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By cx500tc
#14251
ralfs.volis wrote:
cx500tc wrote:
klotzy_550 wrote:I think CX500t is getting more to the point on how to determine burst knock retard. Not all knock is created equal, so speeduino would need to be programmed to handle multiple cases. The amount of signal process that the arduino would need to do on the knock sensor signal would be greatly taxing on the processor. Ideally, with knock sensor signal processing you want the ecu to be able to determine light knock from hard knock (and rate everything in between), and how to respond to each. Then the ECU ideally should have knock learn factors, checking whether it is safe to add timing back into the mixture while the engine is not at a high load. If the ecu is not capable of this, then all it is doing is reacting momentarily to the knock, and will allow the engine to knock a few cycles before it retards the timing to protect itself. It will continue this cycle until inevitably you have a larger issue. Then a fuel quenching factor ideally would need to be added to help alleviate the "hard" knocks.

So long story short, not nearly as easy as just placing a knock sensor onto the engine (location is super critical for this btw) and being like, "yup thats knock."
Yeah, light knock, which may be desirable in some instances, versus hard knock / detonation.
There is a difference between ping under light load, and riding that edge helps with economy, generally speaking. Light knock occurring at part throttle is where the most ignition advance and most lean fuel mixture is possible, so best economy. Hard knock is the opposite, so to speak, where you want as much power as possible, so there is too much advance or not enough fuel and when you knock there, you will be blowing pistons up.

Not so advanced - graph reading knock
Image
if it senses soft - do nothing, if it senses mid - retard timing by 1 degree, if senses hard - retard by for ex 4 degrees and red alert goes off :D .
and mby in user defined steps and degrees per engine cycle
smthg like that.
Maybe something like that, but I do not see Speeduino doing the DSP in firmware, any time soon.
User avatar
By ralfs.volis
#14255
cx500tc wrote:Maybe something like that, but I do not see Speeduino doing the DSP in firmware, any time soon.
Sorry wasnt clear enough. Not doing DSP. User gets graph in megalogeviewr from Speeduino(just voltage reading from sensor), user analyzes it, sets value in TS in newly created menu - knock - when knock occours, in arduino code(very basic) -
if(knockLvl == 0)
{do nothing} // ofcourse this code line not necessary
if(knockLvl == 1)
{retard timing by 1 degrees}
if(knockLvl == 2)
{retard timing by 4 degrees}

and then update to this would be that arduino determins that lvls and filters it, but now i dont know how, thats is what forums are for, ideas and discussion, right?
By evo_lucian
#14256
I would suggest since this gets asked so often that an external arduino based knock control/sensing device be looked into. Since the GM unit is a viable option I think that that should probably be put on the list of things to look into as the firmware/ecu matures
User avatar
By ralfs.volis
#14257
update - not the speeduino, but software analyzes it - and then sends those values to speeduino.
User avatar
By cx500tc
#14263
ralfs.volis wrote:update - not the speeduino, but software analyzes it - and then sends those values to speeduino.
Still back to what will Speeduino do with that signal. ;)
By apollard
#14280
Knock frequency also changes with engine parameters, most notably bore diameter. So while the GM unit will detect knock, there is a high probability it may not detect it before damage occurs in engines with smaller bores (GM V8s use 4 inch and larger bores). They also typically don't detect knock at higher rpm, where engine noise all bleeds together and evaluating the signal becomes very difficult. I've seen a GM small block with melted pistons - and the system above (used for monitoring only) never triggered. Engine was turning 5200 rpm when it detonated and melted 2 pistons.

Much better IMO to have something like your friend uses as a tuning tool only, not as part of the control.
By androidcho
#14282
I'm thinking now of some module that will detect the knock and will output a 0-5V signal depending on how hard the knock is. Do you guys have some graphs of knocking and also on what frequencies the knock occurs (say for example 1-5KHz)?
User avatar
By PSIG
#14286
I ask myself—who would use a knock sensor in daily use, and why? They are used in OEM cars destined for unknown fuels and conditions with careless drivers. When they work, they reduce power and efficiency much more to stop det, than a well-tuned system that does not knock. They invite people to run crappy tunes or crappy fuel, because "the knock sensor will save it". :roll: If you are running greater power, you also need to use greater care, as you are closer to bad things happening. The bottom-line is that you could tune your engine correctly, make more power and MPG, and have higher reliability by tuning it, than developing and tuning a knock sensor to work reliably on your specific engine. It's like taking the time to get a girlfriend that won't cheat on you, or a girlfriend that will text you if she's bangin' someone else. :shock: I'll work for the first one, but hey, that's me. ;)

David
By apollard
#14288
PSIG wrote: It's like taking the time to get a girlfriend that won't cheat on you, or a girlfriend that will text you if she's bangin' someone else.
:lol:

I also agree with your point of view re: knock sensors, but the above was a good laugh for the afternoon...
User avatar
By cx500tc
#14289
PSIG wrote:I ask myself—who would use a knock sensor in daily use, and why? They are used in OEM cars destined for unknown fuels and conditions with careless drivers. When they work, they reduce power and efficiency much more to stop det, than a well-tuned system that does not knock. They invite people to run crappy tunes or crappy fuel, because "the knock sensor will save it". :roll: If you are running greater power, you also need to use greater care, as you are closer to bad things happening. The bottom-line is that you could tune your engine correctly, make more power and MPG, and have higher reliability by tuning it, than developing and tuning a knock sensor to work reliably on your specific engine. It's like taking the time to get a girlfriend that won't cheat on you, or a girlfriend that will text you if she's bangin' someone else. :shock: I'll work for the first one, but hey, that's me. ;)

David
Exactly my point, that if you're worried about knock, you have a poor tune, or maybe have encountered some questionable fuel. I can see the point of it, if the latter is the case, because we can't always know the quality of the fuel entering the tank. So even then it is more of a safety device than a crutch.

For all the crap I might give Honda for doing the system on my bike the way they did, I have to give credit to them for pulling over 150HP per liter from that little engine, running a turbo up to 19+ PSI boost without an intercooler, and doing that on pump grade fuel... with 1980's tech. They actually de-tuned it for production, reducing boost about 4 PSI so it would survive on pump gas. Its '83 650T brother bumped HP another 15 or so, while also reducing boost from 19 to 16. I don't think there is another 'stock' bike that can pull ahead of the 650T from 65MPH to 140MPH in top gear roll-on. And still, no knock sensors to be found.

Still, like I said, I can see the point in knock sense if it is used solely for the safety factor, and not abused to coax more power from the engine than would otherwise be practical given the engine design and state of tune.

As for the girlfriend analogy... I'm on the fence with that one. You shouldn't have to work for a girlfriend that won't cheat on you. Not cheating should be a given. If she cheats and tweets, well, at least she's being honest. And then, if she's cheating, I'd be looking at myself... after shoving her down the road. At least with tuning the engine, you have control over the vast majority of variables.
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