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4.6* of Knock Retard?


Jon

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That's what it looks like to me. Look at that sucker pull timing, sheesh. Tell us about the car. Looks like it wants to pull timing when you stab it, as evidenced by the 2 degree spike past the cursor. Possibly burst knock.

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When did you get this scan....this morning ? Did you log any other data, ECT, IAT, etc ?

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That's what it looks like to me. Look at that sucker pull timing, sheesh.

Tell us about the car. Looks like it wants to pull timing when you stab it, as evidenced by the 2 degree spike past the cursor. Possibly burst knock.

A great learning thread is about to begin ........YEAH !!!!!! :partydance:

Pretty much a stock 2011 LS3 Mn6, right Jon ?

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Where did he go? :blink

He was at LPM getting his shocks put on....maybe he was using Steve's computer ?

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OK, well, I guess while we are waiting for Jon to come back,I can get us underway in our inaugural installment of "Tuning with Two Snails". Earlier in this thread, I used the term "Burst Knock". Everybody say it with me now Buuurrrst Knooooccckkk. Very good. Burst knock is a predictive type of knock control, kind of like your PCM's very own Jeanne Dixon. Burst knock retards timing based on rapid air flow rate changes. Burst knock tables in the PCM prevent actual knock from occurring when rapid throttle openings can actually create knock due to sudden enleanment. This enleanment usually occurs because of a disparity between the MAF and MAP signals the PCM sees during sudden acceleration. These Burst Knock values show up as a knock retard signal, even though no actual knock occurred. And you though TRON was trippy....

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OK, well, I guess while we are waiting for Jon to come back,I can get us underway in our inaugural installment of "Tuning with Two Snails".

Earlier in this thread, I used the term "Burst Knock". Everybody say it with me now Buuurrrst Knooooccckkk. Very good.

Burst knock is a predictive type of knock control, kind of like your PCM's very own Jeanne Dixon. Burst knock retards timing based on rapid air flow rate changes. Burst knock tables in the PCM prevent actual Knock Retard from occurring when rapid throttle openings can actually create knock due to sudden enleanment. This enleanment usually occurs because of a disparity between the MAF and MAP signals the PCM sees during sudden acceleration. These values show up as a knock retard signal, even though no actual knock occurred. And you though TRON was trippy....

I'm guessing this symptom might be exacerbated when cold, dense air is present ?

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Yeah, I am anxious to get his car info so I can pull the calibration. He may have a car where the stock spark tables are too aggressive, believe it or not, they came this way from the factory.

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It is not as much a cold/hot air thing, because the engine knows the air temp. The MAP is much faster to respond to density changes when compared to the MAF, and this pisses off the computer a tad.

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It is not as much a cold/hot air thing, because the engine knows the air temp. The MAP is much faster to respond to density changes when compared to the MAF, and this pisses off the computer a tad.

Really...wow, is that just the normal functionality of a MAF to be slower than a MAP sensor ?

Reason being, there was a recent thread on the big board where a vendor claimed that there may be some faulty/defective MAF sensors installed by GM, which they identified with a specific part number stamped on the housing.

Sounded odd to me...

Bad MAF????

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I saw that thread, LOL. I am personally not putting any large amount of stock into it, there could be a few bad ones out there, but yeah I am not buying it. The problem with the Hitachi slot-style MAFs in these cars is they have incredible resolution. Too incredible, in that the slightest change in airflow can have wild results. So the PCM looks at a wider range of data before making a change, and in so doing, especially when entering PE (Power Enrichment for those playing at home, let me know if you need to know what it is), there is a disparity between MAP and MAF. The PCM will introduce burst knock to keep everything safe. Tuners can alleviate it, make it less sensitive, or work around it. The problem is, it requires recalibration. We will see what Jon says and make a few recommendations.

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Victor, I saw your add of the link. Read TJWong's post under it, I am in his corner here.

Very much agreed with his statement as well...yet the thread persist, even in the ZR1 section :facepalm:

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I saw that thread, LOL. I am personally not putting any large amount of stock into it, there could be a few bad ones out there, but yeah I am not buying it.

