KR knock no matter what I try? How do I tune spark tables?

[04colyZQ8]

Getting lot's of KR under light load to heavy load, when manifold vacuum is high.
2004 colorado V8 swaped in.

My engine is a early 2007 4.8L LR4 cast iron block. Stock small duration 4.8L camshaft.
-Long tube 1 3/4 tube headers
-88mm SSR throttle body
-LS2 intake, fuel rail
-Full size pickup cold air intake (works more like a hot air intake) IAT temps over 114 at idle
-stock 2007 4.8L 24 lb'hr injectors.
2006 6.0L SSR E40 PCM, and LS2 knock sensors.
91-92 octane Gas


I changed the engine displacement, uploaded the smaller injector info, and turned of a bunch of DTCs that were not needed. Wired O2 sensor heaters on allways. For futre reference we will call this the stock tune.

I tried tunning the VE table, MAF table using my wideband, but I see I am getting KR. So I put the stock tune back in, and still get lot's of KR.

I also tried copying over the spark tables from a 2004 LR4 manual transmsison pickup, still got KR. Then I reduced the problem area cells by 5 degrees, and still get KR What the hell??


Can I use the histo I posted to correct timming? By copy and paste subtract?

What should my timming tables look like? Am I just getting false knock?

The tune is for a alluminum block motor, I am running a cast Iron block, do I need to desensitize the knock sensors?

[04colyZQ8]

Here is the LR4 2004 manual trans spark tables loaded into my Tune, along wiht the tuned VE, and Maf tables. And the log file for it.

[04colyZQ8]

Here I tried Zeroing out a lot of the spark modifier tables, and multipliers, trying to eliminate other factors, Is this the right approch? Can't find a how to on spark tunning?

Anyway I also took out 5 degrees of timming in the problem area, still knock!

[04colyZQ8]

I also wanted to post up the 2004 LR4 4.8L motor tune for refernece, these spark tables should work, I just can't directly copy them over as the LS1 computer is quite differnt then the LS2. I tried my best to copy them over.

Sorry for such a long post, just really need your guys help here, so trying to give you as much info as needed, THanks -Jamie

[Mr. 2008 SS]

Are you changing the whole spark table or just part of it?

Thanks,
Mr. 2008 SS

[04colyZQ8]

Are you changing the whole spark table or just part of it?

Thanks,
Mr. 2008 SS

I tried changing the entire spark table with that of one from the LR4 4,8L, but that is a LS1 computer this is a LS2, maybe they won't directly copy over?

I also tried taking out 5 degrees across the whole table, then logging the spark knock, then copy paste special, subtract. Several times, then I hand smoothed the values all down to meat them and re-logged, still had knock so I then -3 across the whole table. I have less KR but still get it 1-2 degrees around the 1200-1600 rpm range light throttle while lugging, or moderate acceleration.

The tune is to the point now where it hardly runs, it is so retarded, up to -18 from the stock table in spots, I still get KR???

There look to be many tables that add or subtract from the main spark table, but I don't know weather I can just Zero the out?? Wish there was a how to guide on spark tuning.


Is there a program generator out there that could genorate me a stock safe spark table?

[04colyZQ8]

I give up!!!!!!!!!!!!!!!!!!!!!!!!!!!

[wayneosan]

take it to a tuner on a dyno that knows their stuff and spend the few hundred dollars and learn something along the way.

[wayneosan]

do me a favor and log throttle position so I can tell when you nail it.

it looks like there is some knock at light load, so yes, take out timing around that g/cyl area, (WHICH you aren't logging so it's like trying to throw darts with a blind fold.) Log g/cyl air as well.

It's just pt throttle knock. Looks like the right idea on the timing table, but don't lower the entire row. Look at low rpm, common sense will tell you that negative timing will not work, so raise the timing in that area and smooth smooth smooth.

You're close! Don't give up...

tip: when you're done with your timing tables, copy the first part over to the idle tables to create a smooth transition from idle timing to off idle timing tables.

[04colyZQ8]

OK.. gonna try some more tuning tonight, took it to a dyno tunnning shop, we had flase knock do to solid engine mounts and long tube headers, doubled the voltage from the knock sensors, and turned off the resulting DTCs then listed for actual knock there wan't any so we left the knock sensors severally desensitized??? took a little bit out of the timing, removed torque management, and turned off the long term fuel trims. tuned Ve and maf.


Still isn't perfect he said it is because of my IAT tmeps up over 140 degreees at times, so I shielded and insulated my filter, I will try and tweek the tune.

[Mez]

Put in the stock rubber motor mounts and make sure the headers/exhaust don't hit anything or your knock sensors will pick it up. Then set your knock sensors back to stock because you want them to help get your timing right.

Re-tune your MAF and VE tables using your WB. These will need a lot of work because of all your changes.

Start out with the stock timing tables. Should only need minor tweaks to the timing tables

[04colyZQ8]

Put in the stock rubber motor mounts and make sure the headers/exhaust don't hit anything or your knock sensors will pick it up. Then set your knock sensors back to stock because you want them to help get your timing right.

Re-tune your MAF and VE tables using your WB. These will need a lot of work because of all your changes.

Start out with the stock timing tables. Should only need minor tweaks to the timing tables

can't put the stock mounts back in. Nobody makes stock mounts for a older Colorado with a V8 in it, there used to be a 4 cyl.


The headers run right buy the knock sensors I think it will allays pick the sound up from there. Plus The cast iron block may have different acoustics then the aluminum block the tune is meant for.

The timing, will be quite different as the tune is meant for a larger cam, taller intake, bigger displacement, and higher compression ratio.

We took as much timing out as needed on the dyno to eliminate knock heard while running the truck hood open, with a guy listening in the engine compartment. Then we reduced timing a few degrees to give a safe barrier.

I would love to re enable the KR sensors back to the stock setting, but I just don't know that it is possible.

I keep tweaking the MAf and VE tables, I get it very close one night, then it runs completely different. the next day temperature difference, and humidity make a huge difference in the truck runs.

My IAT temp also fluctuates between 60-118 degrees in stop and go traffic and hotter days, this makes the truck run like hell!!!

The truck runs best at IAT temps 60-75 outside temps 60-75 and no rain!! Because that's when I tuned it.

[04colyZQ8]

I thought other people had "desensitized" the knock sensors do to headers etc.. with people saying GM knock sensors so sensitive it picks up road noise??

Should I be afraid to leave them desensitized? My tuner said that with a N/A motor , low compression, and high octane gas, stock cam, that with the timing tables the way they are it would be next to impossible to get KR.. IS he wrong?

[04colyZQ8]

also we only changed timing in the high octane tables and low not idle, How do I copy over the first part of the timing to the base idle table?

I could not see a pattern from the stock setup, the idle base isn't even close to the high octane tables, load verses RPM.

it definitely hesitates between the transition of 900 rpm to 1600 rpm. under light loads. Other than that it seems fine.

Also he changed the MAF enable re enable from 3600 /3500 rpm to 2000 /1800 rpm . What
do you guys think of that?

[04colyZQ8]

Here is my base tune file labeled as stock. And the one the RG motor sports did, with a few tweaks of my own. Along with tuned high octane, stock idle and high octane tables.

[pontisteve]

Solid mounts and who knows what other exhaust rattles and vibrations will probably just always cause vibrations that the knock sensors will pick up. If you can't insulate the engine from the body entirely, then you'll probalby just have to forget using knock sensors.

I would forget anything you "learned" with the false knock, and start over with whatever stock timing tables you think are appropriate to start off with.