Tune Review Request/ help with adjusting timing when seeing knock

[willeh_ca]

My truck is 76 C10 with a 2004 LQ4 w/799 heads, BTR Truck stage 3, 2010 flex fuel injectors & 4L80e w/3000 stall. Been through VE and MAF tuning a couple of different times to check things and to tweak after some of the changes that were done in stages(Injectors, X-pipe exhaust, H-pipe exhaust). Also done braf config a couple of times. If some one wants to take a look and tell me if I've gotten something way wrong I'd appreciate it. If not, no biggie, I've been lurking for awhile and a couple of you guys are very knowledgeable and I'll keep reading your posts. I do struggle with stalling coming to a stop occasionally that I can't get 100% licked though I have gotten it better, the Aug9PM log file shows it dipping low.

For the timing when knock is seen, I struggle with how much to pay attention to logged knock. For example we look at 15-50 hits for VE cells and ignore cells without enough hits so it doesn't skew all over the place. With Knock retard should I do the same? Do I ignore less than say 5 hits in a cell or do I make a change after 1 hit of knock in a cell? The tune attached I went back to having the High and low matching specifically to check and adjust for knock. Prior to this I had the whole low table 4 degrees less than the high table.


Logs are from the the other day no changes made in between other than it was hot and humid in the PM. The logs are mostly cruise, not the greatest representation i know.

Even if no one takes a look, thanks for helping everyone else on here I've learned a lot an could not have done the swap without all the info found here.

[willeh_ca]

Can someone please set me straight on the knock portion of my question above?

[kevin87turbot]

It looks like yours isn't very consistent about when the KR occurs. On the first WOT pull, you had 3 degrees of KR at 5100 rpm. You had 0 on the second pull. On the third pull, you had 3 degrees again. Your timing tables are still conservative. What fuel are you running?

[willeh_ca]

91 is the best we really can get up here consistently.

[kevin87turbot]

If you can find some AV gas, or a low lead racing gas, or even a high quality octane booster (Boostane is a good brand.), I'd put some in it and see if the KR goes away. It should easily handle the 19-20 degrees of timing that you're commanding on 91 octane. It sounds like false knock.

[willeh_ca]

Awesome thanks. I'll give that a try.

[willeh_ca]

Followup, I put VPracing Octane booster in and ran it. Looks like its knocking worse somehow(same tank of fuel but way hotter day), does that tilt toward false knock? Should I really pull 7 degrees of timing from the 0.44g/s @2000rpm cell for one hit of Knock or should I only focus on cells with multiple hits?



Aug26afta.hpl

[kevin87turbot]

Followup, I put VPracing Octane booster in and ran it. Looks like its knocking worse somehow(same tank of fuel but way hotter day), does that tilt toward false knock? Should I really pull 7 degrees of timing from the 0.44g/s @2000rpm cell for one hit of Knock or should I only focus on cells with multiple hits?



Aug26afta.hpl

Yes, that's indicating that you have false knock. Your timing tables are conservative enough that it shouldn't have any knock on 91 octane. Look for possible causes of false KR. Possibly an exhaust pipe touching the frame, broken engine mount, etc...

[willeh_ca]

I found that the threaded portion of the parking brake cable could have been vibrating against the catalytic and K&N filter was rattling against the steel inner fender. Made adjustments to those two things and looked over everything else with it up on the hoist and went out and made two mode logs still on the same tank of 91 with the VPracing octane booster in it. It's still showing knock all over, not sure what to do next. Thanks for the help so far kevin87turbot.

Aug29.hplAug29pm.hpl

[willeh_ca]

If I've eliminated any sources of hitting/hard contact and I still have some random knocking would desensitizing be the next recommended step? Or live with it and increase the recovery rate?

[willeh_ca]

After doing some reading and looking at other tunes that I can find with similar cam specs I decided to do some conservative knock sensor sensitivity reduction. I did some other monkeying as well but tried not to deviate too far from my main goal of sorting out the knock. I re-ran it today without octane booster first and then added some to half a tank. It still looks like pretty random knocking to me.

sep11.hpl
Sep11_octaneboost.hpl
142_08Sep2021_Knocksensitivity.hpt

[Matt Vardaman]

Ok, so I looked into the log and tune. I fought some knock retard in the high load low rpm areas such as being in 4th gear at 40mph then speeding up. Some of your knock is in these areas, so I'm going to give you my tune to use as a comparison. Mainly focus on Cylinder airmas .36 - .56 in the 1000-1800rpm area using the compare function. It's most noticble on the low octane table. It should help, but you may also have to desensitize the knock sensors some if removing timing in those areas doesn't help. Let me know how it goes.9-11-21 2002 Tahoe Flex Timing adder adjusted.hpt

[willeh_ca]

Ok, so I looked into the log and tune. I fought some knock retard in the high load low rpm areas such as being in 4th gear at 40mph then speeding up. Some of your knock is in these areas, so I'm going to give you my tune to use as a comparison. Mainly focus on Cylinder airmas .36 - .56 in the 1000-1800rpm area using the compare function. It's most noticble on the low octane table. It should help, but you may also have to desensitize the knock sensors some if removing timing in those areas doesn't help. Let me know how it goes.9-11-21 2002 Tahoe Flex Timing adder adjusted.hpt

Thanks I'll take a look. It's a tad frustrating chasing it down, but I'm learning slowly.

[willeh_ca]

Came back to wrap this up. Since we are running out of nice weather up here in the great white north, I've wrapped up trying to tune knock. I ended up desensitizing the knock sensors some and increasing the recovery rate, probably not the right thing to do, but seems like my only option. I had looked for any interference between the engine, exhaust, etc and did fix two possible issues(fixing them didn't make any difference). I ran the truck with octane booster two separate time to confirm results. Attached is what I have ended up with, I do still need to drop the low octane table 4 degrees for safety. There still appears to be some random knock going on, I may need to desensitize them further, but I want to stay cautious. I will pull timing first to see if I get the desired results. Thanks to those that helped, feel free to point out anything else that needs looking at.



oct11pm.hpl
oct12am.hpl
151_11Oct2021_Final.hpt

[Matt Vardaman]

Sounds like you're approaching the issue the right way, using caution. I ended up desensitizing the knock sensors around 15% and also increased the recovery rate speed. Thanks for the update. My valvetrain sound volume increased significantly with the cam/longtube headers install. No tapping or bad sounds, just louder. I think that plays into the false knock on some setups.