Guys, why the hell is my car pinging at 21-23 degrees of timing, 910-940 o2 reading, and collant temperatures of 201-208 degrees. Is it the coolang temps that are causing me to ping. I have no idea why my car pulls so little timing. I looked under the stock values for my high octane table with ls1 edit and it was set to 19-20 at 4200+ and .56g/cyl+. I am absolutely confused. I bumped the timing 2 degrees from 4200+ and .56 up and got a lot of pinging but my o2s still read around 910-920. I am having a hard time believing my car won't run with more than 20 degrees of timing wot. Is this because of my ported maf even know I have my ltrims right at -2 to 0 through the maf tables of ls1 edit. I then added 10% fuel via maf table and still heard ver slight audible pinging with o2s of 930-940. What is the damn deal. My ltrims are around -2 to 0. HELP HELP HELP.

 

I think you are relying on your O2 sensors too much. They are woefully inaccurate outside of 450 mV +/-50mV, so you cannot rely on them to give you constant 'good' air fuel ratio readings. 910 is rich on some cars, yet lean on others.

I would ditch the ported MAF and put a stocker back on and check and see if the problem is still there. I hate ported MAFs. They can and do cause more problems than they're worth when trying to tune. And put the MAF table back to stock when you put a stocker on. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Good luck,

Andrew

 

Check your fuel pressure. I chased a KR problem for weeks until I finally put a FP gauge on and found out my fuel pressure was dropping down to 45psi at the top of 2nd and through 3rd. I'm currently waiting on the Racetronix set up for the 99's.

 

Both above made excellent points.
My O2s run at 960 to 970mV when I have 13.2 AFR at WOT. When I used LS1Edit or MAFT to get my O2s down to 900mV, I got alot of pinging. So my specific O2s are way off.
To find out where you are actually running at, you must get a wide band O2 sensor (AFR meter on a chassis dyno). It was at a chassis dyno session that I found out that my O2s were off.

Also, maybe you are running out of fuel do to low fuel pressure.

And maybe you are not getting good enough fuel (octane). I run 93 around town and 94 Sunoco at the drag strip.

 

I always put 93 in my car so I don't believe that is an issue. I am going to switch my front 02s with my back o2s once I get my car back and see if I get any different readings. Thanks guys.

P.S. My car is just full boltons and I don't think it is likely that I have a loss of fuel pressure but am not posative either. Can I monitor this with autotap?

 

you cannot monitor fuel pressure with any scanning device since there is no full sweep pressure transducer stock on any GM vehicle. Get one from Auto Meter and put a gauge on an A pillar post.
Anyway, all of the above posts are pointing you in the right direction. the only other thing i'd like to add: a lot of carbon buildup in the combustion chambers and piston tops will keep you from an optimized spark curve. carbon built up from oil ingestion via PCV system. I found this out on my 2001 C5. upon installing my new 389 stroker, i got rid of the PCV system and went to valve cover breathers. wah lah, no more oil in the intake or cc's! this added carbon buildup will affectively raise your CR. carbon is also a 'hot spot' during flame burn. also dicks up flame propagation. bad stuff. there are several ways to try to break up any carbon in the cc's and piston tops. i have always been successful by pouring a small, steady stream of water into the intake with the motor running. NOTE: a SMALL, STEADY stream. dont get out the garden hose and pump 200psi of water at 4000gph into the intake!! water converts to super-hot steam and will blast the carbon off. old garage mechanics trick. Dont use any of the decarbonization kits from your local parts store. many of them have NAPTHA in it. this will leave a bronze nasty mess all over in the chambers and on down to the O2 sensors. i will also back up the fact that the O2's are woefully inaccurate above or below stoich. a bell curve of accuracy/inaccuracy, if you will. on the dyno, the wideband says i am at 13.8:1 yet the car's O2's read 940mv.

<small>[ October 13, 2002, 06:14 AM: Message edited by: nitrousc5 ]</small>