I tried search but its hard to find the right terms to search for this. I have a proven tune I have run for a while now with no knock. The night before I go to track I start getting a ramp up of 6 counts of knock from 5K to redline. Threw in my less aggressive tune and had the same results. It was like 1am when I found the issue and had no where to grab plugs before the track and no one could spare a set of their back-up sets so I added a gallon of GT 100 octane to my tank at the track to surpress the knock (which it did). I am PRETTY sure this seems like a case of bad plugs but wanted to confirm this before I went too in-depth with my troubleshooting. I just had another evo owner tell me his car started doing the same thing so I'm sure this is common...leading me to believe the plugs are the wisest choice to attack first. Thanks guys.

Might be the wrong section but I trust the ECUflash crew the most




UPDATE:
Here is a list of possible causes presented in this thread for a proven tune to start to knock. This is also assuming that the fuel system is functioning properly:

• Bad Plugs
  
• Bad Gas
  
• Increased Boost Level (temp changes affecting MBC settings)
  
• Excessive PCV oil blowby into intake system- lowering the effective octane level
  
• Phantom Knock* (least likely but still plausible in some situations)

* You should never assume phantom knock is the cause without CONFIRMING every other possibility is ruled out first. Once you believe it is definitely phantom knock.....FIND THE SOURCE! Until phantom knock is found and 100% confirmed, its wise to assume its still a threat to your tune. DON'T IGNORE knock with the assumption that its probably phantom knock.

 

How old are the plugs?

 

About 2500 miles on 'em. I know most guys replace them at LEAST every 5k miles with the evo's. BPR8ES' gapped to .022" from turbotrix. I know the range is a bit much but its all they had the day I got dyno'd. I grabbed some 7's and I am gapping them to .026" now. Maybe going tighter if I get misfires at all. Most seem to think .026" is fine though. Just wanted to confirm or deny whether people have this same issue from 5K to redline from plugs. I found it odd that my friend asked me about the EXACT same issue i had the day before so I figured I'd make it public in a thread.

 

If adding 100 oct reduced/eliminated the knock it may be bad gas...I have noticed that in Houston the gasoline quality is not the same. It's like 93 is not 93 anymore ...

 

Yeah, I was contemplating that but I had filled up at a few places since then and I still get a lot of knock. Definitely a feasable answer though. My old tune is verrry conservative which I would expect to even run on 91 octane yet I still got the same results.

 

I have found that the knock sensor is very good at picking up other noise as well. We all know about the downpipe rattle and knock, but I have run into a bad idler pulley bearing causing knock (inconsistently I might add) up to 36 counts with only 10psi of boost. In your case it sounds like something else, but there are alwways things like that that you can check.

 

Yeah, I always worry about chasing phantom knock when tuning. Wastes your time a LOT. My Megan O2 housing and DP yield negative clearance under the oilpan so I wrapped the DP in heatwrap to minimize any metal-on-metal tranferred noises. I still wanna make a spacer so it's at least a 1/4" away. My only concern with the phantom knocks would be why 100 ctane would make THAT kind of knock go away. The only major changes I have seen is the sudden drop in temps here. Its now in the high 30's to low 40's at times. Not sure how the car reacts to temperature changes.

 

How about colder temps leading to more boost, pushing you into different load cells? A MBC setup will be more sensitive to weather changes than the stock bcs.

 

Yeah, that definitely happened but I had adjusted it back down a few days prior. Boost creeped up about 1psi from the cold but the second it happened I pulled over and adjusted things accordingly. Its holding just fine now.

 

Well, new bpr7es plugs seem to have eliminated ALL knock. Only thing is...I also have a new tank of gas,lol. Since I added a tank of gas on my trip home from the track as well and still had the issue leads me to believe that my particular problem was infact the plugs this time. I'd REALLY like to have more people chime in on their experiences with this HIGH RPM knock issue and what was their cause. So far the possible causes are:

• Bad Plugs
• Bad Gas
• Increased Boost Level (temp changes affecting MBC settings)
• Phantom Knock (least likely but still plausible in some situations)
• Excessive PCV oil blowby into intake system- lowering octane level

 

Don't ever for a second blame that damm knock sensor. Its protecting your ***. Spend all the time/money in the world to quiet down your motor, trust me its not hard and you usually find other problems along the line. The second you doubt your knock sensor to being "phantom" knock and you ignore it this happens.

 

A fool would ignore it. A smart person CONFIRMS it and eliminates it. I would never say "oh, its probably just phantom knock, oh well." Besides the fact that phantom knock and real knock affect your tune the exact same way so you need to track down the issue regardless of where its coming from to have a consistant tune. Nothing I'd hate more is for my tune to drop out 4 degrees across the board because of a loose motor mount bolt or something.

Thanks for chiming in guys, I appreciate a thread having as much useful input as possible


P.S. a little JB Weld will fix that piston right up lol, I've had my share of busted connecting rods and ringlands. The carnage can be quite awful.

 

Every month or so I will start get logs with ugly knock (6) at around 5800 rpm. I immediately go into paranoid mechanic mode thinking that the engine is going. It always ends up being the same thing - PVC oil trap is full sending oil into combustion to lower the octane. After emptying the trap the knock goes back to 0.

My car has always (since 2004) leaked alot of oil out the PVC valve - must be from the 188 -182 - 184 - 184 compression making an uneven sump head pressure. I'm just glad it survived the dynoflash days before I had the trap.

"phantom knock" must be one of those liberal concepts - I never really confirmed this happening

 

Hmm, verrry good point! The previous owner just placed an inline fuel filter as a trap on my car. Last I looked at it, it was bone dry but I should really keep an eye on it in the future. I added it to my list and threw the list in the first post. Kudos.

 

What kind of setup are you running for the oil trap? I also have like 180 on all 4 cylinders with 2% leakdown on all 4. PVC blowby could be causing my knock problems too.