Monitoring Engine Knock. Is this normal?

[Eric Arroyo]

Hey guys, before I tune my Stinger, I wanted to get a baseline for how it runs stock. I was logging with a bluetooth OBD2 adapter and the Torque Pro app and I noticed that my timing gets cut at the start of WOT or close to WOT. Below are a few screenshots so you can see what I"m seeing.

Timing drops from 20 degrees to 7 degrees at the start of (almost) WOT before starting to recover. Results are similar regardless of gear and speed. Timing always drops for a bit whenever I pass about 50% throttle.

I know the Stinger pulls timing if it detects knock. Is that what's happening here?

I know that timing also drops to -6.5 degrees and flatlines there whenever you're off the accelerator and either coasting or braking. I'm assuming that's completely normal.

Last question. Is there any easier way to detect knock?

 

[Revvdmedia]

When you say timing, are you meaning ignition advance? It is normal to see this drop when going WOT. What you should see is a slowly upcurving ignition advance to redline. I'm not 100% certain but I think the order of operations for pulling back when knock is detected is reducing ignition advance, then pulling back throttle and/or boost, not sure which comes first though...probably boost?

 

[Eric Arroyo]

When you say timing, are you meaning ignition advance? It is normal to see this drop when going WOT. What you should see is a slowly upcurving ignition advance to redline. I'm not 100% certain but I think the order of operations for pulling back when knock is detected is reducing ignition advance, then pulling back throttle and/or boost, not sure which comes first though...probably boost?

Thanks for the reply. And yes, ignition advance. I'll add RPM to the graph for next time so I can see exactly where the shift points are. That'll give me a much better idea of what's going on. I'll take some more logs this afternoon and see if ignition advance curves up with RPM.

 

[Eric Arroyo]

@Revvdmedia I was able to do a couple longer pulls while monitoring RPM. Looks like it does drop at the start of WOT, then slowly rise with RPM until the shift, then drops back down and starts the process over again, just as you described. Looks like all is good. Thanks!

 

[StungBlueGT2]

Hey guys, before I tune my Stinger, I wanted to get a baseline for how it runs stock. I was logging with a bluetooth OBD2 adapter and the Torque Pro app and I noticed that my timing gets cut at the start of WOT or close to WOT. Below are a few screenshots so you can see what I"m seeing.

Timing drops from 20 degrees to 7 degrees at the start of (almost) WOT before starting to recover. Results are similar regardless of gear and speed. Timing always drops for a bit whenever I pass about 50% throttle.

I know the Stinger pulls timing if it detects knock. Is that what's happening here?

I know that timing also drops to -6.5 degrees and flatlines there whenever you're off the accelerator and either coasting or braking. I'm assuming that's completely normal.

Last question. Is there any easier way to detect knock?

I believe it’s because stock Stingers run too rich at WOT which is why BMS added fuel wires to the JB4. Smoother ignition timing and about 20whp gains just from eliminating the overly rich WOT.

 

[Manaz]

Almost all cars run too rich at WOT. It's done to ensure the car doesn't run lean and suffer damage (running lean destroys engines) even under the worst imaginable conditions.

 

[M'Kehyah]

With your set up - I'm pretty sure you should be able to view actual knock counts.
Also, what octane fuel are you using?

 

[Eric Arroyo]

With your set up - I'm pretty sure you should be able to view actual knock counts.
Also, what octane fuel are you using?

Unfortunately, I can't find a knock count option in the Torque Pro app. I've read that people can also tell by looking at ignition timing and the combination of long and short term fuel trims.

And I've been using Shell 93 Octane since day one.

 

[Eric Arroyo]

I believe it’s because stock Stingers run too rich at WOT which is why BMS added fuel wires to the JB4. Smoother ignition timing and about 20whp gains just from eliminating the overly rich WOT.

Oh wow, I didn't even realize how rich it was running until you pointed it out. I just looked at a recent pull from a stop and my AFR drops from 15 to 11.38 by the end of first gear, then drops to 10.3 by the time I hit the top end of 3rd gear. That said, my ignition advance looks good for that run. Drops at WOT, and slowly rises until a gear shift, then drops and rises until the next shift, etc.

So ignition advance needs to be reduced when your AFR drops?

 

[oddball]

You need a proper scan tool to read the real knock counters. Only problem is the 18+ stuff isn't well supported by the aftermarket yet, so you have to get the "Pro" level tools (generally >$2k).

The Stinger uses very modern engine controls, which means ignition timing is much more variable than older engines. So wild swings in ignition timing is pretty normal. Check out the various JB4 threads - Terry has been really good about explaining what he's seen from the ECU.

Timing has to get pulled when boost goes up. The stinger also pulls timing as part of the traction control - reduced timing reduces power output which keeps the tires on the road. It also pulls timing during shifts to be nicer to the trans.

I'd recommend just going with the JB4. You can switch between the maps and use their logging to see how the car reacts. You need to correlate RPM, throttle, boost and timing to know how the engine is reacting.

 

[Eric Arroyo]

The Stinger uses very modern engine controls, which means ignition timing is much more variable than older engines. So wild swings in ignition timing is pretty normal. Check out the various JB4 threads - Terry has been really good about explaining what he's seen from the ECU.

Timing has to get pulled when boost goes up. The stinger also pulls timing as part of the traction control - reduced timing reduces power output which keeps the tires on the road. It also pulls timing during shifts to be nicer to the trans.

I'd recommend just going with the JB4. You can switch between the maps and use their logging to see how the car reacts. You need to correlate RPM, throttle, boost and timing to know how the engine is reacting.

Thanks for the feedback/explanation! Do you know if the JB4 can access the knock sensors? I'm hoping it can at least sample much faster than 100ms. As you can see, my logs are pretty coarse haha. And I'll take a look through the JB4 threads and see what I can learn from there.

 

[Revvdmedia]

Terry noted that the JB4 actually reads faster than the ECU puts out anyway. As for how it works, basically the JB4 is doing minor manipulations like commanding Boost + "x" amount to give you more boost amongst other minor things. The ECU still maintains the basic protection like pulling timing, boost or throttle if knock is detected.

 

[Terry@BMS]

To more easily determine "knock correction" you need to look at timing in all 6 cylinders, not just 1 cylinder. If all 6 cylinders are moving it's generally a mapped response and not knock. If just a few cylinders are moving, while others are not, it's normally a dynamic knock based correction.

Worth noting it's almost impossible to have "knock" in the traditional sense unless your tuning is *really* off, as the knock detection system is very effective at pulling back timing dynamically before it gets to that point.