I was wondering how many of you took advantage of the DIY FCD article on teamfc3s.org, i needed some feedback on how well the setup works, how much of a bitch it is to tune, and where were the parts acquired from? I managed to cross-over all the part numbers to RadioShack numbers EXCEPT for the dual-op amps...where else other than Jameco could you get these? Does anyone know of a possible easy to find replacement part? I have hordes of used circuitry to pirate from lying around.
Also, has anyone ever tried fooling the boost sensor in another way? Most domestic turbo vehicles rely on juggling timing maps and the wastegate pressure signal to control boost and reaction to detonation, not fuel cut. As it is, these systems seem to work well by bleeding off some of the signal to the boost sensor, usually by means of a small bleeder or spring-loaded adjustable pellet valve. All feedback will be appreciated, as it is just a thought and not some ghetto way to handle a delicate situation. This seems to be one of the only places in the world you can get burned for asking if there is another way.

'87 TII
slowly being
brought to higher
boost, safely

 

shut up! we dont want ghetto ideas! jokes

do you have the link for that article? i'd like to have a look

 

I've bought all the components but haven't gotten around to building it as I'm only running around 8psi. I had no trouble getting the components, they all came from Aussie company Jaycar Electronics (we have a shop locally) and cost just NZ$12! I'm suprised you're having trouble finding that op-amp, I thought it was a common item (Jaycar item #ZL-3358 if it helps). When I get it built and working I'll let you know (just don't hold your breath!).

The ways you mention just seem a little imprecise. IMHO, electronics allow you get alot closer to the cut point with more relibility.

 

Right here....I think I am one of the few people that have actually tried this. I even e-mailed Paul a couple of times about some issues about his circuit. He came through for me

First time around I built it on a breadboard, and didnt actually solder the connections BAD MOVE. I installed it right next to the sensor, and of course after 4-5 days some wires got loose. One sec the gauge would read off the scale, and the next it would drop to -20. In the end I got no boost at all, because the +12V got completely disconnected. I stopped, took off the FCD (luckily I made the connections in such a way that I could remove it easily), and took it home. Soldered the circuit onto a normal board, and -along with my DIY A/F meter- I'll install right next to the ECU.

Calibrating it ? Very easy. You just connect the signal with the Vref (to simulate maximum boost), and you trim the var.R so that your output reads close to 3,8V. Thats it. Connect and go !

 

ive always wondered why doesnt someone build a bunch of them and sell them for about half the $ of the racing beat fcd .....i would pay 50.00 for it ......i just dont wanna solder ...im lazy

 

DigiKey http://www.digikey.com/

Why you wanna mess with the boost sensor?&nbsp It only controls ignition retard and has nothing to do with fuel delivery.



-Ted

 

Ted, are you confused? We're talking about a fuel cut defenser! It hooks up to the pressure sensor (just like all the others) to eliminate fuel cut. You're the last person I'd expect to have to explain this to!

 

anybody wants to make them and sell them?

 

Hmmm...I swear the original poster wanted to control boost via trying to fool the boost sensor, but I've re-read the original post a few times, and I guess I misread it!



-Ted

 

Here's the link to what he was refering to. It's a DIY fuel cut defenser:

DIY FCD

 

bump for a good link that most would benefit from.

search and you shall receive

 

As for how well does it work? It works well. How hard is it to tune? It's not. Basically you want to have the variable resistor set to a point where it will only just prevent fuel cut. I think it took me 3 tries to get it right.

Do you have a local electronics shop? (try looking in the yellow pages) They will carry something that will work for you.

 

awesome. Thanks. I'll post everything up when I'm done

 

NZ have you built your FCD yet?
I took a look at this DIY FCD, probally, 2 years ago but didnt end up making it. I never had a need, but I was thinking about doing it while the engine is out... Anyone else have any feedback on it?

 

I built a couple and had no trouble. IF you look in the archeiver on this site there is a thread there that mentions Paul Stokes and the link on how to.

Need parts? Do a Google for MOUSER. Its an outfit in Mansfield Tx and have everything. Then there;s Jameco and other outfits. Just do a GOOGLE search and put in the part number and you'll get enough hits to keep you busy for quite a while. Like I say, MOUSER.com is the best of the best.

Just get a MittyVac and connect it to the boost sensor inlet. Put a meter on pin 2B of the ECU or pick the output off the brown/red wire at the sensor plug and apply pressure. When the voltage stops rising, thats the clamping voltage. Adjust the pot til you get what your looking for. I think I settled on the 3.65vdc as the clamping voltage.

It;s not a big deal. Just do it. I got a box for it at FRY'S. That's another place to access parts but I hate that outfit. They virtually frisk you when you leave and I'm pretty sure it's foreign owned. As in china men. Ah, my racist tone is showing. Oops. Gotta take some more diversity training at work to clean my brain of bad thoughts. Some humor, but I loathe Diversity Training at work. It's insulting to ones character.Your either civil to your fellow man or not and TRAINING isn't gonna change a thing. Though police. Shades of Mao's Little Red Book.

 

Yep, works perfectly. It took a bit of head-scratching for this electronics amateur to turn the schematic into a physical circuit layout, but as long as you take your time and double-check everything it's not too hard.

I did a similar thing. I set mine at 3.7V using the procedure in the article, and had it sitting by the MAP sensor for a while before moving it to beside the ECU. In lieu of a MittyVac (damn they're expensive...) I unplugged the MAP sensor and plugged a 10k-ohm trim-pot into the connector, allowing me to dial up any "pressure" signal I wanted. With one DMM reading the ECU input and another reading the trim-pot output, I could turn the signal up and watch the ECU input follow the trim-pot output exactly until the clamp point and then stop there as the trim-pot output kept climbing.

For kicks, doing this with the engine running allows you to induce fuel cut at idle. Unfortunately my 3/4-turn trim-pot wasn't sensitive enough to determine the exact voltage the fuel cut occurred at, something you'd need to use a multi-turn trim-pot for. According to the voltage vs. pressure relationship in the article, 8.6psi is equivalent to 3.77V, and it was definitely cutting out between 3.7V and 3.8V.

And another interesting thing noticed. Using the same relationship, 3.63V is equivalent to 400mmHg (the top of the S4's boost gauge). Sure enough when I set the trim-pot output voltage at ~3.63V the gauge sat dead on the top of the scale. Maybe it's not as inaccurate as everyone says after all.

 

Interesting article, cool project, but you can get a used RB FCD for like $50 shipped. That's not a bad price if you don't want to go through the hassle of troubleshooting the thing if you are not really experienced with this stuff. I don't mind electrical stuff but my time is worth the $30 savings

 

No it's not. You get paid for all 168 hours in a week?

And you can do it for ~$10.

 

https://www.rx7club.com/forum/showth...5&page=2&pp=15