ignition timing

[Wolli]

hi everyone.
maybe one of you can clear this for me.
is it possible, to overadvance the ignition without having knock, but to damage the rod bearings?
thanks in advance

[MotorMo]

Hi. My experience tells me the answer to ur question is no, advancing ur timing, and not hitting a knock value wont damage ur bearings. I have friends that run E-85, which seems to have a huge resistance to knocking. so much so tuning the cars that run E-85 , u find the the MBT before u find knock, even on very high powered applications. Knock creates HUGE cylinder pressures that would damage the bearings however.
Oil starvation, knock, and improper clearances are the reasons I've seen for bearing failure.

[Wolli]

thanks for the fast answer! i thought so, but i was not sure.
so it is possible, to map the ignition tables just with knock values. i have tuned it till it started to knock, and than retarded by 2 degrees. this should be a safe way?!

[MotorMo]

Well, the word "safe" there is a gray area. 2-3 degrees before knock, at Wide Open Throttle, is a common "safe zone" I've seen in the (street tuning) industry. As long as the knock sensor is enabled and working, it should clean up any low voltage knock after that if any pops up.
I should point out the obvious here and say the safest way is to get your car tuned on a dyno, by a pro. Nothing is sweeter than a solid tune-
But alot depends on the build.
What engine setup are you running? What type of fuel?

[Wolli]

http://www.hondata.com/forum/viewtopic.php?f=20&t=13956

here is my setup and calibration.
the problem here is to find a dyno!! god bless america, i´m prolly in the wrong counry :D
i monitor my knock levels with an external system, and i get the readings on a display on my dash. so i always see what´s on. i checked the bearings today, and there is nothing wong with them.
but it was more a question which generally interrested me, and i was thinking alot about that.
when you use high octane fuel, an alcohol injection, very low iat, and a well build engine, it may be possible to overtune the ignition without knock. or better said, you loose power, but you have no detonation.

[MotorMo]

The answer to your question is yes. My experience with alcohol is very limited outside of the local pub, haha, but what u say is especially true with these cars as they run super cold, even icing the intake manifold at times.That is one of the problems street tuning on E-85 injected cars. While advancing the timing at WOT, you can over advance the ignition past the point of maximum brake torque (MBT), and still not get any knock values. But since the most power is put to the wheels at MBT, any degrees + or - of that magic number will result in a lack of power, incomplete burn, and "wasted" BTU's. Over advancing the ignition can cause unnecessary high exhaust temps and possibly burn valves due to the mixture continuing to burn as it exits the chamber. Monitoring EGT's may help you tune close to MBT.

[Wolli]

Over advancing the ignition can cause unnecessary high exhaust temps and possibly burn valves due to the mixture continuing to burn as it exits the chamber.

what i thought to know is, that this happens when you retard the ignition. than the combustion is not finished when the valve opens, and it raises egt´s. but when you overadvance it, egt´s drop down. i monitor my egt´s, but there is also the problem with my supercold iat. 50 degrees colder in means 50 degrees lower out. my egt´s are very low for a 550 bhp turboed engine.

i keep on looking for a good dyno!!