Good reason to run a 6.2 on premium fuel

[wsteele]

Wow, that really has me scratching my head as to why timing would jump advance to 40° during decel. I can see why you’d be having KR on 87 octane though. Thanks for sharing, I’m gonna dig into a couple tunes tonight at work to see if mine does that too. Only thing that makes sense is you would increase timing to eliminate decel popping.

I am going to hopefully have enough time tomorrow on some more open and less dense roads to see if I can get the DFCO function to kick in. I suspect I am just not getting high enough in the rpm band before let off to get it to enable. If I can get it to work, I will see if I can capture the difference on the scanner app.

 

[swathdiver]

James (@swathdiver) has been preaching the virtues of running higher octane fuels for a long time. I promise never to doubt him again.

I had to run down to the grocery store and the fish monger this afternoon (higher IATs, coolant temps and ambient than this morning), so setup the Tech 2 to monitor knock detection by cylinder. Even with very modest (in town city street driving), modest acceleration away from a traffic lights caused persistent knock in every cylinder. Only after leveling off the throttle and with the knock retard function operating, did the knock sensors settle down and the knock retard number follow slowly thereafter.

It is impossible for me to record with my phone the Tech 2 display while driving (not enough hands). I will try and do a few screen captures of my ODB app live data with the TPS, knock retard and timing reaction displayed.

The knocking seems so sensitive and persistent, I really wonder if 91 Octane or E85 will be able to eliminate it

I am kind of surprised these engines last like they do with the whole "ride the knock sensor timing curve management". Doesn't seem like much margin for error or component failure.

You can record data on the Tech-2 and then play it back later, such as using your phone to record that playback instead of while driving.

 

[wsteele]

You can record data on the Tech-2 and then play it back later, such as using your phone to record that playback instead of while driving.

Great, I didn’t know the snapshot was an ongoing recording l, I thought it was a single snapshot of the screen (screen capture).

That will make recording things much easier while driving for playback later.

Thank you.

 

[Geotrash]

James (@swathdiver) has been preaching the virtues of running higher octane fuels for a long time. I promise never to doubt him again.

I had to run down to the grocery store and the fish monger this afternoon (higher IATs, coolant temps and ambient than this morning), so setup the Tech 2 to monitor knock detection by cylinder. Even with very modest (in town city street driving), modest acceleration away from a traffic lights caused persistent knock in every cylinder. Only after leveling off the throttle and with the knock retard function operating, did the knock sensors settle down and the knock retard number follow slowly thereafter.

It is impossible for me to record with my phone the Tech 2 display while driving (not enough hands). I will try and do a few screen captures of my ODB app live data with the TPS, knock retard and timing reaction displayed.

The knocking seems so sensitive and persistent, I really wonder if 91 Octane or E85 will be able to eliminate it

I am kind of surprised these engines last like they do with the whole "ride the knock sensor timing curve management". Doesn't seem like much margin for error or component failure.

Truth! But before we had knock sensors, our cars pinged audibly all the time - especially as emission regs led the technology back in the 80s. While pinging isn’t exactly good for pistons, it’s not the same as detonation, which will knock a hole in a piston in short order, though people do confuse the two often.

 

[wsteele]

Truth! But before we had knock sensors, our cars pinged audibly all the time - especially as emission regs led the technology back in the 80s. While pinging isn’t exactly good for pistons, it’s not the same as detonation, which will knock a hole in a piston in short order, though people do confuse the two often.

To be honest, I never knew there was a distinction between knock and detonation. I always assumed it was just a matter of degree.

In any case, it is clear as a bell to me that these ignition systems are designed to ride along on the edge of knock. Looking at how mild I am driving and getting knock lights on every cylinder early in ever gear, watching the retard percentage jump and then taper off as my TPS levels out and the advance is allowed to normalize, it just seems like there isn’t much room for error.

It will be interesting to see the differences as I move up the octane scale. I have started looking around locally at where I can find the highest unleaded octane gas.

 

[wsteele]

So I made a number of recordings of a couple different pages on the Tech 2. I did some runs using the engine data page which allowed me to capture TPS, RPM, Advance and DFCO status at the same time. I finally did get a few times when DFCO engaged, but it was really weird and very random. I will need to go through these videos and see if I can cut one down so it is reasonable length wise to post.

