3 bar map sensor ~ confused

Shawn_alh

Active member
Joined
Mar 25, 2009
Location
BC Canada
TDI
ALH
Hello,

So everything in my car is stock except diesel powerbox. 1.9 alh 00 TDI car running at 13psi stock

I changes the map Sensor today part number #038 906 051c, I had the big hole map sensor so i made a sleeve that is tapered and fits very snug.

this is where the confusion starts

I went for a drive got no boost? i stopped fueled up and took off, now i got high boost spikes at 21-22psi and holds at 18psi

got home and had to go out to pick someone up got no boost again?
shut the car off, started back up boost was back? and ideas guys

Thanks in advance,

Shawn
 

Bob_Fout

Oil Wanker
Joined
Sep 5, 2004
Location
Indiana
TDI
2003 Jetta - Alaska Green (sold) / 2015 GTI 2.0T
3 bar MAPs are for cars with bigger turbos and boost over 21 PSI.

If you want more boost, you need either a "boost fooler" or a chip/tune/remap.
 

Shawn_alh

Active member
Joined
Mar 25, 2009
Location
BC Canada
TDI
ALH
3 bar MAPs are for cars with bigger turbos and boost over 21 PSI.

If you want more boost, you need either a "boost fooler" or a chip/tune/remap.
thanks but that does not answer my question:confused:

it works i am getting more boost.:D

only when i start the car shut it off then turn it on again <-- thats the problem
 
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FlyTDI Guy

Top Post Dawg
Joined
Nov 3, 2001
Location
PNW
TDI
'01 Jetta GLS
One question... how did you come to choose a 3 Bar MAP as compliment to your box? Your car is going into limp mode. Throwing a 3 bar map on a stock ECU is going to make it not happy. You are misreporting boost to the ECU now and it knows something's wrong. Turning the key off/on resets the ECU and it gives your not-so-happy mod combo another chance at redemption.
 

Shawn_alh

Active member
Joined
Mar 25, 2009
Location
BC Canada
TDI
ALH
One question... how did you come to choose a 3 Bar MAP as compliment to your box? Your car is going into limp mode. Throwing a 3 bar map on a stock ECU is going to make it not happy. You are misreporting boost to the ECU now and it knows something's wrong. Turning the key off/on resets the ECU and it gives your not-so-happy mod combo another chance at redemption.
my map sensor was broken and i decided i would install this because i plan to add a vnt17 later this year

I have not lost boost while driving (limp mode?)

anyway can i fix this without going to a different map sensor?
 
Last edited:

eddie_1

Veteran Member
Joined
Dec 27, 2004
Location
Hannover, Germany formerly Toronto & NY
TDI
Jetta Wagon 2003 TDI tuned to 170HP, A6 Wagon 2008 TDI 2.7L tuned to 340HP
My take is that the voltage range from the map sensor between 2.5bar and 3bar is different and the 3bar is lower starting voltage. This is confusing the ECU. In some cases people are getting overboost other cases the ECU is choosing limp mode.
 

FlyTDI Guy

Top Post Dawg
Joined
Nov 3, 2001
Location
PNW
TDI
'01 Jetta GLS
The voltage range is the same but... they represent different ranges. In other words, with the OEM 1.5 bar might return 3v to the ECU. With the 3 bar map, the same 1.5 bar only returns 2.5v. At idle, your ECU knows ambient, say 1000 mbar. Your map sensor, however, is returning lower than expected and they don't match. Some people can run a 3 bar map and not have any bad symptoms, most need to update the maps in their ECU to truly make it work right. Short answer, if you're going to run a 3 bar map, you need to tune for it. That means re-mapping the ECU.
 

