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Discussion Starter · #1 ·
Got this from Brian at VTuner. He REALLY knows his work!

"The knock you are seeing is not real - GM has it programmed to register 1.9 degrees of knock retard at high rpm (over ~ 5000 rpm) and boost. I usually only take that out on our methanol/water tunes."


So don't worry about it when you see it.
 

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Yup Brian is the master at pulling power safely out of the 1.4 !

He recenty set me up with a more aggressive 93 octane tune 178hp/201tq flywheel. No knock retard seen at the 6200 or 6300 rpm shift points either.Perfect driveability to and excellent scan data while monitoring data under full load to, Best of all a measured 41.5 mpg at 65 mph.I dont drive the car hard very often but its nice to have a little bear under the hood when needed.I drive a lot of stock ones at work and they feel completey detuned to me compared to mine
 

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There is static retard set for one cylinder in the OEM tune up to 2012. In 2013, I believe it is three different cylinders with static retard added.

However, even with that static retard, I haven't seen it register as KNOCK RETARD in my tune when logging. In my opinion, nothing should be registering as KNOCK retard unless the knock sensors are doing so.
 

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Thanks ghost interesting info.I would love to see a complete low down on the whole system.I know i dont seem to see any 1.9 show up at all.But with the original stage 0 tune it very well must have.I know the tune is on the edge now so i have watched it close under high loads.The next phase will be in hot weather which really is not here yet.
 

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There is static retard set for one cylinder in the OEM tune up to 2012. In 2013, I believe it is three different cylinders with static retard added.

However, even with that static retard, I haven't seen it register as KNOCK RETARD in my tune when logging. In my opinion, nothing should be registering as KNOCK retard unless the knock sensors are doing so.
Like you, I don't see when logging with HPtuners, but it does show up on my MSD DashHawk which is always in the car. I just got rid of it in the tune.
 

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GM used false knock to get the engine to reduce timing (and torque as a result) during hard acceleration when shifting between gears in their automatic transmission cars. The idea was to reduce wear on the automatic transmission.
 

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Um, wtf? GM "adding" knock to reduce timing over 5000 rpm? Why not just reduce timing on the programming? Complete and utter bull. Why go through a secondary system to do such a thing?Show me the lines of code to prove this or stop spreading misinformation.Now, that's not to say that 1.9* of knock at 5k rpm is necessarily bad. Obviously no knock is better, but 1.9* may be insignificant given the conditions. Stock our motors will show up to 3* far below 5k. There are cases where the knock sensor will "falsely" read knock and is common in the SRT-4/Turbo PT Cruiser world due to internals. Many mods can cause false knock read. But to say that GM would falsely report knock to protect the transmission or whatever else is just flat out silly IMO. The traction control system can cause KR readings to be off as well as many other systems. Only way to know for sure is to get an AFR reading.
 

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I would think most likely its there is because most of these are being run on 87 octane.These cars are big with rental companys to.Basically its made to run some what detuned to run on 87 anyway.Only nuts like us here run them on 93 and max there output with tuning.Now thats not a bad thing when the engine is used sanely and normally.
 

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Discussion Starter · #9 ·
Yup Brian is the master at pulling power safely out of the 1.4 !

He recenty set me up with a more aggressive 93 octane tune 178hp/201tq flywheel. No knock retard seen at the 6200 or 6300 rpm shift points either.Perfect driveability to and excellent scan data while monitoring data under full load to, Best of all a measured 41.5 mpg at 65 mph.I dont drive the car hard very often but its nice to have a little bear under the hood when needed.I drive a lot of stock ones at work and they feel completey detuned to me compared to mine
HEYYYY! What is this new tune you speak of? Is it strictly a tune or is this with the reworked intake?
 

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What i did was try a 96 octane tune which involved using Lucas octane booster.I told Brian i was thinking of adding the booster and he added a little timeing and boost to increase the top end power.So we did it and data logging it.I went from 170hp/180TQ to 178HP/201 flywheel hp.A nice increase with the added TQ and hp.The data logs were done back to back.But since doing it i have tryed the same tune on straight 93 octane and the scan tool data looks just fine so it works on the 93.I am not going to use the octane booster because i have looked into it further and found out it contains MMT which is not good for the cat converter.Although Lucas says it will not hurt cat converters.I sent them a email with my concerns and never heard back from them.So that was a red flag for me.The car still has a max boost of 19 psi but to hit the target power increase it can boost to 21 psi if needed in hotter weather.So the tune by my understanding is a little more boost and a little more timeing and the target TQ is turned up.Keep in mind i have not tryed it in hot weather yet but based on conditions now the car does just find on it.I dont see any knock retard and the auto trans is shifting at 6200 to 6300 at wot shift points.The car does make HP up to those rpms to.As Brain told me the Stage 0 tune is done to be a safe tune with a nice power increase.He is interested in keeping customers engines safe not turning power up to be on the edge.Mine is just closer to that edge now.I drive very sanely and do not beat the car so i do not for see any problems.But the jury is still out for me until i do hot weather testing as the boost will increase to 21 psi to hit the target power TQ in very hot weather
 

