Guys with widebands... what is your cruising AF ratio?

Killercanary · Jul 29, 2008

I just took my car on a trip that was mostly highway and I got HORRIBLE mileage. I got 13mpg over a 100 mile trip. I've since leaned it out to see if I can get better MPG out of it. Since I run a stand alone I have no idea what AF ratio guys with factory EEC's see when just cruising down the highway. I just wanted to see what other guys see.

urban96 · Jul 29, 2008

Killercanary · Jul 29, 2008

Hmmm... I'm already out to 15.5-16.5:1. This is at little to no load though too with under 10% throttle. I wonder what else I can do to get the MPG up. I used to get 20mpg on the highway with my eec tuner/t4mo setup. I wonder if I need to feed in a lot more timing in the cruising rpm's.

gcomfx.com · Jul 29, 2008

14.7 here too.

Stanger007 · Jul 29, 2008

I've used about every consumer wideband out there across quite a few cars, on a properly tuned car I see the AFR hover around 14.7-14.9 +- about .5 AFR as the narrowband O2s cycle.

On my list of things to try is targeting AFR in the 16s at cruise and maxxing out the spark. I saw a couple mpg increase by running upper 40s spark at cruise.

Wes

Mustangless · Jul 29, 2008

my afr is all over the place at cruise. High 13s to mid 15s.

Trbofox · Jul 29, 2008

14.7, and 21 mpg highway.

94-302-vert · Jul 29, 2008

Not WB but when I twEECed it I got 14.64 on my car...

Grn92LX · Jul 29, 2008

Usually between 14.x and 15.x

Stanger007 · Jul 29, 2008

Here's a snippet of a datalog from today at steady cruise and a graph. Please ignore the blank parameters in the log, we are working on some new datalogging features for BE.

This is off an Innovate LC1 sensor in my car. The sensor has about 4,000 miles on it since calibration.

14.72632653 AVERAGE LAMBSE
14.68015694 AVERAGE AFR

Source Datalog: http://www.72mach1.com/research/AFRvsLAMBSE.xls

Hope this helps,
Wes

final5-0 · Jul 29, 2008

Been so long since I had my display hooked up

Level stretch of highway and very light load with just enough skinny
pedal to keep steady highway speeds

I wanna say I see mostly 15's and an occasional 16 will blink across

Grady

95opal · Aug 4, 2008

Grn92LX said:
Usually between 14.x and 15.x

Ditto!

Killercanary · Aug 4, 2008

Man this sucks. I left my house with 5/8th of a tank of fuel, drove and hour to the track and made 5 passes, then drove and hour home with only 1/8th of a tank left. The odometer showed that I went exactly 200 miles on that tank and had used 7/8th of a tank of fuel. My wideband shows my cruising AF to be between 15.5-16.5. I had yeahloh95 in the car with me trying to get the tune even better and he can attest to how easy I was driving the car...

I'm going to try throwing a bunch of timing at it during light load and see if that helps, I've read that it should. I also have a timing/ignition issue that needs fixed first as the car was breaking up under full load around 5000rpms which didn't make for very good times.

Zero Signal · Aug 4, 2008

Yeah the ignition and injector timing is really all that's left to try at that point. I would imagine that if you're timing the injectors too early, you'll be losing raw fuel through the exhuast valves.

Or perhaps the engine is too cool? Or you just need more break-in on the new bottom end?

For anyone not forcing open loop or some kinf of hack, they will pretty much see stoich since the computer will alter the PWM to compensate for anything else that's wrong with it. It doesn't know how to adjust injector timing though. You have to know where to time it with your cam profile.

Redsnk95 · Aug 5, 2008

Paul you are going to need a lot of timing at the low load areas, 40+ degrees is the light load areas to help get that gas mileage back up. Did you use the AEM supplied 94/95 tune? The timing table should be perfect for you with some modifications in the WOT/High load areas.

Stanger007 · Aug 5, 2008

Redsnk95 said:
Paul you are going to need a lot of timing at the low load areas, 40+ degrees is the light load areas to help get that gas mileage back up. Did you use the AEM supplied 94/95 tune? The timing table should be perfect for you with some modifications in the WOT/High load areas.

I agree on the 40+ spark at light cruise. I run 45* on my car and can still go a bit higher.

Also you mentioned the ignition system could potentially have a fault, seems like that would give you some grief as well if the coil is overheating or a shoddy ground getting hot? Just throwing out ideerz.

Wes

final5-0 · Aug 5, 2008

I just thought about something that makes my above post a bit misleading

I forgot I was running forced Open Loop idle for a long, long time

At very light loads ... like at a cruise down the highway .........

It is quite possible I could have been in OL so that would have skewed
my info a bit as the O2's would have been out of the picture with a
condition such as that.

Grady

Mustangless · Sep 4, 2008

Seems as if my wideband is saying I am rich.

millhouse · Sep 5, 2008

Are you running some type of over-run fuel cut? To know if you are or are not, get on the happy pedal a bit and let off quickly to get into the low load/high vacuum areas of your tune. The fuel should shut off and you should get a dead lean reading on your 02 sensor. You need to turn it on if it’s not already as it can save a TON of fuel even on a Sunday drive.

Stanger007 · Sep 8, 2008

He's got an auto which cuts fuel a bit later than a stick (the DFSO tuning is less aggressive stock).

Brett, I'd try to verify with a second wideband just to be sure - sensors tend to get lazy and drift as they age before they go out. I keep a couple on hand for that very reason.

Also, did you get that graph from #s out of Innovate software or out of your twEECer datalog?

Wes

Guys with widebands... what is your cruising AF ratio?

Killercanary

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