Shawn_alh

Active member
Joined
Mar 25, 2009
Location
BC Canada
TDI
ALH
FlyTDI Guy said:
The voltage range is the same but... they represent different ranges. In other words, with the OEM 1.5 bar might return 3v to the ECU. With the 3 bar map, the same 1.5 bar only returns 2.5v. At idle, your ECU knows ambient, say 1000 mbar. Your map sensor, however, is returning lower than expected and they don't match. Some people can run a 3 bar map and not have any bad symptoms, most need to update the maps in their ECU to truly make it work right. Short answer, if you're going to run a 3 bar map, you need to tune for it. That means re-mapping the ECU.
thank you for the answer

am i going to wreck/hurt anything from now till i do the turbo 3-4 months:confused:
 

FlyTDI Guy

Top Post Dawg
Joined
Nov 3, 2001
Location
PNW
TDI
'01 Jetta GLS
When boost is on, you're running your turbo hotter and somewhat unregulated. As the map only returns 2.5v and the ECU is expecting 3v for X boost, it's going to increase duty cycle to the N75 and turbo upping boost until the request is matched. Take it easy, watch your boost gauge (you'd better have one) and don't spike the dickens out of your turbo. Many before you have done it. All TDI's seem to respond a bit differently. Some will tolerate it without going limp, others not so much. Do some searching as I was going to do the same thing a few years ago but held off based on other info in threads here. There used to be a guy over on Geocities called tech4tdi that had charted the voltages of the 2 and explained things pretty well. If you're boosting under 18 psi and not spiking like crazy and can live with the side-effects...
 

eddie_1

Veteran Member
Joined
Dec 27, 2004
Location
Hannover, Germany formerly Toronto & NY
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Jetta Wagon 2003 TDI tuned to 170HP, A6 Wagon 2008 TDI 2.7L tuned to 340HP
I had measured the MAP voltage from before with the 2.5bar stock map so I could compare with current 3 bar MAP.

Stock 2.5 bar MAP:
With Ignition on, Engine Off : 1.94V
With Ignition on, Engine Idle: 1.98V

3 bar MAP:
With Ignition on, Engine Off : 1.62V
With Ignition on, Engine Idle: 1.65V

It appears the ECU does not like the difference at engine turn on.
 

eddie_1

Veteran Member
Joined
Dec 27, 2004
Location
Hannover, Germany formerly Toronto & NY
TDI
Jetta Wagon 2003 TDI tuned to 170HP, A6 Wagon 2008 TDI 2.7L tuned to 340HP
I think you may have misunderstood the thread. I have both maps. I just installed the 3bar and there is an ECU issue with my current tune. I will put back the stock most likely. But thanks for the offer.
 

Shawn_alh

Active member
Joined
Mar 25, 2009
Location
BC Canada
TDI
ALH
right, i realized that after I posted. Your 18 PSI that you see on guage, vagcom or wherever will be under-reporting actual boost.
my gauge is not electric or digital
its analogue mechanical so how would it "under-report" is the boost the gauge showing me not "actual"
 

eddie_1

Veteran Member
Joined
Dec 27, 2004
Location
Hannover, Germany formerly Toronto & NY
TDI
Jetta Wagon 2003 TDI tuned to 170HP, A6 Wagon 2008 TDI 2.7L tuned to 340HP
You are right if you have direct air pressure measurement it will be good, most folks are going with electrical these days, so I was assuming your gauge was electrical. I meant anything based off the map voltage.
 

Bob_Fout

Oil Wanker
Joined
Sep 5, 2004
Location
Indiana
TDI
2003 Jetta - Alaska Green (sold) / 2015 GTI 2.0T
eddie_1 said:
You are right if you have direct air pressure measurement it will be good, most folks are going with electrical these days, so I was assuming your gauge was electrical. I meant anything based off the map voltage.
Who sells boost gauges based on the MAP sensor data?
 

LiLredTDI

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Mar 13, 2008
Location
maryland
TDI
2004 jetta tdi pd-1989 Jetta IDI-1994 F-250 IDI Turbo
i installed one last year at a gtg while waiting for rc to tune. pulled car out of bay after install and had limpmode as well. your car needs the ecu tuned for this part or it will continue to give you problems.
 
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