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Old 12-02-2004, 10:23 AM   #1
EA82TRally
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Default FCD info: I come bearing a gift!!!

For those of you who are having problemos muchos with fuel cut, like myself, and have a basic knowledge of electronic circuits and soldering, then I have some good info for you. I found this while searching the net for a preassembled FCD(HKS,APEXi, etc.). Here is a link to the site, and best of all the person who made it listed all part #'s(Radioshack) and made this for a Legacy Turbo!!! Voila!!!!:Clicky

Patrick
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Old 12-05-2004, 03:58 AM   #2
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Vrg3 on the legacycentral forum designed it. Not bad at all for the money.
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Old 12-05-2004, 11:12 PM   #3
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For about $10 and a little bit of soldering handywork, I don't see why anyone would complain. $10 beats $129-$200 anyday!
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Old 12-08-2004, 01:12 PM   #4
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Yeah, the profit margin on almost all FCDs out there is insane. It's almost thievery. Many of them really aren't anything more than the adjustable circuit I describe on the same page.
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Old 12-08-2004, 04:16 PM   #5
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Ahhhh! You grace our presence. I am honored oh incredibly electronically inclined one! LOL

Let me be the first to say THANK YOU, for sharing your knowledge and experience of building a very cost effective fuel cut defencer. I appreciate it(and no, I'm not trying to kiss butt either ). Hehehehe!!!
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Old 12-08-2004, 06:55 PM   #6
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Hehehehee.... You're welcome.

Wait -- you're using this on your GL-10? I thought 80s-era turbos used a MAF-based fail cut. So you're capping off the MAF signal? Are you just using a monster RRFPR or something to meter fuel?
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Old 12-08-2004, 07:59 PM   #7
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Yes from 87 on is MAF. Sounds kinda scary to clamp the MAF signal.
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Old 12-08-2004, 08:41 PM   #8
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Eh... It's no different from the zener diode voltage clamp that all the speed density RS-T owners use, right? They just rely on the rising rate fuel pressure regulator to force enough fuel through the injectors without increasing pulse width. Crude, certainly, but workable.

Out of curiosity, what did you find was the appropriate clamping voltage for the MAF?
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Old 12-09-2004, 12:33 PM   #9
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Quote:
Originally Posted by vrg3
Hehehehee.... You're welcome.

Wait -- you're using this on your GL-10? I thought 80s-era turbos used a MAF-based fail cut. So you're capping off the MAF signal? Are you just using a monster RRFPR or something to meter fuel?
Well, I haven't officially tried to tackle the project yet, but yes I do have a GL-10. I've been trying to do some research to find out what all is involved in bypassing the fuel cut. Haven't really found out anything about it yet, except for the fact that it is there . I have kinda found a slight way to get around the fuel cut issue. I just re-routed the vacuum lines that go to my boost controller, and now I'm running 11psi of boost, just under the factory fuel cut-out. I do however have an RRFPR that will be going on the car as soon as I can figure out how to get rid of the fuel cut. I also have plans for bigger injectors and a bigger turbo, but those mods will have to wait until I return from Okinawa. I was shooting for 200whp, but now with some encouragement from WJM(USMB & NASIOC), I have been thinking about somewhere in the ballpark of 275whp. But we'll just have to see what the future holds.
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Old 12-09-2004, 12:35 PM   #10
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Cool; sounds fun. Keep us posted on how you do.

The RRFPR might be the way to get rid of the fuel cut, like I described.

You'll want something to monitor air/fuel ratios if you try that though. You'll want that when you start tuning with different injectors and stuff anyway.
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Old 12-10-2004, 07:41 AM   #11
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Oh yeah, oh yeah. No doubt. I'll do my best to keep everyone up to date on my progress.

It would be nice if the RRFPR does the trick. My friend Jeff was also saying something along the same lines. Maybe I'll try putting it on, adjusting it, and seeing if it helps the situation or not. If anything, at least I'll know that the engine is getting sufficient fuel.

