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Discussion Starter #1
Hi All:

With gas prices on the rise, I am going to be doing an experiment to help improve fuel economy a small amount.

I plan on installing wide band lambda sensors with programmable 0-1 and 0-5 volt outputs in the post O2 (sensors behind catalysts) position and sending the ECU an offset 0-1v narrow band sensor voltage. I am starting with the post O2 sensors vs the front because these sensors have limited authority in terms of how much fuel will be taken out. They are there for catalyst monitor and trimming the closed loop fuel for emissions (I work in emissions..). I may eventually move them to the engine out position for larger gains, but this will provide for a very conservative first step.

The concept of offsetting the sensor voltage is very simple: the sensor will report 13.7:1 AFR when it is actually seeing 14.7:1 stoich, for example. This drives the control system to remove fuel (lean out the mixture), until actual AFR is 15.7:1 and reported from sensor is 14.7:1. These figures are just an example of what I'm doing, I will be making a very conservative first attempt at the sensor calibration!

The plan is to leave the stock sensors in their OE position and keep the heater circuit hooked up to those, to maintain the sensor heater diagnostic in tact. I will feed the signal wire from my wide band sensors to the ECU signal harness side wire. I'll have two gauges that will report the actual AFR behind the catalysts.

The bosses are going to be installed next week. You can get these programmable wide band sensors now for a couple hundred bucks. I'm using Innovate Motorsports with Bosch sensors. I think they're about $250 each, which is relatively inexpensive for wide band lambda measurement!

I currently average around 13-14 mph with primarily city driving. The wife is the primary driver. Project goal is to bring this up to at least 15 mph.

Stay 'tuned'! :thumbsup:
 

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I got +3mpg's ( 13.2 To 16.9 0.92 was tire correction) just from getting the super chips programmer and installing the mileage tune just driving my normal route no highways. I think new there about $300 used about $250. If its just the mpg your after this seems a better way to go but your idea is pretty cool just expensive. Maybe you could combine the two.
 

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Discussion Starter #3
I got +3mpg's ( 13.2 To 16.9 0.92 was tire correction) just from getting the super chips programmer and installing the mileage tune just driving my normal route no highways. I think new there about $300 used about $250. If its just the mpg your after this seems a better way to go but your idea is pretty cool just expensive. Maybe you could combine the two.
I've read about fuel economy improvements from the current programmers and they didn't seem that great & have mixed results. I really appreciate the feedback, though, I am still considering one.

I do tuning on the side (as well as work) and have been waiting for HP Tuners to support the 4.7L Jeep, but I'm not sure it will ever happen. I'd really like to tune myself, rather than go with an off the shelf calibration.

What I'm doing is a work around, but it works. I've used the method to tune for emissions. You just need to be careful about partial combustion/misfire when you start heading into the 15-16 AFR range at higher loads. This method is limited for AFR in that it won't be engine load based, like a proper reflash/cal change, so you can only go so far with it. It will universally shift AFR leaner at all engine speed+load points. Aggressively lean AFR's don't work so well at higher engine loads. A proper calibration change, on the other hand, will allow for very lean AFR at low load cruising conditions and then maintain proper stoich or enrichment at higher engine loads. So before someone explains how dangerous this is, I admit it has limitations and am approaching it from that perspective. The post O2 authority to drive AFR away from stoich stops at a certain point, anyway.

I really just am putting this out there to have some quantitative numbers available for an out of the box idea. :thumbsup:
 

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Discussion Starter #4 (Edited)
Just picked up a used Flashpaq. I think I'll do some comparisons of 1) Flashpaq alone 2) lambda offset alone 3) FP & lambda offset.

It would probably be a good idea to get sensors installed in the engine out position to monitor lambda very closely. I have access to these sensors through work, so that's nice.

I will also be collecting a set of OBDII parameters with a data logger we use, check out IOSiX CAFLOR. You basically set it up with a config file and it collects data automatically every time the vehicle runs, it's a cool device.

By doing this, I can summarize the driving conditions (engine speed, load, etc) for the data I'm going to show here in this study. Obviously, everyone's fuel economy will vary based on driving conditions, so this will provide a good reference for my results.

Those that like details and are technical are really going to appreciate this thread..
 

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Though im in a 5.7L I'm still enjoying this read. Thanks for your thoroughness.


Sent from my Autoguide iPhone app
 

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Discussion Starter #6
Though im in a 5.7L I'm still enjoying this read. Thanks for your thoroughness.


