Tuning for Fuel Economy

[alex0856]

Very interesting. Subbed.

[covertrussian]

Went to City A again, this time it was testing my new leaner cruise Stage 2 fuel map (stage 2 because it's expanded not to roll off the map with stage 2 boost levels).

 

Stock 05 LGT Map:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/05LGT_StockFuelMap.png~original

 

Stage 2 fuel map v1.3:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/STG2_FuelMapV13.png~original

 

As you can see I'm forcing closed loop 14.7 until 1.4g/s. This would make the car not be as rich in slight boost, and hopefully use less fuel. Since 1.4g/s is already well into boost, you don't want it to be that lean if you get on the throttle. Thus I updated the Minimum Primary Open Loop Enrichment (Throttle) to have a much lower lean limit at higher TPS %.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/TPS_AFRLeanLimit.png~original

 

Next thing I found is Minimum Active Primary Open Loop Enrichment. This is basically at what AFR ECU will switch to be in Open Loop mode. 05-06 LGT's have this at 14.41afr, but newer LGT's have it at 14.00AFR. Thus I lowered that too.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/MinimumAFRforCL.png~original

 

One last tune change since the last time I did a highway trip. IAT Timing Compensation, set 50*F-32*F to have 0* increase, and 14*F to have 1.04* increase. Stock calls for 1.05*@50*F, 2.11*@32*F, 3.16*F@14*F. Reason for this change is I'm already running 45* when stock runs around 41ish*. I didn't want the cold weather compensation to move me past MBT.

 

 

Anyway, went to City A, temps were at 26-32F, which is colder then my other testing logs, +450lbs to curb weight, tire pressures started out at 42/40@32F and were at 46/43.5@28F after 65 miles. This got me a disappointing 26.24mpg, not pleased at all. Definitely can't blame the tire pressures on this one.

 

Last time I went to City B, I got 31.35mpg, but the temps were much warmer at 46-58F, that and I had my first version of the stage 2 fuel map, which is basically 100% stock fuel map below 1.6g/s.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/STG2_FuelMapV11.png~original

 

Cold weather alone aside (and some random tune enrichment that I haven't found yet). I'm thinking it could be the leaner fuel map at fault. Similar to how having the Closed Loop to Open Loop delay on, where basically the leaner mixture is forcing the motor to open the throttle more to keep from decelerating. This in theory does reduce pumping losses, but you also run less timing, it's all about finding a happy medium.

 

Back to the drawing board I go, I really need to bypass my intake fuel filter, I think 115k miles +E10 is getting it clogged thus my Idle AF correction is very high.

[iNVAR]

Hey, so with all the flashing you've been doing, have you given your ECU a chance to settle in on fuel trims? I mean REEEEEEEEEEALLY settle into them. When I was tuning for boost a while ago, I would make adjustments on nearly a daily basis. Sometimes I would do it over the course of a few days. I had what I thought was a knock free map. Even after leaving a map on for a week, fuel trims seemed pretty stable and were knock free. Timing curved was good, boost hit quick and fast with the right amount of TD intervention. I left the map on and considered my work complete (with something like 150-200 revisions under my belt). Over the course of a few months, I noticed that my LTFT D was going negative. Not a huge amount, but still, going negative. After leaving the map on for half a year, I noticed that D had definitely gone negative (about -7 %) and knock had started showing up in my higher load columns, probably as a result of going lean in OL.

 

You're making some huge changes to your fueling map, and I see that your map is significantly leaner than mine. I only caution you that what you see now (knock free) may not stay that way over the course of months down the line.

 

Because it takes so many months for my LTFT to trend negative too, chasing down a potential "leak" (if that's what's causing it) is really, really, really hard too because I can't very well go fixing something and then waiting 6 months to see if my LTFT goes negative again.

 

Just saying...be careful with leaning out things.

[covertrussian]

Here is what my AFR looks likes shortly after reset right now:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/VD_STG2Fuelv13.png~original

 

You are 100% correct though, so far my Learning D does tend to swing -1 to -3, which is not good indeed. Reading your thread peaked my interest in this topic.

