220TC

Hi,

What MAP sensor does a escort rs turbo have, I hear people mention 3 bar MAP sensors but I assume there for a cossie. Also, why are there different 'value' MAP sensors such as 2 bar & 3 bar ?

cheers, Duncan

Jim Galbally

on an ERST the map sensor is built into the ECU (notice the vac pipe going into the ECU?) and its not replaceable

i think its 2.5bar but you'd have to check that with someone else...

different value sensors are used to read different ranges... a 1bar map sensor is used on a non-turbo car... it measures up to 1bar pressure (and since the air around us is at 1bar that equates to 0psi boost, so in simple terms it reads -1bar to 0bar)

a 2 bar map sensor is used in situations where you havea turbo/SC car and its boosting upto 1bar of boost, so the sensor can read -1bar to +1bar. ofcourse if you're running 20psi of boost or something (1bar = 14.7psi) then this is no good as it can't read that high, so you use a 3bar map sensor that will read from -1bar to +2bar which means you can read upto 2bar of boost (30psi ish)

since they both give off the same readings (0v to 5v) the ECU has no way of knowing if you've changed the map sensor for a different type, so you will need the chip re-mapped for this change (or fit a new chip pre-programmed)

also you wouldnt fit a 3bar map sensor to a car only running standard boost, as it's not necessary, and you also lose 33% resolution on the sensor...

hth

220TC

cheers jim

My car has run up to 26psi of boost though, surely this is too much for a 2.5bar MAP sensor

Jim Galbally

was it set up with 26psi? or did you do it yourself

going into a bit more details now... (imagine were using 2br map sensor, also imagine 1bar=15psi)

if you run say 7psi then your ECU/Map can read that fine also say we're running 15psi, again it can read that fine... now we're running 20... oops... well our map sensor ECU is reading 15psi still even tho there's really 20psi there... what can we do about this?

well, in the map in the ECU all we do is fill in the values in the 15psi column (imagine it like a spreadsheet) to those that we would really need at 20psi...

now, we're flat out at full boost (20psi) and the map is reading 15psi, but since the values we filled in are ok for the boost we're running all is sweet we're effectively "tricking" the ECU... whilst the ECU doesn't really know what's going on, its still doing what we want it to do (ECUs are dumb, theyre only computers, an they do what theyre told)

that's great

however it has flaws...

say for example our car suddenly fucked up and now it's boosting to 30psi! well, our map sensor is STILL reading 15psi and it doesn't know anything is wrong! so its happily chucking in the fuel n stuff for the 20psi we told it about...

however since we're running 30 now there's not enough...

oh dear our engine just melted

also visa versa... what if we think "i'll turn the boost down coz its raining and its spinning too much" or something like that... so we turn the boost down from 20psi to 15psi to make it more driveable...

well again the ECU sees 15psi STILL but its STILL putting in 20psi worth of fuel/spark... so our car is overfueling like a mofo and driving like shit...

this may seem like a big big bodge (and to be fair it is kinda a bodge) but its practiced by just about ever tuner you'll ever meet, becasue if used correctly this method WILL work... the only downside is that there can be no failsafes (and to be fair, most chips you'll ever buy off the shelf dont have failsafes anyway!!)

this will most commonly be used on cars running 30+psi of boost (the 500+bhp boys etc.) and running 3bar map sensors...

Jim Galbally

ps most of that in not applicable to an ERST as its ECU only controls the ignition, not the fueling

Stu @ M Developments

iTrader: (12)

Jim..
It's not exactly applicable to Bosch KE.. but for every other system its great so top marks

Oranoco

OMG!

Jim has swallowed a book on fuel injection

Top answer though mate

220TC

cheers jim

Jim Galbally

FAQ section anyone?

Stu @ M Developments

iTrader: (12)

Oh go on then... remind me in a few days when everyones digested it

Jim Galbally

you want ME to remember something

you obviously don't know me very well stu

foreigneRS

there's a better one about MAP sensors in there already

good work jim. hopefully someone will learn something from that and save themselves a few quid

Jim Galbally

Rick

wow lol

std ecu isnt mapped above 11psi anyway, but it doesnt really matter, as u set ur max advance with the dizzy.

4 degrees ATDC sounds about right

Jim Galbally

Next post "my RST is a big sluggish... what could be the problem"

Stu @ M Developments

iTrader: (12)

Answer:
It needs a daft chip to take advantage of your retardednes....

Private Joke Jim... will make sense to someone

Rick

Yes, i am very retarded.

Jim Galbally

oi, it made sense to me!

BillyCabrio

iTrader: (1)

Digest it?? I've just gone cross eyed!