WHEN to upgrade MAP

Smarten101

Member
Joined
Oct 30, 2019
Location
Kalispell, MT
TDI
2005 Passat wagon
I have read a lot about upgrading to a 3 bar MAP sensor and I know that you don't want to do it without a tune so you don't overboost, but in the grand scheme of things, WHEN do you upgrade it? Is there a point to upgrading the MAP sensor if you are still running the stock turbo?
I am looking at upgrading my '05 Passat TDI (BHW engine) with a stage 2 colt cam, and probably a stage 2 tune (BSM is already taken care of). Is there any point in getting a 3 bar MAP if I'm leaving the stock turbo in? It's not that expensive and it would be nice to get it taken care of in my tune the first time around if it's worth it.
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
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Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
If you're running more than 22-24 PSI max boost, then you need a 3-Bar MAP. I think the limit of the stock turbo in a B5.5 is around 22 PSI, so I'm thinking you'd be fine with the 2.5 bar that's in the car. But ask your tuner when you choose one: They may want the 3-bar in there. Either way, make sure the tuner knows what MAP you have, otherwise their boost programming will be inaccurate.
 

Smarten101

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Oct 30, 2019
Location
Kalispell, MT
TDI
2005 Passat wagon
So according to those numbers, unless you have a turbo that's capable of putting out more boost, the stock MAP sensor should be fine. I'll make sure I pick the tuner's brain as much as possible before I give them all my hard earned money :)
 

QuickTD

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Feb 25, 2002
Location
SW Ontario
TDI
2003 Audi A4Q 5spd 2.0 TDI 2056VK R783, 2006 Audi A4Q 6spd 2.0 TDI
A BHW already has a 3bar MAP sensor. You'll need a 4bar if your going over 27-28psi.
 

Owain@malonetuning

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Jul 1, 2016
Location
Vancouver
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335d, 05 jetta wagon, 84 jetta td
Whenever you plan to run tuning that is within about 4 psi of the maximum readout of that sensor it's worth considering upgrading.

For example: A stock ALH will run 15 psi stock and around 18 psi tuned. A 2.5 bar map sensor (at sea level) will read 22 psi. This means you can diagnose boost spikes up to 22 psi with OBD tools, and anything above that will flat line the sensor.

You could install a 3 bar map sensor with your stock ALH and have a tune set for it, but your frame rate for OBD logging is going to be lower than a mechanical boost gauge, and you won't always have diagnostic tools connected.

On a BHW I'd upgrade to a 4 bar map sensor if running a GTB1756vk or similar (26-30 psi turbo). The stock 1749va is good for 22-24psi so an upgrade isn't required.


For extreme builds a mechanical boost gauge + EGT should definitely be installed, considering how much is invested in the motor having a few extra gauges is cheap insurance.
 
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racerxtdi

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Feb 23, 2011
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Outside of Philly
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2003 Jetta 5spd GLS
So to make it simple the best rule of thumb is:

2.5 Bar 0-18PSI (Tuned to 18PSI to see spikes at/above 22PSI)
3.0 Bar 0-24PSI (Tuned to 24PSI to see spikes at/above 28PSI)
4.0 Bar 0-40PSI (Tuned to 28-40PSI to see spikes at/above 44PSI)

Owain@MaloneTuning Any issues running a 4BAR MAP (when you get a tune) as they are cheaper than 3BAR? I ask because I am getting a turbo and will use you to Tune again.

Also do I have to pay for another full tune (have STG3 Custom @$349) or just the difference (STG5 Custom $449) =$100 or $449?
 
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Owain@malonetuning

Associate Vendor , w/Business number
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Jul 1, 2016
Location
Vancouver
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335d, 05 jetta wagon, 84 jetta td
yes can just tune it for a 4bar.

normally charge 100 for re-tuning plus the price difference between files, depends on circumstance.
 

Smarten101

Member
Joined
Oct 30, 2019
Location
Kalispell, MT
TDI
2005 Passat wagon
Perfect! This is the exact information I needed to know. I'm good with my 3 bar MAP until I upgrade the turbo. Thanks guys!
 

skaude

Active member
Joined
Jun 6, 2018
Location
finland
TDI
7x 1.9tdi passat variant
When yoy are closer than 1.4bar of the map vs boost target.
For example i have 6bar map sensor, its possible to go max 4.6bar boost.

Why? - 1bar atmospheric prrssure, -400mbar overboost control.
 
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