Posted by Walt Barie on September 09, 1998 at 21:31:09:
In Reply to: Re: pinging fix - old message rehashed posted by Samir Shah on September 08, 1998 at 09:02:54:
: Again, this works to eliminate pinging in a *high compression* engine, such as an euro engine. Yes, you have changed the advance /retard curve totally. It helped make my engine more drivable. The key here is that it retards at high rpms.
: Samir.
I don't think you understand what this method really does (reread my previous message). You retard the base timing setting a bunch to get the idle down (and this is what probably suppresses the pinging). You then get more retard at part throttle from the vaccuum retard (when retard is not really needed since it is connected wrong) but the vaccuum retard goes away when you need it most at full throttle so its really odd that you would need to reconnect the vaccuum hoses. To me, this is just a really dumb way to get rid of pinging. Lets use the cliche: You are throwing the baby (performance) out with the bath water. Better ways would be to to just back off the timing slightly and leave the vaccuum hoses connected correctly or more complicated would be to adjust/change the advance weights and/or springs (this assumes that your present distributor is not worn out causing part of the problem). If it knocks at cruise try disconnecting the vaccuum advance. You can also play with the stops for the vaccuum retard and advance. I'm really surprised your exhaust manifold or exhaust system isn't glowing bright red or your car is running hotter than normal due to the retarded timing and unburned fuel dumping into the exhaust. And to respond to your comment about high compression engines, my mechanic who I have had many many discussions regarding timing has been working on custom high performance and racing BMWs for 20 years and personally owns a 2002tii with 14+:1 compression. Personally my VW has something like 9.8:1 which I've had to play with to reducing pinging so I may have had learned at least a "little" about timing and high performance engines.
Walt Barie