Is this false knock or? also, rev-limiter?

I've got a 383 with some noisy pistons. The engine builder put in short skirt 2618 pistons that clatter nonstop, so he's building me another engine (for free) with different alloy and clearances. Anyway, I've been chasing knock since day-1 on this car. The tuner and I have tried darn near everything, including running colder plugs, LT4 module, screwing with timing, different gas, etc. (He's a highly respected tuner, too...) Nothing has eliminated this. Also, the car completely dies at high RPM and I think its because I am hitting the rev limiter. You can't hear any knock with your ear. If anyone is willing, here's a link to the latest TTS Datamaster log. I'd really appreciate a third set of eyes on this since nobody seems to be able to sort it out. My questions are: 1. Is the knock real knock or do you think its the pistons? Trust me - they're noisy AF. The car sounds like a diesel when cold, and even when warm you can still hear them a bit. The engine builder is a HIGHLY respected builder and is making it right, but I'm kind of stuck until then. 2. What happened at the top of the RPM during WOT? 3. Anything else in this that could use some attention?And merry Christmas to you all.

Appologies for the terse reply but I replied last night & got logged out. :-(

I'm running a 383 with Keith Black Icon 718 2316 Pistons @ 11.6:1 compression and they're fine.

I have suffered with knock all over since the rebuild. I already had a LT4 knock module.
Replaced the knock sensor twice.
Even played with detuning the input circuit with marginal results.

I recently bricked my 2nd PCM and replaced it with a spare that's been socketed.
At the same time I also went OLSD from the SD tune i was trying to run.
All the lean running & burst knock has gone.
The VE table needs altering to follow the AFR sensor now not the O2's constantly running it lean.

Virtually No knock at all now.
The sound is miles better, a much deeper bark than before.
All the low speed lean surge has gone.

Since I've checked,changed, removed or replaced everything several times, including buying a milling machine to re-angle the inlet manifold faces, NOTHING made any difference.

Changing the PCM has.


I haven't loked at your log as I use Steveo's $EEHack now and Tunercat was binned by the AV software.
I can't see what you're running at.

Rev Limiter can be adjusted.
PCM Tables go to about 7K rpm but I have read it will run higher ??
I don't know what Mods or cam you have, My Rev Limit is set to 6,703 rpm.
What RPM are you reaching ?

What injector size ? and what pulse rate are they running at. ISTR 7k rpm has around a 20mS window.
I replaced mine with modified Bosch III 42's from FIC. The previous Venom 36's were probably sufficient but were changed when chasing the odd idle fuleing (port leak under the Edelbrock LT4 manifold)

Fuel pressure ? Have you checked pressure under load isn't dropping off ? (fuel gauge taped to the window under load).


HTH for now.

Mitch

Hi
Can't see the graph, it doesn't draw properly now in TunerCat.

1746: Highest airflow is 327 GS at 6175 rpm

1741: Highest Inj DC 91.2 at 6025 18.17 mS. Your O2 are reading 955

I AM NOT A TUNER
+++++++++++++++++++++

so what i can see...

O2's seem to stick around 950's so you are rich (based on o2 reading... a wideband will be better, i'm still learning)
Injectors are open 18mS and 90%DC so not maxing out and you must have fuel or you'd be running lean ).

LT BLM's are generally on the lean side. 132 154 at idle.
Have you done the checks...
Throttle body blades closed as much as possible.
Checks for vacuum leaks etc.


On the knock count, i would guess it looks similar to mine AFAICT.
I would run a log with Steveo's $EEHack as it can plot the data and can be easier to see.
Mine just loked like it had been shot with a shot gun .

