I got my EFI live today and going to data log tomorrow so Justin can tune my compleatly stock Tahoe. I will certainly get a wideband before tuning the 408. For down the road would putting a wideband into my Tahoe help much to tweak the tune?

The main goal in tuning the Tahoe is ecconemy with a splash of fun when I want to. That leads me to belive the wideband may help so I can lean it out more, but I don't know how much the stock 02s can tell you.

 

I have an Innovate wideband that plugs into the cig lighter. You can swap it from vehicle to vehicle in a matter of minutes. If you plan on leaving it in there, I would just mount it. If you are planning on only tuning with it, I would make it movable, and weld in an extra O2 bung.

 

Yes! As far as WOT goes the stock O2s only know that it is more rich than stoich, that's it. The stock narrowbands are very accurate and reliable for keeping the fueling centered around stoich/Lambda =1.00 but trying to read them to dial in fueling at WOT is a total guess.

In regards to the title of your thread, well at GM to build the stock calibration from scratch on these trucks or any vehicle for that matter they use a wideband. So yes a wideband is an important tuning tool to have!

I don't even like using the narrowbands/fuel trims to tune part throttle really because they have a deadband of about 3% because the O2s are constantly switching rich to lean and vice versa so it's like trying to hit a moving target while dialing in the fueling.

 

What does the bold mean!? Rich and lean?

I will certainly look to buy a wideband as soon as possible.

 

Stoich(short for Stoichiometric)/Lambda=1.00 is the perfect ratio fuel is designed to be burned at. The stock oxygen sensors detect the oxygen in the exhaust, and are accurate at the 1.00 ratio. If you were planning on tuning at WOT the stock O2's are not accurate like a wideband. WOT will be richer than 1.00 at WOT. Lambda is easier to tune with than air fuel ratio. A perfect burn for Lambda is always 1.00, and air fuel ratio will change depending on the fuel you are burning.

 

stoich = (lambda = 1.0)

A stoich ratio is the ratio in which, there is enough air to burn the fuel completely, this slightly varies depending on several different factors, such as the additives companies add to their gasoline.

I believe for gasoline, the accepted stoich ratio is ~14.7:1 and the lambda = 1.00

Lambda calculation

Here's the calculation to figure lambda.

 

Once you get familiar with Lambda it is much better and easier to tune with as far as logging with a wideband goes especially. The reason is Lambda is Lambda no matter what the stoich is for the fuel being used. For E10, 10% ethanol which is what's in most of the regular, midgrade and premium gas we get these days has a stoich value of around 14.2 which equals Lambda = 1. For straight gas ethanol free which has a stoich value of around 14.7 is still equal to Lambda = 1. E85 has a much richer stoich value of about 9.7 which is also yes equal to Lambda = 1.

 

So I would want to tune an E-10 fuel to keep the afr at 14.2 the entire time correct.

 

Here is the part that can be sort of confusing. The wideband can only read the oxygen level. The wideband does not know what fuel you are running. It can not tell the difference between alcohol or gasoline. It can only tell you when it is burning properly. If you have A wideband set up for straight gas (like most people do), it will show a proper lambda reading of 1.00 when it is burning properly. If it is set up for gasoline, it will show an AFR of 14.7. If you had it set up for e10, it would show 1.00 lambda with an AFR of 14.2. So the wideband has no idea what fuel you are burning, it just knows how much oxygen is left in the exhaust, and calculates that off of the fuel that is entered in the calibration. I just leave mine at 14.7 gasoline as I use the lambda anyways. I hope that is not too confusing.

And you would like to see a lambda of 1.00 when cruising. When you are getting in the throttle, you want the lambda to lower (lower number means less oxygen meaning more fuel). Depending on what your setup is will depend on how rich you will run it. NA engines run leaner that boosted engines.

 

My very first mod was EFI Live, my second mod 2 days after recieving EFI live was a Wideband.... IMO tuning without one is pointless....