hoping for some mpg help

[notyourdadssilverado]

Hello all. My brother and I have been using his EFI live to do some tuning to my 07 silverado 5.3. I am hoping to get my mpg up as much as possible without giving up any power. It runs pretty decent right now but I keep getting right at 16-17 mpg. Im sure this thing could get better mileage if we could get a little direction from someone with some experience. The truck is stock except for exhaust and the tune on 87 octane. Would run 92 octane if it would benefit me. Also if anyone can bring power and mpg up you will be a tuning god in my mind!
Thanks for your help!

[Highlander]

With these controllers and no access to a loaded dyno, there is not much you can do with regards to fuel economy...

These do not have lean cruise and simply bumping the timing to see if you get better fuel economy is not the way to go...

Do you have ETC on this vehicle? you could play with the way the throttle opens to "pacify" it a little bit more so you can get a softer response and less fuel being spent in transition fueling.

Other than running open loop, have wideband and tune to 15.5:1 in all ranges except Power Enrichment, well... not much more...
or... get a dual wideband like the LM2 and hook the analog outputs to the PCM for them to simulate the narrowbands... Set the LM2 to report 450mv@ 15.5 AFR and then the PCM will adjust it self and save a lot of fuel.

I have always wondered why aren't any other oxygen sensors that have "stoich" @ 15.5 AFR?

But just to answer your question (partly and others may chime in). Use 92oct fuel and bump up the timing 2º across the board... monitor your MPG and then calculate your cost/Tank... then keep the stock timing table and monitor your MPG with 87oct and calculate your cost/tank. You will save $ and have a lot more mpg if you use the higher octane fuel with a few more degrees...

Remember... you can't bump timing till you see KR, because on part throttle when you reach the knock threshold you are way beyond your peak Tq/timing combo.

[smslyguy]

this is may not be the right spot for this but, i have always wounderd why they don't have a o2 sensor that can read everything across the board and not just stioch at 14.62??

[Highlander]

because its cheaper.

[smslyguy]

so you could install a digital o2 sensor in place of the stock ones and the computer would recognize it and be able to read all across the board and not just 14.62??

[Highlander]

No.

You would need a converter for it... Like the innovate LC1. You would then use the analog outputs to simulate a narrowband sensor for the ECU to be happy...

Even if you do that. THe mechanisms for the PCM will NOT allow you to use the whole sensor range.

If you have the stock sensors in place and you put the wideband in, you will see that the PCM will NOT achieve a steady 14.68 AFR and the STFTs are never steady. You will see that the wideband is still oscillating in the range of 14.3 to 15.0.

[smslyguy]

I thought you couldn't tune your car with the stock o2 sensors? From my understanding i thought the stock 02's only recognized stioch at 14.62??? Check this article out it claims you can adjust your afr from a digital volt meter???




Thought you needed an expensive scanning device such as AutoXray or Diacom to view your O2 sensors voltage readings? Think again! You NEED to do this if you have an adjustable fuel pressure regulator or if you have a Q-jet equipped thirdgen and are changing the metering rods to achieve optimal performance.

You will need:


A digital voltage meter,

Approximately ten feet of wire preferebly 12 gauge or smaller
Wire connectors (Screw type "european" connectors preferebly)
Jack
Jackstand

Wire strippers


Disconnect negative battery cable
Jack up vehicle on drivers side
Locate plastic connector for the O2 sensor near exhaust manifold, Disconnect.
Strip end of materials wire approx. 2 inches to expose core
Put exposed end into one end of the weather pack connector for the O2 sensor and reconnect.. Its a tight fit and you might have to trim or expose some more wire. It also might take a little force for it to snap backtogether.
Route wire away from exhaust manifolds or headers back into passenger compartment. If you plan on using this tuning aid temporarily simply route through door jamb. If not, there is a hole under the power booster in which you can route the wire.
Once inside of engine compartment trim wire to an accessable length. Connect wire to the positive probe of your Digital volt meter MAKING SURE that no part of the wire is exposed in any way so as to not ground the o2 sensor accidentally. European wire connectors worked well for me (the kind with a screw in each end to hold the wire in a plastic connector. Avail. at radio shack)
Use the extra length of wire to make a ground for the Digital volt meter. Under the dash there are plenty of places to ground the wire. Connect it to the negative probe of the digital volt meter.
Lower car, reconnect battery. Start car and turn your Digital volt meter on.

