fed up with knock control
Nov 24, 2008, 11:07 AM
#347
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I have seen and logged it on car before. I've noted to people "you need to tear it down and look at x, y, and z parts". Some of these people were in denial. At any rate some of the things that causes such problems were/are, balance shaft 180deg out of phase, cams out of time, spun rod bearing, broken internal parts, loose/broken parts, bad gearboxes, etc.....
Nov 24, 2008, 11:44 AM
#349
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I have seen and logged it on car before. I've noted to people "you need to tear it down and look at x, y, and z parts". Some of these people were in denial. At any rate some of the things that causes such problems were/are, balance shaft 180deg out of phase, cams out of time, spun rod bearing, broken internal parts, loose/broken parts, bad gearboxes, etc.....
The problem is, as soon as most people do engine builds the knock sensor goes crazy. Its simply a problem with the how the ECU monitors knock.
Nov 24, 2008, 11:53 AM
#351
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If a balance shaft is 180' out of phase you will FEEL it, Cam timing you can quickly check yourself, Spun Rod bearings you can hear from outside, Bad gearboxes you can tell.
The problem is, as soon as most people do engine builds the knock sensor goes crazy. Its simply a problem with the how the ECU monitors knock.
The problem is, as soon as most people do engine builds the knock sensor goes crazy. Its simply a problem with the how the ECU monitors knock.
Nov 24, 2008, 01:06 PM
#352
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I would also be not so quick to blame mechanicals as the cause of noise. My car is completely stock except for a Ralliart muffler. No exhaust rattles, no clutch noise (auto), untouched motor still on original timing belt (not out of phase anywhere), and tuned to near perfection, but my knock control randomly goes nuts too. Most days it is fine, but once in a while it will retard itself stupid and I can watch it happen on a Blitz R-VIT on the dash. I even went as far as to mount another knock sensor in various locations around the motor to try and track down what is causing the noise. I am certain it is ECU related, either in programming or there are issues hardware-wise with RF noise.
One idea I might experiment with is that maybe over time the EGR system builds up deposits and as such flow drops. But the amount of advance for EGR is still there and may be "pre-heating" the motor a little before we load it up. Is anyone having false knock problems without EGR present? This will help me stop wasting time on this.
One idea I might experiment with is that maybe over time the EGR system builds up deposits and as such flow drops. But the amount of advance for EGR is still there and may be "pre-heating" the motor a little before we load it up. Is anyone having false knock problems without EGR present? This will help me stop wasting time on this.
Nov 24, 2008, 02:22 PM
#353
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180' balance shaft give a lot of vibration. If you dont have any vibration, check sensor first. Also 180' balance shaft will not give 36 counts of knock.
Nov 24, 2008, 03:25 PM
#356
From JCBanks post in his thread:
Nice one, glad it works for you. I have no false knock to test, I just like logic puzzles 
I have finished disassembling the knock routines
They are sophisticated with adaptation and filtering techniques to develop a background noise level. In addition to the first table I posted as the subject of this thread, there are three other tables which we will be able to adjust. They are all RPM based. One is a multiplier and two are adders that udpate the background noise level as the engine speed changes. The two adding tables are doing the same thing just at different amplifier gain levels for the knock sensor. You will note that rounded off, the triple gain table entries are simply 3x the single gain table entries. Since the ECU can switch between amplifier gain levels mid pull, they should be kept scaled together like this. These three new tables you would expect to have to update on a noisy engine that suddenly increases in noise at say 3500 RPM... if you didn't the background noise estimation doesn't keep up, the ECU decides it is knock and then the background noise estimation is further stopped in its development. So once you reach a noise tipping point it all goes wrong! We should be able to log a knock free noise curve like say AEM to guide setting of these tables with a few calculations.
I will put together a description of the full knock control system soon (there are multiple levels of filtering and lots of switches and conditions, but I have disassembled them all now). Perhaps later we can put together a concise version once people have tested practically.
I have finished disassembling the knock routines
They are sophisticated with adaptation and filtering techniques to develop a background noise level. In addition to the first table I posted as the subject of this thread, there are three other tables which we will be able to adjust. They are all RPM based. One is a multiplier and two are adders that udpate the background noise level as the engine speed changes. The two adding tables are doing the same thing just at different amplifier gain levels for the knock sensor. You will note that rounded off, the triple gain table entries are simply 3x the single gain table entries. Since the ECU can switch between amplifier gain levels mid pull, they should be kept scaled together like this. These three new tables you would expect to have to update on a noisy engine that suddenly increases in noise at say 3500 RPM... if you didn't the background noise estimation doesn't keep up, the ECU decides it is knock and then the background noise estimation is further stopped in its development. So once you reach a noise tipping point it all goes wrong! We should be able to log a knock free noise curve like say AEM to guide setting of these tables with a few calculations.I will put together a description of the full knock control system soon (there are multiple levels of filtering and lots of switches and conditions, but I have disassembled them all now). Perhaps later we can put together a concise version once people have tested practically.
Nov 24, 2008, 06:30 PM
#358
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My car with the brand new built motor gives me some knock cel "flashing" revving in neutral. Everything is tight, and installed in the correct orientation. Race balance shaft, balanced internals including flywheel and clutch, with fluidampr.
I need to log the conditions and see what's up...
I need to log the conditions and see what's up...
Nov 25, 2008, 12:02 PM
#360
I had this same issue before I took my balance shafts out, changed the head gasket, pistons, and con rods. However, I still have nuetral rev knock, lift off knock, hard throttle and light throttle between 2500 rpm and 3500 rpm. At least it doesn't read 36 counts of knock anymore. I'm getting anywhere between 1-12 counts of knock in this area. Everything above 2 counts is pretty rare though.