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Best practices for determining knock

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So tonight I road tune my first car successfully I hope! During so tho I was having a hard time hearing any knock there were a few times I thought I did but nothing that jump out or that was night and day. I even added a ton in the higher cruse to mid load area so 40-60kp around 2500-3500 on this aba 8v Vw and did really hear a difference so my question how do you or what is the best way to confirm the sound you're gonna hear without hurting things... As well could you point me to the link that shows the sound again. Surely this thing has to be knock limited on 91 deck head and cams but past 36 degrees at wot it didn't really seem to do much by the seat of the pants feel anyway


In the mid part of this page are audio samples:


I use "in-ear headphones" under a Peltor set of ear muffs.

Testing the knock threshold to be detected by the "seat of the pants" method sends shivers down my spine, the unpleasant ones to be precise.

No I want to clear that up I was listening through a knock detection system... Just like how you describe

I use the phomula brand

IMO, the best approach is to very carefully elaborate all settings on a sensitive load bearing dynamometer. Road tuning "can" be done and tuners have proven this approach to be "workable". The fact of the matter though is that there is no way around dyno time where when you can approach limits carefully with supporting data.

So maybe I should confirm we are on the same page. This car we only be road tuned since it's not gonna be raced or driven rough! It also has a safe base map. Mainly just what to know if I was crazy or just wasn't hearing the knock.. I have not been able yet to actually hear it at all for myself with my new gear and just wanted to get some ideas. By no means was I looking for mbt just making sure there isn't any on the safe side!

I'm having the same problem, trusting yourself to actually hear the knock and not being afraid your going to miss it I'm finding difficult.

Getuned, where about in the UK are you? I don't mind helping you set up the Plex and introducing knock in a controlled manner on the dyno if you're willing to book it for an hour. Could save you a lot more in the long run compared to either having it set wrong and blowing the engine or loosing out on possible power from being overly cautious.

The ability to detect knock accurately does rely to a degree on experience of what knock sounds like with your particular knock detection system and engine. It's worth purposely inducing some light knock at low rpm/high load so that you can physically tell the difference and know what you're listening for. To complicate matters though, many naturally aspirated engines won't be knock limited on pump gas so this means you're not going to be able to generate knock regardless almost of the timing you use.

The road tuning technique is viable and workable, however properly calibrating the ignition advance, particularly on engines that aren't knock limited, is difficult and often you must accept the results will be a compromise.

I wouldn't be too afraid of inducing light knock at lower rpm. Millions of cars driving up and down the road do it daily ;-) If the engine will knock, you're just going to have to wind it up in order to hear what it sounds like. I currently use a no-frills "Knock Box" with volume and gain adjustments. Ear buds inside muffs. I think once you actually hear it, and get a feel for it, it'll jump out at you every time.

IMO, the best approach is to very carefully elaborate all settings on a sensitive load bearing dynamometer

I spent a bunch of time finding knock thresholds in a particular gear, built up a table and then found that as soon as I shifted to a different gear the knock sensor noise level changed a reasonable amount above or below the thresholds I'd established. (with no other changes, and in circumstances where knock wasnt possible)

Perhaps because of knocky suspension or a creaky engine mount or something like that. But I would suspect that you're going to show a fair bit less knock sensor background noise on a dyno than what you would on the road.

Which is perfect for when you're trying to hear the knock, but not so good if you're wanting to establish the background noise levels for realtime knock sensing later on.

Disclaimer: This was using a Bosch wideband knock sensor, set to 6khz narrowband or 4-10khz wideband in the Link. (tried both)

A factory fitted narrowband one might pick up less backbround noise perhaps.

what im asking me is how much louder or stronger the knock sound is than the engine sound? maybe the thresholds needn't to be so close?

i have an relative noisy engine and set up my sensor that way that the signal from it doesn't exceed 3V without knock. But now im not sure if the knock when it appears would go higher. Damn im to afraid to let my engine knock for testing...........

hi chris.

im in kent but can travel a fair distance for some help. Im assuming there is no messaging system within this forum seen as i cant find it?

There isn't I'm afraid, I'm just south of Glasgow so it would be a fair trek just to get shown some knock. If you run the audio out through your computer you could record what your hearing and post it up for confirmation?

That's a great idea. I'll give that a go tomorrow and see what I can come up with.

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