HTH
Mitch

Thanks a ton for taking a look. I really appreciate it. I've run another PCM, another knock module, as well as a tune from a different tuner and the knock persists. I will load-up $eehack and run/post a log using that software. In looking at the file, it looks like I hit the rev-limiter. I'll need to sort that with the tuner. The bottom end can handle the spin, but I need to know if he tuned it there, or if its something with the trans. Also, I noticed that bank 2 is consistently adding fuel. I will start rooting around for a vac leak on that side. Thanks for the advice. Merry Christmas eve

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Originally Posted by atlantadan

Thanks a ton for taking a look. I really appreciate it. I've run another PCM, another knock module, as well as a tune from a different tuner and the knock persists. I will load-up $eehack and run/post a log using that software. In looking at the file, it looks like I hit the rev-limiter. I'll need to sort that with the tuner. The bottom end can handle the spin, but I need to know if he tuned it there, or if its something with the trans. Also, I noticed that bank 2 is consistently adding fuel. I will start rooting around for a vac leak on that side. Thanks for the advice. Merry Christmas eve

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As i understand it, some of the knock is burst knock when the throttle opens the PCM detects the rise in AFR and retards the timing, Knock counts don't go up generally when this happens.

I suspect your tuner has limited either knock to around 5 degrees max rather than the stock 12.

What mods do you have on the car ? as i've fought this issue for over 12 months until going to an OLSD tune.

Mitch

Everything Mitch said was spot on. At 1745 reported ignition timing is 40 degrees,its too much. Lower that back to 32 in those areas. I dont push that high on anything on the street. Race gas only stuff. Your LH and RH bank fueling is off. Could be cylinder fueling is effected by the cam changing the distribution in the intake manifold. Trims will report differently side to side and need to be adjusted. Also at 1745 the ccp purge cycle begine and the fuel shuts off. Could be where your rpm limiter is set or your running into a calibration issue. Can you post your tune file? Or email it to rocko350@yahoo.com and we can discuss it here. Can you read and write to your ecm yourself?Chris

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Originally Posted by Rocko350

Can you post your tune file? Or email it to rocko350@yahoo.com and we can discuss it here. Can you read and write to your ecm yourself?Chris

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Yes, I can read/write to the PCM myself. I am attaching the current BIN - this is the third revision from the tuner and the one that's currently being run. I'm having a weird issue with the trans as well. Once its warm, going from park into drive will slam the trans into gear, as will drive to neutral, or neutral to anything other than park. I have another BIN (the previous version of this one) and this issue was not there. For reference, the car is a 95, no EGR, 383 with TrickFlow GenX 195s, 3k Yank stall, 3.08 gears, cam is 224/230 .563/.544 112 LSA. BIN is attached. I suspect the rev-cut is set to 6250, and that may be where it should be - but I don't know, nor do I know why the trans is waiting that long to shift out unless it has been programmed to do so. Thanks in-advance, my friend.

Well your mechanical compression ratio is around 11.4 . Its fine on pump gas, but the tune has too much timing in my opinion. Te rpm fuel cutoff is 6000 rpm with a cut in at 5800. There are too many things still active in your tune that need to be accounted for. The VE tables, believe it or not still play a huge impact on the fueling in an LT1. It looks like your running the ford 30lber's from the tune. The voltage tables need to be adjusted for whether you have the thin ones or the fat ones. The cylinder to cylinder trims need to be adjusted. The tune needs to be set up for e10. It looks like a pieced together tune from an older pcmforless file. Im going to richen up the wot fueling so we see an 890 mv reading at higher rpm and increase the rpm cutoff 200 more rpm. Im also lowering timing at WOT to 32* for now. Do a compare and you will see what i did. I also set the mv switch points to 450 to see of your side to side trims even out. hopefully also fixed the shifting issue at higher rpm. Having 293 gears and 20's is a fair amount of load.Chris

download eehack and donate some moolah for his brew fund. www.fbodytech.com it will let you rtt your lt1 and have way better data than datamaster can give.Chris

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Originally Posted by Rocko350

Do a compare and you will see what i did. I also set the mv switch points to 450 to see of your side to side trims even out. hopefully also fixed the shifting issue at higher rpm. Having 293 gears and 20's is a fair amount of load.Chris

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Hey Chris - thanks a ton for the assistance. I've sent you an email directly.