jeremyb

I was taking a look at my knock meter on the commander as i drove... there were several times that it went all the way and i was wondering if it should. So i checked the peak hold and the highest knock number i had was 149. Is that normal? The knock isnt all the way up when im flooring it... but somewhere mid-way with light throttle it hits halfway for like half a second. so 149 peak good? bad? OH NO? its ok?

Jeremy

cewrx7r1

iTrader: (2)

Under normal driving conditions, especially when cruising, the PFC will pick up drivetrain and suspension noise.

I can cruise at 60MPH and have noise above 15. Can do some shifiting and combination acceleration/de acceleration and have noise above 100.

But when I do a 3000 rpm to 8000 rpm acceleration run in 3rd or 4th, my knock levels are usually below 20, and many times below 15.

When it is cold, my knock levels are very high untill I drive about 30 miles and get
everything warmed up. About three weeks ago I went to Kyle's for some quick testing. Just cruising over there my knock levels were going 100+ somethimes.

When we went testing and the car was fully warmed up, the levels dropped back to normal and my levels in 3rd at 13 psi and 15 psi boost were below 12.

jeremyb

whoa whoa wait a minute... are we talking about the same thing? I'm talking about the little bar meter thing on the commander moniter display. It says knock next to it... Is this bar representing knock=detonation, or knock=sound level? I'm kinda confused now... and how do you know the knock number? mine is just a bar meter. and the only number i'm able to see is the peak number. Thats how i got 149. And im boosting the first setting on the commander pri. 80 and sec. 70. So i think thats stock boost on the FD. Im lost?

RotorJoe

The knock sensor is just a mic in the engine, basically. It picks up sound levels. Detonation makes a load ping sound and is picked up by this mic placed on the side of the rotor housing.

We are probably cycling through the pick hold much faster or they have that being the only parameter on the display screen.

RotorJoe

ditto

jeremyb

ohhhh i get it now... well ill do what chuck said. The 3k to 8k WOT... well see how far my meter goes... i guess idle is the quietest rpm hehe.... since my knock meter looks like this " l " when im idling. Thx for the input guys. But another question reguarding boost. If you raise boost... How do you what percentage to set the wastegate cycling percentage to? I want to raise the boost... but want to make sure everything is ok and i dont know if the wastegate cycle has anything to do with it.

Jeremy

TailHappy

Out of curiosity, is REAL pinging ever instantanteous, or is it a more steady thing? I have knock that is frequent enough not to be a fluke, but doesn't occur every single time. I'll get a huge spontaneous spike (up to maybe 190) somewhere between 3000 and 4000 under very light boost. Just one single spike and then it drops immediately again, as shown using the graph feature. WOT runs have low knock, maybe 30-40. I suspect this is just some resonance or engine noise, but I was curious if anyone had seen true knock on their PFC before. Judging from the knock I've seen on piston engines, I suspected true detonation would more likely be a prolonged occurrance rather than a spike.

cewrx7r1

iTrader: (2)

I have never recorded any high knock levels that I can definitely say were caused by detonation. Meaning that I could not hear it when it happend. And I have not blown an engine yet, knock on wood!!!!

But I have seen knock levels in the 60s and higher that occured more than once in the same cell or adjacent cells. When taking out 1 or 2 degress afterwards, the NOISE went away.

These high readings may not be detonation, but I take them seriously as it could be on the verge of true detonation.

I have noticed that knock/noise levels are normally higher on the first couple of runs than on subsequent runs. It think this is caused by thermal expansion of exhaust parts or maybe carbon fluff burning off.

Because of this, I recommend some seriously fast driving or acceleration runs before really tuning. You know what I mean?

jeremyb

Im assuming all of this is recorded using a datalogit. All i have is a commander. But i am talking to reza about him helping me out with his datalogit and wideband so hopefully i can get this sorted out. Ill post up info once i get everything settled or understood. thanks guys.

Jeremy

TailHappy

I think you're right on the money!

Sometimes I think I'm a little TOO paranoid about detonation due to the abundance of posts I've read here concerning it. I think our little engines might be a little more tolerant than they're given credit for. Granted, you can't just advance the ignition until you HEAR the knock, and then retard it some, like I've tuned my other cars, but I don't think I need to be quite so paranoid about my peak knock numbers on the commander. Then again, I just don't seem to be able to help myself...

My datalogit knock readings generally seem to look good. I'm suspicious it isn't reacting fast enough to catch the instantaneous spikes that make my commander peak holds look so bad. My WOT readings are all generally in the teens, with my very light boost or cruise being the areas of highest repeatable knock levels (roughly 40-60). Sometimes I wonder if I wouldn't have been better off without even knowing the readings from the knock sensor. It gets to be too much of an obsession for me. Ignorance is bliss....

Water injection is waiting to be installed...hopefully that'll be the end of worrying with knock.

cewrx7r1

iTrader: (2)

I think most of the higher knock readings while cruising or normal driving are caused by the fact that the drive train is not in a load condition like during hard acceleration. It is loose going back and forth between load and no load.

jeremyb

hmmmmmmmmmmmmmmmmmm