Noise Analysis, Part-2

[coldwar]

OK, so I have now been running a 20-30% blend of WVO / Diesel for almost 2 months, with generally favourable results- more power, less engine noise, and I think a slight increase in MPG. However, I am getting a very distinct "spark knock" sound most noticable when the car is highway cruising.

Let me say in the most definate terms- this noise started long before I started using WVO- I first noticed it back in January, and simply attributed it to cold weather, or #1 fuel. In fact, when I started with the WVO, I noticed the noise went away completely, except now it was very dominant when starting from stone cold, and for about 5 minutes until the engine was warmed up. After the WVO warmed up from injector heat, the noise would never happen, even at cruising speed.

Now, the latest- yesterday was extremely hot here (at last!), and I drove the car for a 300 mile round trip, with a 30% WVO blend in my tank. The car performed beautifly- lots of power, 31 MPG (Imperial Gallon) which is the best I've ever gotten, and less engine noise, EXCEPT the pinging noise was present again, as if I had no WVO in the mix.

I would really like to know what's causing this. It actually sounds like it could be quite damaging, like detonation would be in a gas engine, leaving holes in pistons. I'm not prepared to blame the WVO, as it was defiantely a problem before. Could it be bad injector(s), pre-chambers, or something else?

Another fact about it- when under full throttle / full load up a long steep hill, this pinging noise does not happen at all, until I back off the peddle at the top of the hill- then I get a burst of the pinging.

Any takers?

Dave

1976 300D, 150,000 Miles