2018 A8 Camaro Flex Fuel Knock

[ttyler333]

Details: 2018 Camaro 1SS A8
Mods: K&N CAI, Flex Fuel Sensor, 1 7/8" LT Headers Catless

I use my HP Tuners to mostly check my ethanol percentage after a fuel up. I have 62% ethanol at the time of my data log. I had a local tuning shop do the Flex fuel Tune. He did the tuning with his own wideband. I've yet to add one at the moment.

I'm thinking there may of been a Spark Value that was miscalculated due to the Flex Fuel Multi. I've seen the knock in 6th gear hitting above 12. It was also around 50f outside today. Usually it's been 65+.


run1.hpl
TylerCamaro2018_jQ.hpt

Also, Any tips to help with Ethanol Cold starting is greatly appreciated.

[ShaneB]

Try restarting the scanner and logging again when that happens, happens to me sometimes but goes away when I start a new log

[ttyler333]

Theres a few logs I hadn't saved but they've shown knock as well. Maybe a whole pc reboot wouldn't hurt. I've included another log. So in your opinion there's nothing to worry about?
mix1.hpl

[g26er]

Also, Any tips to help with Ethanol Cold starting is greatly appreciated.

Something to try for cold start
Engine > Fuel > General > Cranking Fuel > Cranking Eq Ratio Alcohol
Add 20% to the top row, ignore the 0.4 column. Then interpolate down to the 46.4 row.

Engine > Spark > Advance > Startup > Alcohol Adder
You could try lowering the spark here. My '18 SS didn't need this table as high as yours is. Granted I'm in Florida so the worst for me was about 80%E @ ~30F which wasn't an issue at all.

If those don't help, just put 'em back. Good luck.


EDIT: Just to add... I didn't look at your logs but,
Engine > Spark > Retard (is that even PC ) > Static Retard > vs. Cylinder will show up as knock on a log even though it's not. I think a lot of people (including myself) zero this table out.

When I installed headers, I was getting more knock than usual. After confirming it was false knock, I desensitized my knock sensors a little. Some people will frown on this but, I still feel I'm safe.
For columns .2, .3 and .4 I have 1,000 = 3.5, 1,500 = 3.6, 2,000 = 3.7 and 2,500 to 6,500 = 3.8

[ShaneB]

Theres a few logs I hadn't saved but they've shown knock as well. Maybe a whole pc reboot wouldn't hurt. I've included another log. So in your opinion there's nothing to worry about?
mix1.hpl

Not saying that at all, just sometimes after a flash I'll see 15* of knock, restart scanner and a new log, and then it all goes away. Im a beginner btw haha. It could be SOI or something else you're not logging, and cant tell if its just in 1 cylinder or all 8 or what not. Maybe one of the experts will pop their heads in and have a look. Also noticed your're on maf only and your maf curve has decently higher values than mine, but maybe the K&N caused that over my RF, but it could be rich knock? And your knock sensors are at stock sensitivity, I've read headers to stock exhaust can cause a lot of false knock. Don't take just my word on it though.

[ttyler333]

Not saying that at all, just sometimes after a flash I'll see 15* of knock, restart scanner and a new log, and then it all goes away. Im a beginner btw haha. It could be SOI or something else you're not logging, and cant tell if its just in 1 cylinder or all 8 or what not. Maybe one of the experts will pop their heads in and have a look. Also noticed your're on maf only and your maf curve has decently higher values than mine, but maybe the K&N caused that over my RF, but it could be rich knock? And your knock sensors are at stock sensitivity, I've read headers to stock exhaust can cause a lot of false knock. Don't take just my word on it though.

I read about the headers and the false knock a few times. That's why I figured I'd ask on here. I know at certain resonances the exhaust will cause my subwoofers to pickup on the tone. Wouldn't surprise me if it is false knock.

I am a beginner as well. I appreciate your input as with everyone else's. I will definitely keep that in mind after I do a flash.

[TriPinTaZ]

The things I see from your tune that would concern me. Your tuner disabled Long Term Fuel Trims, this should not have been done for these minimal mods. Your tune also set the ECU to use filtered MAF for airmass calculations starting at 100rpm vs the OEM of 4000rpm. This also is not necessary for minimal mods. He/She also changed the parameters for entering power enrichment in a weird way, not really bad, but sort of took away the more complex way of applying it and made it old school where you just need to be at 70% or greater throttle position. Again, not bad, just weird.

But my concern here is transient fueling and airmass calculation. With the LTFT's disabled and Dynamic Airflow predictions neutered, I would suspect this is contributing to the KR you see. Also, you could have some false knock for sure. Your Knock Sensors were left at stock values which is too sensitive for headers. Fuel and Spark values look good in the tune though so your tuner knows what he/she is doing there. I would ask them about the above though, maybe he/she has a good reason?

[ttyler333]

The things I see from your tune that would concern me. Your tuner disabled Long Term Fuel Trims, this should not have been done for these minimal mods. Your tune also set the ECU to use filtered MAF for airmass calculations starting at 100rpm vs the OEM of 4000rpm. This also is not necessary for minimal mods. He/She also changed the parameters for entering power enrichment in a weird way, not really bad, but sort of took away the more complex way of applying it and made it old school where you just need to be at 70% or greater throttle position. Again, not bad, just weird.

But my concern here is transient fueling and airmass calculation. With the LTFT's disabled and Dynamic Airflow predictions neutered, I would suspect this is contributing to the KR you see. Also, you could have some false knock for sure. Your Knock Sensors were left at stock values which is too sensitive for headers. Fuel and Spark values look good in the tune though so your tuner knows what he/she is doing there. I would ask them about the above though, maybe he/she has a good reason?

Thank you. I did notice when LTFT were enabled I was going lean. Not sure the cause of that but the tuner never once mentioned any concerns. As far as decreasing the knock sensor sensitivity. Where would I make changes? Spark->Knock Sensor?
So would fixing/returning the dynamic airflow back to stock help compensate for the knock?

[TriPinTaZ]

I wouldn't change the knock sensor sensitivity until you get the KR under better control. If the LTFT's go rich in certain part throttle and transition areas then its likely you need to add more to the MAF sensor in those areas. But you need to change the dynamic airfow back to stock and re-enable LTFT's.