camanding a.f.r.

[smslyguy]

i have a 2000 stock gmc that i upgraded to a 2001 o.s. and the cammanded a.f.r is 14.68. I am seeing a camanded a.f.r. on the efi gauge (no w.b.) of 15.1. How can i have a 15.1 when the camaded a.f.r is 14.68 at stoich?Also by ugrading to this o.s. i have notice knock activity nothing to major at most it's 2-4 k.r. at cruising speed??

[mr.prick]

The KR could be from the lean commanded AFR.
Are you by any chance using E10?

[smslyguy]

The KR could be from the lean commanded AFR.
Are you by any chance using E10?

no, i run 87 octane with 10% blend ethonal like i always have. Why would you think i am getting such a lean a.f.r?

[mr.prick]

no, i run 87 octane with 10% blend ethonal like i always have. Why would you think i am getting such a lean a.f.r?
Why commanded would be leaner from what is set in the PCM is beyond me.
If LTFTs are enabled (I assume they are)
then most likely your actual AFR is close to commanded.
Lean AFR(14.68 or 15.1)+E10*=KR
*E10 needs a richer mixture (14.1)
Did you bump up the spark when you changed tunes?

If everything else is the same except commanded/actual AFR
this would seem most logical.
Drop the commanded down and see if that helps.

[smslyguy]

Why commanded would be leaner from what is set in the PCM is beyond me.
If LTFTs are enabled (I assume they are)
then most likely your actual AFR is close to commanded.
Lean AFR(14.68 or 15.1)+E10*=KR
*E10 needs a richer mixture (14.1)
Did you bump up the spark when you changed tunes?

If everything else is the same except commanded/actual AFR
this would seem most logical.
Drop the commanded down and see if that helps.

Yes, everything is stock even the spark table. I will try to camand a richer mixture and see if this helps. Although this is the same gas i have always ran and in the stock 0.s. it was running 14.68.