CIS: Cruise Air Fuel Ratios

[tyro]

For those with CIS, what sort of AFRs do you see under light load, perhaps just cruising on the highway at the speed limit?

On my 1980 SC, I have the wideband sensor at the "end" of the pre-muffler where it enters the muffler and see (depending on outside air temp and fuel octane rating) anything from 14-16 AFR under "cruise" conditions.

Is this too rich/lean for the conditions I describe?

[stlrj]

"Light-load cruise conditions permit the use of lean air/fuel ratios. Ratios of 15-16:1 can be used in engines with standard cams..."

http://autospeed.com/cms/A_1595/article.html


Air/Fuel Ratio Limits
6.0:1 Rich run limit
9.0:1 Low power, black smoke
11.5:1 Rich best torque at WOT
12.5:1 Safe best power at WOT
13.2:1 Lean best torque at WOT
14.7:1 Chemically ideal
15.5:1 Lean light load, part throttle
16.2:1 Best economy, part throttle
18-22:1 Lean run limit

http://www.qldstreetscene.com/forums/index.php?showtopic=999

[tyro]

Thanks..anyone else with numbers from an SC?

[don gilbert]

tyro, the numbers above are accurate, but some are unabtainalbe without an adjustable wur. since you have an 02, afr's can be easily changed and still have good afr # (14-15 to 1) for cruise and part throttle. i like to adjust my warm pressure to around 48-49 lbs (most factory wur are 50-55) and that give me 10.5-11 to 1 afr at wot, with proper timing, 35 degrees full advance, ssi's, and modified air intake it makes my car very peppy.

[Paulporsche]

Great info. Thanks.

[tyro]

Originally Posted by don gilbert

since you have an 02

80 euro=no O2 sensor.

[T77911S]

i was seeing low 15's at mid RPM's. hi 12's at WOT.
i reconnected my vacuum retard and saw about a .5 increase towards lean at idle. i was able to richen up the the mixture due to reconnecting the retard, plus the car sounds better and idles better with it connected.

don,
10.5 or 11 seems pretty rich. does that work? i think my brother was seeing those numbers for his 930, maybe a little richer. what WUR do you use?
what else have you done to the CIS?

[don gilbert]

it is a little rich, but only past the 35 degree thottle switch, my 02 brings it back to stoiche at idle and part throttle plus ive modified my air box to help with air flow, it looks a little goofy, but it sure makes a difference. im using a stock 82 wur that i have modfied to be able to adjust warm pressure

[T77911S]

why not use the WUR from the 77-79 with the WOT enrichment? mine seems to go very rich when it drops the pressure.
using the LM1, i see low 15's until 4k, then it starts to go rich as RPM's increase. WOT is in the hi 12's. i think mine is going too rich too soon. i am getting a miss around 4500. i put the bigger throttle body from an 80 on the other day and my miss jumped to 5200. then i richened up the mixture and it came back down to 4500 range. i am considering drilling out the bottom of my WUR so i can adjust the vacuum controlled enrichment point to make it come in around 5k, but i hate to mess with a WUR that is only about 8 years old. the problem could just be the mileage on the motor.

jess, if you think i am hi jacking, too bad, JK, let me know and i will drop off.

[don gilbert]

i could use the vacuume reg, but i can dump as much fuel as i could ever need with this wur and my freuqency valve, the problem is AIR, i'm not a fan of turbos, so i did the best i could.

[T77911S]

nice looking car don, more pics?