Sent from my Autoguide iPhone app
No problem! I enjoy this type of stuff, so it's fun for me. I was thinking of testing out a couple different intake setups too and monitoring temps. It's real easy to do with the CAFLOR scan tool device I mentioned in the post above, one of the parameters I'll be collecting is "IAT" (intake air temperature) which is typically a measurement of the air intake charge as it passes through the MAF sensor. I also have a device called a DAQ, which will collect thermocouple measurements and integrate them (time align them) with the OBDII data.

Most of the time any small benefit from an intake is from lowering restriction (removing sound reduction) of the intake and not lowering temperatures...I figure it is time to 'put to bed' all the speculation there is out there about CAI's!

All my data will in general apply to all three Jeep engines. The overall gains/losses will of course vary, but the concepts should hold true across the board.

The work starts this week with the installation of the lambda bosses in the exhaust. Used Flashpaq is on the way. :thumbsup:
 

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Discussion Starter #7
Here is the menu for the scan tool where you can see what initial OBDII parameter set I've loaded. Should be neat to see what differences in fueling and ignition timing exist between stock Jeep and the Flashpaq calibrations. I'll also be able to make a basic RPM vs intake pressure ("MAP") scatter plot to show what operating regime the vehicle is used. I've loaded "IAT" (intake air charge temp) according to previous post and all four oxygen sensors for obvious reasons!

This many parameters should result in about a 2 Hz sampling rate, I think that will be fine for now.

Cheers

 

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I got +3mpg's ( 13.2 To 16.9 0.92 was tire correction) just from getting the super chips programmer and installing the mileage tune just driving my normal route no highways. I think new there about $300 used about $250. If its just the mpg your after this seems a better way to go but your idea is pretty cool just expensive. Maybe you could combine the two.
I'm averaging 11.8 to 12.6 mpg during my daily commutes. All city driving w many traffic lights. Would love to increase milage. With your increase, you notice a dropoff in excell., or perfomance?
 

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Discussion Starter #9 (Edited)
Got the Commander on the hoist today and marked the locations for the new sensor bosses.

Here are some pics showing the placement for the new sensors. You always want them to be horizontal or pointing down at an angle above horizontal so water doesn't collect on the sensor element and crack it.

I just decided to do both pre cat bosses while it was all torn apart, but am only going to be starting with sensors in the post cat location for my experiment.

It should be done tomorrow, I'm using one of my fabricators through work. They had to drop the hot end from the manifold to avoid getting chips inside the exhaust in front of the converter. Metal chips erode the ceramic substrate of the catalyst to the point of eventually going all the way through (I've seen it happen in the industry during testing)

Driver's Side Pre Cat Stock O2 Sensor and Location Mark for New Sensor Boss



Driver's Side Post Cat Stock O2 Sensor and Location Mark for New Sensor Boss



Passenger Side Pre Cat Stock O2 Sensor and Location Mark for New Sensor Boss

 

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Discussion Starter #10 (Edited)
Got the Jeep back today (the Superchips programmer came too, thanks Lt_JWS).

Dropping the hot end was a helluva job. 3 of the 4 anti rotation nuts were seized, so my supplier had to take both wheel splash shields out, as well as remove the cross member for the transfer case. Luckily, he did all this as a favor, but this sort of job would cost a decent chunk of change to do unless you have a connection or are willing to drop the hot end and weld yourself.

The other option would have been to use the stock O2 sensor locations for the wide band sensors, but this would have triggered all sorts of fault codes for the sensor heater circuit. My plan is to leave those hooked up to the stock sensors and simply put a weatherpack single pin connector on the signal wire, so that I can swap it between the stock sensor and my programmable wide band sensor.

I have both sensors and am waiting on the weatherpack connectors. These connectors will provide a clean and professional waterproof installation that allows me to very easily switch back to the stock sensor signal if something goes awry.

Pics of the newly welded bungs this weekend!

Cheers all

P.S. saw another news story here in MI on the 6 o'clock news about rising gas prices...$5 by summer. This is so worth it. I'll do a cost analysis at the end.
 

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Got the Jeep back today (the Superchips programmer came too, thanks Lt_JWS).
P.S. saw another news story here in MI on the 6 o'clock news about rising gas prices...$5 by summer. This is so worth it. I'll do a cost analysis at the end.
Yeah, that's BS. My work is only 5 miles away so I may have to invest in a bike and wheel it to work 2 days a week.:2232censored:
 

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Discussion Starter #12
Today I changed things up with the way I'm looking at my current baseline fuel economy.