The problem with the Hitachi slot-style MAFs in these cars is they have incredible resolution. Too incredible, in that the slightest change in airflow can have wild results. So the PCM looks at a wider range of data before making a change, and in so doing, especially when entering PE (Power Enrichment for those playing at home, let me know if you need to know what it is), there is a disparity between MAP and MAF. The PCM will introduce burst knock to keep everything safe. Tuners can alleviate it, make it less sensitive, or work around it. The problem is, it requires recalibration. We will see what Jon says and make a few recommendations.

Hhhhmmmm.....Power Enrichment. Maybe you can elaborate just a bit on this subject....for CROSS and myself :smilelol

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Victor, after re-reading my post, I did not mean to insinuate I was making light of your question. Please accept my apologies, if that is the case, as it was certainly not my intent. These guys are trying to sell MAFs based on an outcry. We ran into a real problem with these sensors back in '06, and as CAI kits have become more popular, the problem has grown. Remember when 417 Jay was freaking out because he cut his shroud after talking to an ACE member and his car ran like shit? Even in my own humble turbocharged car, it was a real problem. If the air passing over the sensor is not (***alert***, one of my favorite words coming up) laminar, the MAF freaks out. We can fix this, but the sensor is not the issue, the air flowing around the sensor is. The senors are awesome, but boy are they touchy.

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I'm back. Been awake since yesterday at 4pm. So I took a nap on LPM's couch. I wasn't even awake when Mike dropped the front runners off. Back on topic, yes I logged all those other values. IAT was around 42F if memory serves. I did a log because I'm changing the intake to a Callaway Honker and wanted some data for comparison. My car is a 2011 LS3 6 speed manual with 1400 miles on it. It won't be tuned. I'm just using my HPT as a data logger. I'm mainly interested in it so I can record my upcoming road course sessions and watch oil pressure. I want to see if I really need an extra quart of oil or not. On my GTO I was running speed density with burst knock turned off. I had the knock sensor decay rate set a little faster, but I left the sensitivity alone. Crappy tuners will rape the knock sensor sensitivity. I want my motor to pull timing if it senses knock.

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With me putting the Callaway Honker, I really hope the MAF doesn't spaz out. I'm throwing on the dyno in a couple minutes. Unfortunately my laptop battery died and I can't log it. :(

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Victor, after re-reading my post, I did not mean to insinuate I was making light of your question. Please accept my apologies, if that is the case, as it was certainly not my intent.

These guys are trying to sell MAFs based on an outcry. We ran into a real problem with these sensors back in '06, and as CAI kits have become more popular, the problem has grown. Remember when 417 Jay was freaking out because he cut his shroud after talking to an ACE member and his car ran like shit? Even in my own humble turbocharged car, it was a real problem.

If the air passing over the sensor is not (***alert***, one of my favorite words coming up) laminar, the MAF freaks out. We can fix this, but the sensor is not the issue, the air flowing around the sensor is. The senors are awesome, but boy are they touchy.

Oh, no.....I agree with you 100% !!!! Reading the stuff that was written in that thread gave me pause, as it didn't add up based on what I thought I understood. The TJWong wrote his response, which made me feel a whole lot better on what I thought I knew. :lol

Even now, with the relocated MAF in the new KillerBee II CAI I have, the propped shroud trick is causing airflow issues with the MAF...something I didn't have with the older version and shroud mod. These MAF's appear to be VERY sensitive to airflow.

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hhhmmmm.....Power Enrichment. Maybe you can elaborate just a bit on this subject....for CROSS and myself :smilelol

Ahhhh, good old Power Enrichment. More commonly referred to as PE in tuning threads and like.

Power Enrichment is the strategy the PCM uses when the driver commands wide open throttle performance, though it can be tuned to come on much earlier in the throttle position and RPM bands, depending on what the driver and the tuner require. During power enrichment, the PCM uses look up tables (we can tune these), load (provided by the MAP & MAF) and air flow data (provided by the MAF) to determine timing and fueling. The PCM does not look at the O2 sensors, and ignores other data as well that does not directly relate to power production.

Since the PCM wants to look at MAP and MAF for load, if they are not lined up, all kinds of crazy shit starts to happen. Remember my analogy about the guy with two watches? If the MAP and MAF tell two different stories for too long a period of time, you get no traction control, check engine lights, and even reduced power mode, because the PCM does not know who to believe. This is a reason why, for radical combinations, tuners will turn off one or the other. It keeps the car happy.

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A lot of people don't realize you need to think of air as a fluid. I'm having heat transfer and fluid flow flashbacks now. Thanks. :D

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