The range is as follows 3mV being the leanest, 1V being the richest. Part throttle does not matter so much as the computer always keeps it somewhere in this range depending several on variables and inputs from other systems sensors. At Wide open throttle the MOST desireable voltage should USUALLY be somewhere between .850mV an .900mV Make adjustments accordingly to reach the desired settings. Remember, the lower the voltage the leaner, the higher the voltage the richer. This also has an effect on spark timing. For instance if your car was running lean prior to adjustment and you had the base timing set to just before knock you may be able to adjust your timing for more advance with more fuel. The same is true vice versa. In addition, if you have an old O2 sensor take this opportunity to replace it as an O2 sensors sensitivity greatly diminishes with increased mileage.

It is imperative that you DO NOT ground the O2 sensor wire. This will KILL your O2 sensor.



--------------------------------------------------------------------------------
Happy Tuning

Pablo Morales This article was for educational purposes only. I do not condone performing this on any vehicle. Attempt at your own risk.

[Highlander]

You "could"... but you are not going to have consistent results...

Your right sensor can read 800mv and be at 13.0:1 AFR and your left sensor could be at that same voltage and the engine be at 13.4:1 AFR.... It is NOT designed to be accurate at those AFR mixtures.

When I started this, the only way to get to a wideband was with a dyno. I would tune my Supercharged 383 CID camaro to 890mv MORE OR LESS on all situations. When I strapped it on the dyno, I got a 12.5:1 AFR steady. Still... I never knew what AFR I was shooting for, I only shot to 890mV.

Still... the wideband sensor from my dyno dampens the signal a lot more than my innovate that seems to be pretty much INSTANT.

In the end... with efilive... get a wideband from innovate and connect it through the serial port. End of story.

[smslyguy]

do they sell a wideband 02 sensor that has both digital and anolog signals so that you can actually hook it up in place of the stock 02 senser? And if so where can you purchase them?

[Highlander]

Yes...

www.innovatemotorsports.com

Buy the LC1 with the XD16. The XD16 is a nice gauge too.

[smslyguy]

do you need to purchase the xd-16 gauge? Or can you just buy the basic lc1 kit? sorry for all the questions i'm a newbee here. lol.

[Highlander]

No... but it is very useful... You could buy the cheaper QB i think it is... as an alternative...

[dfe1]

There are a couple of ways to command a "leaner stoichiometric" setting. Change the value in B3601, and/or change the O2 rich/lean switching voltage in B4105. In theory, since narrow band O2 sensors are essentially switching devices, you can alter stoichiometry by changing the O2 sensor reference voltage. I understand this has been done with some aftermarket controllers, but I can't confirm that.

[tblu92]

I have had good results with getting rid of the IAT timing subtractions and the ECT subtractions as well---With the IAT deducts i will make all the table "0" up to 122* and then take out about 60% of the balance-With the ECT deducts i make everything "0" up to 205* and leave the rest alone.
Especially with the IAT what happens is that the sensor ends up reading underhood temps rather than intake air temps as the sensor gets heat soaked--espicially bad in city driving-- This also makes it easier to tune because when you ask for 20* you actually get 20*
Also you may get some false KR that will subtract timing--This is really bad on the E38 ECM's If I can't hear a ping or knock i will de-sensitze the knock sensors little by little til i hear it ping--then I'll go back some--
Also make sure your fuel trims are 0 or slightly negative just before going into PE--If you have a positive fuel trim the ECM will add that % to your fuel and will waste gas in PE--Also make your PE AFR richer than what you programmed in--
I haven't had any luck with changing the stoich AFR B3601 nor by changing the switching points B4105 lower---Anyone have any better ideas on getting the closed loop AFR leaner ? With LT headers , they always make the closed loop AFR richer, something like 14.0----Anyone know how to get it back to 14.68 ?????

[ScarabEpic22]

Not sure Id recommend wiping the ECT and IAT correction out, I know for a fact that the TrailBlazer platform has MAJOR heatsoak issues, if you stop in traffic for 5 mins the IATs will spike a solid 10-30F, more with aftermarket CAIs. Not you go to mash the gas, tons of knock because the air coming in is much hotter. Right there you've got an issue, thats why GM built these tables in.

Yes you will get exactly what spark value you command, which is great for getting a solid baseline, but once you have your baseline you need to make sure the IAT and ECT correction tables are properly setup so if you encounter anything but whatever ECT and IAT values you tuned for originally you will have good performance.