Knock acceptable while "cruising", how much?

I have read that positive knock while "cruising" is deemed acceptable. Maybe not desirable but acceptable. My question is….what defines this? Under what circumstances and how much knock is acceptable?

I often see positive knock very briefly at throttle tip-in. Mostly when accelerating normally and rolling back into the throttle after shifting gears. Sometimes I'll see the same thing when on and off the throttle just cruising at freeway speeds. When I see any of this it's usually under 1* and goes away very quickly before turning into negative numbers (adding timing). Every now and then (usually when accelerating more aggressively, but still not WOT) I'll see a larger knock value after shifting gears that stays 2-3 seconds before going away. This is usually around 2* or less but I recall seeing 4* on one occasion. I always see the car add timing at WOT and usually see 27*-29* SAFTOT, which is right around where it should be.

None of this knock is very consistent as a good portion of the time, I'll see spark being added (negative numbers) immediately after each gear change and throughout all acceleration. I really don’t think I'm getting false knock as I am running stock exhaust and there is ample clearance everywhere under the car. However I tried a few gallons mixed with Torco and didn’t notice any difference so it would seem to not be octane related either. I see this on the stock tune and my Lund tune so I'm not blaming the tune, just wondering if this is "normal" or if there is something mechanical going on with my car.

I have never seen positive KR on my Lund 93 Oct tune, for reference.

What tune and device are you using?

Lund 93 tune with ngauge.

They have reviewed a dozen of my logs and swear up and down everything with the tune is fine. Given I've seen the same knock activity on the stock tune I'm inclined to believe them. Obviously I wish there was never any knock at all but I can't see what could really be done about it and am curious if others see the same kind of activity.

I used to think my car never showed any positive knock but now I'm convinced that I just didn't watch it closely enough to see. The knock happens and goes away so quickly you have to be looking for it to even notice.

Brian,

Here is a pic of a log I took that was about 15 minutes of cruising. All I had done at the time was a steeda intake, 170* Tstat, MBRP cat back. I was using the stock timing tables and knock strategy and was just working on MAF tuning. As you can see the max knock I saw was at low load when I let off the throttle, it only occured once in that 15 minutes, and it was probably fuel popping in the exhaust not actual knock.

I can also see besides fuel being cut when coasting my actual lambda is right around 1, with the occasional drop to .93-.92 but nothing really crazy. The only time it was rich was when the engine was still a little cold in the first part of the log.

I found a 30+min log of a 2016 manual car. He was having knock on shifts. In that log there would be a random 0.5-0.6 * of knock while cruising.
I re-scaled from 0 to see the spike easier.
Its pretty much in the same area as my log. My guess is it happens at about where the IMRC it told to close, but have not been told to be open. The solenoid would make a noise similar(quieter) to the one in this video: [ame]
That would be something the knock sensors would register. Too bad you cant sync up GOPRO footage and the log. You could unplug the solenoid, get an MIL, but it should still actuate with manifold vaccum.

I wouldn't worry about knock there at that low load. Cylinder pressure spikes from actual knock would be negligible.

At no/light load a little knock probably is nothing to worry about, I have the same thing.

What mods do you have done? If adding Torco didn't help it's most likely a small amount of false knock.

Only mods to the car are the tune, springs, and MBRP cat back. If the IMRC is unplugged I assume the valves will default to open? If unplugging wouldn't cause any other weird affects I'd be happy to unplug it for a while to see if that makes any difference. I'm about to leave for work and will take a long log of about 30 minutes of driving to show what kind of activity I'm seeing.

Local tuner (Injected Engineering) did a 93 tune on the ‘08.
No knock or pinging ever.
IMHO...it’s never a good thing and I would get it checked out.

A 2008 4.6 is an entirely different animal from the 5.0. I don't believe the knock sensors allow timing to be adjusted on those cars.

i can't think of anything else to check out....

I took a good long log on the way in and will upload it later today to show what kind of activity I'm seeing.

Well aware of the differences between the two engines.
Knocking of kind or at any time would not be acceptable to me.
Hope you find a satisfactory resolution soon.

Can I simply unplug the IMRC connector with no weird effects? I've read that some guys delete them anyway. I've always had a weird surge in power when rolling on the throttle under certain circumstances. Maybe that's when the IMRC valves open and I could kill two birds with one stone by deleting them. I just want to make sure the car will react correctly if the solenoid is unplugged. I imagine they default to the open position, right? I need to find the connecyor(s), too.

EJS2016 said:

Local tuner (Injected Engineering) did a 93 tune on the ‘08.
No knock or pinging ever.
IMHO...it’s never a good thing and I would get it checked out.

Click to expand...

I'd agree with this. I only ever see a small amount of knock, 2-3 deg, under high load (>50% throttle). I am thinking based on this thread and your others that you have a bad sensor or lead and it's creating background noise.

I had someone more knowledgeable than I am when it comes to tuning tell me once that knock can occur from a rich condition. I've noticed that the car goes pretty rich between shifts sometimes and maybe that's causing a knock as I roll back on the throttle? There seems to be a trend...if I toss the car into neutral it will go rich for a few seconds as it returns to idle. If I'm off the throttle and the car is in decel fuel shutoff, as soon as I get back on the throttle at all it immediately goes rich for a few seconds. My guess is that the car knows goes rich for a few seconds to offset the lean condition created with fuel cutoff/engine braking. This happens on the stock tune as well so I don't think it's tune related but I'm wondering if that's to blame for the knock I'm seeing?

I took a really long datalog this morning on the way into work, but its too large to load into datazap. I'm trying to create a zip file to attach here as id love some insight on the log

I've never had positive knock at part throttle with Lund...never.

I was able to take a few columns out of the .csv file and upload the log into Datazap. It so long, I cant figure out how to zoom in to see more detail, though. If anyone is able to see this...how does it look?

https://datazap.me/u/manbearpig/extended-lo-drive-work?log=0&data=1

ManBearPig said:

I was able to take a few columns out of the .csv file and upload the log into Datazap. It so long, I cant figure out how to zoom in to see more detail, though. If anyone is able to see this...how does it look?

https://datazap.me/u/manbearpig/extended-lo-drive-work?log=0&data=1

Click to expand...

Click and drag to select the section you want to zoom in on. click zoom out in the upper right to zoom in on another part.

In the entire 30 minutes you had .65 max positive knock and only 4 positive events, all at very random spots.