Using 3 bar map sensor on 2.5 bar map car

devonutopia

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Dec 1, 2003
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Devon, U.K
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PD300 Skoda Fabia
Is it just plug & play?? Have a spare PD130 3 bar map sensor and someone interested in it has a PD100. Obviously handy for the extra 0.5 bar range of pressure, but will it fit right in with no software changes? :)

I know going from 3 bar to 4 bar map sensor needs work, but never thought about this direction before.
 

Mk2tdi

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Feb 4, 2008
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GTA
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mk2 tdi project
Should drop right in. I changed from a 2.5bar to 3 bar map on a customers car awhile back. Took about 10min to swap.
 

ryanp

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overboost that you cannot actually measure (without an external gauge) will be the only problem.
 

devonutopia

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Devon, U.K
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PD300 Skoda Fabia
Yeah - I realised it will physically be plug and play, but its what it means for the car, etc. :) Not to worry as the owner of said PD100 has paid me for the sensor so it is no longer a concern of mine. :D
 

streeker02

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May 12, 2008
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Halton Hills
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2003 Golf TDI
he may be concerned when his tiny turbo starts overboosting :(

Definitely he needs to be remapped for that sensor.
 

hatemi

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Finland
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Audi A6 4F 3.0TDI
On some ecus you can use it and others you get occasional limp mode at startup from the measured and barometric being too far off.
 

bhodgkiss

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Sep 11, 2006
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Banbury, UK
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AFN Passat Wagon
i have an afn tdi 110bhp in my passat. i assume it has a 2.5bar sensor?
if i swap in a 3bar sensor, does my 'boost map' all scale up by 20%? or does it just stay the same, it just gives you the potential to run and measure above 1.5bar boost (21psi) so up to 2bar (over atmospheric) so 28psi?
 

devonutopia

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PD300 Skoda Fabia
bhodgkiss said:
i have an afn tdi 110bhp in my passat. i assume it has a 2.5bar sensor?
if i swap in a 3bar sensor, does my 'boost map' all scale up by 20%? or does it just stay the same, it just gives you the potential to run and measure above 1.5bar boost (21psi) so up to 2bar (over atmospheric) so 28psi?
I don't know to what degree it affects the boost map, but you are right about it being able to read up to 2 bar of boost over atmos, once all setup.
 

cog

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MIDDLESBROUGH... U.K
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98 GT.TDI 11O
the connection was plug and play but i needed to make an adapter to fit into the hole along with some sealant as the 3 bar map was so small in the hole , unless thats just my 110 that has that problem. i know because changing to upgraded id parts pipes was a pain changing the adapter over and letting the sealant hardnen overnight
 

roy1

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Mehlingen, Germany
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2010 Jetta TDI
You cannot(you can if you want) just swap a 3 bar sensor for a 2.5 bar without changing the engine mapping because, although the voltage range is the same, the voltage to pressure ratio is different. Your fueling will be off
 

Jugghack2

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Spanish On, Canada
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00 Jetta TDI Stick
you will have to offset the voltage output with a pull up resistor as the Map reads in absolute not guage so at rest with eng off the voltage output is diffrent I think someone on here measured 1.94v stock and 1.64v on the 3 bar so if you bring the voltage at rest up to the same as stock you will gain about 4 or 5 psi on the intake with no codes.
 

robnitro

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NYC area, NY
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2001 Jetta TDI GLS silver
You cannot(you can if you want) just swap a 3 bar sensor for a 2.5 bar without changing the engine mapping because, although the voltage range is the same, the voltage to pressure ratio is different. Your fueling will be off
I have, and others have. The turbo I had could handle the 22 psi it gave, and to bring up the fueling I lowered the IQ until I got a bit of smoke. It drove fine, only a bit performance to RC4 which is mapped to 3 bar.
 

bhodgkiss

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AFN Passat Wagon
AS i understand it, the pressure in the inlet measured by the MAP sensor converts to a voltage. Stick the 3 bar sensor in and the same pressure now reads a lower voltage, but the ECU is targetting a voltage (from a voltage/pressure map) and so keeps upping the boost until it hits that voltage?

This will be 20% higher across the rev range. AS its absolute pressure then 17psi boost (31psi absolute) goes up to 37psi so 23psi boost, so a fair amount of increase.

If you're overfuelling this will give more power, but in any case it shower lower EGT's?