 

First of all, why on earth do closed loop learning affect open loop . I found this thread at RomRaider: Stopping D-range LTFT from impacting WOT AFR

I think I personally will do the same, by disabling D+ Learning (by setting D to be very high) you don't have to worry about learning eventually leaning out and killing your motor. That thread does talk about pros and cons of both methods, I think the cons outweigh the pros though. Before someone says, well Subaru knows better, we are talking about a company that gives us the CL to OL Delay and +2* timing comp on detonation prone cylinders, and banjo filters!

 

Sadly I doubt I will have a chance to test a long mile without reset anytime soon, I just have too much to do on this car. People do say after a car self learns it tends to get better gas mileage, I personally believe in fine tuning to the point where it wont matter if you just reset the ecu or drove 1k miles on it.

Edited February 2, 2015 by covertrussian

[covertrussian]

Just got back from a trip to NOVA, since it's about 260 miles total, I usually fill up at the halfway point, which splits it into two 130mile trips, similar to what I do roundtrip.

 

Going there: 29.89mpg, 40-54F, Day, Warm tire psi 46.5/45@54f

Coming back: 26.58mpg, 40-48F, Night, Warm tire psi 46/44@43f

 

This is actually similar to the numbers that I got a few months back that triggered this thread. Then I was running 36/34psi cold and return drive was ~10F colder. Looks like even increased tire pressure didn't help on the return trip. I'm beginning to think the terrain could be the biggest culprit here. Even though GPS showed similar elevations (it's a roller coaster elevation wise), though it could be that south bound part of i66 might be not as friendly to cars.

 

Another thing that I kept consistent to last trip, I didn't reset the ECU. There is also a possibility that self learn is what causes it. My very first documented trip to this location got better MPG returning, but I did flash a different tune. Thus next time I go up, I'll try testing with resetting the ECU for the return.

[covertrussian]

Got my ecu replaced this week due to radiator fans always staying on. I was able to pull a fresh base tune from it (was slightly different then the one posted on Romraider). I also installed a fuel pressure gauge getting ready to bypass the factory fuel filter which I think is clogged, and will test gas mileage post bypass.

 

Anyway I wanted to do a base run with all of these changes and with the latest tune that I crafted up.

 

Current timing map has more city timing, highway timing is about the same as it has been for a while, mainly 45* at 70mph.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Timing%20Advance/STG2Timingv211.png~original

 

The fuel map is modeled after 07+ Legacy GT fuel map. It's leaner further into the load range, stays above 14 AFR past 1.40g/rev. While factory map is already in upper 13's by 1.40g/rev. I also lowered the Open loop AFR window to be 14.0AFR like on 07+ LGT's, 05-06 open loop AFR switch is at 14.41AFR

To make this tune be safer due to leaner map longer and open loop AFR being lower, minimum AFR based on TPS needs to richen up, that way when you step on it, it doesn't lean out.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/STG2%20Fuel%20v1.4.png~original

 

With all these changes went out to city B. Temp ranges were 38-52F, warm tire temps were at 44.5/43.5psi at 38F. Gas mileage a disappointing 25.68mpg. With such warm temps it should have been a lot higher. I've been noticing that ever since I started leaning out the fuel table at 1.00-1.60g/rev range gas mileage has been down. Looks like lean once again is hurting the economy, like the closed loop to open loop delay was. This makes sense since lean means less torque, thus you need to hold throttle down longer. It's all about finding that happy balance.

 

I should also mention, since I had to take the car to the dealer I had to wire in the rear O2 sensor and EGT resistor. My tune does disable Rear O2 CEL's and AF3 corrections, and disables EGT CEL's too. Even with that my EGT was still at ~1300f with resistor, I pulled over 40 miles in and pulled it out, which changed the EGT's to be ~700f. Neither of these items should effect it MPG since I disabled them in the tune, but just in case I'll replicate these settings it post fuel filter bypass.

Edited March 2, 2015 by covertrussian

[covertrussian]

Finally am getting around to posting the first draft of the ECU tuning side of things. We'll be updating the second post of this thread as I gather more data.

 

ECU Tuning for Fuel Economy

 

Most of the items shown here will be based around 05-06 Legacy GT tunes. Since I also have an 04 FXT I test various tune changes on it too and tend to compare the tune differences to the LGT. Most of the things that I've done to the LGT tune to increase fuel economy came by default on the 04 FXT tune. It feels like Subaru spent more time trying to sqeeze every MPG out of the Forester compared to the Legacy. Even after modding the Legacy tune, my Forester (fairly stock) still gets 1-2mpg more city then Legacy does, but the two cars do have different gear ratios, turbos, etc, thus it's hard to do 1 on 1 comparision.

