Is there a real benefit from decatting the 406?
I read in some thread that after that you need to edit the N75 map, which if I understand, controls the aperture of the wastegate.
Editing wastegate's functioning knowing that back pressure is absent sounds cool, but does it give better boost control? or any other improvements? Engine sound maybe? :D

The engine will breath easier. Less power will be lost on trying to push exhaust gases.

RPM freak wrote:The engine will breath easier. Less power will be lost on trying to push exhaust gases.

How much power, more or less? I guess the gain is only at high revs right?

That is difficult to point correctly. It depends on the engine construction, type of cat and the state of it. More soot = more blockage. The gain will be thru the whole RPM range.

I've seen somewhere like Discovery or something, don't remember, an experiment in which they replaced the cat with a high flow aftermarket cat, then with a pipe. On the dyno they got +3hp with the hiflow cat and +4hp with no cat at all. It's little but it's important to know they didn't remap or anything.
So my question is: can we make the engine run better by editing some maps knowing there's no back pressure?
Can you get better boost control, or something like that?

Correct me if I'm wrong, as far as I know, the turbo on the 406 isn't the top, and the internal wastegate is not great, so when incresing boost rapidly, the wastegate has to partially open before the desired boost is reached, in order to prevent an overboost, that means LAG!
If we have no back pressure, more air will pass through the wastegate. So we can keep the wastegate fully closed and open it just a little bit before the boost target is reached. If my understanding of these things is right, this way we'll have less turbo lag :?

noone? :(

Alex.T wrote:Correct me if I'm wrong, as far as I know, the turbo on the 406 isn't the top, and the internal wastegate is not great, so when incresing boost rapidly, the wastegate has to partially open before the desired boost is reached, in order to prevent an overboost, that means LAG!

I have no clue since I'm a noob, but you are talking about the 2.0HDi 110 turbo right? What make and model is it? Is it variable geometry? I seem to recall the 2.0 90 has fixed geometry turbo and the 2.0 110 has varialbe geometry turbo + intercooler.
The Garret in the 2.2 is decent, if not a little noisy, but the turbo lag is not huge for such an old engine. Overboost problems sometimes happen to the 2.2 but I've never heard that of a 2.0.
B the way are you subscribed to the 406oc UK club? Lots of info for 2.0 users there.

I'm talking about 2.0 HDi 110hp
I don't know what turbo I have.. I know for sure I have the intercooler but how do I know the turbo type?

I'm not talking about having overboost problems. PSA engineers mapped it to prevent that.
But if you remap tubo+wastegate because you want it to be more responsive, then you may encounter overboost.
Decatting would improve wastegate flow, allowing us to better remap and control boost.
It's a theory.. I'm asking if it's right

This applies to all engines, not just 2.0 hdi

OdinEidolon wrote:406oc UK club?

I'll check it. Thanks ;)

All 90hp, 110hp and 133hp HDI engines have wastegate turbos. Non off them are classic VNT turbos. The difference between them is that 90hp turbo boost is NOT ECU controlled and 110/133hp boost is ECU controlled. The ECU boost control of the turbo acts as VNT. The 90hp turbo is the same as 110hp. The 133hp turbo is bigger.

RPM freak wrote:All 90hp, 110hp and 133hp HDI engines have wastegate turbos. Non off them are classic VNT turbos. The difference between them is that 90hp turbo boost is NOT ECU controlled and 110/133hp boost is ECU controlled. The ECU boost control of the turbo acts as VNT. The 90hp turbo is the same as 110hp. The 133hp turbo is bigger.

Thank you for the clarification!