hi everyone. it seems like im having a similar problem to Naji's knock thread.

i'm running an 05 evo with the following mods:
-denso 720cc
-255 walbro pump
-TBE (espelir 2.75" dp, RRE hfc, espelir catback)
-hks 272,272 cams with AEM cam gears (-1,-1)
-dejon mbc @ 20-22psi
-stock airbox
-nisei comp intercooler with licp
-safcII (connected, but not used. low&high maps zeroed out)
-logging with zeitronix (AFR, EGT, and boost)
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looking at my logs, i notice that i am getting a bit of knock. most of it seems to start at either 5k or 6k but most of it at 6k. i will sometimes get 1-3 counts before 5k as well. it used to be intermittent where i would get runs with 0-3 counts at some spots the entire run, but then all of a sudden i would 5-8 knocks other runs on the same tune. now it just seems to knock a majority of the time.

i've tried to reduce timing and even richened my fuel map so that my AFR's are at mid 10's. i also tried to lower my boost from 22psi to 20psi and i am still getting knock.

i was thinking about it being "phantom knock" but i've looked underneath my car before and haven't seen anything hitting or touching. another thing is that my EGT's will go up when i knock, so is this an indication of REAL knock? (when my log had little knock, my EGT's wouldn't go above 860-870. when it knocks up top my EGT's hit 890-900)

i was just wondering if phantom knock is what it is, just fake knock. if it's fake, then i don't see a reason why my EGT's would be affected.

i'm trying to tune my car and just having a heck of a time. the next thing on my list is to do ANOTHER boost leak test and check my spark plugs (which are still new BR7ES@ .024 gap).

i am considering just changing my map entirely back to stock settings and just start all over from there (stock fuel/timing maps)

do you guys have any other ideas or input?

thanks. i appreciate it.


-louie

 

91 octane?

 

Your EGTs are going up because the ECU is pulling timing because of the knock, whether it's fake or real.

Since you said that you reduced timing, increased fuel, and reduced boost and still saw the same amount of knock at the same place, then I would lean towards phantom knock.

Are you always seeing this knock at the same RPM and the same relative amount of knock counts no matter what you do?

Another way to check, is to go find some 100 octane gas at a pump and fill up with that. If you still have this knock at the same RPM and same knock counts, then I would almost definitely say it is phantom knock.

If it does turn out to be phantom knock, then it may be difficult to diagnose the issue. There are lot of reason for phantom knock, from a downpipe hitting to noisy lifters. I don't think anyone can really tell you what it might be. It's sort of up to you to find the culprit at that time.

But, make 100% sure that it is phantom knock...just don't assume until you are positive.


Eric

 

C6C6CH3vo, yeah it's 91 pisstane.

l2r99gst, thanks for the reply. thanks for clarifying the EGT's.

well, i had to get my exhaust modified a while ago because i installed the jdm 9 bumper. the tip was touching so the muffler guy shifted the exhaust to the right. he made sure nothing was touching, and i've gone down to check myself and everything looks fine. i guess i'll check again though.

like i mentioned in my first post, i get knock mainly around 6k and above. sometimes i'll get it at 5k. most of the severe knock counts are in these areas. however, i sometimes get 0-2 or 3 counts below 5k at around boost.

i tried 100octane a couple of weeks ago. mixed it with 91 to make a little over 93. i think i still got knock, but just not as much of it. i can't recall that far back.

so i guess these are the things to check so far:
-check underneath again to see if anything is touching or hitting
-boost leak test (again)
-check plugs?

hmm. keep the ideas coming.
again, thanks, you guys.

 

So the EGT's will read higher from the burn being further downstream?

Nonetheless, 100Oct will be a good troubleshooting tool

 

Yes.

 

Do what Eric is saying. Run your tank really empty. You have about 40-50 miles after the light comes on. So make sure you use almost ALL the 91 octane gas up. After that fill about 5 gallons of 100 octane. I would fill a whole tank if I where you. I would use the tank to test for knock and, while I am at it, create a 100 octane gas map.

I would also swap to BPR8ES plugs. Colder plugs help reduce knock. But do not go too cold since this might foul the plugs in daily driving.

 

If it is real knock, then doing something with the stock airbox may help. You can gain about 4% air density by modifying the lid of the airbox (as long as you don't go mad cutting it back so it lets lots of hot air in or live in a really hot area it should be a gain). Doesn't sound much, but after the turbo it is like getting 1.5 PSI boost pressure for free at the boost level you're running. If you run the same boost as before it will mean you can run open the wastegate a bit, slow down the turbo, reduce exhaust manifold pressure, increase compressor efficiency and volumetric efficiency. This should lower EGTs, move you away from the detonation threshold. All nice things on low octane fuel.

I know the mantra on here is that the stock airbox is not a restriction, the data across multiple cars since logging tools became available proves this is not the case.

 

thanks for the tips, guys. first things first. gonna double-check everything underneath the car. i can't run race gas yet since i just filled up all the way last night, but i'll keep that in mind. i'll look into the BPR8ES. i'm not sure if i want to cut the stock air box. i mean, a lot of people are tuned on 91 without having to touch their air box. even if it did help, i still consider it a band-aid. i need to find out exactly what is causing this problem.

 

The point is to be systematic with whatever you try. Fix, do so logs, check the logs for knock. If there is a lot of knock, then fix something else, log again and check for a lot of knock.

This way you can logically eliminate all the possible causes of knock.

 

that's what i'll try to do. one thing at a time. :-\

 

Cars with phantom knock usually get counts in closed loop driving too so keep that in mind

 

i logged on the way home doing normal driving. i saw mostly zeroes but i did see a few of instances where i would get knock counts from 1-3, just cruising. so i guess this is probably normal, huh?

 

Depends how often, I see it very rarely. We've not defined the load and RPM limits for knock control, but one very noisy car needed about 100 load before it pegged the knock count at 36. Maybe the valve noise just wasn't loud enough below that load, or maybe the knock control is not turned on, don't know.

You could say that heat grade 8 plugs are also a band aid given that others can run 7s though?

I agree you need to diagnose your issue and determine if it is false or real knock though. If real knock though, the ECU retards so quickly I think sometimes you wouldn't hear the knock even with headphones on attached to the engine. Hence the higher octane fuel might help diagnose.

 

i've seen at around 3-5 instances during my 35-40 min commute home. if i remember correctly, most of them were at 25-30% throttle.

anyway, im slowly running my tank down. it probably won't empty till thursday. but if i do run 100 octane, or even 95oct i shouldn't see any knock sums during cruise unless it's phantom, right?

oh well, i need a break from the car anyway.