383, 11.2:1 comp, 23x/23x 10x lsa. The car only runs in open loop 24/7. At startup, or when warming up, the knock retard is not present. Once it reaches roughly 177-180°F, it starts to pull roughly 8-12° at idle and part throttle. When you come to a stop you can hear it throught the exhaust, like a small series of low pops. I know the car has longtubes, and poly motor mounts and NSA rockers, but if this was a case of false knock, it would also be present at start up and warming up correct? The car has a new knock sensor, and lt4 knock module in place. The AF at idle when the knock retard is not present is roughly 14.2. Once the knock retard kicks in, it hits the mid to high 13's because it is not burning all the fuel, im guessing. What should I look for? Thanks a million!

 

That's normal.When a engine gets hot it is more prone to knock.
Ya need to run it on 110 for at least a 5 gal worth and see if ya still have the timing retard.If it goes away it is real knock.
The KM modual won't fix it or even help if it's false knock.

Gas engines DON'T rattle at idle(unless the tune is all screwed up) so that kinda tells me it's false but ya need to check it and rule out the possibilities.

 

"Pops" in the exhaust doesn't sound normal. There must be something else going on. You don't get pops from knock.

 

Shoebox,
That could be from the retarded timing.

 

yes the small "pops" are more like bubble sound. Its from the knock retard, that im sure of. Couldnt I also zero out the knock table and get the car to normal operating temp and see if something doesnt sound right? Im almost 100% sure that its not something mechanically wrong, since my car is in tip top shape and all sensors and ignition components are fairly new. Im leaning towards false knock, but if it were false knock, wouldnt the knock retard also be present at cold startups and warming up? thanks a lot

 

I don't buy it. Pops in the exhaust from retarded timing at idle?
Unless it is running so rough it irregularly puffs air out the exhaust. Maybe I am not understanding the nature of these "pops".
I'd be looking over the tune.

 

Shoebox, im trying to get the car ready for tuning, but i cant take it to the dyno and tune it with this issue at hand. The "pops" are hard to describe. They almost sound like a "bubble" is being let out of my exhaust. Its like the exhaust is breaking up, but not backfiring. The car also has stock timing tables, and the comp is 11.2:1, but I dont think I would have to take timing away from a stock table to make this thing run correctly at idle, and part throttle. Can I also zero out the knock table, and let the car reach norm operating temp, and see if I hear something mechanically wrong?

 

So, I guess you are monitoring this retard and knock with a scanner or something. Are you sure the cam or opti is indexed correctly and maybe that is throwing things off?

 

yes, I have datamaster, freescan,lt1 edit, and a WB. Yes the cam and opti are indexed correctly, because the car runs great when its cold, or warming up, it only happens when it get to its normal operating temp of about 177-180° F it starts to pull timing and act funny. I am almost positive its false knock due to poly motor mounts, long tubes, big cam,

 

Poly mounts dont cause KR, LTs dont cause KR.. large cam will only b/c of the valvetrain noise.

Post your datamaster files

What Id do is zero out the KR at idle RPM that way you dont have that problem. On your wideband you should really shoot for a figure in the area of 16-17:1 because of the cam.

Lastly, that cam is pretty small for a 383 so theres no reason you should be running open loop.

EDIT: One last thing... R series lifters will cause TONS of KR compared to OEM. I have seen this on a buddies car with close to the same specs as you what are running. With the R lifters I couldnt get the KR to go away but after switching to new OEM lifters the KR is almost completely gone.

 

so only zero out the kr at idle rpm, not map? On my wideband, I should shoot for 16-17:1 with only 24° of overlap? Isnt that really lean? I was in the 15's and my spark plug tips turned white. I was told to run this in open loop cause of the cam size and overlap, and that it would only screw up my o2's...

 

Who told you to run it in open loop?

That cam is relatively small for a 383... only 24 degrees of overlap, are you sure?? I just thought it would have a lot more than that with the LSA set where it is.

On my car I go really lean at idle to clean up the fuel smell but I have a lot more overlap than you... Maybe 15:1 would be better. My car doesnt get hot and my stock O2 sensors are stuck in the .100s which is close to 18:1ish.

You dont need to run open loop with that setup at all. Try it in closed loop and see how it runs! A lot of guys have run closed loop with cams in 350s a considerabley larger than yours w/o problems.

What Id do with the KR problem is zero out the KR up to 1200 RPM in the KR table, KR fast attack and KR recovery rate. Its pretty unlikely you are experiencing anything more than false knock.

 

How do I go about altering the idle AFR, without altering the crusing AFR, do I just add to the injector offset voltage range? So im going to go into the file and zero out the KR up to 1200 in the KR vs. RPM. Should I do anything to the KR vs. MAP? perhaps zero out the KPA my car idles in?

 

I wouldnt touch the KR vs MAP unless the other tables dont take care of it.

For now just let the PCM take care of the idle fueling. If it tends to run really rich then you can command the PCM to run in power enrichment mode at idle.. then in the PE table you start pulling fuel till the AFR is where you want.

Do a search for PE idle and youll find some good info on it.

 

I zeroed out the KR vs RPM and the car still had knock retard. Im going to zero out the 60-80KPa KR vs MAP, since the car idles at about 70-80 kpa...