BMC filters and MAF's?

[c3nturi0n]

afternoon all,

hope you are enjoying summer hols (mainly applicable to those outside the UK at least).

I recently changed my car's air filters to new set of BMC's... everything was brilliant, super high boost and it worked as expected. After 3k miles and while being in Europe i noticed that it sometimes kind of "stutters" at around 2.2-2.5k rpm and then it boosts fine from ~3k rpm. I do not notice that while stationary and with revs up.

Nothing reported on VCDS and i wonder if BMCs caused MAFs to clog up a bit? or am i talking absolute nonsense ?

Any advice welcome.

ps. least to say is that i did manage to clock 205mph en route to Stuttgart .

[welwynnick]

It's hard to believe that an air filter change could cause a delayed and speed-specific hesitation, and lots of people use them already.

It won't be down to the MAF's though, because there aren't any. The RS6 uses other sensors to measure load - primarily manifold air pressure, also throttle position, engine speed, temperature, etc.

If you think the filter change has brought this about, it could be you've missed one of the many connections on the filters. Crankcase breathing is particularly complicated, and you might be hitting the breather mode changeover off/on boost.

Nice top speed run! Can't be too much wrong.

Nick

[c3nturi0n]

It's hard to believe that an air filter change could cause a delayed and speed-specific hesitation, and lots of people use them already.

It won't be down to the MAF's though, because there aren't any. The RS6 uses other sensors to measure load - primarily manifold air pressure, also throttle position, engine speed, temperature, etc.

If you think the filter change has brought this about, it could be you've missed one of the many connections on the filters. Crankcase breathing is particularly complicated, and you might be hitting the breather mode changeover off/on boost.

Nice top speed run! Can't be too much wrong.

Nick

cheers Nick.

Any suggestions on how to diagnose so as to determine what's causing this "phenomenon" i have?

Car boosts fine past 3k revs... it's on that 2.2-2.5k where i notice that slight hesitation / almost shudder like feeling.

reason why i mentioned MAFs is that i had such manifestation in the past with large TDI Audi engines (A6 3.0 and A8 4.2) and it was cured with MAF replacement.

[Jim Haseltine]

I'd take a look at the air pressure sensors. If the connections are ok take the sensors out of the inlet pipes and give them a spray of silicone free carb cleaner if they look to be oiled/mucked up. Shake them dry or lightly dab them with tissue.

[c3nturi0n]

I'd take a look at the air pressure sensors. If the connections are ok take the sensors out of the inlet pipes and give them a spray of silicone free carb cleaner if they look to be oiled/mucked up. Shake them dry or lightly dab them with tissue.

cheers Jim.

can you advise where they are located in the engine bay or point me to a right part number on the diagram please?

https://audi.7zap.com/en/rdw/audi+rs6+r ... 008-641/1/

[Jim Haseltine]

Parts 39 on https://audi.7zap.com/en/rdw/audi+rs6+r ... 45-145050/
I'd suspect that you get the 'stutter' when you've got your foot down and not when you're at light/medium throttle? If so, chances are that it's a pressure sensor that's either dirty or has an iffy connection.

[c3nturi0n]

cheers Jim... that worked well.

Many thanks.

[c3nturi0n]

Parts 39 on https://audi.7zap.com/en/rdw/audi+rs6+r ... 45-145050/
I'd suspect that you get the 'stutter' when you've got your foot down and not when you're at light/medium throttle? If so, chances are that it's a pressure sensor that's either dirty or has an iffy connection.

silicone / maf cleaner worked for so much... I did order set of new sensors which i fitted today.

Car seems much better but i still do experience that slight misfire like syndrome ~2200-2500 revs.

Again nothing odd or weird reported on VCDS.

any other hints or clues?

[Toady1]

Have you removed the throttle bodies ever? May be an air leak on the gaskets?

[c3nturi0n]

Have you removed the throttle bodies ever? May be an air leak on the gaskets?

Good point Toady1... i did recently replaced o rings under the oil cooler and T/bodies were moved as part of the job. I’ll take a look at it but doubt that thick piece of rubber has any leaks .

[welwynnick]

Throttle body gaskets are important on cars that use mass air flow meters for load measurement, but where load is measured with manifold air pressure sensors, like the RS6, it's not critical.

Nick