Photography by J.G. Pasterjak
For a car that usually operates at 12-15 psi of turbo boost, 0-3 psi wasn’t doing our BMW 435i any favors on track.
One good thing about a large, catastrophic boost leak like this: It should be fairly easy to locate.
[What’s causing our BMW 435i’s boost problems?]
A few other assumptions would also guide our search. Since we had already upgraded the fragile OEM charge pipes on both the hot and cold sides of the intercooler–as well as the intercooler itself–we trusted that those aluminum Evolution Racewerks pipes themselves weren’t the issue. However, we did suspect that the leak would be at one of the many joints we’d touched during installation of those pipes and/or the intercooler.
The engine bay of the F32 BMW is a cramped and inhospitable place, and those charge pipes are snaked and tucked into tight crevices. Add to that the fact that the intercooler is bolted to the chassis of the car, while the engine is bolted to the front subframe–meaning the charge pipes’ flexible connectors can see a lot of motion.
And we were right. The connection that we had the most frustration installing–the flexible connector on the Evolution Racewerks hot-side charge pipe just upstream of the CSF intercooler–had worked itself free and was shooting out boost into the world instead of the engine. Lame.
When we loosened the band clamp on the intercooler side, though, we found very little purchase by the silicone connector on the shorter section of pipe–to the point where we couldn’t satisfactorily tighten the clamp without pulling the band off that end of the pipe.
After a bit of sleuthing and some knuckle blood, we came up with a suitable fix. The issue here likely started when we first installed our charge pipes, as its silicone coupler allows for the natural motion of the engine against the fixed intercooler.
Without the silicone coupler, there’s about a 1-inch gap between the ends of the two rigid tubes. The silicone coupler covers that gap and is designed to overhang each rigid pipe by about an inch and a half, assuming the center of the silicone pipe is in the center of the gap.
On our assembly, however, the silicone coupler was overhanging the upper pipe more than the lower pipe. This scooched the silicone coupler toward the lower pipe and simply didn’t leave enough purchase for proper clamp tightening.
As for why this happened, well, our assumption here is that when the silicone coupler is properly centered between both rigid pipes, the clamp on the upper pipe is really, really hard to access. The clamp’s nut lands behind the coolant pump, so there isn’t an easy way to tighten it.
So, it’s reasonable to assume that during install, the silicone coupler was biased a bit high on the upper pipe to properly reach the clamp, not leaving enough meat to overlap the lower pipe. Eventually, due to the wiggling and vibration, the lower part popped off and our boost fell out.
Our favorite solution here would be a silicone coupler that was around 1 inch longer overall. This would allow for an additional half inch of material on both ends of the coupler to provide better access to the clamps, along with an additional safety margin for sealing. We’ve relayed these thoughts to evolution through BimmerWorld, and we’ll let you know what they all think.
For now, we really wanted to reinstall the supplied parts and make sure the system could work properly as delivered. The answer here was that it’s totally doable, it’s just a pain in the butt.
We ended up using a combination of several extensions and universal joints to get a deep socket on the 10mm nut that tightens the upper clamp. Be prepared to make a blood sacrifice as well, as this is an operation that is largely completed blind.
This ended up being a simple solve but, like many things under the hoods of modern BMWs, not necessarily an easy one. We’ve definitely had to make an investment in tools since acquiring this car, as so many tasks have required very specific configurations of extensions, socket depths, universal joints, wrench handle lengths and head sizes.
Okay, crisis averted and on to fun stuff. Now we have to figure out why our TPMS is freaking out. But that’s next time.
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