Plug-and-Play Fuel Cut Defend (PnP FCD)
For the Turbocharged 1991-1994 Subaru Legacy Sport
Sedan
-- And most other vehicles utilizing a separate MAP-based
fuel cut
Original design by the distinguished Vikash Ravi Goel (http://www.graphics.cornell.edu/~v/fcd/)
of the LegacyCentral BBS
The Plug-and-Play Fuel Cut Defend will eliminate that pesky overboost
protection when running more boost than your ECU thinks is safe.
On a 1991-1994 Subaru Legacy Sport Sedan, the ECU can sense up to 29 PSIa
(absolute pressure, includes atmospheric -- about 14 PSIg at sea level)
and will cut the injectors' pulse width if it sees 28 PSIa (about 13 PSIg
at sea level) or more for about 3 seconds. This is to protect against
the extreme overboost condition where the turbocharger's wastegate actuator
sees no pressure and does not open, allowing the turbo to provide as much
boost as it is capable of.
If you are going to be modifying your turbocharged vehicle for performance,
and increasing boost, I absolutely recommend you install a boost gauge
before anything else. I also recommend you drive around normally
with the boost gauge as your only modification, so you can become familiar
with the behavior of your turbo with the stock control system before installing
an aftermarket boost controller. And of course, your engine should
be in good condition and well-maintained before you attempt to raise your
boost level. Forcing your turbo to work harder in order to compensate
for a tired engine will not end well.
The FCD comes with enough cable to mount anywhere in the cabin you would
like to put it. It does not have to be readily visible or reachable,
although it does have two indicator LEDs and an adjustment potentiometer.
The red LED indicates when the unit is powered (pilot light), and the blue
LED indicates when the voltage is being clamped (when the Fuel Cut Defend
is actively preventing your ECU from detecting too much boost). The
20-turn potentiometer allows you to very finely adjust the highest voltage
your ECU will be allowed to see. On the 1991-1994 Subaru Legacy Turbo,
this voltage clamp level should be set to about 3.9 - 4.0 volts, and will
be set before it is shipped to you. If you intend to use the FCD
in a different application and know the volage you would like it to clamp
at, include this information with your order and it will be set for you.
With the PnP FCD kit, a complete installation will take anywhere from
10 to 30 minutes, depending on your skill level and familiarity with your
engine compartment.
The only tools you will need are:
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10mm socket & ratchet, with a short extension (or a 10mm wrench)
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Pliers
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Something to cut with (razor, dykes, etc)
Everything else you will need is included in the kit and has been
configured for the quickest installation possible.
I performed a sample installation on my otherwise stock 1992 Subaru
Legacy Sport Sedan for demonstration purposes.
Want your FCD in an enclosure?
Thanks to Jeffrey Mahanay for this info:
"Here is a part number for the perfect enclosure box for this device.
A radio shack dual "AA" battery holder (part # 270-408) is the perfect size enclosure.
Simply open it, remove the battery contacts with a pair of needlenose pliers,
remove the center partition right up to the contact retaining slots attached to
the boss for the screw, make an opening for the connector and led's and double
back tape the circuit board to the box.
My openings are a bit crude but I needed to get it in the car so I figured I could always buy another box and do a better job cutting the holes next time. The box is only $1.99 so it's not a big investment."
Photos, diagrams, and instructions are below (click on a photo to view
it larger):
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The Plug-and-Play Fuel Cut Defend kit. I originally wanted
to use velcro as the mounting agent, but all the velcro tested failed within
a few days from the heat. The board now comes with a piece of exterior-grade
mounting tape on the bottom.
Note the single wire facing the opposite direction; this is the +12V
wire that goes to the pressure exchange solenoid. The other 4 wires
go to the pressure sensor.
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The stuffed FCD printed circuitboard.
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This is the pressure sensor / exchange solenoid / wastegate control
assembly. Remove the three 10mm bolts holding it in place and lift
it up a bit to access the MAP sensor's 3-wire connector.
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Remove the brown 2-pin connector from the Pressure Exchange Solenoid
on top of the assembly for easier access. Put one of the quick splices
/ scotch locks on the yellow wire with red stripes (on the brown
connector), and insert the red wire (+12V) from the FCD cable
into the other end. Squeeze the metal piece all the way into the
scotch lock with your pliers, ensuring that it grabbed both wires firmly.
Close the scotch lock's outer plastic.
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Look under the MAP sensor for the 3-wire connector - disconnect
it for easier access, and use your cutting implement to remove the outer
cover for access to the 3 wires. Put another scotch lock on the connector's
green
wire, insert the FCD's shield (ground) into the other
side, squeeze the metal piece all the way in with your pliers, and close
the outer plastic.
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Put another scotch lock on the connector's red wire, insert
the FCD's white wire (+5V) into the other side, squeeze the
metal piece all the way in with your pliers, and close the outer plastic.
Now for the MAP sensor's white signal wire, the only one you
will have to cut. You will have to put a scotch lock on both the
connector side and the sensor side of this wire once you cut it, so ensure
you leave enough room on both sides when you do so.
