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-   -   3 bar map sensor ~ confused (http://forums.tdiclub.com/showthread.php?t=280387)

Shawn_alh April 24th, 2010 18:19

3 bar map sensor ~ confused
 
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 April 24th, 2010 18:23

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.

eddie_1 April 24th, 2010 18:26

I put one in today and lost boost too, although I am running rc3. See my post from a few mins ago.
http://forums.tdiclub.com/showthread.php?t=280386

Shawn_alh April 24th, 2010 18:27

Quote:

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

Shawn_alh April 24th, 2010 18:28

Quote:

I put one in today and lost boost too, although I am running rc3. See my post from a few mins ago.
http://forums.tdiclub.com/showthread.php?t=280386
does yours work again when you shut the car off then turn it back on?

eddie_1 April 24th, 2010 18:31

no. I get the CEL and error code constantly.

Shawn_alh April 24th, 2010 18:53

Quote:

no. I get the CEL and error code constantly.
being i have the glow plug engine code all the time i decided after you said that i should check
here is what i got
http://thumbnails23.imagebam.com/778...9177887412.gif

FlyTDI Guy April 24th, 2010 18:59

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 April 24th, 2010 19:05

Quote:

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?

eddie_1 April 24th, 2010 19:11

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 April 24th, 2010 19:20

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 April 24th, 2010 19:24

Quote:

Originally Posted by FlyTDI Guy
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:

eddie_1 April 24th, 2010 19:34

Your 3bar is bringing the boost up to levels that are around the upper limit of the stock turbo, so you should be ok.

FlyTDI Guy April 24th, 2010 19:43

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 April 25th, 2010 05:17

right, i realized that after I posted. Your 18 PSI that you see on guage, vagcom or wherever will be under-reporting actual boost.


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