Heres the situation:

The car is tuned for street use at around 12 - 12.9 a/f. What I noticed is that when I'm driving on the freeway the a/f goes up to 13+ and stays there So I find myself readjusting the a/f each time I go on the freeway and back on street and vice-versa.

At the moment for fuel mgmt I'm using the afc hack as I'm waiting for full standalone (so save the whine about getting a proper ECU), but until then I gotta drive it as I ain't got a 2nd car, so hence the hack.

Is anyone experiencing this fluctuation in a/f? The air ambient air temp is not much different when it ran at 12 a/f on the street and 13 a/f on the freeway, so my Q is, is this normal ? What is the cause of this? I'm thinking it might be due to the extra air, possibly cooler air entering the car as I'm constantly cruising at a higher speed on the freeway than on the street that may be causing this effect?? Can someone verify this?

 

you run leaner on the street. When you leave the dyno averaging a 12.9 afr, no doubt on the highway you'll be in the 13's. Your car gets more air driving 60mph then a fan blowing on the radiator.

 

The car was street tuned at 12.1-12.5 not on the dyno. Depends on where I'm driving it varies up to about 13+ a/f

 

Up fo da nite...

 

you want a higher afr when crusing, i used to run 15.5-16 while crusing. you want 12.0 afr under load.


are you using a wideband to monitor your afr?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">you want a higher afr when crusing, i used to run 15.5-16 while crusing. you want 12.0 afr under load.</TD></TR></TABLE>
Yep... I run on the highway 14-15 and 14-15 on the streets. under load I run 12-10 afr.

 

Are all these A/F ratios under full boost at wide open throttle?

Is your boost level increasing on the highway due to the higher load?

What size injectors are you running?