Cars characteristics & sound changes from time to time

[Vesh]

Hey everyone
Im driving an c7 Performance with Stage 1 apr 705hp, car has 60k km down now , bought it at 4600km. Ive added a non resonated miltek about 30k km ago. Sometimes the car just sounds different and i cant find out why… exhaust valves are working properly. Can it be fuel related ? Ambienttemperatur related ? Its a bit quieter sometimes and when downshifting Theres only a Single bang instead of 3-5 bangs… it also doesnt Sound as Dirty when i do a Slow Start at the Traffic light for Example. Dont have Any faultcodes when it Happens, usually Happens when my tank is below 40% (thats what it feels like but im not Sure… Adding fuel does for sure not fix it though. Usually using 101 Shell vpower - or normal 98, doesnt matter i think… The Single downshift bang sounds Kinda surpressed too, Not like the valves are closed but kinda like the sound is cut off… usually its a loud bang where you hear it clearly banging at the end / outside of the exhaust But then you hear it like its banging deeper inside the exhaust… Any ideas ?

[Vesh]

So ist Looks like of i do a Service or Oil change reset it changes Oil Quality from 2 to 1 and the Problem is fixed After a few km of driving. What can cause this ?

[Tadass910]

Hey everyone
Im driving an c7 Performance with Stage 1 apr 705hp, car has 60k km down now , bought it at 4600km. Ive added a non resonated miltek about 30k km ago. Sometimes the car just sounds different and i cant find out why… exhaust valves are working properly. Can it be fuel related ? Ambienttemperatur related ? Its a bit quieter sometimes and when downshifting Theres only a Single bang instead of 3-5 bangs… it also doesnt Sound as Dirty when i do a Slow Start at the Traffic light for Example. Dont have Any faultcodes when it Happens, usually Happens when my tank is below 40% (thats what it feels like but im not Sure… Adding fuel does for sure not fix it though. Usually using 101 Shell vpower - or normal 98, doesnt matter i think… The Single downshift bang sounds Kinda surpressed too, Not like the valves are closed but kinda like the sound is cut off… usually its a loud bang where you hear it clearly banging at the end / outside of the exhaust But then you hear it like its banging deeper inside the exhaust… Any ideas ?

I also have Miltek none resonated exhaust but I don’t see any difference as you described, maybe just placebo effect

[Tadass910]

So ist Looks like of i do a Service or Oil change reset it changes Oil Quality from 2 to 1 and the Problem is fixed After a few km of driving. What can cause this ?

What do you mean?

[Vesh]

Hey everyone
Im driving an c7 Performance with Stage 1 apr 705hp, car has 60k km down now , bought it at 4600km. Ive added a non resonated miltek about 30k km ago. Sometimes the car just sounds different and i cant find out why… exhaust valves are working properly. Can it be fuel related ? Ambienttemperatur related ? Its a bit quieter sometimes and when downshifting Theres only a Single bang instead of 3-5 bangs… it also doesnt Sound as Dirty when i do a Slow Start at the Traffic light for Example. Dont have Any faultcodes when it Happens, usually Happens when my tank is below 40% (thats what it feels like but im not Sure… Adding fuel does for sure not fix it though. Usually using 101 Shell vpower - or normal 98, doesnt matter i think… The Single downshift bang sounds Kinda surpressed too, Not like the valves are closed but kinda like the sound is cut off… usually its a loud bang where you hear it clearly banging at the end / outside of the exhaust But then you hear it like its banging deeper inside the exhaust… Any ideas ?

I also have Miltek none resonated exhaust but I don’t see any difference as you described, maybe just placebo effect

Def. Not a Placebo Effekt. I actually think its the apr tune, it Night be resetting to Stock, dies Anyone know how to change program on the Fly?

[TaylorRS6]

If you are in comfort the car might be putting itself into 4 cylinder mode which I notice an exhaust note change. I'm on stock exhaust with valves disconnected. As for shifts mine are also random. Sometimes many pops and bangs sometimes 1 or 2... depends on where in the rev range your shifting and how much unburnt fuel is there..

[Codie247]

I’m running Milltek non res and can definitely hear the change when in 4 cylinder mode. Was a little annoying at first. Sort of used to it now.

Lee

[Vesh]

That’s not what I mean. I’m aware of 4cyl mode.
It’s a permanent issue that keeps being for more than a full tank. ( not like it’s present for 15min and then normal again and so on, when it happens it stays for longer than a full tank)Sometimes it’s there sometime it’s gone. It changes the whole characteristics of the sound of the car and feeling too. Like there’s boost missing, less crackle than usual, and like there’s pressure/force missing at the crackles. No crackle / bang at start. The best I could describe it would be a “in between” comfort and dynamic… it’s super annoying and I don’t know how to reset it. My valves are always open , though the car is definitely quieter when the problem is present. No dtc though… anyone have an idea what to try or how to debug this?

APR updated my maps but that wasn’t it.
Changing oil quality in VCDS from 2 to 1 doesn’t fix it
Exhaust Valves are not stuck, engine is not in safemode
No dtc error at all
Have the apr dongle and app, I’m using the correct map - at least that’s what the app tells me…

It seems like the EPC light (right next to CEL is blinking when I change map with the app
When I change map with the speed limiter the CEL is blinking like it should (apr manual says so)

That’s what I’m currently trying (changing maps analog by speed limiter) and see how that goes… if thats the problem it seems to be that it loads the stock map somehow (and the app still showing apr map) my problem here is I’m driving the car since beginning with the tune(about 60000km now), so I can’t tell if this is just stock or not… but 750hp and 600hp is quite a difference, so that might be it… it’s a waiting game I guess, changing map till everything works as expected seems to take 3-5 engine starts and some mileage … ugh

[Vesh]

Changing maps analog doesn’t solve it either, any ideas ?

Could it just be „bad fuel“ ? Any sensor I could clean ? (MFA maybe ?) I’m lost here, it’s so frustrating, its like I’m driving another car :-/

Anything I could think of is a software problem or a sensor doing false readings and therefore software acting weird.

[Vesh]

Well just got my VCDS and it’s a sensor error. Had something to do with the breaks (got ceramics) (that sensor thing that checks if it’s raining and slightly uses the breaks so they’re always dry in the rain. Therefore ecu got false readings and got into a kind of a limp mode without a cel. Deleted errors and problem was instantly gone.
Guess it’s some kind of loose contact as it didn’t came back yet after about 500km