Improving our BMW 435i’s durability by upgrading the charge pipes

Nothing is worse than putting the car on a trailer early. Well, maybe finding a trailer for the ride home–or trying to exact repairs to get yourself home in a dirty paddock or oily parking lot.

So that’s why one of the first mods BimmerWorld suggested for our 70,000-plus-mile BMW 435i was a fresh set of charge pipes. “Honestly I’m surprised yours have lasted as long as they have,” BimmerWorld’s Phil Wurz said of the original plastic pipes running from our turbo to the intercooler and the intercooler to intake. “It probably means this car has been lightly used, because cars that see max boost regularly usually need charge pipes by 50-60,000 miles or 7-8 years.”

In our case, Phil was thiiiiis close to being right–the fitting where our stock plastic charge pipe attached to the intake manifold broke as it was being removed from the car. It probably wouldn’t have lasted another week of street driving, let alone a single track event.

Backing up, the charge pipes are the intake tubes connecting the turbo to the intake, with the intercooler in the middle, and they’re notoriously fragile.

Constantly exposed to positive and negative pressure, heat and exposure to road chemicals take a toll on the plastic bits, and they inevitable fail. Luckily, their failure is not catastrophic for the rest of the engine. It will still run, just not with any boost–basically, well enough to drive to immediate service.

BimmerWorld’s recommendation was for a reliability upgrade, and in this case, it’s an allowed upgrade in the SCCA Time Trials Sport Division under the rulebook’s allowance for pure reliability and safety modifications that don’t materially affect performance.

BimmerWorld hasn’t seen any actual performance increase simply by installing the Evolution Racewerks aluminum charge pipes–actual engine output is more a function of boost and fuel flow in the N55–but the more durable aluminum pipes absolutely give you the insurance to handle whatever additional boost you plan to throw at the car.

Stock, the 3.0-liter produced less than 10 psi in most cases, and the stock charge pipes still fail regularly. Upping that number is a recipe for disaster and an early exit from the track without upgrading the plumbing.

Installation for these pipes–which start at a little more than $300–is simple, but not exactly easy. Both pipes are well buried within the engine bay, with the driver-side pipe in particular proving rather frustrating to free from the intercooler.

Our final victory came after removing the serpentine belt and loosening the a/c compressor from its mounting, allowing easier access to the lower hose junction.

On the passenger side, it was simply a matter of finding whoever in the shop lived at the intersection of “tiny hands” and “patience.” Years after their original installation, the factory connections remained sticky and took a great deal of wiggling to loosen and remove.

Reinstalling the new Evolution Racewerks bits was actually easier, assisted by the multi-piece design that joins two rigid pieces of pipe with a silicone connection. Sliding the final connection onto the intercooler was still tricky, however, as the C-clipped slip connection needed to be installed at a very precise angle to find its proper seat.

We found that removing the bolts holding the intercooler to the car and lowering it as much as possible gave us the extra room necessary to slip the joints together. It was still a multi-person operation, though, as pushing from both sides of the connection was necessary.

Once in place, though, we’ve checked off one more box in the reliability category, and now when we inevitably throw a little more boost down its gullet, we’re confident it will make it all the way to the intake where it can do some good.

Dropping the a/c compressor off the block gave us just enough room to do a little extra maneuvering to get the stock charge pipe free.

And just in time: Our stock pipe was broken when we removed it.

The aluminum cold-side pipe goes from the intercooler up to the intake. It’s a two-piece unit with a silicone connector, making install actually easier than removal of the one-piece stock pipe.

The hot-side pipe–this goes from the turbo to the intercooler–is also a two-piece unit. This replaces a rubber stock pipe and its shortness and rigidity makes installation a real patience tester.

The Evolution Racewerks pipes all use the OEM-style terminations, with O-rings and C-clips. They’re strong and reliable, but intolerant of misaligned installation. Lube with a small amount of water-based lubricant, lower the intercooler as much as you can, and line them up correctly before sliding them on.