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Still chasing phantom knock... maybe?


EfiniX
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Galant VR-4 org Post #: 1214422 posted 08/12/15 10:12 AM     Remind Me!  Send Private Message   Edit Post      
I've assembled my notes and I'm almost convinced, but I'd love some seasoned eyes on this. I've got 8 logs that show what I'm trying to chase down. 1-4 counts of knock at low RPM and low/no boost. Generally, if I'm in any gear crossing 3100-4000 RPM's w/ 33-38% throttle position, I see knock about 60% of the time. The state of things when the knock occurs looks OK in the log. There are a few things worth noting:

My knock control was set pretty low on the first few logs: 2750R/30TP
I turned it up to 3000R/40TP before the log6 pull. Then guess what; a few counts around the same rpm range, just at higher TP.

My coolant offset is 5, so if the car is at 186 (which is where it seems to like to be sometimes, that's ok)

I've seen in two logs here, and in some other logs I'm not sharing, an odd spike in my AFR's @ around 3300 RPM's. The AFR will spike to 15.0:1 for a split second, then go back to where it should be. It's on two logs here: Log2 and log8

I've got 264 cams and no balance shaft. FP mani, 3" Fujitsubo turbo-back... I rumbles, to be sure. I also have a knock sensor that's less than a year old, and EHMotorsports put it in, so you can be sure it's installed correctly.

Basically I'm trying to figure out if my noisy, shaky engine is causing this, or if it's something I should be trying to tune out. I've not touched the timing yet as the problem is inconsistent, a few counts isn't going to blow the motor up, and this part of the timing map is fairly stock. Obviously, I can use knock control to "fix" the problem, but I certainly don't want to ignore legitimate knock.

Oh gurus of the 4G63, bestow upon me your wisdom. Link to logs and a spreadsheet detailing where the knock is happening for ease of review here:

click

Now I'm wondering if Evan has any race gas....

Thanks in advance!



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tektic
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Galant VR-4 org Post #: 1214426 posted 08/12/15 10:34 AM     Remind Me!  Send Private Message   Edit Post      
Drop 2-3 degrees from timing map in effected area. If knock is gone its real. Add timing till just before it comes back. If it doesn't go away program it to be ignored put timing back.

I made a det can this week. I made some recordings and from what I can tell my counts are not real knock. I don't have a trained ear to listen for it though.
Also My timing is super low right now.

tuner pro log and audio file
For what its worth I'm using the same 268 cams you are and experienceing knock from 2400 3800 rpm below 40 tps. I'm in boost at this time though.


Edited by tektic (08/12/15 10:40 AM)

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EfiniX
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Galant VR-4 org Post #: 1214427 posted 08/12/15 10:46 AM     Remind Me!  Send Private Message   Edit Post      
Yeah, I've got a T3/T04 and my body threshold is around 4100RPM's. Just doesn't seem quite right.

The thing about the knock is that it seems way more consistent with RPM and not with a particular section of the timing map. Here's a plot of where I see knock on my TmngMaxOct table. One dot for each time I saw knock in a log.

I suppose I could drop the affected cells down a degree, but I'd like to see what some others think, first. You can see in the plot what I'm talking about re: the RPM range.



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Edited by EfiniX (08/12/15 11:02 AM)

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Galant VR-4 org Post #: 1214435 posted 08/12/15 12:49 PM     Remind Me!  Send Private Message   Edit Post      
BLUF: Don't worry about it.

Glancing at a few of your logs, worst case you're looking at a degree and a half at partial throttle, which isn't shit. Is this repeatable under the same conditions, e.g. can you make it happen every time? If not, chalk it up to shit happens. Also, keep in mind, anything that resonates in the knock sensor's frequency will show up as fabled "phantom knock". I've heard people claim everything from lifter tick to rod knock have been known to cause phantom knock. Whether or not any of that was/is true, who knows. Each car and scenario is unique.

If you want, sure, you can pull timing from the cells you have charted. You may or may not see a difference. Whatever happens, I'm betting any changes you make won't give you consistent results. You'll probably see a bit of knock here and there even if you pull some timing. It's nearly impossibly to eliminate all cases of knock from a tune. That's because the combustion chamber is such a dynamic environment. As internal and external factors affecting the car and engine change, so does how combustion is taking place. A tune that's perfect under one set of conditions can be imperfect as soon as those conditions change a bit. It's just the nature of the beast.

How's the car look under WOT? Do you see any consistent knock there? If so, I'd be concerned with that. 1.5* under part throttle...sometimes...Meh.

That's my .02



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EfiniX
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Galant VR-4 org Post #: 1214437 posted 08/12/15 12:54 PM     Remind Me!  Send Private Message   Edit Post      
No knock at WOT.

Thanks for the input. Sometimes the spike is worse than others, but honestly, I'm thinking the same way you are. If I want to go quick, I can get on the throttle a bit more and guess what; no knock.

Anyone else have any feedback? I'm quite curious about the AFR lean-spike I'm seeing occasionally at ~3300 R.

Should I leave my knock control where it is? 2750R/30%TP seems a bit on the low side for a car with a boost threshold of ~4000R, but very safe as well.



