Boost increase when swapping MAP sensors

[Ghost Marksman]

Hey everyone !
I've been wanting to improve my TDIs for a long time now (even before owning my 105, I had a PD 90 that I unfortunately crashed and totaled before having any time to work on it).

At first, I wanted to run an Evry mod and a voltage divider on the MAP sensor signal wire to increase boost, and then hide both in the wiring and sheaths (for legal reasons).
However, as I was doing research on overboost, I came across forum posts talking about offscaling of boost maps when swapping 2.5 bar PD100 (wich is, AFAIK, the same as the PD105) and 3 bar PD130 MAP sensors, and other talking about boost increase when swapping sensors.

So my question is, will a PD130/150 MAP sensor increase my boost ? And if it does, what would be the increase range ?

Thanks for your answers, and have a nice day !
(Also, sorry for my poor english, I'm still learning)

 

[P2B]

The two MAP sensors have very similar transfer functions, so boost increase would be roughly the same as the difference in sensor range, i.e. about 15%. However, that won't necessarily translate into increased power because the ECU won't know about the extra air so won't inject additional fuel.

A proper remap will always produce better results than fooling the ECU.

 

[Mozambiquer]

Hey everyone !
I've been wanting to improve my TDIs for a long time now (even before owning my 105, I had a PD 90 that I unfortunately crashed and totaled before having any time to work on it).

At first, I wanted to run an Evry mod and a voltage divider on the MAP sensor signal wire to increase boost, and then hide both in the wiring and sheaths (for legal reasons).
However, as I was doing research on overboost, I came across forum posts talking about offscaling of boost maps when swapping 2.5 bar PD100 (wich is, AFAIK, the same as the PD105) and 3 bar PD130 MAP sensors, and other talking about boost increase when swapping sensors.

So my question is, will a PD130/150 MAP sensor increase my boost ? And if it does, what would be the increase range ?

Thanks for your answers, and have a nice day !
(Also, sorry for my poor english, I'm still learning)

Yes and no... It'll throw a map to ambient pressure correlation fault as they won't read the same. You'll need to get it tuned for the 3 bar if you install one or you'll have issues

 

[P2B]

Yes and no... It'll throw a map to ambient pressure correlation fault as they won't read the same. You'll need to get it tuned for the 3 bar if you install one or you'll have issues

Good point. If the discrepancy is sufficient to throw a correlation fault the car will be in permanent limp mode.

 

[Ghost Marksman]

And if I can modify the pressure read by the ECU on low boost situations ? Would that prevent limp mode ? Also, what pressure below 1 bar will trigger the limp mode ?

 

[P2B]

And if I can modify the pressure read by the ECU on low boost situations ? Would that prevent limp mode ? Also, what pressure below 1 bar will trigger the limp mode ?

In theory you could avoid limp mode if you can simulate a non-linear MAP transfer function, but you would need to experiment to determine the ECU correlation tolerance - but if you can do that you can probably learn to remap your ECU properly.

 

[Ghost Marksman]

I dont want to do a remap as these are illegal here, I only want physical mods that can be removed quickly, hence my first question. Basically, I was thinking about something equivalent to an ECU chip, but easily removable.

 

[Vince Waldon]

I read your question as:

If I take out my stock 2.5 bar sensor and simply install a 3 bar sensor will I suddenly get more boost?

The simple answer is: no!

 

[Mozambiquer]

I dont want to do a remap as these are illegal here, I only want physical mods that can be removed quickly, hence my first question. Basically, I was thinking about something equivalent to an ECU chip, but easily removable.

Well, it sounds like you will simply have to keep using the stock setup then, as most things do require a tune.

 

[P2B]

I dont want to do a remap as these are illegal here, I only want physical mods that can be removed quickly, hence my first question. Basically, I was thinking about something equivalent to an ECU chip, but easily removable.

A remap is easily removable, just flash the original file.

 

[Ghost Marksman]

Well, it requires a computer and a cable. Too complicated and long to do in my sense, but I completely acknoledge and agree that it would be the best solution.

 

[Ghost Marksman]

I read your question as:

If I take out my stock 2.5 bar sensor and simply install a 3 bar sensor will I suddenly get more boost?

The simple answer is: no!

Thanks for the clear answer, but why is that ? Why the ECU wouldn't try to compensate for the low values it reads ?

 

[Vince Waldon]

A bunch of different reasons why this won't do what you want, but one of the main reasons is that the ECU calls for fuel based on multiple internal maps...only one of which is the MAP sensor...and in stock configuration will only call for so much fuel even if certain maps are maxed out.

Want significantly more power due to more fuel? The internal maps have to change, and not just the manifold pressure map.

 

[Ghost Marksman]

What do you mean by multiple maps ? MAP sensors, or ECU mapping ?

 

[Vince Waldon]

Yeah, the terms are a bit confusing.

The ECU decides what fueling to use based on multiple parameters (commonly called "maps", all lower case, because they are 2 or 3 dimensional).

Some good pictures here: https://forums.tdiclub.com/index.ph...l-alh-or-i-intend-to-do-stupid-things.375099/

MAP, all upper case, generally refers to Manifold Absolute Pressure.

 

[powermandan]

You could just clone your ECU and swap it over if needs be.

If you worried about spot checks. You could just cut your k line. So it can't be interrogated. You could theoretically unsolder the pin inside the ECU. Although some research would be needed to confirm that it won't impact other systems. My suspicion is you would need to immo off the ECU.

 

[GlowBugTDI]

You could just clone your ECU and swap it over if needs be.

If you worried about spot checks. You could just cut your k line. So it can't be interrogated. You could theoretically unsolder the pin inside the ECU. Although some research would be needed to confirm that it won't impact other systems. My suspicion is you would need to immo off the ECU.

or put it on a switch so it can be turned on and off for easy access when you need to communicate with the ecu. Things like reading codes ect. A push button switch would be super easy.

 

[P2B]

Thanks for the clear answer, but why is that ? Why the ECU wouldn't try to compensate for the low values it reads ?

There is a barometric pressure sensor inside the ECU. When you turn the ignition on, the ECU compares the barometric sensor to the MAP sensor. If the two don't agree the ECU assumes the MAP sensor is broken and puts the car in limp mode.

 

[burpod]

how could it be any easier than a 90sec flash??? map sensor fooling is useless since as other have pointed out you can't increase fueling. but thats only a small part of it. timing/boost/fuel..... ugh .

 

[Ghost Marksman]

You could just clone your ECU and swap it over if needs be.

If you worried about spot checks. You could just cut your k line. So it can't be interrogated. You could theoretically unsolder the pin inside the ECU. Although some research would be needed to confirm that it won't impact other systems. My suspicion is you would need to immo off the ECU.

Well that's a good idea, I'll probably get one and IMO off it. And it would allow me to have extra power when I want to, but keep its stock as a daily.

 

[diffas]

Yes it increases boost when you just swap 2.5bar sensor to 3bar. Most ecus allows that change, but is it wise...well in long run no. Proper tune and then there is same put 4bar sensor in on the same effort since in some tome you wanna go anyway biger power.