Knocking at throttle let off

[79535]

Hey guys,

I installed my Cobb AP running the stage 2 91 octane v1.05 map. The car is running stock intake and BPV, 1 step colder denso's gapped to 0.028 as per Cobb.

I don't seem to have any issues with knock while running WOT. However, as I approach 6000RPM (or in that neighborhood) and release the throttle, KR spiked to 4.9. This seems to happen fairly commonly when I let off. The highest I have seen it go was 7.6.

Anyways, I'm wondering if anyone else has knock issues at let off.

I'm not convinced this is so much an issue considering the engine is in a huge "tune swing" (for lack of better words) when you go from WOT to off throttle.

Anyways, I probably grab my first log tonight maybe and post it up. Let me know what you guys figure.

 

[ReNaToMS3]

What other mods do you have?

If you don't have an intake, then I'm pretty sure you shouldn't be running a stage 2 map. Also, i don't think you need step 1 colder plugs if you don't have a lot of mods, it will just foul in 2k miles. Cobb says you should have them but you need more mods like a DP/RP, TIP, IC, Intake to really justify it.

Post up a log along with the mods, maybe somebody can help you a bit further.

 

[79535]

Stage 2 map is meant for a stock intake system with a TBE. I forgot to mention I was running a catted CP-e TBE.

With a boost target of ~18 PSI, I think it will be burning hot enough to keep my plugs from fouling. I also push my car more often (all day everyday) than most other people I know.

Anyways, assuming based on your post not mentioning whether you knock or not when you transition from WOT at high RPM to no/low throttle at lower RPM's you likely do not see this knock.

 

[ReNaToMS3]

I went over the notes and indeed it is for a stock intake system.

It states on the notes the map is made for the Cobb Exhaust. This is perhaps where your problems lies? Even a little difference (cpe or cobb exhaust) can turn out to be a big one as far as maps go.

I do have some knock after throttle let-off like you stated, although not at those high RPM.

Things that helped me: Seamfoam, PTP Pill. I would consider doing those to clean up carbon build-up in your engine, which can cause knock.

I would also get a log going and see where the problem might lie a bit better. The map will probably have to be adjusted for your particular exhaust.

 

[8.5MS3]

im tuned for 18psi and my denso's fouled in 1000 miles

http://www.mazdas247.com/forum/showpost.php?p=5115399&postcount=5398

 

[79535]

My denso's are brand new (300km's) and I saw you mentioned you don't go high boost very often. I will keep an eye on them though.

I took my first logs last night in 3rd and 4th gears (seperate logs). I messed it up however due to the lag time when you press okay to start logging.

I'll get some better ones and post them up.

 

[79535]

Here are the data logs from last night. Like I said, there were some coordination issues.

First thing I notice is I'm not making boost targets. AFR looks healthy. Fuel pressure is solid.

What bothers me is the little bit of continual knock happening.

Oh and of course these are useless to helping to figure out the OP. Oh well, I'll grab better ones today sometime.

 

[8.5MS3]

^^^WHOA^^

whats up with your wastegate in the 2nd log??

i suggest pulling timing back a touch to see if that helps.

also, what were the temps outside? boost is dependent on load, so if its cold, less boost is required to hit load targets.

 

[79535]

Lol. I have no idea what happened to my WG.

It was roughly around freezing while I was doing these pulls.

I will get some new logs after I sleep and get up (been up all night, oops).

What exactly should I be logging? I used the list on the MazdaManiac website (minus vehicle speed).

 

[8.5MS3]

RPM (RPM) Inj. Duty Cycle (%) Knock Retard () Calculated Load (%) Mass Airflow (g/s) Throttle Position (%) Actual AFR (AFR) Boost (PSI) Spark Adv. () Wastegate Duty (%)

 

[COBB Tuning]

KR AFTER you lift off is fine. When you take your foot off the throttle you basically shut the injectors off, you are just seeing a timing correction for off throttle. I am not really seeing any knock correction in either log, so that really isn't a worry. Howver, you are only hitting about 14psi in either log and WGDC is about 40%. However, if it is overly cold, then running less boost is perfectly acceptable. Your logs otherwise look fine.

Travis
COBB Tuning

 

[79535]

I will grab some logs (properly timed this time ) just to be safe.

Travis, thanks a lot for chiming in. You guys are great at dealing with customers and it is appreciated. Hearing that you aren't worried makes me feel better.

 

[Darth Vader]

people get this all wrong...KR is a good thing, it's the K that is the bad thing and, only under load. KR at other times is irrelevant.

Knock without Retard is the death knell for your piston crowns.

 

[79535]

people get this all wrong...KR is a good thing, it's the K that is the bad thing and, only under load. KR at other times is irrelevant.

Knock without Retard is the death knell for your piston crowns.

Obviously. The thing you seem to be missing is the fact that if you are getting KR, your engine observed some form of knock and is trying to compensate which means you have an issue.

In my case, I just wasn't sure if what I will call "let off knock" is a bad thing. I've never dealt with ATR and logging before.

I had a Cobb AP before and blew my engine. I was running the v1.03 maps and I did not log anything that time around so this time, I'm trying to be safe.

I should also add that I was running an HKS intake and not a Cobb SRI or MSCAI when I blew up.

I typed all this up and now I'm wondering if there was a form of sarcasm involved in your post. Either way, I'm submitting this post now since I typed it up.

 

[MSMS3]

But Darth is right and so is Cobb's post. You are not measuring knock, you are measuring the engine's pulling of timing to address a particular situation. Pulling back timing when you let up completely on the gas is going to happen.

As long as you are not seeing (and able to log this for us) evidence of knock under load, KR does not matter, IMHO.

We (or I) don't know why your previous engine went boom while running AP. But your present situation of KR only at lift throttle is NOT an engine damaging thing. Maybe you have OTHER tuning or modding issues, but this is not one of them.

 

[79535]

Apparently I'm being misunderstood.

I'm not disputing what Travis said. I was simply trying to imply that I am likely going to be over cautious due to my other engine shitting the bed. Mazda replaced that one under warranty, but I doubt they will replace another.

 

[COBB Tuning]

Smoke,

What was the failure point on your engine? Did you happen to burn your valves?

 

[79535]

The engine was analyzed by Mazda. The only damage they mentioned was a snapped rod which in turn smashed through the side of my block. They told me it was cylinder number 4 and it occurred on the cylinder closest to the driver's side.

Sorry, but I'm not sure if the valves were burnt.

Related to the OP, I would have posted a log up here to get some help from you all, however my mysterious cylinder 2 misfire has reappeared and I need to diagnose the issue.

 

[mazdaspeed32007]

crazy it happened in cyl. 4. from the engines ive seen blown its been in cyl 3. i always thought it was the stress caused by the balance shaft attached to cyl. 3 but i guess not. the broken rod isnt uncommon but weird how cyl 4 was the problem. i currently hit a snag in my tuning as well.

put in a new exhaust mani and threw a p2119 and p2088 code. gunna recheck my wires and s*** first but boost targets in my case are 19psi and im only hitting 15. idk...wish it was easy.

 

[79535]

crazy it happened in cyl. 4. from the engines ive seen blown its been in cyl 3. i always thought it was the stress caused by the balance shaft attached to cyl. 3 but i guess not. the broken rod isnt uncommon but weird how cyl 4 was the problem. i currently hit a snag in my tuning as well.

put in a new exhaust mani and threw a p2119 and p2088 code. gunna recheck my wires and s*** first but boost targets in my case are 19psi and im only hitting 15. idk...wish it was easy.

That sucks man. Sorry to hear you are having problems.

It definitely sounds like some wires are crossed somewhere.