24 Jul 2016

Took the car out last night and found I was playing a bit fast and loose with the tune – and that it pays to have limits set! Checking out boost, the engine hit a rev limit which was unexpected since it was well below max RPM and MAP. Turns out that the many changes in the engine caused the engine to run leaner than the previous engine, which shouldn’t have been a surprise. This morning was spent checking the logs, finding the correction factors, and adjusting the volumetric efficiency table (VE).

The right way of setting up the VE table is to do so on a dyno. Short of that, having a buddy in the passenger seat make the adjustments and issuing instructions on whether more or less RPM or MAP is needed. I just want to get it close then decide whether to take it in for a proper dyno tune.

Related to the above, I read something that I hope doesn’t become an issue. A guy who knows these engines well and has a lot of dynamometer experience tried some “performance” cams. Many are intended for normally aspirated engines and have increased cam overlap (the period of time that both the intake and exhaust valves are open at the same time). For a turbocharged engine this can cause issues. Because the air entering the engine is compressed, it can allow the air to push through the engine and out the exhaust while the intake and exhaust valves are open. As a result, fuel consumption may increase yet the engine doesn’t make any more power. The valve overlap can also affect idle, causing less vacuum than if it had stock cams. While my engine is still being broken in, it’s hard not to notice that idle vacuum is around 32 kpa versus 23 kpa with stock cams. Granted, as the engine breaks in that value should improve, and it pretty much is what it is. The running lean issue is probably a good sign though because it means that the engine has a higher VE than the previous one. It’s a never-ending learning experience.


Test drove the car and the air-fuel ratio is much improved. After some test runs the VE tables was further dialed in and is nearly good to go. The test runs found that the weakest spring produces around 150 kpa (~7 psi) but starting at around 5000 RPM starts creeping, reaching 180 kpa (~12 psi). That’s not great but I wonder if I install a 12 psi spring whether it’ll peak out at the same maximum value. Hope so, else there’ll be some exhaust manifold rework to do – boo, especially in this heat.

Lastly, I recently watched a documentary on a guy who’s company I’d see before and wondered what the heck it was about. It recently relocated to the area so during a test drive I figured it made a good photo op, so there you go. Google “Dr. Bronner’s all one soap” for a look at a very unusual person. In the documentary, it mentioned him telling the guy who picked him up while hitchhiking, “I just escaped from a mental institution.” To say the lest, he had some very unusual views on life, nature, and the universe, while at the same time making a natural soap that’s available just about everywhere.