I also made a number of runs with the ignition data page up and again the TPS, RPM but adding Spark (advance), Knock Retard percentage and then on the lower portion of the page be able to display individual knock sensor status. Again, these are pretty long with a lot of meaningless information with a few brief periods of very interesting information, so I will try and select one and edit it down (something I have no idea how to do), so it isn't a bunch of meaningless capture. One thing I did notice today is the retard percentage seemed smaller on these runs with maybe 9% being tops. Yesterday morning (cooler, counterintuitive) the retard percentage seemed higher on similar runs.

The good news is now I have a lot of baseline data for 87 Octane E10 and my engine. It will be pretty easy for me to compare E85 and Premium to these numbers. One glitch is I have not found any unleaded gas above 91 Octane anywhere. I suspect 91 is going to be it for my tests.

 

[wsteele]

OK first clip, using the Tech 2 in record mode. This first one, I was trying to capture the advance data under certain driving conditions as I posted earlier in this thread, when I pull off the throttle, timing jumps up (advanced more) and then slowly settles down and follows the load on the engine down. I also wanted to try and catch the DFCO kicking in as that is what lead @Snowbound to think maybe something was wrong with my tune.

Sorry for all the useless video (I think this editing thing is going to be a bit of a struggle), but if you skip to about 6:00 in the clip, you will see a sequence (in 4th gear) when I pull off the throttle, the advance jumps like I have always seen and as RPM bleeds off in deceleration, around 2K the DFCO kicks in. One thing that seems to diverge from what @Snowbound expected is my injector PW's don't drop to like a half millisecond, but on my truck I think about 1.2ms is the lowest I get with DFCO engaged. I do get the advance getting retarded down to low single digits though, so that part at least jives with expectations.

Anyway, it is nice to see that DFCO does work in certain circumstances. Just not sure what the exact criteria is for it.

 

[donjetman]

Google "pre-ignition vs detonation". Big difference.

Some of the ole vehicles I had before knock sensors only had 8-9 to 1 compression ratio and very little hp compared to todays engines. It's hard to tear stuff up when it makes no power.

I had a MSD device that allowed me to adjust the timing from the driver seat with a knob. I'd adjust it (advance the timing) until I could just start hearing the pinging begin, then I would back it off a tad.

 

[wsteele]

Google "pre-ignition vs detonation". Big difference.

Some of the ole vehicles I had before knock sensors only had 8-9 to 1 compression ratio and very little hp compared to todays engines. It hard to tear stuff up when it makes no power.

I had a MSD device that allowed me to adjust the timing from the driver seat with a knob. I'd adjust it (advance the timing) until I could just start hearing the pinging begin, then I would back it off a tad.

Yeah, that is what I am learning about modern EFI in the world of CAFE standards. I come from a tech background, but still am amazed by man’s ability to figure things out when pressed.

 

[wsteele]

OK, here is the second clip on what the Tech 2 shows on the "Ignition Data" page in the diagnostics section, while driving. Specially I wanted to see some of the knock sensors, the knock retard number and spark advance reactions in various conditions.

A few things I noticed along the way. It seems maybe the sampling rate on the knock retard reported number is a little slow compared to the rate of actual change, as many times under growing load, when the ECU seemed to be retarding the spark, the knock retard reported number seems to not jive. I saw a few times when accelerating in 4th gear, as the TPS showed an almost WOT, the spark advance went negative like 2 degrees ATDC, but the knock retard number might be showing just a few degrees or even zero. Probably not something I will ever know the details on.

Another interesting thing I observed is there was a significant difference in what the knock retard value was yesterday as opposed to the day before. The day before I saw knock retard numbers as high as 20 degrees. Yesterday, I think the highest I saw was like 9 degrees. The only difference in conditions was the previous day temps were cooler (IAT, Ambient 70F), it was in the cool air of the morning. While yesterday the ambient temps were quite a bit higher as I was running the tests in the afternoon (like 103F). Maybe the denser air of the morning had something to do with it.

Anyway, here is the clip. The first part is idling along, waiting to get on the freeway, so skipping to like 1:25 will probably be a good idea and save anyone interested some time.