quick rundown of the motor:

k20z1
rbc
cai
race header no cat
2.5'' exhaust

i was street tuned almost a year ago when i was living in socal right before i moved back to norcal. only major change since then has been a built tranny with lsd and 5.0FD, engine has stayed the same. elevation was around 2000ft and temps around 80-90*. 3rd gear WOT datalog from that session shows afr holding steady around 13.5:1 from 2k-8.6k rpm.

today i was at the drag strip and did some datalogs from 1-4 and they showed afr around 16:1 at WOT! elevation where i'm at now is around 30ft and temps were about 80*.

i didnt think the change would be so drastic. hopefully i can get retuned by a local shop within the next two weeks but now i'm afraid to even drive the car.

 

Do you know what the iats were for each datalog? And you did mean 30ft right?

 

IAT's for these recent runs were only 4-5 degrees cooler than the ones from last year. google says elevation here is anywhere from 20 to 40 feet so i just went in the middle.

 

Yea im not sure I'd expect to see some change but not that much.

 

any other input?

 

if the correction tables are setup right altitude should make little difference to your air fuel ratio. if it was tuned at lower altitude on a dyno the only thing you would really change at high altitude would be timing...the higher you go the more you can bump timing do to the drop in atmospheric pressure.
if your a/f ratio is changing drasticly with altitude change you need to make adjustments in the correction tables....fuel curves should remain the same.

 

10% per every 1000 meters (~3300 feet).
Or you could say ~3% per every 1000 feet.