Post-P/GPF M4 Competition Pack quieter?

[rhm_SIIM4]

Hi all,

So I’ve just replaced my ‘16 M4 standard with a new (September ‘18 build date) M4 Competition Pack with the new Petrol/Gasoline Particle Filter. Car feels great and I’m liking the suspension and TCS setting better - however it is really a lot quieter than my non-CP one.

In some ways this is a helpful as I couldn’t really use S/S+ engine in towns/villages in the old one as it was often embarrassingly loud. But on the other hand it is really a bit quiet - and now I’ve turned off ASD which made a bloody racket especially on the motorway and had to go - its positively civilised even in S+.

Also, the burbles/pops are there but pretty quiet - I can’t hear them at all on the go - if I park up and rev the engine they’re there and it is clearly different to my previous one - but I was kinda expecting it to be more overt.

So I am wondering whether the filter is taming the exhaust - any other experience? Hopefully with the reported 0.1atm extra boost there is no loss in power. It certainly feels quick enough.

Other observations with the switch to a 2-year newer CP.

1. Suspension/ride much firmer - which I like - and rides B-roads as well or better - clever stuff. I will get flamed for this but the overall solidity vs the non-CP feels more Porsche like.
2. Steering feels a little heavier and more natural - maybe coding, maybe wider tyres but slightly better in my view.
3. MDM mode seems more playful
4. The MPSS tyres are lethal compared to the 4S tyres I had on my last one - in damp conditions
5. DCT seems smoother - in S3, much less thuds through gears - doesn’t want to spin its wheels on the 2nd to 3rd change anymore but doesn’t seem slower. Probably a good thing as it was a bit silly before.
6. And I got San Marino Blue for a sensible price now its been added as a ‘standard’ colour.

Richard.

[Zippee]

Very useful feedback, Richard. Thank you.

[OneExtra]

Originally Posted by T_M4CP

Very useful feedback, Richard. Thank you.

I bet you were all of this Tony

[Zippee]

Originally Posted by OneExtra

I bet you were all of this Tony

Even so, massively useful to hear it from the horses mouth as it were. Nice and reassuring the drive is an improvement. Now, just to tweak with the noise!

[OneExtra]

Originally Posted by T_M4CP

Even so, massively useful to hear it from the horses mouth as it were. Nice and reassuring the drive is an improvement. Now, just to tweak with the noise!

That's my point, it was the Perfect Post for you

[Zippee]

Originally Posted by OneExtra

That's my point, it was the Perfect Post for you

[Nigelo]

Interested in this myself - mine should be arriving in the next week. I'm fond of a burbly, noisy exhaust within reason, and it seems the route of removing the 2nd cats is now closed to us (this being where the GPF is hiding).

Also.... anyone know what "status - workshop job open" is? According to the BMW genius livechat, this is where my car is and has been since last Monday.... It's somewhere in the UK......

[rhm_SIIM4]

Originally Posted by Railgun

On a side note, can't say I've ever seen anyone use atmospheres in casual automotive conversation when talking about boost pressures.

Ha ... sorry should have said “bar” ... but maybe you’re just in the wrong casual automotive conversations

So nobody is surprised with the car getting quieter? Can you put MPE on this or is the GPF doobrie a blocker?

... and now you’re going to say you don’t hear about doobries in casual automotive conversation either

R.

[rhm_SIIM4]

Originally Posted by Railgun

On a side note, can't say I've ever seen anyone use atmospheres in casual automotive conversation when talking about boost pressures.

And before anyone else gets in first - 1 bar isn’t quite an atmosphere I know ... but 0.987 is close! Same thing to me... must be my subsequently completely unused science degree speaking

[Zippee]

Originally Posted by rhm_SIIM4

Ha ... sorry should have said “bar” ... but maybe you’re just in the wrong casual automotive conversations

So nobody is surprised with the car getting quieter? Can you put MPE on this or is the GPF doobrie a blocker?

... and now you’re going to say you don’t hear about doobries in casual automotive conversation either

R.