 

Fueling

Primary Open Loop Fuel Map

Only areas that really need attention are higher load areas that are very rich. Cruising portions of the map are pretty good as is. But I'll test various settings.

 

This graph shows how rich stock tune is and how innacurate the factory wideband is compared to a standalone wideband.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/WBOStockvsUEGO.png~original

 

Closed Loop Target Compensation

05 LGT tends to target 14.2afr at idle and 14.6afr cruising. I noticed that highway AFR range goes from 14.4-14.7 on my UEGO, which is on the richer side. Usually you want to see 14.5-14.9 ranges, constant rich lean helps insure proper catalytic converter function.

 

05 LGT Stock Closed loop target fueling

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/05LGTCLTargetFuelingComp.png~original

 

STUB: more research and testing to be done in this area

 

Closed Loop to Open Loop Delay

While calm city driving, CL to OL delay didn't increase my fuel economy at all. But with aggressive driving it does seem to help slightly, around 1mpg, not worth the engine damage keeping it on though.

 

AF3 Correction Disable

Disabling AF3 correction disabling has helped by 1-2mpg increase on my FXT, but nothing noticeable on my LGT (Could be because Legacy sensor was not as bad?). This tune change is a must for catless downpipes.

 

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Rear%20O2/AF3CompsZeroing.png~original

 

Tip-In Enrichment

STUB

 

Cold Start Fueling

These cars tend to not be too rich while cold idling. Within a minute of cold starting at 30*F the car was already in closed loop hitting 14+ AFR's. The stock tune might be richer for longer periods below 30*F, but otherwise so far I'm not seeing much gain in this area.

 

STUB: more research and testing to be done in this area

 

 

Ignition Timing

Timing table

 

05 LGT Stock Total Timing:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Timing%20Advance/05LGTStockTotalTiming.png~original

 

04 FXT Stock Total Timing:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Timing%20Advance/04FXTStockTotalTiming.png~original

 

 

Highway Range Timing

Increasing timing to 45* at 70mph range +1mpg (STUB)

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Timing%20Advance/45Deg70-75mph.png~original

 

City Range Timing

05 LGT tune runs very little timing below 1600rpm, could explain why it's such a dog in higher gears in the city. 04 FXT tune tends to run more timing down low, which could be another point that helps with city MPG.

 

STUB: Currently testing more city timing.

 

Base Idle Timing

STUB

 

IAT Timing Compensation

STUB

 

AVCS Tuning

AVCS tuning has been the holy grail of improving fuel economy on my Legacy.

 

05 LGT Stock AVCS

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/AVCS/05LGTStockAVCS.png~original

 

Stock Downpipe best MPG came from AVCS being at 15*. Sadly I ran over a dear before I could do more testing with stock downpipe. I did recently aquire a newer one and plan on eventually installing it to test again.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/AVCS/AVCS15v11.png~original

 

With aftermarket downpipe, the car preferred AVCS to be at 10* at cruise areas. Going from stock AVCS 0*, to 10* improved my winter highway fuel economy by 3mpg!

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/AVCS/AVCS10DPv2.png~original

 

 

04 FXT Stock AVCS:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/AVCS/04FXTStockAVCS.png~original

 

With FXT, since I rarely drive it on the highway, I am able to test city mpg more often. I've played a little more around with AVCS for the FXT in city areas.

 

Stock AVCS has gotten be the best MPG at 19.38, AVCS 15 got me 18.08mpg, and AVCS 10 got me 18.30mpg. Basically the smaller turbo of the FXT is more sensative to overlap (even with a catless STI up pipe).

 

 

Boost & Wastegate

Target Boost

 

Wastegate Duty Cycles

 

Mas Airflow Sensor

MAF IAT Compensation

STUB

 

MAF Sensor Scaling

STUB

 

Drive by Wire Throttle

[Flinkly]

it's nice to add the bit about AFR, catylitic converter and alternating rich lean (make sure everyone reading knows), but what would be the preferred AFR for MPG without CAT? just a suggested addition to cover the bases.

