Piston & Lorentum
Piston Piston
Lorentum Lorentum
Lorentum Lorentum
Hey Piston, I was thinking about how the incremental changes in compression ratios affect the power curve and fuel consumption. Have you ever plotted that in a spreadsheet to compare it against your lap times?
Piston Piston
Yeah, I’ve run the numbers in a spreadsheet more times than I’ve spun a clutch. Push the compression up, you get a sharper power spike early in the rev range, but the fuel mix has to get leaner or the knock alarm will bite. I’ve set up a simple graph with compression on the X‑axis, peak power and mpg on the Y‑axes, and I’ve superimposed a line for the lap time at each point. It turns out that a 10‑percent bump in compression gives a 1‑second win on the straight but costs about 3‑percent in fuel economy. The sweet spot for me is right in the middle where the lap time drops but the consumption stays in the low‑double digits. So yes, spreadsheet is a great cheat sheet – just don’t forget to test it on the track before you trust the numbers.
Lorentum Lorentum
Nice. Just double‑check the assumptions in that model – make sure the ignition timing curve and fuel injection map are aligned to the same temperature range. Even a 0.2° error can shift the knock threshold and skew your mpg figures. Keep the data tidy, and run a few trials at the exact compression you plan to use. The numbers look good on paper, but the track will confirm if the model holds.
Piston Piston
Right on, you’re talking real science there. I’ll re‑run the timing curve and make sure the injection map is on the same temperature scale. I’ll tighten up the spreadsheet, pull a few laps at the target compression, and see if the knock sensor’s still giving me a green light. Nothing beats a track check to keep the numbers honest.