The factory N54 valve cover is known to crack and leak oil and when looking for a replacement it can be tempting to opt for one of the Aluminium Valve cover options from M18 or Vargas Turbo Technologies (VTT). I recently purchased the M18 valve cover and wanted to share what I had to go through to get it installed and all of the hurdles that came along with it. Hopefully my experience will help people make a more informed decision before buying one of these types of valve covers.
tldr
- Externalizing the PCV System can be a costly tedious pain to get working properly and you are risking all your engine and turbo seals if it is not done correctly.
- Even if you do you get a working high and low external PCV system, you will very likely have excessive oil blow by filling your catch cans daily due to no baffling inside of these aluminium valve covers.
- You have to remove your injectors to install the M18 valve cover which means you need an injector puller and injector seal tool along with new seals and decouplers. This adds a lot of additional cost to the install.
- Carefully read the return and exchange policies of these manufacturers. For example, M18 has a 50% restocking fee and the valve cover + accessories can cost $1,000+. Policies like this appear to make it so that it won’t make financial sense for you to return it. These types of policies are why I think it’s important for people to make the most informed decision possible on this.
- Bottom line – In my opinion, don’t waste your time on an aluminium valve cover, yeah they look cool but not worth the headache. Stick with the factory valve cover, get an upgraded PCV Valve, with a high and low side catch can. Everything will work properly without all the nonsense of externalizing the PCV system and losing the internal baffling of the OE valve cover.
Externalizing the PCV System
The factory valve cover contains a PCV valve that works in conjunction with a flapper valve to allow crank case pressure out under boost and regulate vacuum at idle. The N54 needs a certain amount of crank case vacuum to help drain bottom mounted turbos properly. The aluminium valve covers do not have any PCV system, you have to put together your own way replicating the factory PCV system utilizing Check/PCV valves routed to catch cans. This can be very tedious and expensive to put together something that works. For a more in depth explanation of the N54 PCV System, check out the Bimmer World article here.
There are two places you need to check vacuum, the intake manifold and the valve cover(crank case). The Intake manifold should have 20-21inHG when the engine is up to temp and you should have a BOV spring rated for that amount of inHG like the Yellow Tial Spring for example.
For the vacuum on the valve cover side, the closest number I could find from a BMWTIS document is 0.5inHG (17mbar) for an N54. However I do not think this is a correct number because when testing, if I get anywhere close to that number my car would smoke terribly. The smoke is because its too much vacuum and it pulls on your motor and turbo seals which allows oil to leak out. I found that closer to 0.13-0.25inHG resolved any smoking at idle. I was checking this with a Manometer T’d into my valve cover an10 fitting lines.
Excessive Oil from Blowby
Inside the factory N54 valve cover, there is baffling with vortexes that keep most of the blow by oil inside of the motor while allowing the blow by gases out. These aluminium valve covers have no baffling at all inside of them, they just have a port going out. In my experience, this results in excessive oil blow by going out to the catch can and it fills up within about 80 miles of moderate driving. There is no issue with my motor, there is not more blow by than usual, it is that there is nothing inside of these aluminium valve covers that actually help separate oil from blow by gases. It just blows it all out into the catch can filling it up quickly.
I have the VTT Catch can system. Initially I installed the breather on the high side however I found out very quickly that all the blow by gases that emit from the breather immediately come into my car through the cabin filter resulting in an oil smell in the car.
To rectify this, I decided to run a hose instead of the breather leading somewhere other than being so close to the cabin filter.
The Bottom Line – Back to Factory
After going through all these hurdles with installing an M18 valve cover, I ultimately decided to go back to the factory OE cover and will be using an RB Turbo External PCV adapter ran to my VTT Catch Cans. This will resolve my excessive oil from blow by issue. I do not want to have to constantly check my oil level and empty my catch can just to drive my car on a daily basis.
Note: The intent of this article is not to defame M18, VTT, or any other manufacturer but to share my experience and opinion on installing one of these types of valve covers and other parts. I believe there is not enough consolidated information out there for people to understand what they’re getting into when wanting to install one of these valve covers and I hope this article helps people make a more informed decision.