[TELVM]

I've tested the SGs in a four cylinder SOHC engine with crossflow parallel 2-valve bathtub chambers:











I made lots of modifications in parallel with the SGs, so I can't scientifically prove anything. However this I can say:

- Oil remains cleaner beyond belief. Even the running-in oil (usually black after 50 miles of bedding fresh rings) remained clean.

- No trace of pinging, in spite of compression raised from 9.2:1 to 11.0:1. Not even lugging uphill flat throttle in summer with low octane gasoline (this I chalk to the grooves, my favourite benefit from them).

- Smoother idle.

- No tremble accelerating from 1200 rpm in fifth gear.

- Fuel consumption improved a ~15% (this due also to higher CR and the other mods).


As I see it, the grooves most definitely do not harm, and very probably do a noticeable amount of good, particularly by allowing higher CR without pinging.