Cammed L83, lots of KR@WOT

don't want to sound clich? but im asking for some help. L83 with GPI cam, L86 Intake and TB. Got the fueling pretty close tonight and started adding some timing. Getting much KR starting at 4400. Been reading posts about KS sensitivity and or torque model issues. Im only asking for like 10 degrees at 4800 and its knocking it down to 2. Need a little bit of help if that's ok. Things to try or things to check. I appreciate every bit of help. I will attach current tune and small log of said issue. Thanks in advance.

Ive been reading all night, just need some clarification. When adjusting the knock sensor sensitivity, which way is the scale? I see 0 to 32. is 0 non sensitive and 32 very sensitive or vice versa. Also, before all this I was reading about torque management advance, which is why im logging it. I thought that would show that I need to modify the TT but it doesn't move, only Knock Retard. Thanks.

I desensitized the KS this morning all the way and no KR. So maybe sensors too sensitive?

If you turned them all the way off then obviously you wont see kr. You basically told it not to look for it. The scale is 0 to 32, 32 being the least sensitive. Tuning the knock sensors should only be done at the track, or on a dyno. Where you can verify that the settings you have are correct. I didnt look at tune, but you need to verify all spark adders and multipliers are in check, therefore the timing you "think" your commanding you actually are. I see it a lot where someone thinks they are commanding 24 degrees, but fuel adders are adding 4 degrees and vct is assing 8, all of a sudden your chasing massive timing problems.

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Originally Posted by Srblacks13

Ive been reading all night, just need some clarification. When adjusting the knock sensor sensitivity, which way is the scale? I see 0 to 32. is 0 non sensitive and 32 very sensitive or vice versa. Also, before all this I was reading about torque management advance, which is why im logging it. I thought that would show that I need to modify the TT but it doesn't move, only Knock Retard. Thanks.

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Higher numbers is less sensitive but, I don't think you ever want to be in double digit territory even though it maxes out at 32.

See attached screenshot for how I had to setup a friends L86 w/ headers and small cam AFTER confirming the knock was false. This was done to Cyl 1 to 8 tables.
Attachment 98155

Have you adjusted your injection timing to go along with the now different cam event timing? If you post your cam specs, I can help with that.

I actually have all the adders zeroed out at the moment. Started at 32, halved to 16, halved to 8 and ended up very close to the table pictured. Thanks for your assistance!

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Originally Posted by g26er

Higher numbers is less sensitive but, I don't think you ever want to be in double digit territory even though it maxes out at 32.

See attached screenshot for how I had to setup a friends L86 w/ headers and small cam AFTER confirming the knock was false. This was done to Cyl 1 to 8 tables.
Attachment 98155

Have you adjusted your injection timing to go along with the now different cam event timing? If you post your cam specs, I can help with that.

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Have not messed with injection timing. Feel like I missed that step but you live and you learn. Not sure if my buddy still has his cam card but it was GPI stage 2 truck cam. I just dropped his truck back off cause the labtop battery died but I feel like I made some progress today. Could you tell me more about injection timing? I’ve read about it on gen 3 and 4 so I’m sure I’ll have to redo fuel, which is fine. Thanks.

One of the highlights I read was if injector pw is higher than 4.5 then think about it. Right now it’s 4.5 WOT. Thanks, I’m sure there is more to it

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Originally Posted by Srblacks13

Have not messed with injection timing. Feel like I missed that step but you live and you learn. Not sure if my buddy still has his cam card but it was GPI stage 2 truck cam. I just dropped his truck back off cause the labtop battery died but I feel like I made some progress today. Could you tell me more about injection timing? I?ve read about it on gen 3 and 4 so I?m sure I?ll have to redo fuel, which is fine. Thanks.

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On a gen 3/4, which are port injected, even if you injected at the "wrong" time the fuel will just sit on the back of the intake valve until it opens and the fuel gets pulled into the cylinder. On the gen 5 engines with direct injection, the fuel is sprayed directly into the cylinder. If you injected before the intake valve opens, it wont sit on the intake valve like port injection and the exhaust valve is still open immediately before the intake starts to open (or they could both be partially open at the same time if the cam has overlap). So on a gen 5, if you spray before the exhaust valve is closed then you're spraying some/most of the fuel right out the exhaust.

I'll look up the specs of the cam and compare with the tune you posted and post back later.

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Originally Posted by Srblacks13

One of the highlights I read was if injector pw is higher than 4.5 then think about it. Right now it?s 4.5 WOT. Thanks, I?m sure there is more to it

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I thought it was closer to 7ms when you should start to be concerned but, you might be right.:)

thanks!

Assuming it's the GPI 5.3 low lift stage 2, they don't give the full specs as the don't display the last number of each spec (21x/23x .54x/.54x 114+4). Even if we assume worst case (219/239), Your injectors will not spray too early going by the SOI table in the posted tune.
The EVC (exhaust valve close) event is 2ATDC @ .050 and @ .000 (fully closed) it would be even later than that so using the specs above and the fact the cam phaser isn't being used there is no problem. 360 - 2 = 358 meaning if your SOI was 358, you'd be injecting while the exhaust valve is .050 from being fully closed so I usually subtract another 10 or so degrees from that which would give you 348ish <-- the earliest you'd want to have your SOI. The reason you don't just set the whole table to the highest SOI possible is because you ultimately want your pulse from start to finish to inject when air velocity going into the cylinder is it's highest. That will help to mix/atomize the fuel.

