WHEN to upgrade MAP

[Smarten101]

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]

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]

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

 

[Smarten101]

Really? It already has a 3 bar MAP sensor? How did I not know this?!

 

[Owain@malonetuning]

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.

 

[racerxtdi]

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?

 

[Owain@malonetuning]

yes can just tune it for a 4bar.

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

 

[Smarten101]

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]

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.