all and would make the thing much clearer.

zub

 

Right after I make that little puppy, I'll make that request to that site. I want to make sure it works first. Maybe if it works, I can make a scan of it on the scanner.

Snrub.....you be the man too. Somehow I missed your post earlier. I was probably writing when you posted and I missed it. And yes, I'll buy the first AFC you make. I only think that as the first buyer I should get a discount. So $9.99 seems a fair and just price for the first one off the bench. Thanks for the information on the fcd.

 

I checked the clamping voltage on the store bought fcd today. Sad. It clamps at 3.20v. Not good at all. Fuel cut is at 3.65v. Wonder why they set it so low.

 

Zub, or anyone else that might know.........(EE types).
and I apologize if this is thread hijacking.

I want to build an adjustable rpm activated switch - I know you can buy them from summitt, msd, etc. but I like soldering together $5 of parts to make something useful!! It is for a VDI manifold on a series 4 car.

I built the following device, but it is not configured to switch a relay.

Would you know what I would need to do to make it work? As it is now, I can see the LED pulsing (input is the tach connection on the trailing coil). When I increase the resistance with the pot, the LED glows only faintly, still pulsing; then as rpm increases, the LED will again light, with pulsing proportional to rpm. So it seem the basics are there to make it workable, but I don't have a clue, just a soldering iron.
I am concerned about the pulsing, though. Would that be a problem for a relay coil? One thing springs to mind - the transistor in the diagram isn't spec'd, and I used what the elec. shop person thought would be O.K.

http://home.maine.rr.com/randylinscott/mar21.htm

Help is much appreciated.........
Thanks,
Curtis
'86 GXL autox'r

 

dang, you fixed that ECU? Rats! I knew you were scammin me!!!! HAILERS!)&*$!)$ Haha, I'm just kidding man, glad you fixed it

 

hey guys Ifound this link to shed some light on the subject
http://www.ggimages.com/rx7/fcon2.jpg
does anyone have any picsof the finished product??

 

Hailers-I did it the easy way-got in touch with Paul and traded some parts for an FCD and 2 rebuilt wiper switches.The FCD works fine.

 

Six Rotors......Good for you. Like I said in a earlier up above, I have a RB bought thru Rotary Performance. I a bit puzzled by it. I put a meter on the output to the ECU. Then put a MITTYVAC on the pressure sensor and applied pressure. The clamping voltage of the RB fcd is 3.2 volts.

Fuel cut happens at approx 8.6 psi. The voltage to the ECU from the factory sensor w/o fcd, will be 3.65-3.75volts when that happens.

Seems the fcd should be set higher than 3.2 volts. Seems you'd want it set as close to fuel cut voltage as possible so the ECU will follow the maps as far as possible. Make sense??? Sure.

That said, my EdgeTech 02 meter says I'm at 11.2afr to 11.4afr when winding out in third to six grand(touching ten psi), so I'm not tooooo worried. Seems the timing isn't going to be correct if the voltage clamp is at 3.2v, though. I'm fairly sure the timing advance/retard is controlled at least partly by the boost/pressure sensor. Don't know for sure.

 

Thats awesome! 5 stars for this. LETS HOPE MANY PEOPLE see this and save the $80 that RB charges!

 

Just finished soldering one up and getting to the point where you adjust the pot(read article). I set it at 3.65(the RB one that I have is at 3.20v). So now I spend the rest of the day finding a male connector and putting some kind of potting compound on the connections.

Although not thru yet, I can see the value of buying a store bought one. First you don't have to round up the parts. I ordered them from Jameco, and to save on expenses, shipped slowwwww boat. Still has not arrived. It will be on week tuesday. I went to FRY'S yesterday and rounded up all the parts except the N914 diode. Got it from RadioShack. I also bought another soldering iron from Fry's. The one I own is toooo big and clumsy.

So now you've wasted time and effort rounding up parts. Don't forget the soldering iron cost if you don't have one. HAS to have a small tip. Then take a look at the OpAmp that makes this work. Look at the tiny pins on it. Even as a dead bug you've gotta be careful. Not too much heat like the man said.

The one I made really looks sad as far as the soldering. Its functional,(solder joints are good) but sad looking. And its not in a case. I just bought a board and JBWelded the OpAmp and pot to it. I'd have been better off if I had selected a larger board where I would have had more room to work. The tiny box size isn't needed if its put next to the ECU instead of the engine bay. Screw tiny boxes.

Back to finishing up. If you have any soldering skills I recommend making one over buying one. As of now it works. I'll put plugs on it and put a MittyVAc on the pressure sensor and make sure it clamps the voltage. So far so good.

 

The RB one is made with a safety margin. By that I mean with all the tolerances in the circuit it's not always going to read 3.2Volts. When you operate over a wide temp range the output of the circuit is going to change according to the tolerances of the components in the circuit.

Likewise, although your homemade one will work great at room temperature on the bench and put out 3.65 volts, when it's in the car and starts to get warmer or cooler then the output is going to change and you may hit the cut-out again.

There are ways around this but it costs a little more and is a little bit more involved.

Remember some gas is better than no gas.

slvr7....did you get my PM??

zub

 

Finished it off yesterday. Works plenty good fine. I adjusted its pot and while doing so put the mittyvac on the sensor and put pressure it. Monitoring the output I can see it clamp just about anywhere I darn well please.

I also noticed that without the fcd, I can idle the car and with the mittyvac raise the pressure to the boost/pressure sensor and hit fuel cut at idle. Duh. Runs a little rough at idle on one rotor.

Should be getting my original parts from Jameco today so I can make another, but this time a little neater. Enough of fcd for awhile. On to bigger and better things. Maybe a datalog for the TechEdge 02 sensor of some sort.

 

Here's a picture of a constructed one unmounted and no plugs. Really don't need all those wires. Like two go to 12v power so they can be spliced together and two go to ground and they can be spliced together.

About three bucks worth of parts there. Depends. Like JAMECO sells the Cermet pot for about a buck sixty but Radio Shack sells it for three fifty.

JPG:

 

Picture of the bottom. I make no apology for the solder job. I did it during breaks and lunch with a hugemongous soldering iron at work.

Jpg nickel:

 

Picture of the bottom. I make no apology for the solder job. I did it during breaks and lunch with a hugemongous soldering iron at work.

Jpg nickel: