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as you may have read, Marc does give the proper settings but 99% of all aftermarket ECUs do not have good capabilities of knock detection because of added noise to the rise of revs of the engine. Thus although the settings are there, im not sure if they are usable. Besides if you ask all professional tuners,they will tell you that they tune with possibly headphones and then experience to prevent knock,and are taking things safe,rather than put their faith in a system that may not provide adequate safety
But if all aftermarket ECUs can not guaranty knock detection, how can a OEM ECU do it then? They must suffer from the same issue of added noise to the rise of revs of the engine
it appears that to some extent they do suffer,but i have read that on OEM ecus they have more complicated ways to filter noise through possibly maps of frequencies that enable to read the knock more clearly.I have read that this is very difficult and expensive to achieve in aftermarket ecus,that is why it is not implemented
An OEM ECU is internally matched to that specific type of engine in therms of filtering noise on knocksignals.
Still there is no 100% accurate way of electronicly spotting knock on an engine. Knock can't be defined at a certain frequency or intensity.
Do you know how the OEM ECU copes with this problem? It wil advance your ignition until it hears knock. Then is will retard it back again to be on the safe side. This proces continues on and on.
The only way of being accurate is by measuring in-cilinder pressure. But then you have to know the cilinder geometry to place the probe at the right place because of rapidly expanding/changing flamefronts due to squish areas and/or potential hotspots like sharp edges on piston crowns.
Proper way is to spot (high speed) knock is to mount a pipe boulted secure to the engine, from the engine compartment into the passenger compartment connected to a pair of hearing aids. (But then you need to know what knock sounds like obviously).
Aftermarket knock sensing aids are rubbish. You can alter the frequency on the device to an extend whereby you think that what it displays isn't knock anymore.
I've seen people hammering with spanners on the block to define the right threshold for the knock sensing kit...
Knock is the hardest part of mapping/controlling an engine. It defines the limit of the engine's capabilities with that given fuel.
as you may have read, Marc does give the proper settings but 99% of all aftermarket ECUs do not have good capabilities of knock detection because of added noise to the rise of revs of the engine. Thus although the settings are there, im not sure if they are usable. Besides if you ask all professional tuners,they will tell you that they tune with possibly headphones and then experience to prevent knock,and are taking things safe,rather than put their faith in a system that may not provide adequate safety
I have not read this anywhere, could you give some more details?
Knock is very difficult to measure at high revolutions and self oem controllers have difficulty in doing so they often run on the safe side at high rpm
Some controllers disc increase ignition 3-7 degrees if knock is dected at low rpm or switch to another soft Ignition Map.
Many have tried to make electronics that could detect knock but with negative results.
Andrey has made a firmware 1.1.51-1.1.52.2 that should be good fore knock (knock table)
I heard from a reliable source that Jaguar recently spent several million pounds in an R&D program to improve knock detection on one of their engines / ECUs - this is complex stuff - there is so much noise at high revs and its hard to program a computer to recognise it accurately. I think they had a bunch of DSP involved doing FFT analysis - looking for characteristic signals that could more confidently detect knock and ignore the other noises.
Just gathering some information right now, think I wont try it out before september, have to much other stuff that needs to be fixed right know
Cheers
Jonas
Originally posted by peter_jensen
Hey Jonas, and congratulations on the new Vems
Knock is very difficult to measure at high revolutions and self oem controllers have difficulty in doing so they often run on the safe side at high rpm
Some controllers disc increase ignition 3-7 degrees if knock is dected at low rpm or switch to another soft Ignition Map.
Many have tried to make electronics that could detect knock but with negative results.
Andrey has made a firmware 1.1.51-1.1.52.2 that should be good fore knock (knock table)
the system consists of microphones basically. they are prone to wear, suseptable to interference from water lines, they even use the coolant as a medium to pass the signals. most are on good after 60k or so.
If you get bad fuel, a boost spike through a failure or other threatening issue is it gonna save the motor?
i would never trust any knock/ retard based system like that. det cans are the way forward or maybe for everyday use a knocklink or similar. knocklinks use bosch mic sensors like our factory ones. however if not over a water jacket or too close to the gearbox they light like a christmas tree. also thats not the sensor that will save the engine so its what the real one sees thats most important
peter,do you know when the new official firmware will be available?
A official firmware release is problematic because Vems is not a official company but a kind of open source. Some of the firmware is made by volunteers from around the world and its hard to blame anyone if something wrong with the code. See the new firmware´s as experimental. You can upgrade with grate results but always keep the engine under observation. I have been using 1.1.44 the parts year and the car is feeling great yes better then ever Vems is the best thing happen to Audi s cars the past years I think and you will get a lot of power in even a stock S2. 5 cyl 20v maybe the best engine ever made by Audi you joust have to control it by Vems and you will get a big smile on your face.
the system consists of microphones basically. they are prone to wear, suseptable to interference from water lines, they even use the coolant as a medium to pass the signals. most are on good after 60k or so.
If you get bad fuel, a boost spike through a failure or other threatening issue is it gonna save the motor?
i would never trust any knock/ retard based system like that. det cans are the way forward or maybe for everyday use a knocklink or similar. knocklinks use bosch mic sensors like our factory ones. however if not over a water jacket or too close to the gearbox they light like a christmas tree. also thats not the sensor that will save the engine so its what the real one sees thats most important
looks very similar to knocklink too. my mate used to be uk suppliler for them at one point. lots in subarus with good results. the subaru box makes more noise than the average engine though.
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