E38 Knock Retard?

[Jayrcr3]

Which knock retard value PID should I be logging? GM.KR, or GM.KNKRET? GM.KNKRET usually shows some value in the MAX column, but I never see any of its other values change. GM.KR seems to always say 0 in all the columns. My car is a 2011 Camaro SS LS3. It has cam, headers, high flow cats, a cold air intake, pulley and a tune. I had it dynoed yesterday, and it was about 30 low on HP and TQ (430RWHP 400RWTQ) from what everyone else is getting with the same mods I have. It was about 70*F outside with low humidity. I thought if anything I would get higher numbers in those conditions. It may have just been that particular dyno I guess. My AFR is just about dead on 12.8, and the tuner running the dyno said to look at my timing. I attached a quick log from this morning. Thanks.

[Redline Motorsports]

Use GM.KR

[Chalky]

Could the dyno operator be implying that you could use more timing? I had more knock with my stock LS7 than you do with your current setup. Not sure about knock sensors in the LS3 but I would think the headers would make the sensors even more active.

Can you include a copy of the tune as well? Someone with LS3 experience might be able to make some suggestions.

What does your LS3 typically make HP wise in stock form?

[Jayrcr3]

I was under the impression he was saying it might be able to take more timing. Typical stock figures are about 365 hp and tq. It very well could be the dyno. It was a car show, and a portable dyno. There are several guys that have the exact same package installed that I do on a forum I visit. They have all put down 455-465hp and about 430tq. I will upload my tune when I get home tonight. I'm probably just being picky, but if there is 30hp left on the table, I would like to find it. : ). I found it odd that it was exactly 30 short on hp and tq. This is what makes me think it's the dyno.

[Jayrcr3]

Here is the tune I'm running. The cam is 227/239 .614in .624ex 115.

[swingtan]

Use GM.KNKRET in the E38, it will show "total" knock retard.

Looking at the log data in post 1 it seems that most of your detections are actually "burst knock". Most occur as the throttle is snapped open and very few when throttle movement is low. There also appears to be no KR during heavy load.

Providing you have a good intake and exhaust and you are certain about the fuelling being correct up top, I'd start by adding about 5' timing through the top end as a start. If the VVE has been dialed in correctly, then I'd say you "should" be seeing that 450-460HP mark

Simon.

[Chalky]

Timing tables are still factory stock. I don't know how the LS3 responds to timing but it just seems like you could definitely add some timing down low in the rpm band to help offset some of the affects of the cam. Even at 6400/6800 rpm, car is only seeing 20* timing. I would think the car could handle more timing from 5600 out to your red line.

G0101-G0104: You can reduce these values to cycle ac off at lower rpm/tp. Pick up a few HP for free.

[Chalky]

Is this a Thunder Racing cam?

[gmh308]

To add to what Swingtan mentioned, burst knock is purely predictive knock retard. Not real knock retard as on quick throttle openings regular knock control is not fast enough and burst knock retard then prevents real knock and seeing timing pulled on transient throttle when it doesnt really need to be pulled. It is worth zeroing for tuning purposes so it doesnt confuse things.

[Tre-Cool]

i have found both gm.kr and gm.knkret log the exact same values.

[Jayrcr3]

Is this a Thunder Racing cam?

Vengeance Racing.

Thanks for the tips guys. I'm still learning the tuning software and I'm nervous about just making changes without asking. I haven't messed with the VVE table, but my WB says I'm right on about 12.8 AFR. Vengeance did 3 mail order tunes for me after I installed all the parts and sent them log data, so I'm sure they tweaked it. If I lived closer I would have had them dyno tune it. Where I live we can get 93 octane fuel, so I figure the timing can be bumped up a bit.

[tadmur]

I've seen some dynos give lower readings when run is done at lower speeds,
looks like that pull was done in a really low gear..

[Jayrcr3]

It was done in 4th gear.

[The Alchemist]

I run in a standard LS3 up to 24deg at 6500rpm. Timing should gradually increase once past peak torq (max VVE) from say around 18 to 19deg at 4400rpm up to 24 deg at 6500rpm on our 98 octane fuel in NZ(rated differently to fuel in the US so don't compare)
Any cammed LS3 will run more timing than this and the peak torq point may be much higher say 5600rpm so the timing "low point" will need to be moved accordingly. To start with find your peak torq point (highest VVE) say 5500rpm > throw 20deg in here, blend up to about 23 to 24 deg at 6500rpm.
At 2000rpm fully loaded start at about 20 to 22 deg blend up to 24 to 26 deg at around 4000rpm, blend down to 20 ish at peak torq then up to 24deg at the limiter. Should show as a nice gradual curve not steps. This is a guide to get started then you have to dial it in on the dyno mate.
Mike

[Jayrcr3]

Thanks for the advice. I will give it a try, and see how it comes out. According to my dyno sheet max torque is around 4800.

[izaks]

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