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Part Throttle Knock

ManBearPig

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My car has 7k miles, and has been tuned since 5k. I had to reflash the stock tune for a very brief period of time, and since I have flashed my performance tune back in, Ive been seeing positive knock at part throttle; Something I have never seen before. Now while its possible I may simply be more aware now, I don't think that's the case. I tend to watch my ngauge pretty closely and don't think ive ever seen any positive numbers before. I have sent my tuner some logs and they say everything is fine, and that knock under partial throttle is normal. I'm not so convinced as I'm pretty confident i've never seen this before. I had another knowledgeable member here review the logs and recommend I check the plugs as one bank was a few percent richer than the other under certain conditions and a weak spark could attribute to that. I put a new set in and nothing is any different. Mostly the positive number will flash briefly at throttle tip in after a shift. Occasionally it will stay positive for slightly longer, maybe a full second or two. After a positive value it always switches to negative and continues to add timing as I accelerate harder. I never see positive values at WOT, just as I touch the pedal after a shift. It isn't terrible consistent, but happens often enough that it bothers me. I have not recently made any mechanical changes, and I'm confident the knock is not false. Ive checked and rechecked every exhaust component to make sure its not close to anything. I suppose my next step is to get a bottle of octane booster to see if that will make the knock go away. If so...whats my next step? My concerns are that this seemingly started out of nowhere when I flashed my tune....I have also flashed back to stock, and back to my performance tune again to make sure nothing was somehow corrupted. Are there any mechanical abnormalities that can cause something like this? My tuner doesn't seem like they think its a big deal, but I wonder if they could modify my tune anyway? I'm hesitant to request that though, as the sudden onset makes me suspect something not tune related. Anyone else experience anything like this?
I suppose I'm just rambling now but any insight is welcome
Thanks
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Kahboom

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Do you tend to use fuel from the same gas station or have you tried other gas stations and got the same results? Have you checked your ignition coils? If Lund says it's normal it's probably normal. Is it between a specific RPM? 1500-2300?
 
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ManBearPig

ManBearPig

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Ive gotten gas at a dozen different places and never had this issue until now. Ive been through two tanks at two different stations that I've had good luck with in the past. I haven't checked the coils...not sure what there is to check. They all look brand new and there isn't a misfire or really any other symptom. I'd never know the car was knocking if my ngauge didn't tell me. It is not rpm dependent...just situational. Always when I roll into the throttle after shifting.
 

Kahboom

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Has your gas station just switched to winter blend? Just going over possible causes.
 
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ManBearPig

ManBearPig

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Has your gas station just switched to winter blend? Just going over possible causes.
That's s really good question and one that I thought of, too. I've been through two tanks from two stations but maybe the whole area is switching over. Is winter blend notoriously lesser quality in terms of octane?
 

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MakStang

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Although I have an EcoBoost, I thought of joining the discussion. I have the exact same problem after reflashing the tune (Tune+ by the way). I actually monitor OAR and Ignition Timing Correction on all cylinders. OAR sometimes moves to higher values than -1 (-0.99, -0.98, one time it even moved to -0.93) but then settles to -1. I also get some negative corrections at part throttle. No negative corrections whatsoever at wot.

My own diagnosis is that the ECU relearns fuel and my driving habits because it was reset after reflashing the tune. Will have to drive the car for a while and see if OAR sets to -1 constantly and if I stop seeing negative ignition timing corrections.

Have you driven the car for a while after reflashing the tune? I would suggest that you monitor ignition timing correction and OAR for a while after reflashing the tune, as these parameters are more informative.
 

stevnoof1

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Story of my life. Have knock all the time at part throttle in 1st and 2nd. ^ and the eco and gt are not similar in any way.
 
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ManBearPig

ManBearPig

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Story of my life. Have knock all the time at part throttle in 1st and 2nd. ^ and the eco and gt are not similar in any way.

What are you doing about your knock? Just living with it?

When this first started I assumed it was because the fuel trims hadn't adapted yet. I gave it 200 miles and saw no improvement. I've since flashed to stock, then back to my Lund tune again at the reccomendation at several others. I'm bout 50 miles in after that and while the knock is still there it does seem to have gotten less often and less severe. Initially I was seeing it almost every time I accelerated and it was as high as +3 t times. It seems to be getting less frequent and is usually around +.5 now. Maybe it will continue to get better but I'm not holding my breath. The fact that it has seen improvement makes me think the knock may be due to something other than octane. Maybe fuel trims are off or something.
 

smann

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Can you post your log here?
 

