Peak boost

[Dippy]

I went a bit mad last night, and during my fun I noticed my boost gauge read a peak of 1.42 kg/cm2 which is about 1.39 bar. That's the highest I've seen and it surprised me a bit.

[smurfbus]

when I'm datalogging. I think its ok if its in the midrange.

I hope it was not a shift peak, did not sound like it.

If you like it lower you can try to adjust n75-valve 1 mm clockwice. not for everyone because its very sensitive and can brake when tinkered to much.

[Dippy]

Actually it was a shift-peak, from 5th to 6th.
I'm not worried about it (especially because I have the APR bipipe), I was just surprised.

There's no way that I'm messing with the N75 - that valve should only be touched when there's something wrong with the forced induction system.

[smurfbus]

Ok, if you are bipipe men I think you also now when your dv's are to blame. I have also seen one spike although I just installed new 710N's. Nothing wrong with the old ones but changed them anyway. I did have a torn f-hose witch I also replaced. How much did you pay for the bipipe and where did you buy it from?

As for the N75 I did turn it a little less agressive setting when I was feeling there is something wrong with the system! Might do it again if lower boost is needed. If someone has very agressive chip and then goes stg2+ the boost might get too high. then one needs mbc-paraller or N75 detuned.

My boost is now quite agressive and I thing I'm near 600NM at 3250 rpm?

Lets hope turbolady did not hear that [img]images/graemlins/newsaw.gif[/img]

[keyser]

such a boost peak is a normal think when you're mapped with circumstances like +25celsius
I guess it was preetty cold yesterday night, wasn't it? [img]images/graemlins/smile.gif[/img]

[Dippy]

How much did you pay for the bipipe and where did you buy it from?

I got it direct from APR when they were at a show in the UK last year. They discounted it for me and I think it was £150 but I really can't remember.

As for the N75 I did turn it a little less agressive setting when I was feeling there is something wrong with the system! Might do it again if lower boost is needed. If someone has very agressive chip and then goes stg2+ the boost might get too high. then one needs mbc-paraller or N75 detuned.

My boost is now quite agressive and I thing I'm near 600NM at 3250 rpm?

Lets hope turbolady did not hear that [img]images/graemlins/newsaw.gif[/img]

I think I understand your case. It is clear to me that the ECU should control the wastegates and the N75 valve is ONLY to calibrate the system. So if you change the N75 then then the max boost may change from what the ECU thinks it is. However since the S4 still has the boost sensor, the ECU should compenstate. So the only time when you can override the ECU with the N75 is when the ECU's control point reached it's limit.

I think if you have to do this to protect the engine then you really do have the wrong ECU map.

That's what I think about the situation but I may be wrong - what I know is just based on reading Audi technical manuals.

[Dippy]

such a boost peak is a normal think when you're mapped with circumstances like +25celsius
I guess it was preetty cold yesterday night, wasn't it? [img]images/graemlins/smile.gif[/img]

The best I've seen before was about 1.3 bar. Yes I have an AmD chip. It's not that cold at the moment actually, and I'd have thought that the temperature would need to change quite a lot to affect atmospheric pressure surely???

[keyser]

second option is, that you MAF is becoming useless [img]images/graemlins/frown.gif[/img]

as MAF starts not to indicate correct numbers your ECU is raising boost to supply more air...
but even as it does boost more, ECU isn't giving more fuel, as it reads lower amounts of air from MAF sensor [img]images/graemlins/frown.gif[/img]

[smurfbus]

I think I understand your case. It is clear to me that the ECU should control the wastegates and the N75 valve is ONLY to calibrate the system. So if you change the N75 then then the max boost may change from what the ECU thinks it is. However since the S4 still has the boost sensor, the ECU should compenstate. So the only time when you can override the ECU with the N75 is when the ECU's control point reached it's limit.

I think if you have to do this to protect the engine then you really do have the wrong ECU map.

That's what I think about the situation but I may be wrong - what I know is just based on reading Audi technical manuals.

I think I'm ok for now. It peaks at 1.4 and tapers down like every other chip. I guess my split dp and catback have changed the boost curve with colder wether.

[Dippy]

second option is, that you MAF is becoming useless [img]images/graemlins/frown.gif[/img]

as MAF starts not to indicate correct numbers your ECU is raising boost to supply more air...
but even as it does boost more, ECU isn't giving more fuel, as it reads lower amounts of air from MAF sensor [img]images/graemlins/frown.gif[/img]

I think it's OK - the last time I logged air flow with VAG-COM it maxxed at 280 which I think is good for a chipped car.

Anyway, the car's in at AmD for it's 40K service this week, and I've asked them to do a RR test and specifically check the MAF. Seems to me that the MAF will fail at some point and maybe it'll be a good idea to replace it before it fails!