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Ive read about the N75 and how adjusting it can "help" but Ive never read about this mod before:

http://vwroadtrip.peterbeers.net/GTI/GT ... J/N75J.htm

What the advantage of doing this and would it make any difference to out babies?

Answered My own question all on 1.8 T tho.....
moobturbo wrote:
i fitted the n75j valve to mine at the week end which is also a agu bit with apr remap and i like the valve. It boosts much harder and quicker than the stock one up to about 4000 Rpm but then tails off from 16Psi down to about 12 Psi. Its drivers choice really, dont think you gain a lot of power from the different valves but it deffo feels alot quicker when you put yr foot down with the n75j valve on. one thing make sure you connect it up right when you fit it as i connected mine wrong at first and lost 5psi pressure.



This has been tried and tested, it does feel quicker due to higher boost at low revs, however at higher revs the ECU is backing off so you will actually loose power.


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I've now tried both the valves and yes the j definitely feels quicker off the line but the h seems to hang on to the boost for longer, i don't seem to be seeing anything like 16psi tho ! Mine boosts to approx 13psi then backs off to around 10psi ! Any ideas ?

isnt 14psi 1 bar..if thats the case then you mite be running less boost hwich would make your car slower..

s4woody wrote:isnt 14psi 1 bar..if thats the case then you mite be running less boost hwich would make your car slower..

This valve does boost up quicker and hits harder, sorta like adjusting the wastegates tighter about 2-3 lbs. Most take it out for winter use since it tends to overboost and throw you into limp mode temporarily. most of the 1.8T guys like it but for the 2.7T engine it's really hit and miss.

Tried a H valve on my S4. Constant limp mode (i.e. straight up to 1.5 bar)

Surely modding or changing the N75 is just for people who want to fool a standard ECU into giving more boost. If you have a remap to increase boost, why the hell would you want to fool the ECU???

Thats what I thought but I would imaginr there must be sime merit in it....
It would seem all it really does is change the power delivery.... which isnt a probalem in a V6...... I think i'll leave that one to the 4 pot lot.......

OK stretching the limits of my knowledge here (I flunked control theory at uni), adjusting the N75 will change power delivery, because it is part of a control loop. I have tuned PID control loops before, and if this is anything like one, then it can be adjusted to give a more rapid rise in boost, with the downside of overboost, just as Jonny mentions.