O2's .850 and .860 too lean?
Thread Starter
TECH Resident
Joined: Nov 2002
Posts: 996
Likes: 0
O2's .850 and .860 too lean? I know that our stock O2s are not accurate enough for the perfect tune, but after installing my mac headers they were reading .930 to .940.
(I adjusted my LTFTs to -1 during cruising and they are at 0 during WOT)
I adjusted my PE VS RPM to 85 percent and now my 02s are at .850 and .860. (I adjusted PE VS RPM about 4 times before I got to these numbers. Seems PE VS RPM need relatively big changes to make a difference)
I have 0 KR, and my timing is almost always 28 degrees? If I was running too lean wouldn't I be getting some KR or timing reduction?
My car feels as fast as it ever has, so if these numbers are good, I would love to leave it like this. Thanks for any advice.
Tommy <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ March 10, 2003, 02:42 PM: Message edited by: TaTommyWS6 ]</small>
(I adjusted my LTFTs to -1 during cruising and they are at 0 during WOT)
I adjusted my PE VS RPM to 85 percent and now my 02s are at .850 and .860. (I adjusted PE VS RPM about 4 times before I got to these numbers. Seems PE VS RPM need relatively big changes to make a difference)
I have 0 KR, and my timing is almost always 28 degrees? If I was running too lean wouldn't I be getting some KR or timing reduction?
My car feels as fast as it ever has, so if these numbers are good, I would love to leave it like this. Thanks for any advice.
Tommy <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ March 10, 2003, 02:42 PM: Message edited by: TaTommyWS6 ]</small>
Re: O2's .850 and .860 too lean? I would be a little concerned.
Shifting your PE table 15% is pretty drastic. As a rule of thumb, I use a 2-4% change on the PE table will shift the a/f 1 point. Using my rule loosely you probably shifted your a/f 2-3 points. Thats a pretty big jump (ie 11:1 to 14:1)
Just because the car is lean doesn't mean that you are going to get knock or detonation, especially with this colder weather.
It is assumed that you can add 1 degree of timing for every 10 degrees of ambient temperature (ie if you tune your car for 28 degrees of timing on a 70 degree day, you should be able to tune your car for 30 degrees of timing on a 50 degree day)
FWIW, my personal car with no cats, the O2's read .97 and .98 at a 13:1 a/f. The car I tuned yesterday on the dyno w/ no cats and a LT's read .95 and .96 on the O2's at a 13:1 a/f. The other car I tuned yesterday on the dyno w/ no cats and LT's read .94 and .96 on the O2's at a 13:1 a/f. The other car I tune dyesterday on the dyno w/ cats and LT's read .91 and .92 on the O2's at a 13:1 a/f.....
this one time, on the dyno......
I woudn't make that much of a change to your PE table if I were you.
Good Luck,
Kevin
Shifting your PE table 15% is pretty drastic. As a rule of thumb, I use a 2-4% change on the PE table will shift the a/f 1 point. Using my rule loosely you probably shifted your a/f 2-3 points. Thats a pretty big jump (ie 11:1 to 14:1)
Just because the car is lean doesn't mean that you are going to get knock or detonation, especially with this colder weather.
It is assumed that you can add 1 degree of timing for every 10 degrees of ambient temperature (ie if you tune your car for 28 degrees of timing on a 70 degree day, you should be able to tune your car for 30 degrees of timing on a 50 degree day)
FWIW, my personal car with no cats, the O2's read .97 and .98 at a 13:1 a/f. The car I tuned yesterday on the dyno w/ no cats and a LT's read .95 and .96 on the O2's at a 13:1 a/f. The other car I tuned yesterday on the dyno w/ no cats and LT's read .94 and .96 on the O2's at a 13:1 a/f. The other car I tune dyesterday on the dyno w/ cats and LT's read .91 and .92 on the O2's at a 13:1 a/f.....
this one time, on the dyno......
I woudn't make that much of a change to your PE table if I were you.
Good Luck,
Kevin
Thread Starter
TECH Resident
Joined: Nov 2002
Posts: 996
Likes: 0
Re: O2's .850 and .860 too lean? I just got home from driving (cold night), and holy s%%#, the car feels ridiculously fast. I can rip through first and second gear instantly! It feels like it is leaping off the pavement... <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
With that said, should I really change my PE table <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />
BTW, I adjusted 4% then 7% and it only made a slight difference. That is why I went to 15%. Maybe when it gets a little warmer out I will set it to 10% and see how that goes. It really feels great now...
Kevin, those examples you listed are great to know. I will probably take a run up to your shop one day soon to get dynoed and have the a/f checked for real. Thanks!
Tommy <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ March 10, 2003, 11:17 PM: Message edited by: TaTommyWS6 ]</small>
With that said, should I really change my PE table <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />
BTW, I adjusted 4% then 7% and it only made a slight difference. That is why I went to 15%. Maybe when it gets a little warmer out I will set it to 10% and see how that goes. It really feels great now...
Kevin, those examples you listed are great to know. I will probably take a run up to your shop one day soon to get dynoed and have the a/f checked for real. Thanks!
Tommy <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
<small>[ March 10, 2003, 11:17 PM: Message edited by: TaTommyWS6 ]</small>
Thread Starter
TECH Resident
Joined: Nov 2002
Posts: 996
Likes: 0
Re: O2's .850 and .860 too lean? OK, I changed my PE vs RPM table to 90% (Instead of 85%)
My O2s are reading 915 amd 899. I guess I'm safer this way. Car still feels very fast and no knock retard....
If I hear (or see knocking while I log my car), I'll adjust again. Thanks.
My O2s are reading 915 amd 899. I guess I'm safer this way. Car still feels very fast and no knock retard....
If I hear (or see knocking while I log my car), I'll adjust again. Thanks.
