In this post on the
Prius engine swap thread I was wondering about how easy swapping one of the Prius engines (1nzfxe) for the engine in my 03 Pontiac Vibe GT (2zzge) would be. This got me to wondering if since my current engine has 2 different cam profiles (1 for regular operation, and the 2nd for high rpm power) if by taking manual control over the switch between profiles would I be able to selectively "derate" my engine?
Almost certainly this could be done with a new/recut camshaft, but I was curious if my existing cam could do the job. Looking at the numbers (copied below)
from this pdf it seems the intake stays open later, but I'd like to get the opinion of someone who actually knows about this as to how they think my engine would behave if I switched it to the 2nd cam profile at 2500-3500 RPMs (abt55-75mph in top gear). Pictures in the pdf make it look as if both profiles are on the same cam, so while one profile can't be rotated relative to the other (without regrinding), I believe intake can be rotated relative to exhaust if that will make a difference.
2ZZ-GE Valve Timing Chart
| . | . | Exhaust | . | . | . | . | Intake | . | . |
| . | Open BBDC (CA) | Close ATDC (CA) | Lift (mm) | Duration (deg) | . | Open BTDC (CA) | Close ABDC (CA) | Lift (mm) | Duration (deg) |
| Low | 34 | 14 | 7.6 | 228 | . | -10 to 33 | 58 to 15 | 7.6 | 228 |
| High | 56 | 40 | 10.0 | 276 | . | 15 to 58 | 97 to 54 | 11.2 | 292 |
All data from PDF linked above, with exception that duration is from
Wikipedia
The goal of this would be to get my throttle open more when cruising at highway speeds: since at 65ish I'm already pushing 3000rpms I'm at a very low throttle opening, by switching to a "modified atkinson" cam profile I cut my power produced, resulting in a wider throttle opening, less pumping loss, and higher mpg at the same speed. Right now the 2nd cam profile dosn't kick in till above 6000rpms, and I never go up that high in daily driving.