With that said, you could push the high RPM/high airmass areas of the SOI base table to 345~350 and smooth the edges out. This will give some more headroom for injector spray time. If your injectors are not spraying soon enough it could possibly retard the spark to allow the spray pulse to finish. Your EOI spark offset is 5 (stock) so if your injector pulse ended @ 10BTDC (just throwing out a random number) because SOI was not soon enough, it won't spark until EOI + EOI spark offset (10BTDC + 5) and you'd end up with 5deg advance timing no matter what you're trying to command in the tune. I believe this shows up as knock in the logs when it does this.

Hope that made sense.

Yes. Thank you very much for the explanation. A future endeavor I will tackle.

I concur with g26 on the SOI tables. I got rid of allot of "knock", according to the sensors, without desensitizing sensors and adjusting these tables. I've read a few other older posts on here and seen some other math work out to say 338-332 was perfect at high rpms but I'm not here to contradict g26 logic it sounds legit, just saying what else i'd read. Also appreciate the explanation g. I knew what i was doing was helping KR but I've been trying not to get past 330* because i'm not sure if i'd get cylinder wash injecting TOO early so I've made that my max for now...? Do you see any reason why this 330* SOI would hurt at lower rpms and lower loads?

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Originally Posted by MrFixIt86

I concur with g26 on the SOI tables. I got rid of allot of "knock", according to the sensors, without desensitizing sensors and adjusting these tables. I've read a few other older posts on here and seen some other math work out to say 338-332 was perfect at high rpms but I'm not here to contradict g26 logic it sounds legit, just saying what else i'd read. Also appreciate the explanation g. I knew what i was doing was helping KR but I've been trying not to get past 330* because i'm not sure if i'd get cylinder wash injecting TOO early so I've made that my max for now...? Do you see any reason why this 330* SOI would hurt at lower rpms and lower loads?

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If you think about how the crank rotation vs piston movement is related, the piston is moving very slow at the top and bottom of the stroke. In the middle of the stroke, the piston velocity will be at it's highest and in theory, also when the air velocity coming through the intake valve is highest (though the current amount of valve lift at a given crank rotation angle comes in to play, I don't worry about that). My goal is to have the start and end of the injection happen while piston velocity (and air velocity) are at it's highest or at least close. When you are low RPM/airmass, you'll have a very short injector pulse combine that will the fact at low RPM air just isn't moving that fast into the cylinder so, I'm really aiming to inject when air velocity "should" be it's highest per the given RPM. This is what helps atomize/mix the fuel with the air entering the cylinder. This is why people can get their engine to run smoother or gain power when messing with SOI, because you're creating a mixture that's easier to combust more efficiently.

Once the pulse is long enough that I'm needing to inject past the intake valve close event, I start injecting earlier in an attempt to get most of the fuel to inject while the intake valve is open and less so while the piston is moving up for the compression stroke (or try to as much as possible). And like was said earlier, injecting as early as possible during high fuel demands helps to make sure your EOI ends soon enough so it's not pushing your timing back just to complete the pulse. Especially when you're pushing your fuel system to it's limits.

Off Topic a little:
I made a spread sheet that would allow me to enter the cam specs and paste in some cam and spark tables from the tune and it would create a a table of the earliest SOI and latest EOI for the particular setup which I then have a table that tells me the maximum pulse width possible for a given RPM/airmass based off of the SOI and EOI tables.

If I log pulse width into an SOI formatted table and then copy/paste it into the Excel table, it will calculate the optimal SOI based on my criteria.

This is a screenshot of the spreadsheet where I can paste in my logged pulse width
Attachment 98225

This is a screenshot of the spreadsheet where I use the logged PW from above and calculate a suggested SOI taking all the other data into consideration as well
Attachment 98226
@MrFixIt86 - Check out the suggested SOI from the screenshot above. Notice the high load/rpm areas are right around what you said. This was for a 6.2 w/ headers on 93. If he had a cam, forced induction or running E85, these number would be higher so, it seems like your numbers are pretty accurate for stock/close to stock.

I was modifying the spreadsheet so I could log my pw for E85 and create a suggested E85 SOI, get the difference from the base SOI and create a table that could be pasted into the SOI alcohol offset table in the tune. I end up editing the wrong sheet in Excel and screwing it up. :doh: I haven't had the time to go back and figure out what I messed up to get it back working correctly again but, will one of these days.

Apologizes for topic swerving:hi:

Disclaimer: I just want to add that tuning is just a hobby for me and I enjoy tuning my cars and helping friends with theirs. I could be completely wrong with my thinking so please don't take anything I say as gospel.

Here is what worked for me on a lot of different vehicles from stock Yukons to Z06 with whipple, port injection, cam, etc

Set the whole SOI table to 280

Log SOI into a table set up like the Editor has it.

You will see the car idles and drives super smoothly and if it needs more injection window under more load, the ECM will back it up (advance) by itself.

The SOI table is obviously not a fixed value SOI table, but it is fixed as to how LATE it can inject, it won't inject later than the SOI table, but it can still inject earlier.

Setting values higher is limiting in that regard.

Setting values too low and injecting too late will make the car run poorly and 280 is the value I found that worked best, on the most vehicles.

Hopefully that will help simplify things for some of you guys.

I got 320* at 1400 rpm and loads around .36 cylinder airmass of my SOI table, and they gradually go up from there. this took care of cruising speed knock. I'm thinking about starting back over from stock and refiguring that table. It seems that the injection makes more sense to start sooner rather than later because of the piston speed n such... and at that 280 mark the piston is at its fastest...

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Originally Posted by MrFixIt86

I got 320* at 1400 rpm and loads around .36 cylinder airmass of my SOI table, and they gradually go up from there. this took care of cruising speed knock. I'm thinking about starting back over from stock and refiguring that table. It seems that the injection makes more sense to start sooner rather than later because of the piston speed n such... and at that 280 mark the piston is at its fastest...

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You wanna spray as late as possible with DI while maintaining an acceptable pulse width range.