I've already got an Air/Fuel Gauge, but I have yet to invest in a wideband 02 sensor. I have been contemplating purchasing an EGT gauge for tuning purposes. I just haven't gotten the courage to try and explain to my wife that my car needs "something else." She is already ticked because I just got the car running good and now it needs new struts all around.
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Old 12-10-2004, 10:15 AM   #12
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Fuel cut = 9psi for >5 seconds
clamping voltage ~.5v
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Old 12-10-2004, 11:09 AM   #13
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EA82TRally - Yeah, those things people call "air/fuel ratio gauges" aren't very useful. But, if you're using such a crude method of controlling fuel anyway, you might be okay just tuning for a very rich signal from the narrow-band sensor and safely low EGTs. If you go that rought, you should probably pick up a nice quick-response EGT probe like the one from Team Rip Engineering (http://www.teamrip.com/accessories.html).

How does the EA82T control ignition? Is timing controlled by the ECU?

Don't forget to put the high-output fuel pump in before the RRFPR. The stock pump probably can't do really high pressures like you'd need. And you'd need to put the FCD in before trying to tune with it, because it's what's going to stop the injector pulse width from increasing.

Calebz - Just half a volt? I guess the MAF sensor signal goes down as airflow goes up, then? Is this the flapper-door airflow meter?
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Old 12-10-2004, 11:22 AM   #14
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Quote:
Originally Posted by vrg3
EA82TRally - Yeah, those things people call "air/fuel ratio gauges" aren't very useful. But, if you're using such a crude method of controlling fuel anyway, you might be okay just tuning for a very rich signal from the narrow-band sensor and safely low EGTs. If you go that rought, you should probably pick up a nice quick-response EGT probe like the one from Team Rip Engineering (http://www.teamrip.com/accessories.html).

How does the EA82T control ignition? Is timing controlled by the ECU?

Don't forget to put the high-output fuel pump in before the RRFPR. The stock pump probably can't do really high pressures like you'd need. And you'd need to put the FCD in before trying to tune with it, because it's what's going to stop the injector pulse width from increasing.

Calebz - Just half a volt? I guess the MAF sensor signal goes down as airflow goes up, then? Is this the flapper-door airflow meter?
Typo on my part.. its ~5v and thats for the hotwire type.. I never messed with the vane style.. Although sometimes I wish I had.. they are really easy to bypass fuel cut on..

Though I have to admit.. fuel cut has never been a problem for me.. We'll see how well that works with the new setup.

You mention bigger fuel pump.. The stock fuel pump is rated for 62-72psi.. The stock FPR regulates at 36psi and rises at a 1:1 ratio up to 46psi.. I can't remember what the GPH is right off the top of my head.. I'm sure its in the FSM somewhere, but I believe its somewhere in the area of 30GPH.. that seems like there would be some wiggle room before fuel pump upgrades would become necessary.
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Old 12-10-2004, 11:31 AM   #15
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Ah, okay, yeah, I 'd expect the limit to be close to 5 volts, since that would mean Subaru did a good job of matching the sensor to the rest of the system.

About the pump, the flow number drops as pressure rises, though... A fuel pump rating is a flow vs. pressure curve that does eventually hit zero. And if you cap off injector pulse width and rely on an RRFPR to provide enough fuel, you're going to have to raise fuel pressures a lot because injector flow is sublinearly proportional to the pressure differential across the injector.

You may be right that the stock fuel pump could handle it, but my thinking is that it's probably not worth risking it, particularly if the stock pump might be very old.
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Old 12-10-2004, 03:05 PM   #16
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When I had a 87 GL-10 I was going to just rewire it for the VAM, and 86 ECU. Might be better to just do that, JY parts for 80's subes are pretty cheap. And get a fuel pump, it's a lot cheaper than a new engine.

275 WHP? Are you high? I won't say it can't be done but the wife is complaining about the cost of replacing the struts and you are throwing numbers like that around? out of an EA82T? I hate when guys throw HP #'s around. Have you ever been in a car with 275WHP? Don't take this the wrong way, build a fun fast car just leave the dyno queens to all the "ahh ohhh 275WHP..."
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Old 12-11-2004, 01:58 AM   #17
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get a new car
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Old 12-12-2004, 12:17 AM   #18
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Quote:
Originally Posted by EA82TRally
I was shooting for 200whp, but now with some encouragement from WJM(USMB & NASIOC), I have been thinking about somewhere in the ballpark of 275whp. But we'll just have to see what the future holds.