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Um, wtf? GM "adding" knock to reduce timing over 5000 rpm? Why not just reduce timing on the programming? Complete and utter bull. Why go through a secondary system to do such a thing?Show me the lines of code to prove this or stop spreading misinformation.Now, that's not to say that 1.9* of knock at 5k rpm is necessarily bad. Obviously no knock is better, but 1.9* may be insignificant given the conditions. Stock our motors will show up to 3* far below 5k. There are cases where the knock sensor will "falsely" read knock and is common in the SRT-4/Turbo PT Cruiser world due to internals. Many mods can cause false knock read. But to say that GM would falsely report knock to protect the transmission or whatever else is just flat out silly IMO. The traction control system can cause KR readings to be off as well as many other systems. Only way to know for sure is to get an AFR reading.
Go read on the 3800 forums about false knock to protect the transmission. My Buick had it, and lots of Grand Prixes and other 3800-powered cars have it also.
 

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Like you, I don't see when logging with HPtuners, but it does show up on my MSD DashHawk which is always in the car. I just got rid of it in the tune.

I see 1.9 degrees randomly flash while at steady state velocity, I see the static retard but cylinder#0, really? I'm guessing its there for a reason. Siamese block issues?
 

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I think we should clarify if we're talking about false knock that occurs randomly, or programmed-in knock that is repeatable across multiple tests. If it's programmed-in, we shouldn't worry about it. If it's false, let's find out what's setting the knock sensor off.
 

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This is Static Retard. Not knock retard. nothing to do with knock sensors and or pre ingnition or detination. @5200 rpm+ it pulls 2 degs. thats all. IMO, I don't think its for the trans. The normal torque management takes away so much timing on it own, whats another two degrees? I could be wrong though.
 

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For our cars, the ECM dumps boost when shifting, hence the "no lift shift" feature of the tunes and may do other things that I'm not aware of. So why would it add false knock?

There are two types of Kr, Long Term and Short Term. Short term is what we see where it will spike and adjust timing until it goes away. This is temporary. Long Term is a more global setting that notices a pattern of too much ST KR and will permanently pull timing. This will happen when running lower octane if it's a problem.

What snowvette shows is making sense. The higher the RPM the less timing you should run. This isn't Kr, this is just reducing the timing advance.
 

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GM used false knock to get the engine to reduce timing (and torque as a result) during hard acceleration when shifting between gears in their automatic transmission cars. The idea was to reduce wear on the automatic transmission.
Incorrect. GM did not use "false knock" anywhere. GM reduced timing on specific cylinders in the form of static retard. What you describe is transmission torque management which is also not "knock", it is retard.
 

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This is Static Retard. Not knock retard. nothing to do with knock sensors and or pre ingnition or detination. @5200 rpm+ it pulls 2 degs. thats all. IMO, I don't think its for the trans. The normal torque management takes away so much timing on it own, whats another two degrees? I could be wrong though.
GM must have a reason to have static retard for a specific cylinder and even more cylinders for the 2013 tune. It could be similar to the issue with the LSx motors where one of the cylinders would go lean. Guess we could monitor each cylinder for knock and see if it is Cylinder #0 that is the most common cylinder knocking, that may help understand the reason.
 

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So there is 2* pulled from only one cylinder above 5k RPM, and this is a static retard independent of any other factors like load and IAT? Very interesting... and now the 2013 tune shows added cylinders?

This almost sounds like GM compensating for uneven flow distribution in the intake/exhaust manifold or something along those lines. Is there any other cylinder-to-cylinder "trimming" going on in the tune?
 

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Remember that while we have cam phasing, it's the same camshafts driving all 4 cylinders. So if a cylinder calls for 2* timing retard, they're all going to get it. What might happen is the fueling gets changed.
 

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Remember that while we have cam phasing, it's the same camshafts driving all 4 cylinders. So if a cylinder calls for 2* timing retard, they're all going to get it. What might happen is the fueling gets changed.
Huh? What does timing being retarded have to do with the cam? We're talking spark.
 
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