 

an awesome start to a summary post. compliments the thread well. keep up the good work with logging and analysis!

[covertrussian]

It's really hard to say which leaner AFR would help with fuel economy. Every motor seems to be different. I keep on hearing that EJ255 doesn't like anything too lean, basically starts misfiring at 16's. I probably will do some testing with it, even with a cat, and see what improves economy. But I also keep on hearing that E10 stoich ratio is actually at 14.3 AFR. That means going richer might actually be better.

[covertrussian]

Wanted to test the previous stock like fuel map and open loop AFR limits. Went again to city B, this time with ~280lbs extra. Temps were a colder 30-38F. Got 26.63mpg. Which is a slight improvement from last week's 25.68mpg. Not much though, but with the colder temps and added weight, means the changes worked.

 

This once again tells me that this car doesn't like lean mixtures, just like it didn't like the open loop delay leaness.

 

Here is the fuel map that I used this time:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/STG2%20Fuel%20v1.0.1.png~original

 

Compared to Last week's:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/STG2%20Fuel%20v1.4.png~original

 

Car is still down on mpg from before, the only real change has been new ECU from dealer and fuel pressure gauge installed, and Rear O2 plumbed back in. The stock tune from the new ECU did have code differences (non tunable). I wonder if these 5-6 different hex values is what's causing the gas mileage to suffer. I also wonder why two A2WC522N's would have any differences at all.

 

EDIT: Just remembered that Rear O2 is still wired in too, I did a data log today and AF3 correction was off. Thus next time I go (hopefully Friday), I'll test same tune just with Rear O2 unplugged.

 

 

On another note, new version of ECU flash has been a bit less reliable. The other week it threw an error while flashing on my Foz, scared the crap out of me. Today after I got back from the trip it threw the same error on the Legacy, luckily my battery was good and I could continue flashing from where it left off. Double checked and verified the ECU tune against my file to make sure they were they same post flash.

Edited March 2, 2015 by covertrussian

[covertrussian]

It's been a while since the last update, ever since I got the ECU replaced and my fuel pressure gauge installed I've been chasing my tail trying to figure out why my gas mileage dropped. Since then warm weather hit my mileage increased again which kind of masked that. Thus I started playing with AF learning.

 

I've been tuning D learning for couple months trying to disable AF adjustment but every time it has resulted an MPG loss.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Fueling/D-Learning/D%20Learning%2080.png~original

 

I just got back from a NoVA trip running the map above and got 30mpg going there and 29.8mpg coming back (both at the pump not gauge which was way off), which is some of the better MPG's that I've gotten going there and back. This gives me hope that this AF learning values might be good long term.

Edited June 16, 2015 by covertrussian

[covertrussian]

Did two more highway trips with above AF Learning ranges, this time to City B (more tested and controlled then the place I went to last time).

 

First trip was half day half night, temp ranges 68-85F, 28.28mpg.

Second trip was all day, temp ranges 82-93F, 29.60mpg.

 

I've been seeing a trend of night driving yielding slightly worse mpg. This car is just sensitive to any climate changes (rain has so far shown 1-2mpg loss too). Just like with cold weather, this makes it harder to do actual tune testing.

 

I'm trying another AF learning airflow range map next, I've gotten 31mpg to City B multiple times on stock airflow ranges. I wish we could have a 4th tunable range here, would make life simpler.

[xt2005bonbon]

What was your average speed on the highway?

[covertrussian]

What was your average speed on the highway?

 

I stick to 70mph, cruise control keeps it at 69-71 usually. I'll go 75mph a few times to pass cars, but usually not for more then 5 miles for the whole trip. Due to ~6miles city driving at the city, my average MPH probably gets lowered to 50-60mph though.

 

My Scangauge and GPS has this info, I just keep on forgetting to write it down .

[xt2005bonbon]

That's just amazing you can reach 29 mpg with a 70 mph average. What power/torque do you make?

[covertrussian]

Last virtual dyno that I have is from May, I made 225wtq/229whp@12.3psi on a 60F day. Which is actually down on boost, since I'm still tuning my temp based WGDC tables, goal is 13.5psi at all times (for now).

