In Part 1 of this series I introduced my BMW M140i and talked about some of the initial modifications I made to it. These mods were mostly cosmetic and made for great starter mods but now, in Part 2, we're going to go a little bit further.

The series

As I post more parts of this series I will update the links so you can easily browse through them. Part 1 was a great starting point with mostly visual mods but now it's time to step it up a gear (see what I did there?) and continue the journey of customising my BMW M140i.

The BMW M Performance Exhaust

The B58 sounds phenomenal. That 3 Litre inline 6, the twin-scroll turbo, the aggression. It's all amazing and sat on wide open throttle listening to it climb through the revs and hearing that turbo spool and hiss like an angry snake, it's enough to make grin from ear to ear every time. My one point of hesitation though was the standard exhaust which is incredibly reserved and makes the car sound so quiet. As a car enthusiast I can hear all of the right sounds in the background, the burble from the exhaust on the overrun and a flutter from the turbo when shifting, but it was all so quiet. I understand in many ways why BMW made it this way, the mass market appeal of a car quickly fades away if it's too loud or obnoxious, but I wanted just a little bit more.

It turns out that BMW were expecting people to want that little bit more because they created the M Performance Exhaust. There aren't any power gains here yet, those will come later with further exhaust upgrades, but it improves the sound of the car in so many ways. The pops and bangs on the overrun are far more pronounced with a less restrictive muffler and the engine burbles with a little more aggression on the up shift too. Fit by BMW to maintain the warranty on the existing exhaust system, this is a short job where they literally cut the pipe to the old muffler, drop it out and then hang the new muffler and connect it up with a sleeve.

The new exhaust tips are wrapped in carbon fibre, which is always cool, and they feature the M Performance logo engraved into the top. On the bottom image you can see the sleeve just to the back of the muffler where the new exhaust connects to the existing system showing just how simple this mod is. But how does it sound?

😍 To some, this will sound like a loud car starting up, but to me, I can hear that little hint of a snarl in the exhaust note that tells me there's a serious engine up front. A car is always loudest at startup from cold because it will run at higher revs to warm up the catalytic converters (cats) but you can hear the revs drop and the noise reduce through that very short video. Just listen to the burbles with the throttle blips at the end! If they don't give you a little fizzy feeling inside then you're just not a car person, and that's absolutely ok, not everyone is, but understand that to me, they make me smile every time I hear them.

Winter tyres

The next modification may not seem particularly exciting but it's definitely an important one and that's tyres, winter tyres to be specific. We don't have any legal requirement for winter tyres here in the UK so basically nobody uses them, making me somewhat of an exception to the rule here. Other parts of the world will be used to the idea of winter tyres and many countries even have legal requirements for them in certain months of the year. Other countries never freeze so you may have no idea what a winter tyre even is!

I've used winter tyres with various cars in the past and a car that's putting down 335bhp through the rear wheels is a definite candidate for winter tyres, it's just common sense! Winter tyres will give you far better traction in wet and cold conditions and really start to come into their own when we drop below freezing here. The rubber compound the tyre is made of doesn't go hard at those lower temperatures and by staying softer, it allows for better grip. Just looking at the tyres you can see the obvious benefits in the tread patterns and winter tyres should be used in temperatures 7c (44f) or below, rain and snow/ice. So, that's plenty of days to use them here in the UK then...

The first image shows the factory fit summer tyres, Michelin Pilot Super Sport. These tyres are awesome and of course why BMW fits them on their powerful vehicles, but they are designed for warm, dry roads and don't do as well as I'd like in the wet. I've had quite a few OH SHIT moments in this car when the rear end has stepped way out of line without any intention to do so. Having fun and kicking the rear out is great, but not when you're cruising in Eco mode and not expecting it!

You can see the MPSS here in the first image and look at how much rubber there is to contact the ground. The second image shows the winter tyres, Evergreen EW62, and there are a lot more larger grooves to allow water to escape and the smaller zig-zag grooves are called sipes and are for gripping snow on the road.

Winter tyres are not magic and you can't continue to drive as normal in winter conditions. They still require larger separation gaps and longer braking distances than normal, but let me tell you, if I stand on the brakes with the winter tyres on a wet road it's amazing how much sooner I stop compared to the MPSS tyres. Seriously, they are a world apart.

K&N panel filter

Switching back over to the performance and sound side of things now, I talked about the exhaust earlier, where air gets out of the engine, so let's take a look at the intake, where air gets into the engine. The first thing I generally do with most cars I own is to drop a replacement air filter in. The K&N panel filter is a drop in replacement for the OEM filter and is generally a little more free flowing. Having less restriction in the filter is good as it allows air into the engine more easily and can often give you better throttle response or even slightly more power. Imagine going for a run and trying to breathe through one straw or five straws. When you have five straws, less restriction on the intake, you can suck that air in with less effort, resulting in better performance.

