30 April

Replaced a short -10 AN hose that runs from the remote oil filter to the engine block; it’s plenty tight but has been weeping for months so it was time to fix it for good. Because it’s downstream of the filter it was critical to clean the replacement assembly well, so carb cleaner was first sprayed through it then a paper towel segment soaked in more cleaner was pushed through. I expected some rubber dust and there was that – but I wasn’t expecting this. When this popped out I though, “You gotta be kidding me” – I can only imagine the antics it had in store for my engine had it made it inside. The segment is partially anodized and that stuff can be hard as hell. Either it was left over from manufacturing or broke off when I screwed the assembly together. I’m not sure which would have done in my engine faster, this or the 1/8″ segment of stainless steel braid that also washed out…

In other news, it’s always been a mystery why my boost control valve is so sensitive. While it seems that everyone else on earth runs maybe 10-50% in order to set similar boost levels, I can only run mine up to maybe 20% and that’s roughly 20 psi boost. I’ve tried different boost control valves, I’ve tried changing the plumbing, and of course the ECU’s been changed, nothing helped. Then today, comments by someone suddenly made the lightbulb in my head go on. I think this header has such good flow to the wastegates that they only have to open a tiny bit to dump all the boost. My mistake was comparing my figures to engines with poorly-designed headers. Wastegates on many cars are mounted in all sorts of wrong positions, often at right angles to the main exhaust flow. What most people don’t realize is that if you shoot exhaust gas at right angles across an open tube, it actually sucks air out of the tube. As a result, people have to use crazy huge wastegates to make up for the poor design and run high duty cycles to get enough wastegate flow. I’m almost positive that this is what’s going on so some restrictors will be made up as a test.

With the above mystery probably solved, we of course need a replacement, which of course showed up today, a new mystery noise. I wouldn’t even mention it had it happened only once, but it happened twice. The first time I thought I ran over a rock, or maybe a tool left in the engine compartment dropped out and bounced. However, there wasn’t anything in the rearview mirror so I dismissed it as whatever it was having shot off to the side before I could see it. Then about 5 minutes later it happened again. If you’ve ever had a coil-over spring pop back into its seat with a bang, that’s about what it sounded like, but the car hasn’t been on a jack in months. Both times it happened during ordinary driving: straight and level road, maybe 45 mph, no brakes, no turns, no hard acceleration. After that I took the car out on the freeway for a few miles then back home and of course it didn’t do it again.