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Edited by EfiniX (08/12/15 01:01 PM)

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Galant VR-4 org Post #: 1214440 posted 08/12/15 01:14 PM     Remind Me!  Send Private Message   Edit Post      
Just to give you an example:

While doing some street tuning, I was making 3rd gear pulls trying to get things dialed in. I'd stat my pull around 2.5k and rip until redline. Over half of the time, I'd get a bunch of knock right off the bat. I'd immediately have to abort the pull and start fucking with my tune, trying to figure what was going on.

I found that my tune was fine, but by beginning my pulls below 3k, the drastic change in load at such a low RPM caused a ton of knock. If I stated my pull closer to 3k on the EXACT same tune, the car ripped knock free up to redline. In reality, you're probably never going to be WOT in 3rd gear at 2500 RPM during any performance related driving scenario. The only real reason to start at such a low RPM in 3rd gear is to collect a greater range of readings for your log to tune with. If I didn't make a single change, but started my pull closer to 3k, the car would never knock. This sounds pretty obvious in retrospect, but at the time sitting in the driver seat staring at the laptop, it wasn't. By being able to consistently recreate the issue, I was able identify the problem. Without that consistency, it's hard to narrow down, especially in scenarios like yours.

That's just one of many examples I've experienced that made me realize that you need to examine outside factors, as well as the actual tune itself. Temperature, altitude and driver habits are all big factors outside of the tune itself.

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Galant VR-4 org Post #: 1214443 posted 08/12/15 01:36 PM     Remind Me!  Send Private Message   Edit Post      
I always found that if i was having knock when moving the throttle that I had to adjust my throttle tip in. but that was only if it was showing a lean condition. seemed to alleviate the problem.



click

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EfiniX
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Galant VR-4 org Post #: 1214444 posted 08/12/15 01:50 PM     Remind Me!  Send Private Message   Edit Post      
Yeah. I see it generally when I'm holding acceleration in the mid-30% throttle position. AFR's seem ok. Anything over 50% throttle position and I've got no knock.



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Galant VR-4 org Post #: 1214446 posted 08/12/15 03:33 PM     Remind Me!  Send Private Message   Edit Post      
That's where you need to log the base tip in throttle and adjust fuel delivery based on rate of throttle given. Basically give it a bigger squirt of fuel with a rapid WOT transition to prevent the lean condition that happens no matter what system your using.



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EfiniX
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Galant VR-4 org Post #: 1214530 posted 08/13/15 06:25 PM     Remind Me!  Send Private Message   Edit Post      
played around today in link and frankly, my tip in is pretty great. I don't go lean when I whack the throttle and I"m happy with the roll-on, even on aggressive accel from low RPM's.

I'm beginning to think things might just be fine and a count or two here and there really isn't worth losing any sleep over



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Galant VR-4 org Post #: 1214587 posted 08/14/15 09:25 AM     Remind Me!  Send Private Message   Edit Post      
It's normal to see some random light knock pick-up, the knock sensor is only looking for vibrations so lots of things can confuse it.



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matt92vr4
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Galant VR-4 org Post #: 1215449 posted 08/27/15 03:52 PM     Remind Me!  Send Private Message   Edit Post      
I get the same weird knock counts around 3000 rpm, no boost, and partial throttle. Only sometimes... Stresses me out.



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Galant VR-4 org Post #: 1215450 posted 08/27/15 04:27 PM     Remind Me!  Send Private Message   Edit Post      
I get this also sometimes. freaks me out and shit lol



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matt92vr4
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Galant VR-4 org Post #: 1215488 posted 08/28/15 09:21 AM     Remind Me!  Send Private Message   Edit Post      
Yeah, I've pulled timing in that area, fuel, added fuel, etc. and it still occurs. No balance shafts.

I've picked up knock counts from rod knock and broken piston rings before. Everytime I get weird phantom knock it brings me right back to the broken piston rings lol.



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tektic
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Galant VR-4 org Post #: 1215492 posted 08/28/15 10:45 AM     Remind Me!  Send Private Message   Edit Post      
I'm seeing the same thing only its more than a few counts. I am on the rich side with very low timing. Higher rpm i see a count or two sometimes but nothing like the part throttle lower rpms.

I was told by an old timer to try to reduce water and oil temp to see if i can get it to go away.

When degreeing my cams I found the center line to be -1.5 degrees on the exhaust side and am wondering if that was a mistake and causing elevated combustion temps and my detention problem.

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Galant VR-4 org Post #: 1215505 posted 08/28/15 02:35 PM     Remind Me!  Send Private Message   Edit Post      
Now that you mention it, it seems to happen more often with the coolant temp are above 210.



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EfiniX
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Galant VR-4 org Post #: 1215506 posted 08/28/15 02:48 PM     Remind Me!  Send Private Message   Edit Post   
For my part, it happens at 193F, which is where my car likes to live. I'm going to be putting in an oil cooler and IAT next month. I'm eager to see what (if anything) changes.

In the meantime, I've set my knock sensor threshold to 3750/30% throttle. I've got a T3/T04, so I'm not building boost until right around 3700RPM's, and I'll never see over 5lb's until I hit 3900rpm's. Seems happy for now.



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