how reliable are the knock sensors?

my knock sensors seem to go off when times i dont think they should be....

and now that i am playing with timing... i fear that i am getting some knock, but the sensors are not picking it up.

Maybe the knocking i hear is just lifter tick, or exhaust leak or soemthing minor....

but i just fear it si real knock... but when i think i hear it, the knock sensor is totally quiet.

so do i rely on the sensors, and ignore my ears... and keep tuning?

or play it safe and quit while i still have an engine?


just curious what kinda timing maps you guys are running... i have added a TON of advance to the stock maps... and still only get a few peaks of KR, and they only show up in high load places. i just fear ive gone too far. but man every degree makes noticably more power.... so i want to keep tweaking.

i just hope the knock senor and/or my ears dont fail me... or my engine may

My question is how do you know you are making more power with adding timing? You on a dyno? To me it sounds like you need to get another set of ears involved. Always play it safe. Unless you do not mind replacing motors.



FU Tuning

i can FEEL the difference in my butt dyno... forcing the hi-oct maps made a noticable difference. and then adding even more timing made even more difference. Since i started messing with the timing, changing timing from stock to my current maps, feels like i have an extra 4 cylinders under the hood.

and i even let my buddy test drive it... he was AMAZED. he had driven it after i did my VE tuning, before i got to ignition.... and he thought it was a good improvement over stock.
and then i brought it back over after a good bit of timing adjustments... and he couldnt believe the difference.

since i left his house, i added another 4 degrees or so, and it has even more power than when he drove it.

i had no clue how much power these engines have hidden in them. i just fear trusting my knock sensor too much.

problem is that most of my friends who know cars dont know all there is to my car.... one guys knows cavaliers well... but not Superchargers at all.
another guy knows v-8's like the back of his hand, but only knows a little about computer controls and very little about superchargers.

so it is hard to get good opinions on my situation, as it is over the heads of most people i look to for advice.

I plan to get it on a dyno soon.... for final tweaking... but for now i am just doing what i can with my butt dyno. i am still working at a very crude level. to use the analogy from my one tuning book... i am beyond the chainsaw, and have moved to chisels now.... then once i have it chiseled to my liking, then i hit a dyno for some sandpaper, paint, buffing and wax..

Sorry but butt dyno's are crap.
When I said another set of ears I meant someone who knows what knock soun ds like. You do not need to know a cavy, or a cavy with a charger to know what knocks sounds like. You know it or you don't. Trusting your knock sensor when it is showing knock is much safer than not.



FU Tuning

If my understanding is correct... knockk sensors are supposed to detect and prevent knock before it even gets to an audiable level....

so even if my knock sensor is busted or something... i should still hear/feel the knock before it blows my car up.

i know older cars knocked all the time... anytime you were going up a big hill, or pulling a load of people... anytime the engine was under heavy loads, ,you would hear it pinging away..... that was not an unusual occurance on those older non computer cars.... they didnt blow up at the first sign of knock...
granted they rarely made it to 100k miles...

but my point is that while tuning, if i do happen to hit some audiable knock, wether my sensor detects it or not, if i hit it, and then get off it... just a few bursts here and there while tuning wont kill my engine... will it?

i mean 99.999% of cavalier owners dont even know if or when their knock sensor is going off, and 99.5% of them wouldnt even know what knock was if it was audiable to the ear...

so maybe i am just worring about this all way too much.

i should just keep tuning, and watch my KR levels, and keep my ear peeled for sounds of knock... and just keep "chiseling" till i can get on a dyno.

Audibal Knock is plenty noticeable. If it is lifter tick, then you aren't going to hear a change with timing. If you are getting so much lifter tick that you can hear it from inside the cabin and over the charger whine, then you have some very serious problems. So, you can decrease timing very conservatively, and if you are still getting a ticking sound, then there is a good chance you have a couple collapsed lifters and not necessarilly a problem with knock.

i USED to have a lifter tick so loud you could hear it from in the car.... but i put on a new head, new cams and all new lifters. since then THAT noise has gone away... but i still have some other more faint noises i cant put my finger on.

i have heard many 2.4L's and they all have some sort of odd noises....

but i just want to make sure i am not hearing knock and blowing it off as "inherant 2.4 ticks"

i am currently up to 16 degrees above stock Hi-Oct spark map for the GM SC reflash... and still no audiable knock, and only a few appearances of KR at random places.

So i am going to keep pushing it for now... see how far it will let me go.

i have run differnt fuels, from 91 up to 100something octane... and the knock all seems the same... just a few spots here and there... depite the fuel or the timing... add 15 degrees of timing... knock still pretty much the same... add 10 octane... knock pretty much the same... so something tells me this is fantom knock, and i havent yet hit any real knock.

Let me get this straight. You are running 16 degree's extra over the stock GM reflash HO PE spark table? SO at 6400 RPM and 210 KPA you are at 39 degree's advance? If so I feel for your motor.

YOu have really confused me in this post. If you will not trust your knock sensor what are you going to trust? I have heard knock before, but still going to trust my knock sensor. This is not to mean you can't get other things causing knock, or ghost knock. I was getting up to 4 degree's retard, but not hearing anything. I still pulled timing until I figured out the deal. Turns out the bolt on my crank pulley was backing out. Once that was fixed over half of my KR was gone. Still have a little left. I plan to run some high Octane to see what that does. If that does not fix it then I might swap in my stock tranny mou nts to see if the stiff ones is causing some ghost knock. I would never blow off the knock sensor reading unless you have very good reason to. TO me sounds as if you are new to tuning as I am, so without trying some things or letting sopmeone with better tuning experience check it out I would trust the knock sensor.



FU Tuning

Quote:

SO at 6400 RPM and 210 KPA you are at 39 degree's advance?

If i'm not mistaken after a certain RPM won't the PCM start to ignore any knock sensor feedback? Which would also show you 0 knock counts on a laptop or datalog.

SHOoff wrote:

Quote:

SO at 6400 RPM and 210 KPA you are at 39 degree's advance?

If i'm not mistaken after a certain RPM won't the PCM start to ignore any knock sensor feedback? Which would also show you 0 knock counts on a laptop or datalog.

I do not think so. I think it was a good chance he did have some knock seeing as he spun a rod bearing from reading another post he made.



FU Tuning

39,,wow

granted it will never see 210kpa, but

i dont know if my W41 with cavfan's tune has that much timing....

Chris


'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08

39 degrees on a supercharged engine?? HOLY... sorry man its probbaly knockin so bad that its far to late to help it now. A non intercooled car on pump gas should be around 18 - 20 safely at high rpms. 39 is rediculous. Close to stock table map.

I do know that at a certain rpm, the spark will hit the ramp out numbers.

You my friend need to flash your stock file back on, check your knock sensor to see if it works, and step away from the laptop....


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