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

 

nice write up Simon

 

OK Simon...........

Tell me, do I need a 5 bar sensor?

And will it work with a sophisticated turbo like a T4 ?

 

how bizarre. what is the original application for this sensor?

good information SECS

 

Yes Doug, I will sort it out for you !

"Sophisticated turbo"

 

Not sure but I overheard someone say it was for Indy cars as they
run turbos with about 40 psi boost .

 

 

what and indycars never back off the gas?

what a strange design (imho)

good to see you got around it tho

 

maybe they have a higher idle speed or have some sort of antilag and pull less vacuum?

 

well i got a sensor ready to go, just need an ECU simon about 2weeks max if possible

 

Got the Sensor... and the SECS ECU.

 

haven't got either



























though never requested one

 

well i never knew that simon about the vacuum

 

These 5 bars are off a lorry engine!!!!

I sell loads to certain tuners

 

So.......perfect to use with a T4 then

 

Quote of the day!

 

that'll be why they don't have a very high (or low?) vaccum range then. damn diesels.

 

Took the words out of my mouth - Funny as FOOOOKKKKKKK

 

So basically then when i have mine built (550+bhp) then a 5 bar will be needed.
How much do they go for then?

good info secs

 

you not funny!!!!

 

good info simon

i may have read it wrong or just not understand but should you not run an element of over run fuelling to cool the crowns down on throttle shut off?

 

May i present you with this prestidgious award Matt:

 

I was gona say what Matt did but i also thought "nah i mustve read it wrong"

 

Excellent write up...

And if the same bit that Matt has just highlighted is true, that'll be why, on de-accelaration, my car only starts popping below 2K RPM... Always wandered why, as I thought fuelling on over-run was thru-out the range... So I've learnt summut new...


Luv
Chrisie...

 

matt , theres cooling the piston crowns and theres drowning the piston crowns

theres a fine line with large injectors !!

 

My "Can O Worms" by the way was related to all the "Expert" opinions we are now about to find CLASH

 

Ben, when you have your 550+ BHP engine built, the price of that 5 BAR sensor will be the least of your worries......At Ł75.00 odd.......it will end up being one of the cheapest components in your engine build costs
......then theres also the cost of the heavy duty g/box/diffs/brakes etc

 

According to my data these are actually 4.0bar sensors....

 

Phil,

In the data sheet, are the 3 BAR sensors not actually 2.0 BAR rated anyway ????

+ 1 BAR of atmospheric = the quoted figure?????????

 

Ima-Racing500,
nar they do go to 4.6 bar phil,,,

 

yeah I know that lol, hence why the coss is gonna be of the road for a year
Just wanted to know so I can sell the 3 bar to the missis

 

Benn... still think you are doing the wrong thing mate

 

LOL i didnt mean to open any worm cans here!!

markk, "Turn the fuel off completely if the throttle is closed and the engine
speed is above 1800 rpm" will that cool or drowned the crowns? i read it as if they'd be dry as hell lol no extra fuel, no extra cooling, base fuelling only.

like i say im out of depth here but always interested to read such info

 

interesting stuff

 

whos that bird in that cheesy pic of you rick?

 

Good reading Simon

ME TOO ; How can it be good for the crowns if fuel is turned OFF over 1800 rpm , I'm talking about overrun ?

I even dap on the throttle if I drive downhill for longer periods....just to ad more cooling to the piston crowns (mine is only std. )

Cheers Kennert

 

Ive had arguments with many a technical boffin over this and the school of thought is definately split into 3:

1) DEFFO needs fuel to cool.
2) DEFFO doesnt need fuel to cool.
3) Who Cares?

I always pose the same question though, and to me its "Virtually" this simple...

"What is coolest?"
1) An engine passing "unburnt" air through its cylinders with no fuel added to make it flammable.

2) A burning fuel mixture of any strength whatsoever.

Ive heard some interesting arguments over the years though for sure. Some of which certainly had me racking my brains, which is always nice...

 

NUMBER1!!!

Like on Autronic managment etc you can run "Rotational Idle" where it cuts the fuel/ign/both (i forget now) TOTALY to 1 cyl at a time rotating between them each time to help cool the car at idle.
Works VERY well, very very well (sounds pretty mad too)
I had actual results once on a modded car (supra or skyline i think it was) of coolant temp drops in a set time with rotational idle compared to normal idle, improvment was huge.

 

Hi Stu

I see what you are saying!
So a lot of cold intercooler air is the way for you and Simon.

I have always heared there should be fuel to cool down (I'm not a tuner...... just very interested )

I learn everyday
Cheers Kennert

 

Me again

I just remembered one thing, the car is driving with the throttle closed, so therefor there is not a lot of air going through the engine ...(me thinks...)
I could better understand it if the ignition was cut and at WOT (But that sound really wierd....so I'll just go to bed now )

Cheers