Stock Engine Cover/Intake

Well I’m a fickle person.  Over the course of the past week and a half, I’ve been tinkering with my intake and diverter valve setups.  I think I’ve finally settled on one; stock.  I know it is quite an about face, but I’ve come to the realization that the stock setup is actually quite good and does not detract from power.  It has excellent filtration, a good source of cold air, and is excellent at avoiding water intake.


The stock engine cover, not exactly your worst enemy

MAF Design

The stock engine cover uses an oval maf sensor housing, one that isn’t easily duplicated in aftermarket housings.  In fact, I don’t think there are any aftermarket intakes that accurately mimic the stock housing.  Round intakes can come close but not 100%.  The necessity of 100% accuracy is debatable but the closer you are, the better.  Fujita ignored this and was rewarded with the worst performing intake for the MKV.  Wholly inaccurate maf measurements and worse performance.  Even certain versions of the BSH diverter valve kit threw the maf sensor readings off, not to the degree of the Fujita, but enough to reduce performance.  The stock housing also contains a flow straightening screen which helps the maf read air flow as accurately as possible.  In short, you do not want inaccurate maf readings.


Oval tube and flow straightener

Inaccurate maf readings can lead to a multitude of problems such as reduced performance, poor gas mileage and poor throttle response.  Most of these result from messing with the short term (STFT) and long term (LTFT) fuel trims.  Here is a good article from Ross-Tech explaining how fuel trims work: Fuel trim info.  Basically you want to keep your trims around as close to zero as possible.  STFT has a +-5% range while LTFT is +-10% I believe.  I’m not so sure on the LTFT.  If you exceed these ranges, your performance will begin to suffer.

With the stock intake, my STFT is less than +- 1% and the LTFT is less than +-2.5%.  The aftermarket intake showed trims of -2.5% and around 5% respectively.


Maf position in stock intake

Stock vs. Aftermarket

The stock intake feels much better down low.  Chalk it up to the MAF area design or location but I cannot deny that it feels much more responsive down low.  The metal of the aftermarket intake pipe may be absorbing heat when the car isn’t moving.  In the upper rpm range, the aftermarket intake feels like it pulls harder/better.  It’s possible that an advantage in air speed may show up once the engine starts requesting more air.  Another possibility is that the airflow in the tube becomes less turbulent as speed increases, allowing the MAF to read the mass correctly.

Filtration is one area where the OEM intake will always win.  As good as the AEM filter may be, it is not going to beat the OEM cellulose filter.  The stock filter also has a huge amount of surface area, with more material and pleats than the aftermarket filters.

The noise difference is not drastic between the BSH and stock intake.  The BSH is already one of the quietest intakes and stock is well, stock.  BSH’s intake does have a deeper growl.

Why would you want stock?

I’m not going to say that aftermarket intakes have no place.  I’m just reorganizing the priorities for my car.  If the stock intake can provide me with 98% of the performance of an aftermarket intake, why not?  I ran an aftermarket intake for around 40,000 miles.  It has certainly served me well.  I just like to tinker with things.  Nothing purely scientific, I know, so take my experiences for what it is. But you can be sure that the MAF area has certainly caught my eye and a lot of engineering did go into the design of the cover.  I’m just deciding that they did a pretty good job.

Spark Plug DIY

Here’s a spark plug diy I wrote for the MKV 2.0T.  Hope it comes in handy for you do it yourself types.  If there are corrections that need to be made, drop me a comment.

Spark Plug DIY


New OEM Spark Plugs – 06H 905 601 A / NGK PFR7S8EG


New OEM Plugs

There is a new part number for the OEM spark plugs – 06H 905 601 A.  They are made by NGK now instead of Bosch.  The corresponding NGK part number is NGK PFR7S8EG.  This new plug is a double platinum laser plug that is also one step colder.  I guess all those people advocating one step cooler plugs were correct.  Anyway, I installed these last night and the engine is purring as always.  The BKR7EIX’s I had in there had begun to show erosion at the ground electrode and the gap had opened up considerably.  I did not notice any real change in performance, slightly smoother idle is pretty much it.  I’ll report back if it affects mileage considerably.

This plug supercedes part number 101 905 631 H which superceded 101 905 631 B.  The previous part was a Bosch FR6KPP332S.

Anyway, here are some pictures showing the new plugs.