 

I've hit 31mpg multiple times, I just need to isolate what causes me to hit that and replicate it .

 

Also little data about summer tire pressures. On a 82*F I pumped my tires to 42/40psi, after the trip I checked the tire pressures after pulling into the gas station, they were 46/45psi at 88*F. For perspective, tires pumped to 42/40psi on 32*F day were 46/43.5psi @ 28*F after highway trip. I also tested lower pressures, starting 37.5/35.5psi @90*F were 42/40psi @91f after 120 constant highway miles.

 

I'm beginning to suspect that higher rear pressure = better mpg, because of 40/60 power split. On a cold day rear tires don't get as warm as front tires (due to no engine bay heat to keep them warm). Thus cold days suck more gas.

[xt2005bonbon]

So you're stage 2 and only hitting max boost of 13.5psi? Was that your choice or is it really the maximum boost you can ever achieve?

 

Also, I forget, what boltons do you have installed?

[covertrussian]

So you're stage 2 and only hitting max boost of 13.5psi? Was that your choice or is it really the maximum boost you can ever achieve?

The only reason I'm stage 2 (aftermarket downpipe), is because my stock one got destroyed when I ran over a deer. I adjusted the wastegate duty cycle tables not to overboost (free flowing downpipe will do that), but I kept the target boost tables at stock PSI's.

 

At this point I'm more interested to see how much power I can make with stock boost levels, so far I'm about 40whp over stock (my car made 187whp bone stock).

 

Also, I forget, what boltons do you have installed?

 

120k, Valvoline 5w30 motor oil, smurf blood in the transmission, valvoline Synpower 75w-90 in diff, new front O2, new PCV valve

 

Invidia UP Pipe, Divorced Shorty Downpipe and 2.5" mid pipe, rear O2 corrections disabled in tune, STI Perrin Turbo Inlet, GrimmSpeed Crank Pulley, Sidegapped spark plugs, custom grounding kit, retrofitted fuel filter to engine bay and bypassed the intank one (I have gotten up to 31mpg even on stock 110k mile fuel filter though).

 

225/45/17 Cooper RS3-A Tires, Whiteline LCA caster bushings, stock suspension, 0 toe front, around 1/8" rear toe (did my best to zero it out but still failed), rebuild all of the calipers and caliper guide pins&boots.

Edited July 9, 2015 by covertrussian

[xt2005bonbon]

The only reason I'm stage 2 (aftermarket downpipe), is because my stock one got destroyed when I ran over a deer. I adjusted the wastegate duty cycle tables not to overboost (free flowing downpipe will do that), but I kept the target boost tables at stock PSI's.

 

At this point I'm more interested to see how much power I can make with stock boost levels, so far I'm about 40whp over stock (my car made 187whp bone stock).

 

Interesting. Do you recall if you were hitting that type of mileage with the stock pipe before? Or do you think the free flowing dp is helping with mpg?

 

Also interesting that you gained 40whp without increasing boost level.

[covertrussian]

Interesting. Do you recall if you were hitting that type of mileage with the stock pipe before? Or do you think the free flowing dp is helping with mpg?

 

My records show the best stock downpipe MPG that I've gotten is 29.75mpg to City A, with only one person in the car. Tire pressures were cold at 45f/42r on a 88*F day with AC, so it could have been the tire pressures helping.

 

I should mention all of my MPG's on 65*F+ days are with using AC 100%

 

Also interesting that you gained 40whp without increasing boost level.

 

It's all in the tune and supporting mods. Stock up pipe alone was robbing me of around 7-10whp. But it would have robbed more as the boost increased.

 

Tune has a lot to do with it, my stock boost on a 100% stock car was at 10-12psi, so even then the car is said to do 13.5psi I would never realistically hit it. By adjusting the wastegate duty tables I forced the ECU to hit that 13.5psi max, which gained me some power of course .

[Flinkly]

Covert, how did you choose the timing to go along with your AVCS angle when testing different AVCS angles at cruise? or did you leave timing alone and just change AVCS?

[covertrussian]

I try not to change more then one major variable at the time, thus I tested AVCS first then mocked with timing. I have tried running 20 AVCS and 35* timing, which didn't seem to help, but I tested it on a one way trip. With this car I've noticed the only accurate way to test MPG's is going to the same exact city consistently and long one way fill trips are to be taken with a grain of salt.

