Ken in AZ

I always thought my lean tip in has been a "fueling" issue, so I switched to 1 Bar SD tune, messed with the injector settings, messed with fueling, changed FPR, messed with the Multi table for the VE/TPS adder, transients, Base idle airflow, VE table adjust, separate IAT sensor install in the intake tube, nearly everything I could think of.

Then I went out and did some logs and noticed that I wasn't going lean any more. I wasn't going rich, but the lean tip in response was gone, but the stumble was still there.

Then I noticed the Timing was being dumped like it was it's job - like down to .7 advance in some cases. Huge upsidedown spike only off idle when I stabbed the throttle.

Adjusted burst knock out in the 800-1600 fields and upped the base timing in the lower rpm high g/s and Holy Shamboly! I have a serious traction problem now.

Needless to say this is how I feel

I'm thinking of switching back to a MAF tune now that I have this figured out so I can really dial in my AFR's.

Corrected*

madmann26

iTrader: (7)

Not sure if it's related Ken.

Burst knock on the trucks suck *****. Big, hairy, elephant *****.

Just put 8.0 in all the cells. There isn't a reason to have it enabled (some will debate this).

Keep going, you're headed down the right path.

Ken in AZ

Thanks - getting there is a process to say the least.

2002_Z28_Six_Speed

iTrader: (20)

Are you talking about stumbling off the line? I used to get that a lot.

I have all burst knock turned off and I have the areas of the stock timing table that had like -8 degrees in the high load low rpm cells filled in with a more reasonable number. I saw that my truck jumped around to weird cells under careful exam of logs. Timing was critical to the truck not running like ****.

I also had "real" fake knock. I desensitized the knock sensors by copying what was in the Corvette ASA tune. I can't say this is the right thing to do but it help get rid of knock I saw in the logs and the truck ran better.

One final thing I did notice is my exhaust sometimes banged and this made the truck fart. Fixing it helped a lot.

Tuning is very frustrating and mail order never seemed to get me anyways. It is hard to get advice. Perhaps the people that know dont want to give up hard earned information or are too busy to check forms to help random people.

smokeshow

iTrader: (16)

Report back when you swap to MAF only. You changed nearly everything, the least of which being the move to SD. That alone helps lean tip-in vs MAF only. Considering the physics, spark has no effect on leanness during a tip-in because the mix is lean before it enters the cylinder where the spark plug is.

chris99gmc

Good old burst KR.... Max out the table and zero out the retard on the burst KR completely and then be done with it... All it is, from what I've taken from it, it's a predetermined setting that that ECM has stored away for when it "thinks" that it might be getting close to a normal KR event. It's like a buffer and it's beyond annoying to try to tune around with these truck PCMs. IMO, if you are seeing it at all, then u oughta remove it from the tune, so u don't end up wasting any more of your time going in circles with your tune. I actually turn a the KR tables off in my tune after I get the ltft's in check and make sure the advance doesn't ever go above a certain degree. I eventually ween them back on to fine tune the timing at the end. I keep Burst KR off on any truck, esp the earlier PCMs.

madmann26

iTrader: (7)

Could it be just the sheer amount of air entering the cylinder, before the PCM can compensate for it? Sure, it's theory but not one that can be "tuned" for. One would think the PCM would be "fast" enough to cover for that.

The tip-in lean should only happen for a split 1/2 second or so. If I'm rolling down the road and I blip my throttle, sometimes my afr will blip to 15.x, other times it will blip to 13.x. All the while my fuel trims are +-2. (running SD)

It's not something I'm going to worry about. I'll start worrying when I here it pinging/knocking.

Ken in AZ

My lean tip in is only off idle - and strangely enough its kindof a part throttle issue. I haven't done any recent logs as it drive really good right now - not perfect and it's more pissy when cold, but I have to be honest...it shreds down low and pulls strong up top.

I'll be dynoing it soon with the stock intake manifold vs my ported manifold to see what differences there are.

Also - I found a 14bolt I picked up cheap and I'm installing 4:11's with a truetrac so I want to see the differences there too.

smokeshow

iTrader: (16)

Yeah, that's it pretty much. The PCM is fast enough, but the engine might not be turning that fast. For a single pulse fuel delivery in a warm engine, the PCM calculates how much fuel a cylinder will need based on current VE/MAF/trims/etc and schedules the beginning of the injection to enter the cylinder as soon as the exhaust valve closes. The idea is to vaporize all of the injected fuel as soon as possible but not let it out the exhaust. Since fuel is injected ASAP, MAP and therefore cylinder air mass can change at lower engine speed after the fuel is finished injecting. Extra air + no extra fuel = possible detonation. So burst knock is there to mitigate that. These days with better/faster injectors, we can use a make-up pulse to inject two or three times independently and still make it into the cylinder before the intake valve closes, but it can't account for every scenario. So burst knock still serves some purpose.

MikeGyver

iTrader: (5)

I had to look up makeup injection target on VCM Editor. Like a lot of things in HP Tuners, the explanations aren't very explanatory. Reference periods after boundary vs engine coolant temperature. 0.00 to 8.00. Makeup target on a stock 2002 6.0 pickup tune is 5.55 across the board, normal target ranges from 2.55 to 5.55 according to temp.
How do Ken and me decide how to adjust the makeup target?