Hey man, I'm sorry. I just wanted to remind you that 275whp is a HUGE gain. I'm talking 200hp more to the wheels than stock. I dyno'd my RX turbo stock and posted here as well as USMB.


I know Will is pretty encouraging. It's not all about the numbers though. I have the same plans as you as well. Bigger turbo (GT17), header/uppipe and downpipe from TechWorks along with two different intercoolers in my garage (can't decide which to use).


I realized one of my XT6s stock puts out around 35hp more than my RX turbo stock.

It's a shame these cars put out such low numbers and it does it at 5psi of boost. That 7.7:1 compression ratio and low displacement HURTs. You'll need a pretty big turbo (and probably nitrous) to get that 275hp figure you are shooting for. I wish you all the luck.
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Old 12-12-2004, 10:41 AM   #19
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Quote:
Originally Posted by -k-
When I had a 87 GL-10 I was going to just rewire it for the VAM, and 86 ECU. Might be better to just do that, JY parts for 80's subes are pretty cheap. And get a fuel pump, it's a lot cheaper than a new engine.

275 WHP? Are you high? I won't say it can't be done but the wife is complaining about the cost of replacing the struts and you are throwing numbers like that around? out of an EA82T? I hate when guys throw HP #'s around. Have you ever been in a car with 275WHP? Don't take this the wrong way, build a fun fast car just leave the dyno queens to all the "ahh ohhh 275WHP..."
Whoa!!!! Slow your roll for a second!! I have been told by a very reliable source, of EA82Ts that have put out 400hp(keyword:"told"), so don't go knocking 275whp. It is a feasible number with the proper parts and tuning. Besides, I'm not going to get deep into this project until after I return from Okinawa, and that won't be for 4 years. Right now I'm just trying to get input on what will work, and what won't, as this is my first Subaru.

And the only reason my wife is complaining about replacing the struts, is because I refuse to replace them myself. I have grown tired of replacing struts as our former car(2000 Dodge Stratus) was eating the SOBs left and right(It had been in an accident before we got it). So every time you look around, I had to replace them, which was a total of 3 times in 2 years. The 2 alignment shops we took it to, both said that they looked it all over and couldn't figure out what the heck was going on. So we got rid of it.

And as far as riding in a car that has 275whp, yes I've ridden in one. Hell, I've ridden my friend's car(after it was dynoed at Wasabi Racing) that just so happens to be putting out 474whp @ 15psi(95 Acura Integra; completely built motor w/ turbo kit), so how's that strike ya? I have been lucky enough to ride in cars that have produced a miriad of hp numbers in my short life. I'm not trying to build a dyno queen. I'm attempting to build a sleeper that will be able to suprise the pants off a few self proclaimed "Super Cars." That's all.

Last edited by EA82TRally; 12-12-2004 at 10:55 AM.
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Old 12-12-2004, 10:50 AM   #20
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Quote:
Originally Posted by Kevin Thomas

Hey man, I'm sorry. I just wanted to remind you that 275whp is a HUGE gain. I'm talking 200hp more to the wheels than stock. I dyno'd my RX turbo stock and posted here as well as USMB.


I know Will is pretty encouraging. It's not all about the numbers though. I have the same plans as you as well. Bigger turbo (GT17), header/uppipe and downpipe from TechWorks along with two different intercoolers in my garage (can't decide which to use).


I realized one of my XT6s stock puts out around 35hp more than my RX turbo stock.

It's a shame these cars put out such low numbers and it does it at 5psi of boost. That 7.7:1 compression ratio and low displacement HURTs. You'll need a pretty big turbo (and probably nitrous) to get that 275hp figure you are shooting for. I wish you all the luck.
I really appreciate it. The reason for my build up, is that I had some jack@^% tell me,"Oh. You got a GL-10? Those things are slow. You should've got an Impreza." Those words have been burning deep in my soul since that remark was made. I refuse to give up until I get where I want to be, and whoop the stuffing out of his prized Impreza. We haven't raced yet. But we will one day, and I just want to be able to lay the smack down on him, and some of the other little wannabes that are running around here.
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Old 12-12-2004, 10:57 AM   #21
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Quote:
Originally Posted by 05 Subaru-STi
get a new car
Well, why don't you give me yours?
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Old 12-17-2004, 08:42 AM   #22
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BOT:
I run the VRG3 Phase II FCD on my SS and it works great! The ECU never sees more then about 12.37 psi.