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MakStang

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As I said I noticed the same on my EcoBoost and, although I know that it is a different engine, the theory behind knocking and negative timing corrections is the same.

You, like myself, started noticing knocking (I noticed negative corrections which are the effect of knocking) after reflashing the tune. When you flash a tune the ECU is trying to adjust to your driving habits and fuel trim. When you drive around the ECU starts adding timing, until it "hears" knock and then it starts pulling timing until there is no knock. This will happen several times until the ECU determins the optimal timing for your driving habits and fuel trim. Then you will stop seeing knock and negative corrections, or they will be insignificant, minimal. I always have this when I flash a new tune, or when I reflash my tune, it's normal.

I asked my tuner and he confirmed that negative corrections only matter when you are at full throttle. When you simply drive around it is normal to get negative corrections.

Drive the car for a while and, normally, knock (or negative corrections in my case) will correct by itself.

There is a very interesting reading on this subject:

http://stratifiedauto.com/blog/how-the-knock-detection-system-works-in-the-ecoboost/

Or if you want to go into more details:

https://www.iav.com/sites/default/f...ons/34242_iav_ottomotorisches_klopfen_ans.pdf

Hope this helps.
 

stevnoof1

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What are you doing about your knock? Just living with it?

When this first started I assumed it was because the fuel trims hadn't adapted yet. I gave it 200 miles and saw no improvement. I've since flashed to stock, then back to my Lund tune again at the reccomendation at several others. I'm bout 50 miles in after that and while the knock is still there it does seem to have gotten less often and less severe. Initially I was seeing it almost every time I accelerated and it was as high as +3 t times. It seems to be getting less frequent and is usually around +.5 now. Maybe it will continue to get better but I'm not holding my breath. The fact that it has seen improvement makes me think the knock may be due to something other than octane. Maybe fuel trims are off or something.
Yep just living with it for now. As I mod I see if the changes make a difference. First I changed to an x pipe and it made things worse. So I thought maybe it is false knock which was what I was initially told. Changed To a catback went back to "normal" random knock in 1st 2nd 0.5-2.0. Changing headers this coming Friday probably won't help. Sometimes I wonder if it Might be somethin related to the transmission or intake side? My car will be basically fully bolted on after the headers install. If that doesn't help I will just live with it until the spring and then try a new tuner. If that doesn't help then I will consider it normal.
 

smann

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Do you see the knock at WOT? or only part throttle?

If you're seeing it often at part throttle, it may be false knock (usually from something exhaust related). If its knocking at full throttle.. That is going to be a problem

Just check over the exhaust, trans mounts, Motor mounts make sure everything is tight and not rattling or vibrating excessively. Also make sure their is plenty of clearance between the piping and under body and trans mount of the car.
 

dubster99

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I wouldn't worry too much about part throttle knock. Things are changing rapidly as you get on off/throttle and different throttle percentages, and giving the car too much throttle in a tall gear at low rpm can cause knock readings. WOT is where it really counts.
 
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ManBearPig

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I took a few logs today. Theyre pretty long, but I wanted to make sure I got some good data. Log 3 starts out in traffic with lots of on/off throttle. Once traffic clears up theres a few miles of interstate cruising with some heavier throttle passing cars here and there. I also made a WOT pull through gears 1-3. I was spinning a lot but tried to keep my foot in it. Log 4 is more crusing and regular driving with another pull toward the end. Log 5 is some stoplight to stoplight driving with light to moderate accelerating.

What I noticed is of course is the knock at throttle tip-in after a shift. Pretty inconsistent but it's there a good bit. I'm also seeing the car go pretty rich under certain circumstances when I toss the car into neutral and coast. This, too is pretty inconsistent. Is this something the tune is commanding on purpose to cool the cat converters or something? Seems unnecessary to me but I don't know if its supposed to be happening. My understanding is that under these conditions the car is in open loop, but as soon as it goes back into closed loop the STFT brings fueling back to Lambda pretty quickly. Just weird that it spikes rich for a few seconds in the transient period.

I welcome input on these logs, and appreciate you guys looking them over for me.
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