I wouldn't do it myself without a remap, smaller turbos may not like that much increase, taking into account spikes.
 

robnitro

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NYC area, NY
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2001 Jetta TDI GLS silver
Thats 2 bar on the graph. Between 2.5 and 3, at 1 bar (14.7 psi) it would be around 20 psi. But because the 3 bar map reads lower at idle, the ecu changes the boost map somehow.
example: When I ran a 3 bar map on a 2.5 bar tune - rc3 with 18.5 psi, I was doing around 21 psi afterwards. Not what the graph suggests but still, if I didn't have a VNT17 it would be dangerous. Plus I was using a boostvalve to control spikes.

I would guess a stock tune that asks for 15 psi would be doing 18 psi or so. But yes it will be spiky because the ecu doesn't have as fine of a control of the boost as the 3 bar map line is steeper.
 
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bhodgkiss

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Banbury, UK
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AFN Passat Wagon
I now have a 3 bar sensor installed instead of 2.5bar on a stock tune, but have a BV43 turbo and not the standard one.

Max boost is now 20psi and not 14psi so a decent increase (20% absolute) so unless the turbo can take it then its not a good thing. Just waiting to get the tune done now which will use the 3bar sensor.... :)
 

drejck

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Jan 17, 2010
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slovenija EU
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golf3 1,9tdi 81kw
i have a question,does anyone have a wiring diagram for 3 or 4 bar mapsensor into mk3,mk3 sensor is in computer,witch wires to collegte,i have seen once a link with instructions but i cant find it anymore..
 

drejck

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slovenija EU
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golf3 1,9tdi 81kw
waw! :D
is there still a sensor in comp.? a see a presure line coming in...
did a do wrong to buy an external sensor mk4 style?(4bar sensor)
with this i can help yes but i dont know witch wire takes what position on sensor,there are 4pins(on sensor)
enyway thanks for pictures.
 

robnitro

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2001 Jetta TDI GLS silver
Maybe you can run the sensor wiring from where the sensor is (on pipe) over to ecu instead, even make a connector.

4 wires: ground, 5v feed, pressure, temperature.
The older ecu with internal map doesn't use temperature, I'm not sure whether they ignore it- and just use maf readings (which are automatically changed my temperature) or they have some sort of second sensor.

Here's the colors and pins based on the plug/wires/ecu that have the external sensor.

1 Signal ground Brown/blue pin 25 of the ECU
2 Temperature output voltage Grey/green pin 13 of the ECU
3 5V supply and reference voltage Purple/red pin 39 of the ECU
4 Pressure output voltage Yellow/black Pin 40 of the ECU

For your ecu, you would run wires from 1, 3, 4 to your ecu, but you need to find out what wire does what on your ecu
 
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drejck

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Jan 17, 2010
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slovenija EU
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golf3 1,9tdi 81kw
finaly i think i made it,if we are looking upper picture
yellow- ground- pin 1 on the sensor
green- signal -pin 4 on the sensor
red- + 5v -pin 3 on the sensor

i hope this it will work,for test i will have to wait a little....
i was thinking to get the - and IAT wire (to pin 2 ) from IAT sensor,...Rub i think make it so...
 

Byd1380

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Jun 10, 2010
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Belfast
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Mk2 Golf - VNT20 setup
I have a ASV running a 3 bar map for 30k, just scales up boost a bit. Car drives really well. I had to fit a rubber sleave around the sensor as the 3 bar one was smaller.

Ivan
 

drejck

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Jan 17, 2010
Location
slovenija EU
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golf3 1,9tdi 81kw
Hi. I cant figure it what is wrong, after swap to 3bar map, computer read always the same pressure, temperature, n75 valve, requested pres.seems to be ok, only actual is always the same,-min(996mb)
Any ideas?
 

mojogoes

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Joined
May 1, 2003
Location
england
TDI
mk3 tdi golf
Hi. I cant figure it what is wrong, after swap to 3bar map, computer read always the same pressure, temperature, n75 valve, requested pres.seems to be ok, only actual is always the same,-min(996mb)
Any ideas?
Check the p/n to see if you got the correct part if not then it will need rescaling.
 

drejck

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Jan 17, 2010
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slovenija EU
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golf3 1,9tdi 81kw
I think it is something with the wiring,even if the scaling is wrong, at full boost it has to move a bit..temp is reading correct,atm press is osame have 2 sensors and both are reading the same.so i havent got ideas any more what is wrong.
Can i ask in what is better car comp from mk4, maybe i will make a swap for a new one if is worth, and if exsist some wiring guide.
 

drejck

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Jan 17, 2010
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slovenija EU
TDI
golf3 1,9tdi 81kw
i made a log,and a graf
blue line is requested pressure, grey line are rpm, orange line duty cycle,
and red line is actual boost pressure
 
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