Here is a short dialogue about my experience with implementing a
5 bar map sensor on my escort cossie.
Its not all roses.......

Fed up with 3 bar map sensors failing like lemmings,
About a month ago, I fitted a 5 bar map sensor to my car.
BOSCH PART No 0281002257-000
I obtained this part from Martin @ Reyland (Via IMA_Racing500)

I should add here for those who do NOT know, you cannot fit this
sensor to your car without having the calibration in your ECU
modified and on some ecu's a FULL remap may be required.
Most after market modern ECU's need only minor adjustments.


The first problem was actually mounting the device so that it could
receive air pressure/vacuum from the engine.
The 5 bar is designed to mounted DIRECTLY on the inlet manifold.
As I was TOO lazy to take my inlet manifold apart, I had a boss made
from alluminium to mount it on and run a pipe from this to the existing
MAP sensor port on the inlet manifold.

Here is a picture showing the sensor in my escort mounted on the original
map sensor bracket. The sensor is about half the size of the original
weber item. Sorry for picture quality, as it was taken with my camera phone.


Next, the original plug on the wiring loom that connected to
the MAP sensor had to be rewired to suit the new sensor.
The connector on the 5 bar is physically the same as the original BUT two of the
pins need to be swapped around to make it work.
These are the 5 volt supply and the signal ground connections (pins 2 & 3).
I did this by using a special pin extraction tool rather than cut the wires
and rejoin them.

After checking all my installation mods, I then connected my PC to the ECU
and turned the ignition on.
On my ECU the only changed required was to select the 5 bar option and
download this new setting.
Once the ECU was restarted, I checked that a value of 0 was being displayed
on the live data monitor screen.
I then proceeded to start the engine and it started first time.
After the engine had warmed up, I then took the car up the town bypass
with a wide band lambda meter just to check that all was well.
SORTED.

The next day I did a track day at my local circuit CASTLE COOMBE and
discovered that my car was overfuelling alot.
On overun, I.E High RPM and throttle fully closed, large amounts of fuel
was being ejected out of the exhaust and making the engine cough and stall.
OH foookkkkkk........My track day was over.

The problem turned out to be the NOT the car or the ECU but the way the
5 bar sensor works.

It turns out, the actual 5 bar sensor itself was NOT at fault but rather what
its limitations are and as I did not have a full BOSCH technical data sheet on it,
I found out these limits by trial and error.

The problem is that the 5 bar cannot measure below -10.0 psi (-0.68 bar).
When the car was in overun, a high vacuum of about -11 to -13 psi is normal.
But as the sensor could not measure this low, the ECU fuelled for what the sensor
was saying and of course too much fuel was being added.
The car was shooting out excellant flames as a side effect though.

The solution was to enable the decelleration fuel cutoff above 1800 rpm.
Problem solved.
I.E. Turn the fuel off completely if the throttle is closed and the engine
speed is above 1800 rpm. Most ECU's have this function built in.
Most modern ecu's also can use throttle position and engine speed to determine the
required load for the engine in these conditions but this will be usually different
for each type/state of tune for a particular engine.

Other limitations of the sensor are that it is actually a 4.6 bar sensor.
This equates to 3.6 bar (52 ish psi) on boost.

In summary, I really do recomend this sensor for your car as it is very stable
at all operating temperatures and seems to be extremely reliable when compared
to the original and uprated weber parts and is about the same price but
will require a few other mods to your ecu !



Why use a 5 bar ? .....

Most high boost big power cars that run the original weber 3 bar sensor
are running on a knife edge in my opinion.
The 3 bar sensor is being forced to work outside its design limits.
Also, because a 3 bar can only measure 29.5 ish psi maximum,
the map sensor CANNOT give a higher signal output for higher boost input.

E.G If your car was running say 34 psi, the ecu would have to be mapped for
this at the 29 psi point in the map.
I.E. The boost between 29 and 34 psi would have the same fuel.
(Some ecu's assume a rising rate fuel curve after a short time - still not ideal)

If like a friend of mine the boost control or actuator fails and your turbo
produces 40 psi boost you would not have any automated additional fuelling
let alone any boost limit and the result is a meltdown or turbo failure.
Using a 5 bar, allows the fuel map to be correctly set up and also a boost
safety limit to be set.

Thats enough technobabble for now