Tuning for Fuel Economy

wow. 40$ shipped from Rock auto for 4 plugs? that's good. I will probably buy these and put them in my 05. I need to pm you to help get a fuel eco tune. Planning a 4000 miles road trip with a heavy load on the car (3 bikes and one cargo box on the roof, one cargo box on a hitch receiver, 2 adults, 2 kids, and a trunk fairly full of stuff). I would love to get like 18 mpg and not 14 or something

wow. 40$ shipped from Rock auto for 4 plugs? that's good. I will probably buy these and put them in my 05. I need to pm you to help get a fuel eco tune. Planning a 4000 miles road trip with a heavy load on the car (3 bikes and one cargo box on the roof, one cargo box on a hitch receiver, 2 adults, 2 kids, and a trunk fairly full of stuff). I would love to get like 18 mpg and not 14 or something

 

With Rock Auto discount codes it was closer to $35, so yeah well worth it .

 

I don't have a separate fuel economy tune, my power tune (which is almost 300whp) is my fuel economy tune too, non of the dull throttle crap, etc. It's a combination of right parts and having the right ignition timing for them, which takes hours and hours of driving and testing to figure out .

 

I also do all my fuel economy testing at 70mph, and have my tire pressures at 40f/38r psi.

300 whp and 30 mpg. Very nice.

 

 

Something is either still wrong with the 05 tune or mechanically. I mean the car runs fine, is tuned similarly to the 06. And yet, gas mileage is definitely worse than the 06.

Yeah both should be very similar. I would start looking at mechanical differences, maybe the brakes are dragging, maybe the trans/diff fluid is gone? Etc. etc.

Well I am running them on my 2005 LGT

 

 

Would you say anything in the tune needs to change?

Would you say anything in the tune needs to change?

 

Cruise wise mine liked the same timing that it had before. Full throttle & boost wise mine liked 2* less timing, otherwise it kept on fine learning -1*.

 

As usual my fuel and engine load did change, but I blame my previous setup that I was fine tuned for more then spark plugs themselves.

Yeah both should be very similar. I would start looking at mechanical differences, maybe the brakes are dragging, maybe the trans/diff fluid is gone? Etc. etc.

 

 

The 05 has fresh fluids in both the trans and the rear diff (same cocktail as the 06 trans---motul/redline).

My 05 had the same cocktail, I replaced it with walmart's fluid and haven't looked back. No grinding in any gears, especially after replacing the clutch. Funny how a worn out pressure plate was the reason for my gear grinding and not the fluid.

 

Keep in mind that coctail has race fluids, which are not adequate daily driving heat/cold cycles and for long mile protection, thus you need to change it more often. This is why I went back to regular fluid instead.

Glad you all are still running this thread. Need to get off this stock tune and get better than 23-25mpg. And then a new turbo and block. Cheers.

Thanks! I haven't been actively testing anything for the last month, between being busy or out of town heh.

 

I am now testing my MAF wire connectors being tightened up after discovering that they were loose on the MAF pins.

 

Unfortunately I don't know how much data the bad connections have invalidated :/

I'm parting out a 2006-07 WRX and it so happens to have those nice and fancy 4 pot calipers. I wasn't going to use the, but this weekend as I am removing them I noticed they are WAY lighter then LGT's ones.

 

Earlier this year I replaced Legacy rotors with brand new Subaru OEM ones meant for 05's and those came in at 21.4lbs each (rotors meant for 06+ LGT's are actually 22.8lbs each):

 

WRX 4 pot rotors came in at a much lighter 13.8lbs. That's a pretty massive 7.6lbs in rotational weight savings per side (9lbs for you 06+ guys):

 

 

My 2012 2.5i Outback has similar sized rotors as the WRX (and actually has better braking performance on the street then the LGT) comes in at 16.6lbs/per:

 

 

The question is, braking efficiency aside, would reducing 15-18lbs of rotational weight have a noticeable positive impact on fuel economy? Everything I read always says to reduce weight, especially rotational weight. But lighter wheels don't seem to help all that much, and since rotors are very close to the hub, physics dictates that their impact wouldn't be as bad as having heavier wheels/tires.

I'd double check the diameter compared to your LGT rotors, if I remember correctly the WRX had smaller rotors, which should account for the mass, but you'd lose overall braking performance.

