Engine Knock, again

[SallySpeed3]

Ok I know this topic has been talked about, but I'm posting this because I feel like its unique to other similar threads. I have been monitoring knock for the last few days because I've put at least 25k on my current Denso plugs and just found out you should be replacing them every 15k, not something I realized. So anyway, I get the normal glip of "knock" while shifting which I know is normal and not really knock. I also will get the occasional reading of 1 then .7 then .3 while cruising which I know is just the ECU adjusting for better mpgs.
But what has been scaring me as I have been monitoring I notice that when accelerating and then backing off the gas (not letting off completely, just applying less pressure) I'll get readings sometimes up to 5, 6 or 7. They usually will go away after a second or two, but today while driving I noticed it jump up to 7 as I let off the gas and then fell down to zero in increments of .3, so 7, 6.7, 6.4, etc. This seems bizarre to me. While flooring it I only get .35 or .7 which I have been told isn't much to worry about. Any input is appreciated.

 

[the_caruch]

Let me guess, when you back off the throttle a little you are above 3000 rpm? This happens to me and it's still the computer adjusting timing. No worries.

and yea blips of .3 and .7 at WOT is fine. lots of people get those false blips.

 

[Domino81]

Wait, wait, wait... replace IRIDIUM after 15k??? A suspstance that's supposed to be several times harder than platinum. And platinum, we know platinum to give thousands of miles of life in spark plugs and you were told every 15k out of a plug that's 7 or 8x harder?!? Why? Who said it? Where are they getting their information? What's so corrosive about our combustion cycle that's warrants replacing a ******* $10+ plug?

 

[MSMS3]

Well, what is so corrosive is the combination of high compression ratio, high boost, extremely high chamber temps and 1800 psi direct fuel injection in an engine that deliberately uses an over-rich AFR as a part of combustion chamber cooling. This is an extremely exotic but hostile enviroment for spark plugs. This ain't a normally aspirated car with port fuel injection. That's why platinum plugs are fail in most forced induction applications and especially in this application.

The thin wire iridiums are necessary. And even then, I find that my plug gap opens up over time, sometimes in as little as 10,000 miles and I start getting boost induced spark blow out. If you want long plug life, get a n/a car with spot on AFR's and slap platinum plugs in the cylinder head(s).

Back on topic, OP's reported KR readings appear to be normal operating conditions.

 

[SallySpeed3]

Thank you to all, I feel much better now. And yes its always when I'm above 3000 rpms.

 

[the_caruch]

Thank you to all, I feel much better now. And yes its always when I'm above 3000 rpms.

Be sure to keep your foot on the gas, or not move your foot while it's doing this or you'll interrupt it. (as long as it's safe for you to do so on the road)

I will also get this quite frequently when i use cruise control, and i'm below 3000rpm. On my way to work over the 45 minutes i'm driving it did it at least 5 times at random intervals. Pretty neat if you ask me, trying to find the highest timing advance for better mileage.

 

[ReNaToMS3]

Wait, wait, wait... replace IRIDIUM after 15k??? A suspstance that's supposed to be several times harder than platinum. And platinum, we know platinum to give thousands of miles of life in spark plugs and you were told every 15k out of a plug that's 7 or 8x harder?!? Why? Who said it? Where are they getting their information? What's so corrosive about our combustion cycle that's warrants replacing a ******* $10+ plug?

His plugs are "1-step colder" as well, so they go out quicker than the normal ones we have. The regular temp. one can last more than 50k.

 

[spdjnke]

Ah no! even tho he's running 1 step colder plugs it has nothing to do with wearing out "quicker" because of that. cuz the whole purpose of step plugs is to transfer heat faster based tip housing length plus his plugs are also iridium, so unless your referring to platinum then your way off on ur statement.

His plugs are "1-step colder" as well, so they go out quicker than the normal ones we have. The regular temp. one can last more than 50k.

 

[MSMS3]

Ah no! even tho he's running 1 step colder plugs it has nothing to do with wearing out "quicker" because of that. cuz the whole purpose of step plugs is to transfer heat faster based tip housing length plus his plugs are also iridium, so unless your referring to platinum then your way off on ur statement.

+1. Dead on accurate statement. The colder plug will not wear as fast, although the difference may be slight for our cars. It does pull heat away quicker. The colder plug also helps prevent KR by helping prevent detonation, at the possible expense of being more likely to develop carbon deposits and foul when driven in slow stop and go traffic.

And to disagree further with ReNaToMS3, you just can't generalize that way regarding plug life. This engine is hell on plugs because the operating environment is so hostile and so different that high performance cars of only a few years ago. Even our "regular" plugs are colder than those in the n/a Mazda engines. Ultimately, the correct plug will be the hottest heat range plug you can run without experience detonation and resultant KR, and the coldest heat range you can run without carbon fouling the tip. Those are not mutually exclusive goals. You find the sweet spot in between. And this will vary, even on our platform, depending on mods. Most mod levels put the user right between the two ranges, and most of the time either will work fine. Neither is going to last anywhere close to 50,000 miles. Driven carefully and without a lot of romping, maybe half that, with at least one regap along the way.

Sorry for taking us off topic. Not trying to be disagreeable, but there are some fundamental misunderstandings out there about spark plugs, heat range, plug construction and the role they play beyond spark itself. BTW: Heat range has nothing to do with the intensity of the spark, itself, but it will affect how rapidly the center electrode wears.

 

[SallySpeed3]

I'm gonna pull mine out tommorow to check the gap and see how they look not that I'm worried too much because as stated, my kr readings seem normal and I haven't had any misfiring issues.

 

[MazSpeed3]

I have an 07 MS3 with the following;

Cobb DP/SF Intake/AP Stage 2 93 v 108 with Denso 1 Step colder plugs
Forge BOV/Corksport Cat back.

About a week ago CEL flashed and became steady ( Multiple Misfire ) cleared it. Plugs were on over 25000 miles which should have been changed at 15000. Next day steady CEL this time ( CYl 3 Misfire) cleared and I put on a new set of Denso's 1 step colder.

Now when accelerating above 3500 RPM I hear Cracking and popping sound and KR on the AP reads 8.1

Put the car on a lift and ran up to the 3rd gear with no sound. Not sure on what it could be.

Can someone please tell me your thoughts ??? Thank you

 

[MSMS3]

I have an 07 MS3 with the following;

Cobb DP/SF Intake/AP Stage 2 93 v 108 with Denso 1 Step colder plugs
Forge BOV/Corksport Cat back.

About a week ago CEL flashed and became steady ( Multiple Misfire ) cleared it. Plugs were on over 25000 miles which should have been changed at 15000. Next day steady CEL this time ( CYl 3 Misfire) cleared and I put on a new set of Denso's 1 step colder.

Now when accelerating above 3500 RPM I hear Cracking and popping sound and KR on the AP reads 8.1

Put the car on a lift and ran up to the 3rd gear with no sound. Not sure on what it could be.

Can someone please tell me your thoughts ??? Thank you

Please check my reply to your original thread on your question. Hopefully others will have chimed in there too.