Coyote with nitrous - crazy knock

[brandonconner]

ok...so working on a 2016 Mustang GT A6 with an NX plate kit. Car is basically stock other than a JLT CAI - still has cats, does have an axle back exhaust. Sprayed a 50-shot on it with good results (at least initially, didn't intend to fully tune for 50 shot) - saw right at 50hp at the tire, good response, perfect A/F and most importantly at this point no knock. ECU actually added about 1.5 degrees above 4500rpm. Swapped the pills up to a 100 shot, pulled another 2 degrees timing (4 total from stock) and it goes nuts. Immediately into the pull, knock retard pulls 10 degrees. Thought maybe it was tq mgmt, disabled it (at least I'm fairly confident it's off) and it does the exact same thing. Attached partial tune file and log, this is by no means complete but we're kinda stumped at this point. Anyone have any pointers?

[Higgs Boson]

turned off traction control?

what are fuel trims while spraying?

will look at tune tomororw.

[murfie]

When ever you look at knock you always what to look at what happened just before the knock not during it. I see you have a lean spike .92 lambda. This probably caused a very large knock event as your timing was 24*. This is probably caused by the change to your driver demand table increasing at 2600 rpm and your torque management tables only starting to increase at 4000 rpm.

[FLtuner]

For a 100 shot on 93 octane I'd command .82 lambda wot fueling. For timing on 93 I keep it very conservative.

[brandonconner]

Thanks for the feedback so far guys, I appreciate it. I'll make some modifications to timing down lower and add some fuel and see if that helps. One other question - I've read people who argue both ways but at that power level do you think it's necessary to modify the torque and torque inverse tables? I made some changes to it before making the pulls and it's within around 5% of what the dyno reads (dynojet).

[Higgs Boson]

Torque/inverse should be engine torque not rwhp...or even rwtq...

[brandonconner]

gotcha...so should I set it back stock or calculate flywheel tq from the dyno?

[R8Bill]

My buddy is having the same problem. What did you do to fix it?

[Jn2]

My buddy is having the same problem. What did you do to fix it?

We need to see at least a datalog of the issue. I've tuned a 50 shot, 100 shot, and a 150 shot with no issues. I know what some of the common issues can be, but need to see the log to confirm. Lean spikes are usually the most common cause though. Need to see datalog and information on the kit(how long is the nitrous and fuel line(from solenoid to plate). Ideally you want the fuel line to be 1/3 the lenght of the nitrous one. This will prevent any lean spike on the initial hit and also prevent KR from these lean spikes.

[R8Bill]

Unfortunately, the datalog was done using SCT, I cant get it to upload on here due to file size and when I zip it, the site doesn't allow me to upload. Let me see if I can import it into HP. Timing looks to be at 21-23 degrees which I was surprised to see 10 degrees knock on a 100 shot running E85 (measured). Here are a few screen shots.

100-Shot-05.jpg100-Shot-04.jpg100-Shot-03.jpg100-Shot-02.jpg100-Shot-01.jpg


Update, attached is SCT datalog: SCT Log - 100-Shot-V1.csv

Furtheremore, some one told me this could be false knock; they said the S550 has more sensitive knock sensors, is this true? If so, any recommendations on a setting to use or how to change this?

[caniggia]

Is that wet or dry? Best would it's wet.

[Jn2]

Unfortunately, the datalog was done using SCT, I cant get it to upload on here due to file size and when I zip it, the site doesn't allow me to upload. Let me see if I can import it into HP. Timing looks to be at 21-23 degrees which I was surprised to see 10 degrees knock on a 100 shot running E85 (measured). Here are a few screen shots.


Update, attached is SCT datalog: SCT Log - 100-Shot-V1.csv

Furtheremore, some one told me this could be false knock; they said the S550 has more sensitive knock sensors, is this true? If so, any recommendations on a setting to use or how to change this?

I am not a fan of SCT, can you post a HPT log, look for the layouts, I've posted them on someone else thread, but you should be able to find them.

From what I can see it looks like you are leaning out during your pulls, hard to tell, I really really dislike SCT logs, but that aside, it does seem your lambda goes down to WOT PE but then raises itself for some reason, then goes down, then goes even higher than before...this looks like lean spikes, again, Im no expert at SCT logs so I could be reading it wrong...

This is the one I am referring too;
100-Shot-01.jpg

[murfie]

Looks to me like either a transient fueling issue for rich tip in or possibly fuel enrichment requirement for OP. First part looks like accelerating up to speed through gears not at wot. Seems rich with it trying to go to lambda. The second part looks like a wot pull. Rich in the beginning. Middle is ok Then at the end of the pull it goes to lambda like a limit or COT.

Knock activity seems excessive. Could possibly be false knock.

[caniggia]

If it's dry, all this may happen as it will not add fuel because it will not register MAF change. Should be wet in my opinion and i finally made it wet. Had same issues, initially i thouglt it's tune problem, but later i realised fuel jets were plugged. After change plate all was fine.

[R8Bill]

Is that wet or dry? Best would it's wet.

It was a WET shot. Let me see if we can do another pull but this time logging using HP Tuners, I too don't like SCT.

[R8Bill]

Thanks Murfie!

Have you heard of issues with over sensitive knock sensors on S550's? If so, any recommended settings to use to reduce sensitivity?

[Jn2]

Thanks Murfie!

Have you heard of issues with over sensitive knock sensors on S550's? If so, any recommended settings to use to reduce sensitivity?

Never heard of this, every Coyote i've worked with had working knock sensors...if you are worried about false knock then check your exhaust with a rubber mallet and see if anything is rattling, but don't mess with knock sensor sensitive in the tune to try and fix a assumed issue.

[brandonconner]

In my case, we ended up pulling some timing. Not sure why the 100 shot was so different than a 75, but in this particular case it was.

[caniggia]

So looks you downgraded tune for no nitro condition.That's why I don't like nitro, so I cured this problem by changing resistance of maf sensor, I added relay that adds resistor into maf sensor so when activating nitro car see around 20c iat more. Then tune is not downgraded when in no nitro condition.

[4wheelinls1]

Never heard of this, every Coyote i've worked with had working knock sensors...if you are worried about false knock then check your exhaust with a rubber mallet and see if anything is rattling, but don't mess with knock sensor sensitive in the tune to try and fix a assumed issue.

I always tune with knock ears, I find it is common for mechanical changes to alter knock sensor sensitivity, headers and certainly PD blowers that sit on top of the sensors cause additional noise, they are great in a stock car but you need to know if the knock is legitimate.