These K&N panel filters also change the induction sound of the car and as I said earlier with the exhaust, a little more drama was required in the sound department. Because the filter material is less dense it will allow that sound to rise up and out of the intake to be heard a little more clearly. Whilst I was changing the filter I also removed the sound deadening foam installed inside the OEM intake which again is there to dull down the sounds coming from the car. In the first image here you can see the foam in the lower half of the filter housing with the second image showing the foam removed.

With the original filter and foam removed, it was a simple case of dropping in the new K&N panel filter and closing up the OEM intake. The thing I love about mods like this is that no tools are required, it takes about 5 minutes, just about anyone can do it and there is an immediate difference that you can notice.

Whilst some might claim that there are power gains to be had from a filter, I'm not entirely sold but maybe there is 1bhp or 2bhp in it. As I said before we are removing a restriction on the intake so the engine can breathe more easily, but this wasn't about chasing power for me. The main reason is opening up the intake to let the sounds of that amazing twin-scroll turbo out! When the turbo is spooling up now there is considerably more boost hiss that's audible and the flutter from the turbo is far more pronounced. More of those great noises that seriously excite the 5 year old kid inside me!

Eventuri carbon fibre intake

The K&N panel filter was good and definitely gave the intake a lot more grunt, especially with the sound deadening foam removed, but it wasn't quite cutting it. There was a hint of boost hiss under full throttle but you really couldn't hear the turbo chatter and the intake was still really quiet. Turns out that the standard intake, even on an M-class BMW, is called an 'intake muffler', implying it's designed to reduce sound. Here's the part in the factory parts catalogue, number 01.

Not only that but the intake pipe from the filter housing also had a resonating chamber built in, which further kills any sounds trying to escape. Look at the top left of part 6 on this diagram.

*Also notice how parts 14 and 15 are missing for my car, more on that soon.

This little chamber on the intake is designed to capture and kill sound. 😱

There are ways to modify the OEM system by cutting this chamber off and sealing the pipe, or you can look at aftermarket intakes which is the easier option and allows you to return it to stock later if you like. I looked around and came to the very easy decision that it was going to be the Eventuri Carbon Fibre Intake, which is a masterpiece of beautiful carbon fibre.

The intake pipe on this doesn't feature any sound deadening or resonating chambers and it's a 'hard pipe' too meaning there is even less sound deadening properties. Straight from the depths of the engine right in front of the turbo, all the way up to the back of the filter there is nothing to get in the way of that beautiful chorus of sounds. Now it just needs installing and it turns out that was a breeze too. Here is the original filter housing removed on the left side of the engine bay and the following shots are the Eventuri intake installed. I may have gotten a little excited and I forgot to take pictures during the process so yeah... err... here's the finished product after that.

Apart from looking absolutely stunning in the engine bay, the intake completely changed the sound of the car. It's amazingly well engineered, fitting perfectly into the OEM location, aligning perfectly for mounting and including things like little bump strips to install on the frame of the car to protect the intake. The MAF mounts up perfectly and everything just fits. This is a serious bit of kit. As for the sound, the hard intake pipe doesn't dull any sound, you get full boost hiss under even mild acceleration and the turbo chatter is outrageous! You don't get any blow-off or dump-valve sounds from a modern car like this, my car comes with an electronic wastegate to take away some of that fun but it does have some other cool tricks and produces a really distinctive sound when handling excess boost. On top of this, there is an extra performance perk for the Eventuri intake and that's the 'hot climate conversion'. For cars built and shipped to countries with hotter climates, there is an extra air intake feed that goes from behind the grille into the air filter chamber which is missing on my car and many others. Colder air is denser than hotter air meaning there is more of it in the same space and I said before, getting more air in is better. Here's the front grille popped out and a closer look at the opening on the left side that you have to open up and fit the new carbon fibre ducting through.

I will show you a shot of the finished product in a later blog post as I made some other changes while I was in there that I don't want to spoil so stay tuned to see what the full air scoop looks like when fitted.

Before we wrap up this section it's worth pointing out that all of these changes aren't just about sound, the previous exhaust work and this intake work is laying the foundation for future modifications that will require the car to breathe more freely. If you ever want to make more power from an engine then one of the most important things is to get air in faster and get air out faster, and that's exactly what new intakes and new exhausts do.

More to come!

With everything covered off in Part 2 I've started the ground work for some future mods and made enormous changes to how the car sounds. For some people, driving a car is about getting from A to B, but for car people, driving a car is an experience to enjoy. Hearing what's going on inside the engine and listening to the sounds it produces are deeply addictive and I'm thrilled with the changes made here. Coming up in Part 3 I have some minor repair work I did myself to save some money, more groundwork for future big power mods and a heap of cosmetic mods that you can DIY on the cheap to really improve the looks of a car.


Here's the list of parts used in Part 2 and where you can get them:

M Performance Exhaust + Exhaust Tips

Evergreen Winter Tyres

K&N Panel Filter B58 F20 F21

Eventuri Carbon Fibre Intake

View all of the other blog posts here: The BMW M140i Project Series