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nchristian
August 26th, 2009, 02:11 PM
Hey has any one out there been seeing spark knock on the Gen 4 engines that a factory tunes.I have seen this in tbss and the new silverados. Has anyone else ran in to this and what can be done to correct this.
gmh308
August 26th, 2009, 04:46 PM
Hey has any one out there been seeing spark knock on the Gen 4 engines that a factory tunes.I have seen this in tbss and the new silverados. Has anyone else ran in to this and what can be done to correct this.

Seems to be pretty normal. All engines typically factory tuned to knock a little depending on gas quality.

You can retune your timing table to cut back on the knock.

Can you hear it or only log it?

There is a GM patent document around somewhere that states that some knock is beneficial, but does not say why. Maybe best gas mileage and/or emissions occur when the engine is always on the edge.
nchristian
August 27th, 2009, 01:51 AM
I do not heard any knock. but when i log it shows 16.2 degrees of knock with the stock tune.I tried to tune it out but the engine falls on its face when you get it hard.
RonC
August 27th, 2009, 02:30 AM
That sounds like it could be false KR. The Gen 4 seems to be prone to it. Quite a bit of info out there about decreasing sensitivity of the knock sensors, especially on the E38.
nchristian
August 27th, 2009, 02:39 AM
Any info on decreasing sensitivity of the knock sensors
RonC
August 27th, 2009, 06:28 AM
I increased B1977 Knock Learn Min Voltage from 50 to 90. I eased up 10 at a time to that point for my applications. BUT do so at your own risk (disclaimer). It worked for me.

Anyone know of a better way or anything else to work for this?
gmh308
August 27th, 2009, 09:20 AM
Both running 93 octane?

Dont hesitate to post your logs. :) Then we can see where you are referring to.

Knock sensitivity can be set on a cylinder by cylinder basis B1967-B1974, or factored by rpm for transient throttle movements @ B1975.

Logging essential to identify where the knock is on the airfow/rpm scale.

It can also be logged on a per cylinder basis, and also worthwhile logging burst knock. It could be either.

And even though you may not hear it, doesnt mean it is not there.

Cheers. :)