N75 Question

[MarkB]

If it had been messed with before, I would think that could be a time.

[flashyg]

If your having concerns with the n75 log 115 post up and we will see.
All n75 is doing is controlling wastegates to requested.
Some will over control others under.
Mess with the screw risk damage to n75.
You could trick your car into all sorts of issues map sensor, fpr, maf, knock sensors. Whats the point? You take it to a good tuner, you in trust the whole package and accept the tune that they are comfortable with based on their knowledge and experience after you have paid for it.
Keeping the car in good nick is hard enough. Hope this has helped. Log block 115.

[Julesm]

in some cases - yes.

Hi Doug,

What cases would these be?

If the car had had a remap and then the N75 failed and needed to be replaced, then surely the N75 would just need setting to the same parameter as before? I can't see how this would constitute a remap. Or is the N75 adjusted as part of a remap so that if it is replaced then it would need setting to the same again (which would not be its standard setting)? If so then I can understand why a "mini" remap may be required.

Jules

[Doug_S2]

A wgfv is just a mechanical device(solenoid) that pulses and being controlled by the ecu. If the car was mapped on an old wgfv that was reacting slow then the new wgfv will not perform the same way.

[S4TAN]

Please remember that MRC are in business to make money and therefore not obliged to share their knowledge or experience beyond a certain level on forums.

I am perfectly well aware that MRC are a business DavidT, I have, after all, spent what to me is not an inconsiderable sum of money with them since owning my S4! - it was simply a question related specifically to MRC re-maps (and the N75 valve - a topic that pops up now and again and seems to generate a certain degree of interest within the forum) - in no way did I feel that Mihnea was obliged to share his knowledge - but having had the pleasure of meeting him a few times he comes across as a very personable guy and I thought it ok to ask what is to my mind a fairly innocuous question - and, as it transpires, it would seem that he didn't mind either (and neither did Doug).

I thought I'd use the forum as the platform for the question considering the large numbers of S/RS owners who have benefited from Mihnea's "ecu magic" - I thought others may like to know too (and it would seem that I was correct in this assumption judging from the subsequent posts by other members) - and just in case there were some sensitivity surrounding the issue of answering this question I took the liberty of pm'ing Mihnea to allow him a less public avenue to answer.

This is what I thought forums such as this were for! - but apologies if i've broken any rules.

@Mihnea and Doug - thanks for taking the time to answer the question guys, much appreciated.

[S4TAN]

Totally agreed with Doug, sorry Julian, haven't had lots of time last week for forums unfortunately...

No worries Mihnea - totally understandable considering what I've just read about your 188mph spin! Sounds like a real brown-trousers moment! Glad you're ok man...

[DavidT]

Please remember that MRC are in business to make money and therefore not obliged to share their knowledge or experience beyond a certain level on forums.

I am perfectly well aware that MRC are a business DavidT, I have, after all, spent what to me is not an inconsiderable sum of money with them since owning my S4! - it was simply a question related specifically to MRC re-maps (and the N75 valve - a topic that pops up now and again and seems to generate a certain degree of interest within the forum) - in no way did I feel that Mihnea was obliged to share his knowledge - but having had the pleasure of meeting him a few times he comes across as a very personable guy and I thought it ok to ask what is to my mind a fairly innocuous question - and, as it transpires, it would seem that he didn't mind either (and neither did Doug).

I thought I'd use the forum as the platform for the question considering the large numbers of S/RS owners who have benefited from Mihnea's "ecu magic" - I thought others may like to know too (and it would seem that I was correct in this assumption judging from the subsequent posts by other members) - and just in case there were some sensitivity surrounding the issue of answering this question I took the liberty of pm'ing Mihnea to allow him a less public avenue to answer.

This is what I thought forums such as this were for! - but apologies if i've broken any rules.

@Mihnea and Doug - thanks for taking the time to answer the question guys, much appreciated.

We encourage discussion and debate here, that much is clear and it is not a question of rules. Tuners/suppliers etc who support the site are encouraged to post.

Thank you for taking onboard my point about what is reasonable to ask a commercial entity to divulge on a public forum.

[S4TAN]

My pleasure!

[Dr-Al]

If the car had had a remap and then the N75 failed and needed to be replaced, then surely the N75 would just need setting to the same parameter as before? I can't see how this would constitute a remap. Or is the N75 adjusted as part of a remap so that if it is replaced then it would need setting to the same again (which would not be its standard setting)? If so then I can understand why a "mini" remap may be required.

