15. STETT charge pipe & cold air intake
Concerning the charge pipe, there have been some reports of stock charge pipes blowing off due to the increased boost pressure of a tuned N54 engine; I wanted to avoid something similar happening if I choose to considerably increase the boost my turbos are running at. For comparison, the stock turbos run at around 8 psi maximum boost, my Evotech flash had a maximum boost of 14 psi and my future GIAC stage 2 flash would have about 18 psi - and this is even without taking into account additional airflow due to upgraded turbos which is also something I intend to tackle in the near future. So, avoiding boost leaks by upgrading the charge pipe seemed a good idea to me! - Secondly, I had heard that a certain charge pipe already features bungs for methanol injection, i.e. openings where a methanol nozzle could be placed without having to drill any additional holes. As I also had the intention of installing a methanol/water injection system (from Snow Performance
) in the near future, this was a nice bonus from upgrading the charge pipe.
As far as the cold air intake is concerned, anybody active on this forum has seen the countless threads on intakes. For forced induction cars a good air supply is vital, as a turbo car is in fact just a huge air pump and more air means (in simplified terms) the possibility for more power. Also, the colder the air is the better it is, as colder air means denser air and thus more power at the same boost level and less stress on the turbos. Now, I had already decided not to go with a dual cone intake as I found them much too obtrusive in the engine bay; I also had some doubts that sucking in air from the (usually quite hot) engine bay was structurally speaking a good idea. Now, I know that this is an endless debate and emotions tend to run high in relation thereto, but these were just my subjective preferences. Also, my decision was strengthened when I read Former_Boosted_IS' thread comparing DCI and CAI
, the result of which was that a cold air intake provides better cooling than a dual cone intake. Another reason for me in my particular configuration to go with a different intake was also due to the placement of my additional oil cooler: It is situated in front of the radiator and directly below the stock intake pipes behind the grille, partially blocking one of them and potentially radiating heat to the air that is sucked in through them. I did not find that ideal and suspected that this setup could lead to higher intake air temperatures (IAT) or even insufficient air flow for the turbos.
Although there are several charge pipes on the market for the N54, the choice for STETT Performance
was comparatively easy as it seemed to be made of high quality materials and had gathered a number of positive reviews from customers. It is made from 100% 304 stainless steel plus a custom designed throttle body connector that forms a tight seal, and it is therefore highly unlikely that it will come of or produce any boost leaks, when properly installed. Furthermore, it featured the two meth bungs I mentioned earlier, which will come handy once I get my meth kit installed. The STETT charge pipe can also be used with a number of aftermarket diverter or blow off valves, which was also important to me as I had the Forge diverter valves (see my previous review). One should note, however, that due to the fact that Forge has changed the design of their DVs somewhat, I was in need of an adapter for my DVs which STETT also provided. What's more, the adapter was initially in silver, but I absolutely wanted it in black to blend in with my black DVs - and STETT anodized these without any extra charge. Thanks for this! Here's a photo of the charge pipe prior to installation (in silver, though, mine is black), as well of the clamps connecting it to the throttle body:
As to the cold air intake, there is not that much choice available actually. Dinan has just released their CAI which looks nice but is extremely expensive (plus I'm not sure it's compatible with my charge pipe and diverter valves), and Mr. 5 has designed his own CAI. As I had already taken the decision to acquire the STETT charge pipe, it was fairly self-evident to have a look at their CAI as well. Moreover, at the time I was contemplating this, there was a group buy going on which combined both items, and made the decision even easier. Several positive reviews in this forum and a look at the build quality of the CAI on their website also convinced me that it was a good choice. Here's what it looks like prior to installation:
This time, the installation of the charge pipe was done by Birds in the UK (on the same occasion when my M3 components and the Quaife differential were installed), whereas the installation of the CAI was done by Daum Motorsport
. Actually, Birds claimed that the CAI would not fit or that in order to make it fit the whole xenon light assembly on the left side of the car would have to be removed and probably modified. Luckily, that was not correct and although it was a VERY tight fit (mainly due to the big air filter), it did fit indeed. Here are some photos of what the engine bay now looks like with the cold air intake (on top) and the charge pipe (mostly hidden, but you can see the chunky black hoses leading away from the diverter valves):
Installation picture 1 (view from in front of the engine bay):
Installation picture 2 (view standing on the left side of the car):
As far as the charge pipe is concerned, there is not much to say - it looks nice and solid and does its job. I will probably be able to say a bit more once my meth kit is installed and the meth bungs operational as well.
The CAI looks nice too, and it also sounds amazing. You can't really hear the stock intake, but if you push down the throttle now, you can easily hear the CAI sucking in air. It's not an annoying noise, and once you're driving fast it's drowned out by other noises anyway, but between let's say 0 and 80 km/h it is noticeable. I like it very much, it gives the car a nice sporty performance sound. I also have the impression that the car pulls better now, in particular in high rpms. I haven't been able to verify this on the dyno, though - and in any case I think the CAI will be most useful in summer when temperatures are rising, to provide low intake air temperatures. I would somewhat doubt that it really provides an additional 20hp as STETT claims on its website - but an improvement is (at least for me) definitely perceptible.
Problems / disadvantages?
The fitment of both items in the tight engine bay of our cars isn't obvious, as with other aftermarket items. Another disadvantage is also that it is quite obvious that these are not stock items - so you may want to consider taking it out for any maintenance at the dealership (which is a hassle as it's not that easy to take out).
The main issue I had was however with something else: The inside of the CAI was dirty and rusted, and big flakes were coming off. Had my installation shop not noticed this, the flakes would certainly have damaged the engine as they would have been fed directly into the turbos. A recipe for disaster! Even though I don't think it happens often, STETT should improve their quality control in this respect. Also, I wasn't quite happy with the fact that neither installation instructions nor a shipping list were provided when I received the package, but these are only minor criticism.
In summary, both the charge pipe and the CAI are solid quality products and are a definite improvement over the stock items, in particular if you intend to go with a meth kit or have the ar design oil cooler installed.