The plan is to reset the veh monitor every night and look at average fuel economy on a daily basis, to analyze along with the OBDII parameters shown in the scan tool software above. This will provide for some pretty cool data- 1) see which parameters impact fuel economy the most 2) provide a better basis for comparing the stock fuel economy vs Flashpaq & sensor offset.

I decided to approach it this way because otherwise there is just too much OBDII data for a full tank of gas that extracting any valuable info out of it becomes a lot harder.
 

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Discussion Starter #13 (Edited)
Some pics of the MTX-L lambda gauge and dash pod I got from egauges:

Hookup of the MTX-L is pretty straightforward:
Switched power, ground, headlight power (night time dimming feature optional), two analog signal outs (both programmable: one is set to narrow band and the other is set to wide band output voltage curve from the factory. I'll be modifying (shifting) the narrow band in the software. The wide band output probably won't get used, although one could use both and install a switch to make the input to the ECU select able between the two different outputs (curves)- but for now I'm not going to do this as it adds another layer of complexity).

They've also improved up on their connections.

Seeing as how everyone loves pics:






 

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Discussion Starter #14
This will be my last post for awhile. I'll be collecting fuel economy data on the baseline calibration throughout March and will slowly be installing / wiring up the sensors in the post catalyst position on both banks.

I was thinking again about moving the wide range lambda sensors into the engine out position and realized that if the signal were shifted in the pre catalyst (engine out) position, in order for it to work, the same shifted signal would have to be applied to the sensors behind the catalysts, or the post catalyst sensors would simply apply their correction to the fuel trims to keep things at stoich.

Yikes! Now we're talking 4 wide band sensors, super expensive (some of you I know are already thinking I'm going to extreme measures here and I'm sure are skeptical of the outcome and that is ok...someone has to prove it will or will not work and this is fun!). Anyway, I verified w/my buddy that works in calibration at a popular off road vehicle OEM that my thinking was correct and it in fact is. So hopefully the offset signal in the rear position will trim the fuel enough to give me a decent improvement in fuel economy, while leaving the front stock sensors be.

Keep in mind folks, this is intended to be a real and quantitative improvement, with expectations within reason. We're talking it might take 5,000-10,000 miles of driving to break even (I hope lol!)

Signing off for now.
 

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Discussion Starter #17 (Edited)
Hi All:

I'm back. Just returned from a FL trip from MI (upper 80's all last week, I *really* did not want to return). Anyway, I figured it would be a great opportunity to log some fuel economy data and do a comparison of the stock calibration to the Flashpaq economy calibration. I haven't done much w/the programmable sensors, and this data provides the additional motivation to do so.

Here's the data I logged. Everything on the vehicle is completely stock. I replaced the air filter with a fresh Amsoil filter and run their signature series syn oil, as well. Platinum plugs. I like to run higher tire pressures, I was low 40's cold for this trip (please don't turn this into a discussion about tire pressures..)



If you look at the overall picture w/o normalizing the data for things like ambient temperature, speed, wind (wasn't much), etc (I have some of this data, but am short on time), the Flashpaq eco calibration resulted in slightly over 1/2 mpg improvement, relative to the stock calibration. The plot of $ saved vs miles driven shows the delta fuel cost for three different $/gal levels: $3 (yellow), 4 (blue), 5 (red) per gallon. Now mind you, this is all highway based, so 'what does it look like with city driving?' is of course what needs to be answered now. Nevertheless, if you use your Commander on the highway a lot, this should be a useful analysis for you in determining if the tuner is cost worthy or not. Hopefully the rest of you will find it interesting, at least. @ $5/gallon (yellow data), it will take about 35,000 miles of driving to pay for the tuner (~$300).

Mid way during the last leg of the trip through OH, where speed limits are lower (55-65), I managed to peak at the following. Then we got into MI (70 mph) and it dropped off significantly. The difference even between 60 and 70 mph on these trucks is huge.



The wife was leading, otherwise I would have backed off to see 21 mpg, since that has never happened!

Thanks for reading all!
 

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Discussion Starter #19
Lose any pep?
Nah. I would highly doubt the cal guys over at Superchips are messing with the power enrichment cal. They're likely changing converter lock cal and maybe a bit with trans cal/shift points. I'll be able to assess if they did anything with spark timing, since I have all that data.

They're small/conservative changes. I knew they would be, which is kind of where my idea was born. If you look at my data plotted with an error / standard deviation, one could say there was no difference. I do think the difference for city type driving will be more pronounced, which I should be able to report on in another month or so.

But to answer your question, when I needed to give'r, she still gave. :icon_biggrin:
 
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