N75 valve - anyone ever tweaked the screw...?

[S4TAN]

....I ask out of interest because I've recently installed a new one (along with new N249 and various hoses etc as i am replacing all the easy bits and bobs gradually).

The new valve came with it's screw set in a certain position (about 11 o'clock) and I was assured by vagparts that they're calibrated at the factory - but, after reading various articles on AW, and being a curious tinker, I decided to have a little play. Now I know that the top adjustment screw is very delicate and only tiny adjustments are required to elicit a difference - turn anti-clockwise to decrease turbo lag and give more boost (but with spikes), turn clockwise to give smoother throttle response and smoother boost curve according to AW - so I decided to turn it just slightly anti-clock as an experiment (and I mean EVER SO SLIGHTLY! - i.e. to about 10.30 o'clock) - well it made a real difference to my car! Seem to get more boost and get it quicker! It feels really aggressive and instant!

Now I suppose I'm gonna get responses telling me I'm gonna kill my stock turbos by doing this or something equally heinous - but I just wondered if anyone else has fiddled with their N75 adjustment screw, and what results did they find, which way and how far did they turn the screw etc......I look forward to hearing owners experiences/results if they've done this......

BTW - My S4 has a custom MRC re-map, Milltek 3" cat-back, Hyperboost DVs, Samco TBB and f-pipe, Bosch F5DP0Rs, AWE Boost gauge (so I can see the extra boost!), DTS, B&M SS, K&N panel-filter + "drilled and cut" air-box, various nice new hoses everywhere etc etc......

[s4woody]

well now that you have adjusted the boost curve does that mean that your custom remap is out of wack ??
mite be worth MRC answering this 1...

[S4TAN]

I did wonder this myself and a few days after I'd done it I had to pop into MRC to get a new MAF (it was starting to fail before I tweaked the valve), then me and Doug went for a spin with vagcom plugged in and he reported that everything looked good - except timing was retarded a little bit but he put that down to fuel.....

No-one else turned their screw then...?

[smurfbus]

They dont call it crew for nothing. mine was crewed after some minor tinkering.

I bought the J version as it was cheaper but it gave spikes over 1.5bar so I had to use tcd and later MBC to control the spikes. with k04s it was spikes to 1.8bar without MBC paraller

[S4TAN]

I got the "B" version (£29 from vagparts) which is the correct one for our cars so I'm told - and with my K03s i don't get up to 1.8bar - average peak is about 17psi (~1.25bar?) and the odd spike in 3rd/4th gear up to ~20psi (according to boost gauge) - works for me!

[MarkB]

I beleave that adjusting the N75 will change the way the boost is delivered but not the total boost obtained. The ECU will still adjust it back. The worry is if you go too far the ECU won't catch the boost in time. OVERBOOST.... BANG!!!

[S4TAN]

As i said earlier; I tweaked it "EVER SO SLIGHTLY" (the slot of the screw moved about 1.5mm)...........

[CliveH]

Blimey, you're brave S4TAN I'd work on the "if it aint broke" motto with this one, and I've not seen this sort of tweaking documented elsewhere - what did Doug have to say? (about the idea, not what you've said above)

[Paulm]

I played with mine a few months ago and basically it's now at it's max (but then that is pretty normal for me ). I do notice a wee bit more peak pressure but nothing to write home about.

[S4TAN]

Blimey, you're brave S4TAN I'd work on the "if it aint broke" motto with this one, and I've not seen this sort of tweaking documented elsewhere - what did Doug have to say? (about the idea, not what you've said above)

There's quite a bit of material about this on AW - I "S'dTFA" as they say - check it out; there's a mix of views on this - some say don't touch, others say have a tweak - I opted for the latter being a curious sort of person and it yielded good results (less turbo lag/quicker turbo response) - but I reiterate: I only turned it VERY SLIGHTLY!!!!

[Paulm]

Had a quick blast just now and with my MRC chip and the N75 at max I am getting max of 18psi on peak boost

[Julesm]

Is the N75 a type of EBV (Electronic Bleed Valve) that regulates boost via the ECU? If so then altering the screw setting to allow more boost will initially allow a degree of overboost until the ECU can control it, hence making the car appear faster. If you have only slightly adjusted it then your MRC remap will be ok, it could alter the fueling slightly (potential to run lean) but the ECU should compensate for this, or there may be enough "safety" in the map?

Jules.

[dummi]

its a solenoid valves that works in controlling the wastegate

[S4TAN]

Well I worked on this piece of logic:

Say (for example) you had an MRC custom re-map (as I have), then some time later your N75 deteriorates/breaks/dies......then you're gonna have to get a new one aren't you?? When you get your new one from vagparts (or whoever) and install it then regardless of the fact that it is calibrated (allegedly) at the factory it can't be EXACTLY IDENTICALLY set the same as your original N75 that was in the car when you had your re-map done.......therefore I don't think that it's beyond the realms of sensibility to have a LITLLE tweak with it.....you never know; you MAY even get a little bit more performance from your re-map (as i feel that i did)........otherwise every time something like this valve dies on your car you're gonna have to go back to MRC and get another re-map, and you could end up revisiting your ecu map every time you change anything on the car!!!!

These solenoid control valves DO deteriorate over time (as does the N249) - I replaced both purely as a matter of course and maintenance - after replacing my original N75 i felt that the car wasn't quite as aggresive as before so had a tweak - I now have really good performance and a nice new N75 turbo frequency regulator that has replaced the 6 year old one I got with my car when I bought it 7 months ago....(along with a nice new motronic diverter valve - the N249)

Now you may find my logic flawed (and probably will) but all I know is this: it worked for me!!!

[Julesm]

Good logic.

Does anyone know if MRC alter the setting on the N75 whilst doing their remaps?

On a std S4 will just altering the N75 give more boost hence more power, or will it just give overboost until the ECU controls it?

Jules.