It's an easy install too.
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Old 12-17-2004, 12:25 PM   #23
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Quote:
Originally Posted by vrg3
EA82TRally - Yeah, those things people call "air/fuel ratio gauges" aren't very useful. But, if you're using such a crude method of controlling fuel anyway, you might be okay just tuning for a very rich signal from the narrow-band sensor and safely low EGTs. If you go that rought, you should probably pick up a nice quick-response EGT probe like the one from Team Rip Engineering (http://www.teamrip.com/accessories.html).

How does the EA82T control ignition? Is timing controlled by the ECU?
I plan on tuning it toward a rich signal. I still need to invest in an EGT probe & gauge. I don't want to have to replace this motor, as it is the car's second engine and it has somewhere in the ballpark of 46,000 miles on it.

As for the ignition, it is a gear driven distributor w/ electronic timing advance if I remember reading the repair manual right.

I've got a question for you too. Why wouldn't the FCD you designed work on an EA82T? I'm just wondering because after looking at the design again, it seems like everything would work right. The voltage all seems to be the same. If you know why it wouldn't work, could you please explain. I'm still confused on the whole issue. Thanks.

Patrick

Last edited by EA82TRally; 12-17-2004 at 12:30 PM.
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Old 12-17-2004, 01:00 PM   #24
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Quote:
Originally Posted by EA82TRally
I still need to invest in an EGT probe & gauge. I don't want to have to replace this motor, as it is the car's second engine and it has somewhere in the ballpark of 46,000 miles on it.
Just about the cheapest EGT setup is a Westach 712-series probe and a 2A2-series gauge. You can get both of them for something like $75.

Quote:
As for the ignition, it is a gear driven distributor w/ electronic timing advance if I remember reading the repair manual right.
Is there a camshaft position sensor inside the distributor housing? Does the ECU just charge and fire the coil through a simple single-transistor ignitor?

Quote:
I've got a question for you too. Why wouldn't the FCD you designed work on an EA82T? I'm just wondering because after looking at the design again, it seems like everything would work right. The voltage all seems to be the same.
If you want to clamp the MAF sensor signal at around 4.1 volts, the circuit on my FCD page will do the job. If you need a different clamping voltage, just play with the resistances or, better yet, use the adjustable design.

Quote:
If you know why it wouldn't work, could you please explain. I'm still confused on the whole issue. Thanks.
Well, you can't just wire the FCD in and then go play. The MAF sensor is how the ECU knows how much air is coming in. And that's how it knows how much fuel to dump in.

Let's say you do have a clamp at 4.1 volts. And let's say 4.1 volts on the MAF sensor means 150 grams per second, for example (I just picked that number out of the air; it's just a reasonable random guess). Whenever the engine is ingesting less than 150 grams per second, everything should work fine. But once it starts to ingest more than 150 g/s, the ECU will only be aware of 150 g/s flow. So say you manage to flow 200 g/s. ECU won't know about all that air and so you'll run terribly lean.

And if the ECU controls ignition timing, you might need to do something about that too, since it'll be sparking at a time appropriate for the load of 150 g/s. That might be okay if you have a good intercooling setup and an efficient compressor though. You'll have to determine that for yourself.

Basically, at a minimum, to get around fuel cut on your car you need to both eliminate the fuel cut and find a way to increase fueling. Do not for a second think you can just slap on an FCD -- any FCD -- and start increasing boost.

1st-generation DSMs work the same way, I think. You may want to read up on some 1G DSM web sites.
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Old 12-17-2004, 01:11 PM   #25
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Quote:
Originally Posted by legacy92ej22t
It's an easy install too.
'Course it's an easy install when you have the designer come install it for you!
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