[covertrussian]

It's been a while since the last update, I was busy building and testing before I got enough data to post it up.

 

I built a 3" cold air intake to see if power and gas mileage would be improved. I used a spare stock maf housing and shaved it down to be able to use inline with a 3" pipe and flow stack.

 

At first I ran it as a warm air intake and made tune adjustments based on that. As expected engine leaned out and overboosted, had to increase MAF scale by 25% and reduce Wastegate duty cycle tables by 8% to get it back inline with stock AFR's, Timing, and boost levels.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Intake/WAI%20v1/WAIv1_010.jpg~original

 

Gas mileage results:

City Stock: 18.95mpg (Amb: 60-90F)

City WAI: 19.37mpg (Amb: 70-90F)

Highway: Not tested

 

I will admit my data size with WAI is pretty small, stock intake has done 19.53mpg before with stock AF1 Learning Ranges (D learning on), but I noticed disabling D learning does reduce mpg. I'm willing to take a loss for engine longevity though

 

Cold air intake was just an addition of a 45* 3" aluminum pipe, helped keep IAT's much lower compared to the WAI, though I'm not sure IAT's were as good as they were with the stock airbox.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Intake/Custom%20Intake/CAIv1_001.jpg~original

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Intake/Custom%20Intake/CAIv1_002.jpg~original

 

Gas mileage results:

City Stock: 18.95mpg (Amb: 60-90F)

City CAI: 17.85mpg (Amb: 65-90F)

Highway Stock: 30.03mpg (Amb: 75-90f)

Highway CAI: 30.75mpg (Amb: 80-87F)

 

CAI made city gas mileage worse, but increased the highway gas mileage to be what it was before with stock intake and D learning enabled. I should have tested the intake with stock D learning, might have broken into 32's!

 

Intake increases your engine's efficiency, which means you hit MBT (Minimum Best Timing) sooner and can start going over the efficiency hill. I figured I should try running less timing to see if we are past peak torque. I changed Cruise timing from 45* to 40* (what stock LGT map has) and I increased IAT based timing retard to avoid detonation, my Timing was between 39-40* for the most part. My highway gas mileage went down to 29.56mpg (amb 80-98*F).

 

This makes me think that I'm still far from MBT, thus I will try running cruising timing at 47-50*. Problem is, cold weather is here, It's gonna be hard getting 70*F+ highway or city runs.

 

 

Thanks for reading this long post, I think writing this post is more beneficial to me . Makes me carefully review the data and analyze it to better understand why something is happening the way it is.

Edited October 5, 2015 by covertrussian

[covertrussian]

I've been running 45* with great success for a while, with the last post I was curious if running more would help. Figured I would try out 48* as a in between 45 and 48, this is with AVCS being at 10*.

 

Timing Map:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Timing/Base%20Timing/STG2_v2.1.4.2_48ignMax.png~original

 

This was a A-B Trip, not a nice A-B-A roundrip, thus MPG's are hard to compare to round trip ones, but in this case I'm looking for certain ranges to see if changes helped. Anyway got 28.60mpg with ambient temps at 55-62*F (expected some loss with lower temps). This direction of travel (81 south) tends to hurt MPG, but I think it's because I would usually fuel up ontop of the mountains. You loose MPG going up a mountain, if you fuel up ontop of the hill you don't get a chance to regain it by going back down the mountain. For this reason I fueled up at about 400ft lower elevation then what I started out at at home.

 

That's not where things got interesting though, my learning view was not good. IAM dipped down to 0.875 with ECU increasing the timing in certain spots. I don't believe I've seen my IAM drop at all before, thus the Engine wasn't happy with this much timing.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Timing/Base%20Timing/LW_60F_STG2_v2.1.4.2_48ignMa.jpg~original

 

I went back to 45* and instead played with AVCS, specifically 15* and 7.5*. Will post an update with that later since it's pretty late already .

Edited October 14, 2015 by covertrussian

[xt2005bonbon]

If you recall, I am running that much timing too. At least, that's what I see when I cruise. Last week, went on a trip from Burtonsville MD to south of PA via i70 and highway 15, and got like 28.6 mpg. I am stage 2 now though. While I was stage 0/1, I was getting less.