Cruising AFR

[opethmike]

Just curious what everyone has their cruising AFR set to?

[Nicholas R]

When I used to run open loop I would set mine based on my O2 output. I'd try to have it hover around .7v which is a hair richer than stoichiometric AFR (probably closer to 13.5-14.0 or so) but I always felt the performance was better than setting it at .5v. 14.7 is the best ratio for clean burning but 13 or so is best for power. Plus it helped make sure I never ran lean. I'd certainly rather run rich than lean.

If you're running closed loop you have no say in what your AFR is because the lambda system is constantly changing it.

[BABIS]

I have just bought the Innovate #3822 kit which has the LC-1 Wideband Controller, AFR Gauge and a Wideband 02 Sensor..

http://img26.imageshack.us/img26/1728/11032013329.jpg
http://img841.imageshack.us/img841/1826/11032013330.jpg

[Bitsyncmaster]

I also have the LC-1 and found you will find 14.7 AFR for cruse is best. Now around town 13.5 AFR will make the engine run better if you don't mine a little less MPG.

[BABIS]

I also have the LC-1 and found you will find 14.7 AFR for cruse is best. Now around town 13.5 AFR will make the engine run better if you don't mine a little less MPG.

very nice to know

[dmc6960]

I tend to cruise a little on the lean side, around 15afr at RPMs less than 2500. 14.7 at cruising speeds above that. Did I mention I get over 30mpg on the highway?

Of course thats the wonderful part about EFI, the moment I hit the gas a little harder I'm instantly at 13.5. Need to be VERY careful when setting such a range though on a car with long cams, if the transition between lean/stoich and rich is not handled properly, you'll get a bouncy little cruiser. Kinda hard on the drivetrain, and tires you our more easily. I still have a lot of smoothing out to do.

[Nicholas R]

I just now realized this was in the EFI section so my comments were rather irrelevant. For my EFI setup, I just let the engine computer do whatever it wants, lol. I'm not going to do a full tune on it until I cam the engine.

[Spittybug]

~13.7 unless the RPMs are above 3,000, then it's 14.0 A little rich. That's .932 and .952 lambda respectively.

I'm thinking I need to reexamine my timing table. I think I feel some very minor "bucking" on closed throttle decel, in the 2,000 RPM range. My advance is at 45* in that range right now.

13* static + ~10* centrifugal equivalent for RPM + ~20* for max vacuum equivalent = 43 So it looks like I may be a bit over advanced and should knock it down. It's not like I need power in that area.....

My centrifugal (RPM based) goes up 20* between 1000 and 3000 rpm (1*/100 rpm linear) and my vacuum equivalent (for charge density) goes from 20* at 53 kpa to 0* at 80 kpa (roughly linearly). This mimics the stock curves including the zero vacuum advance with throttles closed. In my case however, on decel, throttles closed, I'm not zeroing out the vacuum advance..... but I need to lower it.

While the AFR targets you discuss certainly impact the fuel economy, the spark has the most impact on performance.

[Josh]

Just reviving this thread. Im looking into doing some more tuning to get better mileage on the highway.

I was previously getting about 25-26mpg cruising at 14.5 afr, so i bumped it up to 14.8 and Im getting closer to 30mpg.

I would like to get into the 15s but im scared of leaning things out too much. I would just modify the cells that correspond to 2600rpm-2000rpm at fuel loads <45%. This roughly translates to cruising at 110kph.

So what would be things to look for if i set it at say 15.3-15.5 afr? Im scared of melting pistons, and wonderful stuff like that. But im reading guys with sbcs are cruising with afrs up to 17.0!

Interested to hear your guys input.

[opethmike]

I'm cruising in the low 15s without issue.