What is the optimal a/f ratio while cruising, and what should it be under boost?

 

Under cruise, you can lean it out to at least 14.7:1 and Chuck goes into the 15's:1, if I remember correctly. Then as you transition to boost you want to smoothly drop it down to anywhere from 11:1 to 11.5:1 to be completely safe.

If you want more detail, cewrx7r1 has posted some good info on this, fairly recently. Also check out the pre-tuning document that's a sticky up top.

 

thanks for the info

 

You can lean it out until the motor starts to run a bit rough and then richen it back up a little, I got my cruise cells tuned to 16:1 or leaner without issue. If it leans out at throttle tip-in there are other PFC adjustments to correct the lean condition.

 

Now that gas has gotten so ridiculously expensive, I tried to lean out my few cruise cells a little more. As I got to roughly 15:1, it started feeling very noticably non-responsive to giving it partial throttle changes, though it wasn't necessarily leaning out any more. Is that just a consequence of running so lean, or will something like Acceleration Enrichenment (which I tried but had no luck with) or INJ vs TPS help?

 

Leaning it out from 15 to 16:1 is a big change, requires roughly 9% fuel removal. Sluggishness sounds like a lean tip in, verify with wide band since you are using it to tune anyway. The inj accel maps worked for me, keep playing with them.

Every setup is different so you will need to tune your setup until satisfied.

 

Such lean mixtures resist burning and can be difficult to ignite. A MSD or other multi spark on the leading coil will help mitigate this. As you continue to go leaner, you will hit a point of diminishing returns with respect to mileage and you will offset any gain with a greater throttle opening to get the required amount of fuel for a given engine load.

The primary advantage of going lean is to insure that all of the fuel is burned by providing excess oxygen; when you go beyond this (too lean), not only will combustion be unstable, but it takes energy to heat the excess air and you will lose any mileage advantage in the heat balance.

 

While I have your attention, I could use some more help. I'm EXTREMELY frustrated this morning after putting my car in the garage running, and waking up to one that wouldn't get me to work.....

Got some advice to try reducing the lag to negative numbers to get my 850's primaries to work. That did in fact lean out my idle, where fuel map changes would never work. Most of my map seemed pretty good, but I still have very bad tip-in problems. I've tried increasing the acceleration inj all the way up to 20 which I would expect to be ridiculously large, but I still get leaness on tip-in. I've only been adjusting the first number, though, other than just experimenting with the second. I'm still not clear on what the second column on the accel inj does. Is a higher number a longer duration or a shorter one?

MAN these primaries are a PITA to get right. I had no problem tuning out the WOT but getting idle and tip-in and cruise to all behave seems IMPOSSIBLE. As I fix one, I break the other....