I had to turn-off all the knock retard/detection tables. I was constantly getting knock retard even though it wasn't knocking. It seems that more lift and roller rockers mess with the knock sensor unless you have a LT4 knock module.
I had to turn-off all the knock retard/detection tables. I was constantly getting knock retard even though it wasn't knocking. It seems that more lift and roller rockers mess with the knock sensor unless you have a LT4 knock module.
I've researched up and down that subject and though I'd be open to trying one out, LT4 knock modules have become as rare as hen's teeth. Without a wideband and better knowledge of what I'm doing I'm extremely reluctant to detune knock retard.
I'm sure some amount of what I'm logging is false, as I can get the knock count to increment at hot idle by just blipping the throttle. In addition to that, the exhaust system seems like it resonates well at the frequency the knock circuit is tuned to. I picked up huge amounts of knock count by whacking the collector with a small piece of brass rod. I also found I had cracked one of my exhaust tips with a backfire (killed my MAF cleaning it, severe flood condition) and it's "quacking" like a goose was picked up. I've also seen drivetrain noise set it off, hard shifting, acceleration over rough pavement.
But...
The really debilitating stuff is happening between 1300-2100 rpm at 60-75 mph. In cold air it's barely noticeable, but the warmer and thinner the air gets, the worse it becomes to the point it "feeds" itself and KR ends up pegged at 12 until you downshift. Switching from OL to CL with eehack, the counts start climbing as soon as BLMs are enabled so it seems pretty obvious it's going lean in CL.
Knock graph from 5-12
Current OL tune
My take on this as i've been through it, is most of what you have read about anything doesn't relate to any observations you will see.
Most of my changes have seemed counter intuiitive to anything i've read. YMMV
Steveo's Trimalyzer is now on version 1.3b
Have you viewed the knock counts in EEHack and in the analyzer view?
The LT1 doesn't have AE acceleration enrichment so any blip of the throtlle leans the motor until the PCM can figure out a new pulse width.
This is/can be burst knock which has it's own tables of retard.
You can get knock without counts increasing & increasing counts without knock.
OL runs with a lot less counts as i can run it richer. In CL i keep retarding timing and still get knock counts.
That image does look heavy though. So to cover some ideas, You have checked nothing is loose or catching underneath?
You have the right knock sensor for the PCM?
Also my current PCM has a fewer knock counts with an LT1 knock module than the previous PCM with an LT4 knock module, so don't get fixated by that notion either.
HTH some
Mitch
'95 Z28 M6 -Just the odd mod.
'80 350 A3 C3 Corvette - recent addition.
I'm aware. I've modified the build I'm running to ignore frames with corrupt data as these inevitably get picked up as knock events. See here. Some of my logs have as many as 300 trashed frames, but my commute is about 65 minutes each way so that's a lot of data. I think this might be a y-body quirk but haven't had the time to investigate further.Originally Posted by Terminal_Crazy
Always.
It was my understanding that burst knock is pre-emptive timing retard that is added to compensate for the lack of a pump shot. I would have to review all the code again, but as I recall all of steve's knock analysis routines only plot an event if knock count increments [edit] regardless of if there's knock retard.
Did you possibly mean "increasing counts without retard" in the last sentence? If so I think what you're getting at is knock in MAP cells lower than 45kpa generates no KR. Got it. [edit] If I cover up the knock plot with my thumb so I can't see anything to the left of 45kpa I'm no less freaked out.
I'm going to get it on a lift tomorrow and verify, but yes. I see nothing to indicate the exhaust is touching anything. I'm going to put a fuel pressure gauge on it tomorrow too - I installed a new racetronix 255l/hr pump before I started doing any serious tuning and pressures were good after that so I didn't think about it further.
Pretty sure. Delco 10456126 both replaced during build.
Logging tonight in OL wasn't as good as I'd hoped - the knock plot isn't great (456 points in ~60 miles). But I still feel like it's running leaner than I'd like b/c I filled up and calculated 22.3 mpg for today. Seems unlikely with the way I drive. But some logs from last week were in the neighborhood of 1100 events.
I feel like some of what's getting picked up as knock may be misfires / lugging that gets amplified by the drivetrain. It's a 22 year old car and has rattles and squeaks like any other with 160,000 mi on the odometer. Maybe I'm operating it in a load range that the cam won't allow except with dense air.
Thanks for bouncing the ideas around - always good to discuss with someone who's been there and done that!
Last edited by spfautsch; 05-17-2017 at 05:29 AM.
assuming you have ruled out a dead fuel pump or large fueling error, just disable the knock sensor already. you really don't need it if it's causing you this much trouble. knock detection on modified engines is hit or miss, yours is a miss.
I just got back from my buddies exhaust shop where we went over the exhaust system looking for anything that might have been touching and he didn't see anything that bothered him. I'm going to go drive a bit with a fuel pressure gauge and then I think I'm ready to kick caution to the wind and take all the teeth away from knock detection.
Already? You're telling me to do the equivalent of pulling the pin out of a live grenade and wedging it into a stongbox along with about $10k in cash. Already...
How the hell do the LS guys get away with stuff like this? Are the noise filters that much better on those PCMs?
Have you tried OL with the wideband rather than narrow band O2's ?
I wouldn't turn off the knock sensor yet until you've exhausted all paths.
I would check your VE tables, the fueling is very jaggy and looks like it needs smoothing a lot.
sent you a pm.
Mitch
Last edited by Terminal_Crazy; 05-17-2017 at 10:15 PM.
'95 Z28 M6 -Just the odd mod.
'80 350 A3 C3 Corvette - recent addition.
if you don't botch your timing table or run shitty unpredictable gas the knock sensor is 100% useless. think of all the points distributor engines that ran for 500,000+ miles without one (with occasional points/cap/rotor, of course)
i have the same thing to say about trying to get a perfect stoich ratio across the board. if a carb guy can come along and get his engine running better in 5 minutes, you're doing it wrong.
if i came over to your place and did a really good open loop tune on your car and chopped your knock sensor and o2 wires you would probably crap your pants when you found out how smooth, how cool, and how efficiently it ran across the board after a few runs of just tuning by feel.
just because the tools came with your stock vehicle doesn't mean you have to use them. your target needs to be a good running and reliable car, not good sensor feedback and factory-like reactions to events.
i ran my last trans am wideband tuned. before i sold it, its final tune aimed for 16.5:1 or sometimes leaner at low loads and nearly 60 degrees of timing advance for cruising. really lean for decel too, so DFCO transition was really nice. 13.5:1 and ~30 degrees of all in timing for heavy throttle.
i had pipe plugs where the o2 and knock sensors were. no cats. it smelled like a chemical fire going down the highway, water was pouring out of the exhaust, and the engine loved every minute of it.
the plugs read perfectly clean. no soot in the tailpipes. the fans almost never kicked in it ran so cold, you could lug it up hills, you could redline it down hills.
the kid that bought it off of me drives the piss out of it still and it wont blow up. i'll tell you what too, that kid will never have to worry about any sensor failing except his optispark...
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