Future plans for the 635CSi

I’ve grown quite fond of the E24 during my short tenure of ownership. It has a few problems, but it’s been well worth the effort in my humble opinion. And (other than my wife) who else’s opinion would matter?

Whats next? The next phase…those inevitable upgrades! Let’s start off with the motor. I’ve considered many options (M60/6, V12 650CSi?), and narrowed it down to two basic choices. One is a hybrid M30. The other is a turbocharged M30 or M106. I finally have enough parts to consider either of these choices as highly likely.

The hybrid M30 is simply bolting together all the best parts BMW offered. The M30 came in many versions with quite a lot of interchangeability. With a little skill you can develop a truly beastly version. So what’s my current planned recipe?

  1. It starts with the Euro B34 bottom end. It already has the 10:1 high-compression pistons.
  2. The single mass flywheel will be staying, of course. I’ll never give that up! In all honesty, that flywheel is the most effective performance upgrade I’ve ever done to a car.
  3. I’ll likely add an oil cooler and a windage tray to the B34 pan.
  4. The next component will be the B35 head. It has larger ports, larger valves, a more aggressive cam and better intake manifold design. There is a slight problem with the B35’s larger combustion chambers slightly dropping the compression ratio. I’ve been lucky enough to find a skimmed head that should mitigate that snag.
  5. Likewise, I’ll keep the B35 electronics with the Bosch/Volvo EV6 injectors and AEM wideband. That 1.3 version of Motronic is a little quicker and a bit more reliable in my experience. I’ve also been doing a little research into an even newer Motronic, the 3.3 version. It supports a lot of extra goodies, and reacts far faster. The full sequential injection is what I’m really looking for. The individual coils and MAF are just icing on the cake.
  6. I’ve also been researching other mods. There is a rumor floating around that aircooled 93mm VW pistons and 143mm Honda H22 rods will make a hellacious stroker. I’ve also been tinkering with setting up TunerStudio for a little monitoring. Eventually, a Moats Ostrich might find its way inside the DME too.

The M106 I just bought is also a strong contender. It’s a really powerful engine, easily tuned, and ready for an install. The turbo is not an easy fit, and a complete exhaust system will need to be cobbled together.