NickLovin wrote:So what's the deal with knock retard on the 6.1's anyway? Is the factory tune just too aggressive? Is the detected knock even legitimate? Does the knock sensor threshold simply need to come up?
No, the factory tune is not to aggressive. And the knock is legitimate. and no, the threshold does not need to come down. Haha, all this is true because that's the way it was designed. People would like to think that the factory engineers or the SRT team are bumbling idiots and made huge oversights and errors but that's just silly. They designed to their criteria. One of those criterium is 100K (or something like that) duty cycle on the engine. Another is meeting emissions.
Take the catch can thing. They know about the oil. It's not like they missed that huge puddle in the manifold after the hundreds or thousands of stress tests runing the engine in various scenarios including to failure and then completely tearing it down. It's within the critera. Your engine burns most of it, some of it builds up and the engine runs just fine for at least 100K. Putting a catch can on the car to allow tuning for a little more performance is not feasible. There's the significant cost of the catch can, the cost of getting it EPA approved and approved in every single state, and it would have to have a huge resevoir to be sure to make it from one regular service interval to the next, yada, yada. And, no, I don't think it's due to a bad design on the PCV system. It's just that our motors inherently generate more atomized oil in the crankcase than others. LS motors do also.
Let's consider the knock (retard). The PCM is designed/programmed to handle that (up to a point). An event is detected and the PCM reacts to pull the appropriate amount of timing to eliminate it. It's variable. They have to design for widely ranging quality of gas, additives, and ambient conditions. From what I've seen the PCM does not over compensate. If you consistently get 3* of knock retard and you tune to eliminate it, you'll end up pulling 3* of timing. It's not like the PCM over reacts. (naturally you can usually adjust fuel to move towards the same end but that effects emissions, duty cycle on the cats, MPG, etc. etc.
With a tune (like with the Predator or CMR tunes) you can get another 20 to 40 HP? "for free". But you've just reduced a lot of margins. To realize that gain you're going to have to use good quality gas, you need a catch can, maybe a cooler t-stat, maybe tighter tolerance on air/fuel relative to timing, etc.
By the way, I think all the tunes desensitize the knock sensors to some extent. and false knock is VERY uncommon. I've only heard of it with aftermarket valve springs and maybe a couple of loosely mounted sensors.
But Mike's right. You do need to log to understand what's going on. Just looking at the symptom like a dyno result without knowing why is not very useful.
