Theory
As boost pressure sender toyota has chosen a regular 2 bar MAP
sensor. The output signal is shown in the picture below. As
reference I have used a cheap pressure guage so I can't guarantee
that the values is absolutely correct. But at least one bar
should be possible measure.
This is needed:
- Solider equipment
- Wire
- Trimpotentiometer 47 - 100 kOhm
- Eventually a capacitor på ca 4,7 µF
- Laserprint for the dial
Yes, that is everything. Cost: about a bottle of beer.
Electronics
The work is shown quite clearly on the pictures. Replace the little orange capacitor with a potentiometer. Replace the diode with a piece of wire. As a bonus you can replace the larger blue capacitor or remove it. This makes the guage react much faster.
The box that shall be tricked with is placed behind
the instrumentation. Remove the black panels on both sides
of the stearing wheel first. Then remove the panel above the
instrumentation. Now you can remove the apparature.
Component side
Raster side
It will look like this after the modification
Dial
You should make a new dial. You can make it of 3 - 4 laser print glued onto each other. Inc will not do the trick.
Here is some examples
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| 600 dpi jpg | 720 dpi png | 720 dpi png |
| 720 dpi tif | 720 dpi tif | |
| Paint Shop Pro 7 | Paint Shop Pro 7 |
Calibrate
To have some resonable readings the guage must be calibrated. First you put the nedle high in the scale, then slide it down to a little bit under 0 bar. The give the the box a signal corresponding to 1 bar. Iether give pressure the the signal sender at the left fender or input 4.2 volts in the green cable. With the power turned on. Adjust the potentiometer until the nedle points at 1 bar. Also check that it shows 0 bar with the power on and engine off.
Finished!
Now you can screw everything back and be happy! Here
is a picture that shows how it can look like:
pelleman81(at)euromail.se