Jules

As I understand it, each N75 is factory calibrated (using the screw) to pass a certain amount of air through the control/vent ports at a given duty cycle. By standardising the units as they come out of the factory, the manufacturer is removing the need to re-calibrate the car's ECU to match the valve if it is ever replaced. IE, the valve is made to fit the ECU's boost versus duty cycle table simply because it is easier to do this than to change the map every time a new valve is fitted.

By messing with the screw, you would be causing the valve to react in a way that the ECU is not expecting. I cannot see how this would be desirable because the ECU would detect that the car was getting over- or under- boost and would correct it by altering the N75 duty cycle or opening the DVs. At best, this will have no effect, at worst it will cause the ECU extra work to correct the 'problem' that has been introduced from the 'faulty' N75.

This would apply equally to both mapped and stock engines.

IMHO, the only time the screw should need to be touched would be if the valve is getting weak/sticky and is no longer performing within acceptable parameters. In this case, it is probably on its way out anyway and should be replaced, but a slight tweak could help until the new part was fitted.

However, this does beg the question - why does the manufacturer leave the screw exposed and not fill the hole with thread-lock?

[Julesm]

If the car had had a remap and then the N75 failed and needed to be replaced, then surely the N75 would just need setting to the same parameter as before? I can't see how this would constitute a remap. Or is the N75 adjusted as part of a remap so that if it is replaced then it would need setting to the same again (which would not be its standard setting)? If so then I can understand why a "mini" remap may be required.

Jules

As I understand it, each N75 is factory calibrated (using the screw) to pass a certain amount of air through the control/vent ports at a given duty cycle. By standardising the units as they come out of the factory, the manufacturer is removing the need to re-calibrate the car's ECU to match the valve if it is ever replaced. IE, the valve is made to fit the ECU's boost versus duty cycle table simply because it is easier to do this than to change the map every time a new valve is fitted.

By messing with the screw, you would be causing the valve to react in a way that the ECU is not expecting. I cannot see how this would be desirable because the ECU would detect that the car was getting over- or under- boost and would correct it by altering the N75 duty cycle or opening the DVs. At best, this will have no effect, at worst it will cause the ECU extra work to correct the 'problem' that has been introduced from the 'faulty' N75.

This would apply equally to both mapped and stock engines.

IMHO, the only time the screw should need to be touched would be if the valve is getting weak/sticky and is no longer performing within acceptable parameters. In this case, it is probably on its way out anyway and should be replaced, but a slight tweak could help until the new part was fitted.

However, this does beg the question - why does the manufacturer leave the screw exposed and not fill the hole with thread-lock?

Agree with most of what you say. But if an N75 is adjusted the ECU only corrects once, I can't see how it can continually correct the duty cycle on the N75 as it's adjustment is determined by it's screw. Is this not the case?

The main question I want answering is; is the N75 adjusted by the tuner during a remap? If so and then the N75 failed, it would be replaced with an N75 that is preset at the factory, therefore it would need adjusting to bring the cars performance back to where it was originally, alternatively you could adjust it yourself until the car felt "right" again but this would not be the correct thing to do. Is this why a car would need to be returned to the tuner for a possible remap?

Jules.

[GrahamS4]

Don't believe it's touched during a remap, at least not mine.

[Dr-Al]

The main question I want answering is; is the N75 adjusted by the tuner during a remap? If so and then the N75 failed, it would be replaced with an N75 that is preset at the factory, therefore it would need adjusting to bring the cars performance back to where it was originally, alternatively you could adjust it yourself until the car felt "right" again but this would not be the correct thing to do. Is this why a car would need to be returned to the tuner for a possible remap?

Jules.

This is my point. The N75 should be left at the factory setting so that it can be replaced if necessary without having to edit the map.

[Julesm]

Both valid answers...........but, is the N75 adjusted during a remap? I think that it is as I don't see any other way of increasing the boost, is there another way of increasing boost without changing the setting of the N75? If so can somebody shed some light please?

Jules.

[GrahamS4]

I have no technical knowledge on this, but from what I have read you are off the scent Jules.

[MarkB]

Boost is set within the ECU. The N75 is a regulator controled via the ecu