Officially, BMW will not sell or fit them due to them exceeding the new regs (5 or 6a or whatever the fuck it is this week).

On the technical front, removal of the OPF/PPF could throw an error up as it detects pressure differential either side. One hopes the aftermarket world comes up with coding (if possible) or a module across the sensor that could fool the differential.

Its most certainly an area I'm am watching closely too. As a side note, Paul at PCW exhausts can still do the mod but now obviously without removing the PPF (secondary cat as was). He can remove the resonator and do work on the back box. I'm not 100% sure whether this will have a significant pressure change to flag an error. Will get more info off him.

It opens its throat a bit more but the PPF will always deaden and filter the sound.

[Nigelo]

The gpf sensor seems to detect a build up of back pressure, rather than a differential as there is only one sensor per downpipe and nothing downstream. Once the back pressure builds to a certain level, the exhaust valves get shut and a high egt fuelling strategy comes into play to burn off the particulates.

[rhm_SIIM4]

Does anyone have any info about what sort of power increase 0.1bar would produce to compensate for the PPF? I’d be happy to assume that I have a more powerful car because they had to overcompensate ... would just need some random dyno chart and I’d be set

[Zippee]

Originally Posted by Nigelo

The gpf sensor seems to detect a build up of back pressure, rather than a differential as there is only one sensor per downpipe and nothing downstream. Once the back pressure builds to a certain level, the exhaust valves get shut and a high egt fuelling strategy comes into play to burn off the particulates.

Ah ha, excellent info thanks. That could be a bit trickier to fool or bypass then. I'd assume someone somewhere may need to write a new map to take this in to account (OpenFlash, BM3).

[Zippee]

Actually, it might be a bit simpler if thats the case. If the OPf is removed, an output module would only need to send a 'I'm ok at x pressure' signal back to the ECU therefore never initiating a regen.

Petrol partic.filter sens./mounted parts

[Nigelo]

Not entirely sure, but from some quick reading and guesswork... 0.1 bar could yield around 15-20 ish bhp more

[Nigelo]

Originally Posted by T_M4CP

Actually, it might be a bit simpler if thats the case. If the OPf is removed, an output module would only need to send a 'I'm ok at x pressure' signal back to the ECU therefore never initiating a regen.

Petrol partic.filter sens./mounted parts

Hmm, looking at that diagram, the sensor is looking at the pressure differential... Only across the primary cats... Must be using the pre cat pressure as the baseline and the after cat pressure would increase if the gpf is blocked.

[bry777]

Originally Posted by Nigelo

Not entirely sure, but from some quick reading and guesswork... 0.1 bar could yield around 15-20 ish bhp more

Where does the .1 bar increase info come from? I have googled to death and cannot find anything about it.

[Zippee]

Originally Posted by bry777

Would love to know what the power is because they are still spec'ing it as 431, whatever is on the V5 is what it is as that would be another potential diesel gate if they start lying on there.

Its a question I directly asked BMW Genius due to it being published on the configurator (431bhp for CP). The brochures state 450 (or 444). They confirmed it was a mistake on the configurator and it is indeed 450.

[bry777]

Originally Posted by T_M4CP

Its a question I directly asked BMW Genius due to it being published on the configurator (431bhp for CP). The brochures state 450 (or 444). They confirmed it was a mistake on the configurator and it is indeed 450.

let us know what the V5 says as that is the official BMW declaration. I have always found those girls on that online chat have a brochure in front of them and thats the limit of their knowledge.

[bry777]

How did you turn off ASD? I want to do mine but a bit concerned about before first service. Can't they pick it up with a program cheksum or are they not bothered?

[Zippee]

Originally Posted by bry777

let us know what the V5 says as that is the official BMW declaration. I have always found those girls on that online chat have a brochure in front of them and thats the limit of their knowledge.

What does your V5 say?

[rhm_SIIM4]

Didn’t know v5c had engine power listed. I’ll check my post-PPF when I’m back at home ... did pre-PPF competition packs say 431 or 450ps? Lots of BMW docs say 431 even though brochures and staff say 450ps.