I ran a simple experiment with water wetter. I thought the results we worth sharing.
Preface... I frequently run a pretty aggressive timing curve, with around 38 deg. total timing on stock comp. ratio. In the past, this has required the exclusive use of premium fuel. Any L6 I've run with this ignition tune, using regular unleaded, produces significant audible detonation.
The experiment was to run aggressive timing on regular unleaded, with and without water wetter.
With 85+ deg. ambient, WOT, up hill, fully warmed and premium fuel, day after day, My 260z produces no audible knock. I let the tank run nearly dry, and refilled with reg. unleaded. True to form, it rattled fiercely. Sounded like a diesel truck up every hill from the pump to my shop. I poured a 12oz bottle of water wetter in the system, and drove the car again, same conditions, 24 hours later, for 2 hours.... with no audible knock. This is the first time I've ever run that much timing on reg. fuel an not heard detonation, carb'd or injected.
The only exception was extended periods of abuse... 2nd gear, WOT, 5000rpm steady, holding the brakes. After about 8 or 10 seconds audible knock would creep in and get worse with time. Let the car coast for 10 seconds and do it again... no knock initially, but again, after 8 seconds or so, it would creep back in.
The test is far too crude to prove anything, but does raise an eyebrow. In my eye's it deserves a second look.
P.S. The test car... L26, mild cam, mild exhaust, poorly tuned Holley 390, Magnecor wires, mid-range coil, and one of the most stable cooling systems I’ve witnessed in a Z. I haven’t verified the accuracy of the gauge, but it reads about 165.... and stay’s there. Once up to temp, it never fluctuates more than +/- 1/4 needle width under any condition I’ve subjected it to, including all the above testing.