"In this Special Series, during VANOS bulletproofing of my S54, we took a slight detour in internal performance upgrades: let's cam it!

On this entry, I splurged and got a self of a set of big cams - sort of. We look at what BMW did with the CSL, we sit down for a 101 lesson on cams with the Americans.

We move onwards and go bigger: I unbox my Schrick cams. "
-Matt 

Let CSL owners brag

The CSL airbox and the slightly bigger cams are responsible for achieving the CSL's 355hp / 360PS power ratings over the 338hp / 343PS of the original engine. 

[...] with their small cams! 

BMW M engineers fitted barely any bigger cams to the CSL engine with 268 intake and 264 exhaust duration camshafts.The original S54B32 found in every other E46 M3 came with 260 intake and 260 exhaust cams.

These original cams were taken out of my S54.

From afar, the differences with the Schrick cams are negligible. 

Even up close, little differences can be discerned. It's another game of millimetres.  

 

Understanding cams

When we compare the cam duration profiles, we first need to understand what it means.

I tap into the knowledge of the American Muscle scene where most of the folklore perception of cams come from for most for obvious reasons: cams are frequent upgrades for pushrod engines. 

This will remain a high level overview to harness the fundamentals - my bad race engineers, you all know better!

Duration. 

- Ref: Camshaft Duration / SummitRacing

Duration is defined as the number of degrees of crankshaft rotation that each valve that spends off the seat. All camshaft specs are expressed in degrees of crankshaft rotation. Crankshaft degrees are used because that’s the easiest way to measure these points on the actual engine.

Keep in mind that the camshaft turns at half engine speed because the cam drive gear is twice as large as the crankshaft gear. That means the crankshaft has to spin twice for the cam to turn one revolution.

That orientation is designed into all four-stroke engines.

Lift. 

- Ref: Camshaft lift / SummitRacing

When someone refers to lift, they could be talking about 2 different things.

Valve Lift

When talking about camshafts and lift, people usually mean valve lift. This is the distance the valve actually moves. It is also called "gross lift." All camshaft manufacturers list this value.

Cam Lift

This is the distance the cam lobe rises away from the base circle of the camshaft. It is the distance the lifter will move. It is also called "lobe lift." Some camshaft manufacturers list this value.

More lift is better?

Increasing valve lift allows more open space in the intake and exhaust ports of the cylinder. Theoretically, this means more air and fuel can be drawn in. More exhaust gases can be pushed out.

Understanding the CSL cams. 

Coming back to the CSL cams, we'll notice the duration moved from equal 260 duration between both sides to offset duration favouring the 268 intake side over the 264 exhaust side. 

At high rpm, longer intake duration fills the cylinder. It also allows more exhaust to escape. This creates more power.

However, at low rpm, the open valves theoretically reduce the pumping pressure of the piston. This results in lower cylinder pressure and less low-end power.

I can only offer hypotheses on why BMW would limit themselves on the stock engine, and the small duration increase with the CSL:

1. Did they have a complete understanding on the potential of VANOS technology?
2. Did they understand the tuning potential of MAP and IAT sensors over MAF?
3. Were they time and budget limited?

I looked onwards, and thought bigger.  

I opted for 288/280s

Looking back with 20 + years of experience with the S54, we now know BMW M left a lot on the table relative to a highly strung naturally aspirated engine. 

I ordered a set of Schrick camshafts in the Winter of 2023.  It's always been on the wishlist. I was glad to be in a position to afford it over the Winter.

These are expensive upgrades getting into the realm of diminishing returns. They're a luxury! 

Schrick is one of two manufacturers of camshafts for the S54, and the only one I trusted based on their track records of making Formula 1 and various OEM components for German manufacturers.

The camshafts are made from iron using a metallurgic process called chilled casting. It is excellent for its resistance to abrasive wear. The batch lot is engraved in each camshaft.

There is no room for error with cams. 

The 12.5mm lift specification was designed for the OEM head clearances of the valve train and rotating assembly. 

The optional 14mm lift specification would have required a new valve train and custom pistons to achieve the required clearances. That was a bridge too far for me. 

DLC coated rocker arms. 

Schrick mandates their DLC coated rocker arms starting with the 288/280 duration and upwards onto bigger cams. 

You need all 24 of them. At approximately 90$ each, these come out more expensive than the camshafts themselves. Alternatively, 

Considering the cost to performance benefits is up to you. Food for thought. 

DLC stands for Diamond Like Coating. As the name suggests, it adds hardness and resistance properties to the iron. Its thickness is measured on a nano-scale.

This coating was also used by BMW Motorsport on the rocker arms of the P54. This race engine used the E90 320i rocker arms (SKU: 11337549034) which are originally uncoated. It's a great hack to save on cost.

Up next: we get the OEM camshafts out, compare them side by side with Schrick, and get the new camshafts in fast.

Or so I thought, AH!

It'll be a great opportunity to touch on the valve adjustment service and what it entails. 

I can help you source Schrick cams year long here.