A DIY is located here if you need it.  >DIY Spark Plug Change


Some more information regarding the newer OEM NGK sparkplugs from a forum member on

When comparing to a bosch stock plug many goof on the difference in how their ranges work. Because of that some cross references out there show the 6 heat range NGKs being stock. If you go to NGK themselves and check THEIR application guides it shows a heat range 7 as being stock.

06H 905 601 A / NGK PFR7S8EG

06H 905 601 A / NGK PFR7S8EG

06H 905 601 A / NGK PFR7S8EG

Revision D Diverter Valve – Stock Location

Well it’s official, I’ve gone nuts.  I went back to the stock diverter valve location after all the time I spent thinking about diverter valve relocations.  The mechanical valve was nice but I wanted ECU control.  The ecu controlled relocate was nice but required some rigging to get it to work with the stock intake.  So I’ve gone full circle and landed back at a nearly stock intake system setup.  My stock intake is back in, and the diverter valve is back in its original location.


New piston design

Initial impressions are that the D valve feels better in the stock location than in the relocated position.  Maybe something was leaking?  No logs yet, they will come eventually.  Boost response felt a little “off” with the valve in the relocated position.  It bogged sometimes and the car felt labored in the very low rpms.  The boost ramp up was a little strange, it felt like it would spec too much boost at a low rpm.   I should have run some logs but didn’t think of it at the time.  With the valve in the stock location, boost response feels better and is more linear.

There are a handful of reports stating that the valve does not seal correctly on the FSI, leading to decreased throttle response and delayed boost peak.  The cause was never determined but in most cases the problems were resolved by switching back to a diaphragm version.  It could have resulted from a faulty valve or improper installation.  My valve seals and functions just fine.  The summer heat should really put the valve to the test, we’ll just have to wait and see if it holds up.

I think Volkswagen and Pierburg (manufacturer of the actual valve) have finally come up with a bullet proof solution to an annoying problem (torn diverter valves).  The valve is maintenance free and if it proves reliable, is perfectly fine for a mildly tuned 2.0t.

Oil Change With Pennzoil Platinum Euro 5w-40

I finally filled up the GTI with this.  Car feels nice and smooth again, although that darn placebo effect is always lurking.  The old fill was feeling a little tired (Lubromoly Synthoil Premium 5w40) and I was only a little off from the interval so I decided to throw it in.  The Lubromoly Synthoil Premium is different from the older Lubro 5w40.  It is no longer fully synthetic, I supposed due to cost cutting, and the car did not seem to like it as much.

The car feels smooth on the new Pennzoil Ultra fill, too bad it is so pricey.  Even so I might switch to this as my new regular fill, unless I find a stock of the old Lubromoly.  I will try to swing an oil sample on this interval to see whether the car truly likes it.

Pennzoil Ultra Euro 5w40


AEM Dryflow Filter

If you are interested in replacing the filter on your aftermarket intake system, give AEM’s Dryflow filter design a try.  The filtration media is designed to work dry and requires no oiling.  It’s easier to clean than the K&N oiled filters and is supposed to filter better. Since it uses no oil, it avoids the risk of over oiling the filter and contaminating the MAF.  This is admittedly a rare occurrence if you take care in re-oiling a K&N.   The oiled filter design flows better but I’d sacrifice some flow for filtering any day.  The filter muffles intake noise a bit more than the standard oiled filter so keep that in mind.

This particular filter was fitted to the BSH Trueseal intake.  Take note that the BSH filter is a very narrow design.  The AEM fit there is not much clearance.  It ends up contacting the liner on the hood, not too badly, but it is something to keep track of.  The correct size is a 2.75″ inlet and 5″ length.  I think the part number is 21-202DK.

It is interesting to note that AEM’s Dryflow filters now also have the K&N logos on the box.  The filter division was bought out a little while ago, but nothing seems to have changed, save for the color (now red instead of gray) and the addition of a metal mesh(originally plastic reinforced).  AEM has another line (Bruteforce Dryflow) that maintains the design of the original Dryflow with gray filter media and internal plastic reinforcement.

Pennzoil Ultra Euro 5w40

Pennzoil Ultra Euro 5w40

This is a bottle of the so-rare-it’s-magical Pennzoil Ultra Euro in 5W-40 grade.  You are all but guaranteed not to find this stuff in any brick and mortar stores.  I had to order this direct from the Pennzoil site.  It is quite pricey at $50 for six quarts but is reported to be a robust oil.  It has a long list of approvals, including VW’s 502/505 and Audi’s 503.01 spec.  I haven’t poured this in yet, I’ll be trying it out for the next oil change.

OEM Approvals