Put a scotch lock on the sensor side of this cut white wire,
insert the green FCD wire (signal input from sensor) into
the other side, squeeze the metal piece all the way in with your pliers,
and close the outer plastic. Make sure the cut wire is not sticking
out of the end of the scotch lock, so there is no chance of a short.
Put a scotch lock on the connector side of this cut white wire,
insert the black FCD wire (signal output to ECU) into the
other side, squeeze the metal piece all the way in with your pliers, and
close the outer plastic. Make sure the cut wire is not sticking out
of the end of the scotch lock, so there is no chance of a short.
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Now you're finished with the hardest part! Reconnect the
two connectors you previously removed, maneuver the assembly back into
place, and reinstall the three 10mm bolts.
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There are many ways to route the wire -- you could go through the
firewall if you'd like for an ultra-clean install. I chose the quickest
and simplest routing - run it under the hood as shown here...
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... then, run it through the gap between the quarter panel and
the door, and up behind the dash and the windshield as shown here...
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...choose a location for the FCD itself, place the velcro there
and on the bottom of the circuitboard, and mount it. Connect the
wire to the 5-pin header on the board (please double check which pin is
positive + and ensure this is connected correctly. While there is
a diode in place to prevent damage to the FCD should this connector be
plugged in upside-down, there are no guarantees on what might happen
if the vehicle is driven with an improper connection here -- please see
the below disclaimers) and hide the wire as you see fit. The wire
can reach pretty much anywhere you'd like it to. I chose this central
location so I could see the LEDs while driving, and adjust the potentiometer
if necessary without any trouble. It was also very easy to mount
here.
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I chose to coil the extra wire behind the strut tower, under the
hood. This is, again, up to you.
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Here is a basic schematic drawing in .PDF format with quick installation
info if you'd like to have a single printed sheet with you during the install.
I found it very useful and convenient during mine.
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There are two ways to purchase this Fuel Cut Defend:
The complete Plug-and-Play Fuel Cut Defend kit as shown above
sells for $50.00 USD + shipping / handling costs.
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CpE-SLFCDk
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$55 shipped to continental U.S.A.
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CpE-SLFCDk-Can
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$60 shipped to Canada, Hawaii, or Alaska
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CpE-SLFCDk-Int
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$50 + shipping internationally (calculated)
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Or, if you would like to be more involved with the FCD, you can purchase
just the empty printed circuitboard with a list of parts & suppliers
for $20.00 USD + shipping / handling costs.
This would require you to create your own cable, obtain your own components,
stuff your own circuitboard, and solder the parts in.
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CpE-SLFCDb
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$25 shipped to contintental U.S.A.
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CpE-SLFCDb-Can
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$30 shipped to Canada, Hawaii, or Alaska
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CpE-SLFCDb-Int
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$20 + shipping internationally (calculated)
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I prefer Paypal (using my email chris.paiano@gmail.com),
but will also accept personal checks, money orders, or cashier's checks.
Paypal orders will ship immediately, whereas any check-based orders will
not ship until the funds have been cleared. Depending on the shipping
method you request and your location, shipping costs will vary. Please
email me (chris.paiano@gmail.com)
with your specifics to get a shipping quote.
The majority of domestic orders will be covered by $5
shipping / handling.
For international shipping, please calculate shipping based on a
10" x 13" x 1" package (envelope) weighing approximately 1 lb from the
mailing address below, and select your service (USPS, UPS, FedEx).
Or, email me with your shipping address for a quote.
I can prepare custom, easy-to-use PayPal invoices / money requests
to international customers with shipping costs included.
My mailing address to send orders to:
Chris Paiano
462 MVR Unit 16
Elko, NV 89801
Disclaimer: Please use this
product responsibly, always watch your boost gauge, and immediately stop
pushing your vehicle if you see more boost than you intended to set!
I will accept no responsibility for any damage resulting from use of this
product -- by installing the Fuel Cut Defend, you are removing a safety
feature in lieu of increased performance. Please do not run more
boost than your current setup can safely provide enough fuel for.
On a 1991-1994 Subaru Legacy Turbo at sea level, stock boost is about 9
PSIg. With a properly-installed intercooler and a more free-flowing
exhaust, it should be safe to run around 13-14 PSIg on the stock fuel system
with the stock VF11 turbocharger, assuming everything is running properly.
Additional disclaimer: Please
keep in mind, you are working with a sensitive signal that directly connects
to your car's ECU! While the FCD does have a diode to protect itself
from a backwards cable, this does not ensure that your ECU is protected
in any way. Charges of static electricity, two wires touching, wires
touching metal, or poorly-installed scotch locks / connections can result
in serious damage to your ECU, pressure sensor, and related systems!
Plugging in the connector off-center (i.e., to the wrong pins) will have
unpredictable results. Always keep track of where the positive +
pin is on the FCD and on the connector / wire, always discharge yourself
by touching some car metal before touching any wires or equipment, and
don't drive with an improperly-wired FCD as this can seriously confuse
and damage your ECU. I will accept no responsibility for any damages
resulting from the improper wiring, handling, or misuse of this product.
Number of website visits to http://fcd.chrispaiano.com
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Last updated: 9/11/2010
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