Ultragauge and Lean Burn - Estimate MPG?
 

OK, so I know the Ultragauge doesn't read Lean Burn properly, and bases mileage off air flow rather than fuel flow. So... is there a good rule of thumb to estimate it? I watch the O2 sensor to determine if it's in Lean Burn or not.

If my UG shows 40mpg and it's in Lean Burn mode, I assume that is figuring about 14.7 A/F ratio. If I assume a 19 A/F ratio, can I estimate my instant MPGs are 1.3x higher, so 52mpg?

Or is it not this straightforward?

I don't know about the HX, but the Insight's lean burn air:fuel ratio varies quite a bit based on load. It doesn't just snap to 23:1 and sit there until you kick it out.

Here is an old article on smoothing out the lean burn in an Insight, it gives an idea on how the LB works in Hondas, plus it might be a mod you'd want to try on your car. Browser Warning

Interesting article, War_Wagon. Thanks!

The reason I was asking was to try to determine if it's better the pulse and glide or keep it in lean burn on the section of my commute that is freeway. On my commute to work, I've been resetting my Ultragauge and trying different methods over the 18.0 mile stretch of fairly level, 60mph freeway.

Day 1, I tried to keep it in Lean Burn mode, it reported 40.9mpg and I was able to keep it in Lean Burn for about 90% of that drive.

Day 2, I used pulse and glide (coasting in Neutral though) ranging from 65-50mph to try not to impact traffic too much. Ultragauge reported 54.0mpg.

Initially, it looks like a wash to me, (assuming an average A/F ratio of 20:1 gets me 53.7mpg for Day 1) and if I start EOC, then P&G is likely going to be the better choice. Am I wrong?

I guess it depends on how you like to drive. P&G probably does give you a higher FE, but if you can ease into LB and just keep it there, well that's how I'd rather drive. Up to you, and thanks for posting your numbers, more data is always a good time lol!

Can you use ultraguage to modify the fuel settings? I'm looking for an obd2 fuel which will enable me to lower overall hp and hopefully gain mpg in my 2004 silverado 4.3L (V6)

No, it just reads data from the obd2 port and displays it. While you can't tune the engine with an Ultragauge, you can use it to tune the driver...

Are there any obd2 scanners that can change the fuel settings?

My S10 has the 4.3L, and I can't imagine how sluggish a full size Silverado with the 4.3L, tuned for less horsepower, would be.

Have you researched all the Jet Performance type chips available? I see they have an OBDII-to-PC programmer.

You may not actually want to tune specifically for less power... Leaning it out a little will often increase power a bit. Maybe something like Black Bear Performance tunes might be what you are looking for:
Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles
Not sure if they do V6s though. I was considering this with my Silverado before I gave up on it and bought the Civic. Blackbear also turns on the ability to use an electric fan and sells a harness for that. The e-fan mod should bump your mileage up a little too.

There are also devices like Superchip, Hypertech, and Diablo that are more DIY, but still pretty pricey.