shadowSS

Can anyone explain this? How can I keep it this way always? lol <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

LS1derfull

Yes PCM when it senses knock it will retard timing, and will not restore full timing untill it sees gas level change. Judson massingill from S.A.M. pointed this out in one of his car craft articles with his 99 Camaro. I wasnt sure if this system was all years or not but it seems like it must be. anyone no more about it , i would like to know all about this subject?

Stab & Steer SS

I forgot all about this.I'm thinking that if you found the sender wire and put in a switch to short it out so the computer could sense a full tank.( cant remember if it is high res or low res to make the guage read full)

Ben99Z28

I think when the gas tank is full, the PCM use the High Octane Spark Advance table, that's probably why our car runs a tard stronger after we'd filled up the tank.
Now, If we change the entire Low Octane table and mirror all values to High Octane table, then technically our car would perform like it should be...regardless of the level of gas tank. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> hmmm....I think I'll have to try that sometime LOL <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />

Team ZR-1

PCM does not need to see a full tank to reset gas bit, it needs to see a 20% increase from the last time key was turned off.
Mirroring is not a good idea if there is real knock over time will cost you in repairs.
Bring up low octane scaling but I would not set the same as high octane values are so that PCM could back down timing just a bit if there is real knock,

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Catfish:
<strong>I think when the gas tank is full, the PCM use the High Octane Spark Advance table, that's probably why our car runs a tard stronger after we'd filled up the tank.
Now, If we change the entire Low Octane table and mirror all values to High Octane table, then technically our car would perform like it should be...regardless of the level of gas tank. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> hmmm....I think I'll have to try that sometime LOL <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

shadowSS

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Team ZR-1:
<strong>PCM does not need to see a full tank to reset gas bit, it needs to see a 20% increase from the last time key was turned off.
Mirroring is not a good idea if there is real knock over time will cost you in repairs.
Bring up low octane scaling but I would not set the same as high octane values are so that PCM could back down timing just a bit if there is real knock,

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Catfish:
<strong>I think when the gas tank is full, the PCM use the High Octane Spark Advance table, that's probably why our car runs a tard stronger after we'd filled up the tank.
Now, If we change the entire Low Octane table and mirror all values to High Octane table, then technically our car would perform like it should be...regardless of the level of gas tank. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> hmmm....I think I'll have to try that sometime LOL <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"></strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">John I understand what you are saying but can't you just crank up the fuel a tad bit to fix the knock problem? I had a knock problem on amaco gas until I switched to Chevron so I just turned up the fuel and the knocking stopped.

Team ZR-1

ShadowSS said

John I understand what you are saying but can't you just crank up the fuel a tad bit to fix the knock problem? I had a knock problem on amaco gas until I switched to Chevron so I just turned up the fuel and the knocking stopped

Sure adding octane can solve knock issues but if there was enough knock for PCM to set the bad gas bit then unless you add 20% more of fuel your stuck in low timing table until enough fuel is added and when that fuel is being used by engine and knock stops since it takes some miles for that added gas to reach the injectors.

If knock happens because internal engine has become too dirty due to oil passing through then the increased octane may not even help the knock issue.

In any case if the WOT timing is below what it normally is then you can assume the bad gas (knock) bit is set and when it is reset the WOT timing would inrease, if not then other issues are causing the low timing such as being too rich.

shadowSS

Ok i am starting to understand this entire bit .. I have another question I autotap'd my car yesterday and recieved 0 knock which is excellent.But at around 6000 RPM i am only getting like 24 degrees of timing advance . It this normal? Please take into mind that I do have a MAF translator and I have to dump more fuel up top because it gets to lean. There is only so much I can do with the mas translator because it doesn't tune for every RPM as would custom programming. I ordered custom programming for my new setup I just wanted to know if that amount of timing is normal or is it on the low side? Or if its to low could it be caused by me running it a little to rich in the upper band?

Team ZR-1

As a compare my 372 stroker LS1 with 11.3:1 compression has 28 degrees of timing at WOT but I tuned the PCM to achieve that.
Keep in mind if your injectors are a bit too small for high load spikes and you have to force PCM to go richer, it will pull some timing out due to PCM thinking there is higher engine load.

IMHO, your always better off with a slighty larger injector for then your tuning to go a bit leaner which means less load so PCM cranks up the timing plus injectors are working at shorter pulse widths ( duty cycles) and spray control is better. If you scan the PCM for injector pulse width and see pulse widths of 18 mSecs and higher then your hitting to 80% plus duty cycle max.