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Diode Mod (aka. Clamping The MAP)

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Diode Mod (aka. Clamping The MAP)

Post by LhYnxz on Tue Oct 21, 2008 7:31 pm

(Click here for a text-only version)

What does the Diode Mod do?
The MAP (manifold absolute pressure) sensor is what reads how much
actual boost you are making It sends that signal to the ECU (engine
control unit). Once the data that the MAP has collected has been sent
to the ECU, it then compares it to the specified boost that the car is
supposed to be making (this is one parameter a chip modifies among many
others). If the ACTUAL boost is over the SPECIFIED boost then the ECU
puts the car into LIMP MODE. Limp mode is a safety mode so that the car
does not make more boost then it is supposed to. This is an attempt to
stop you from damaging the turbo or anything else.

There are 2 types of limp mode...soft limp where the ECU only allows
the car to make 15 lbs of boost and there is a hard limp where the ECU
only allows the car to make 5 lbs of boost.

The DIODE(s) is connected to the correct wire(s) in the MAP sensor
wiring harness. Before I continue let me first explain what the 2
different diodes clamp the boost at (ill explain what clamping the
boost means later). The 4.7 clamps the boost at 17PSI and the 4.3
clamps the boost at 11PSI. The MAP sensor sends signal to the ECU is
voltage increments (so for 10PSI there is a corresponding voltage that
is sent to the ECU when the MAP is reading 10 PSI).

The MAP sends 4.7 volts to the ECU when itís reading 17 PSI and 4.3
volts when itís reading 11 PSI. Once the diode(s) (whichever size you
chose) is connected to the correct wire(s), the MAP sensor continues to
read the actual boost that the turbo is producing and sends the voltage
signals to the ECU corresponding to the amount of boost its reading, UP
UNTIL THE VOLTAGE THAT THE DIODE IS INTENDED FOR. (For
example...if you have the 4.7v diode in the MAP will send the voltage
signal to the ECU up until its sending 4.7v...once it hits 4.7 volts it
will keep sending 4.7 volts instead of sending the ACTUAL voltage for
the ACTUAL amount of boost the sensor is reading which would be greater
then 4.7 voltages, which would ordinarily without a diode installed,
send the ECU into limp mode).


Therefore, it "tricks" the ECU into thinking it is only making 17PSI
(because that is what the 4.7 volt diode clamps the MAP sensor at)
instead of seeing what the turbo is actually making. Since the ECU is
receiving signal from the MAP sensor showing that the turbo is only
making 17 PSI (with the 4.7v diode in), which is what the specified
boost is for a chipped ECU, THEN THE ECU WILL NOT PUT THE CAR INTO LIMP
MODE - AKA, you can run as much boost as you want without hitting limp
mode!

(Explanation courteousy Spooled_AWP - Thanks John!)



This mod will result in the following:
1. Enable the operator to switch between three boost settings: stock mode, 11PSI and 17PSI - on the fly!


Listed below are the parts and tools necessary to perform this
modification. I have provided several links as examples where to
purchase each item. NOTE: All electrical connections were joined
together by soldering.

WARNING: This mod was performed on my 2001 Volkswagen Jetta. I
cannot gaurantee this will work on your vehicle. Work at your own risk.
Installation times will vary upon the installer's experience. It took me about 20 minutes to complete this Mod.

Items and Tools Needed:

  1. 2 Zener Diodes (1 4.3v and 1 4.7v)
  2. 1 On/Off/On SPDT Toggle Switch
  3. 3 pieces of automotive wire approx. 8ft each
  4. Wire Cutter/Stripper
  5. Soldering Iron
  6. Solder
  7. Electrical Tape (optional: heat shrink tubing)
  8. 5ft. of Wire Loom & Zip Ties
  9. T15 and T25 Torx to remove the Trim Panels under the steering wheel (depending on switch mounting location)





Procedure:


Step 1:

Begin by determining where you want to mount the switch. This is
necessary to plan the length of wire you will need and also to prepare
the tools needed. For me, I decided to mount the switch just above the
radio where my turbo timer is mounted.





Step 2:

A.) Insert the panel removal tool behind the top and bottom portion of the fuse panel cover and release the 4 panel clips (I used my hand for this but a panel tool or screwdriver will work also). Remove the cover. B.) Remove the 3 T15 screws underneath the column panels. Pull the left column panel straight out to release the panel clips. C.)
Now remove the T15 screw you see that was covered by the left columng
panel. Insert the panel removal tool behind the top portion of the
column panel and release the panel clip. Insert the panel removal tool
behind the right portion of the column panel and release the panel
clips. You should now be able to remove the panel completely. D.) On the left side of the metal support bracket, remove the 2 T15 and 1 T25 screws. E.)
On the right side of the metal support bracket, remove the 2 T15 and 1
T25 screws. You should be able to remove the bracket completely.


A.)

B.)



C.)


D.)
E.)





Step 3:

F.) Locate the unused grommet (or you may have used it for something else already) and pull it out or slice a hole into it. Route your 3 wires through that grommet. G.) Wires are in place now and ready to be hooked up to the switch and Map Sensor wires.


F.)

G.)





Step 4:

H.) Route the wires through the engine bay any way you like.
My path is highlighted by the yellow arrows. Route your 3 wires through
that grommet. I.) Pull out the Orange/Light Blue and Purple/Grey wires from the loom. (Now is the time to slide your heat shrink tubing over the wire before you make the connections). Connect one wire to the Orange/Light Blue wire. Connect both diodes to the Purple/Gray
wire, striped side towards the map sensor wire. Connect each of the
other two wires you ran to one diode, each on a different diode. Take
note of which color wires are connected to what. You will need to hook
them up correctly to the switch. Solder, heat shrink or tape, and clean
up your connections.


Click here to see a diagram of the wiring



H.)
I.)






Step 5:

J.) Route the wires to where you will mount the switch and make the connections. Be sure the wire you attached to Orange/Light Blue
is connected to the middle terminal of the switch. You can mount the
other two wires on any of the other two terminals. Keep in mind, when
the switch is to the left, it is actually clamping the the diode on the
opposite side of the switch. For example, position 1 is actually
clamping the diode on position 3 and vice versa. Whether you are using
crimp connectors or soldering, make the connection and either heat
shrink or tape to prevent short circuiting.


J.)





TEST YOUR CONNECTIONS.

Method #1: Flip the switch to either side.
Start your vehicle. If the vechile does not start then you have the
diodes installed backwards. Go back to where you made your connections
at the map sensor wires and flip the diodes around. Be sure the striped
side of each diode is towards the map sensor wires.

Method #2: Start the vehicle with the switch
in the middle position. If the car starts ok then flip the switch to
either side. If the vehicle begins to hesitate, rough idle, and then
shut down you have the diodes installed backwards. Go back to where you
made your connections at the map sensor wires and flip the diodes
around. Be sure the striped side of each diode is towards the map
sensor wires.








Your finished! Enjoy your new mod and show all your friends what you can do Smile

_________________

LhYnxz
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Re: Diode Mod (aka. Clamping The MAP)

Post by LhYnxz on Tue Oct 21, 2008 7:33 pm






_________________

LhYnxz
Site Administrator
Site Administrator

Number of posts : 485
Age : 37
Location : Bayamon, PR
Reputation : 0
Points : 30
Registration date : 2007-12-01

View user profile http://www.vwfusioncrew.net

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