They are about an inch (23mm) shorter, it's not much but is noticeably shorter. The real weight difference is in the WRX rotors being about 1/4" (6mm) thinner.

 

But Like I said before, I'm not concerned about brake performance for this proof of concept

 

More detailed comparison of the rotors (based on Centric Premiums):

LGT

 

06/07 WRX 4 Pot

I haven't posted in a LONG time, but I've seen doing a lot of MPG testing in the background. While I was testing headlights usage gas stations switched to summer fuel here, and while it ruined my headlight test it did provide me with a nice data point for Winter vs Summer fuel MPG difference in the city.

 

Winter gas: 19.71mpg

Fill date: 04/20/2019

Temps: 55-83F

Runtime: 267 minutes

 

Summer gas: 20.97mpg

Fill date: 05/03/19

Temps: 60-83F

Runtime: 274 minutes

 

MPG Increase: 1.26mpg

Percent Increase: 6.39%

 

 

I filled up about 15 gallons after that winter test, which should have flushed out all of the old gas. Since I wasn't testing for this change for say I didn't get the exact date it switched but all of my runs after 04/27/19 were in 20's while prior to that they all stayed 19.71 or less.

Edited July 9, 2019 by covertrussian

Another item that's worthy for this thread. I also came across this issue/fix during my headlight test, which once again set me back a few weeks .

 

The MAF connector's female receptacles tend to over-compress overtime (or repeated unplugs). Thus one day during my baseline MPG test, car starts running pig rich and short and long term adjustments get maxed out pulling fuel (-25% and -15% respectably). As soon as I touched the MAF connector, the car's idle rose up and short term correction dropped into adding fuel (to correct for the -15% learned trim).

 

I pulled the pins out and pushed in the receptacle's connection, which fixed the issue. Compare the before and after gap in this picture:

 

More details on how I did this can be found in my build thread.

 

 

Onto the numbers

All the runs were done in the 60-91F weather, similar traffic patterns (as seen by run times), and similar driving styles (up to 0psi, staying in closed loop).

 

Before the fix:

20.51mpg (Gauge: 21.3) - 267min Runtime

20.78mpg (Gauge: 21.3) - 268min Runtime (Failure and fix happened about halfway through this run)

 

After the fix:

21.44mpg (Gauge: 22.5) - 265min Runtime

21.38mpg (Gauge: 22.2) - 284min Runtime

 

Real world gains (Averaged): 0.765mpg or 3.71%

 

 

If I stayed in Closed Loop then why did I see some gains?

Part of it is the closed loop turn on delay, but in summer months this delay is about a minute tops. I think the biggest reason is timing related. With the MAF reading higher loads, which caused the over-fueling issue, the timing would be reduced too. Basically the ECU would think I'm in boost when I'm really in vacuum or 0psi.

Yep. Suffered from this (MAF connector issues) numerous times.

wowsa, bringing this thread into the new year!

 

anyways, i was just browsing some ecomodder threads and saw one about "drag reduction clips" for disk brakes. couldn't think of what this meant till i started reading the thread, but they (try) to keep your pads off the disk unless you're actively braking, thus eliminating drag and helping MPG (among other things).

 

Raybestos sells them for the front on our cars, but maybe you could mod them to work on the rear as well.

 

will have to look into it and see how it does. they're super cheap, super easy to install and should prolong the pads/disk life as well, so a win-win-win.

Clips.pdf

Let us know how it goes. I am interested..

so there is one thing about the Subaru brakes we have that don't help: they're floating/single sided.

 

So this will still help, but will probably only move one pad from the disk, rather than move both pads back from the disk. But since I've not used one, maybe that cute dimple in the middle of the spring located the center of the spring in the center of the disk, but then you're adding back drag if it's touching the disk to locate, and i would imagine it wouldn't last long.

 

but who knows what it will do in practice. just need to order some.

 

or maybe get some brembo's or 4 pots to upgrade to and reap ALL the benefit! Justification!

also, regarding the whole spark plug discussion, i did some additional homework and here are my results (documenting for all of us):

 

Plugs in "rank" order with part name/number/cost (from RA)

 

Fancy GND tip

Ruthenium HX

LFR6BHX

P# 93420

$7.85 each

 

Iridium ?

SILFR6B8

P# 373

$11.72 each

 

 

Tapered GND Tip

Iridium IX

LFR6AIX

P# 93893

$5.14 each

 

LFR6AIX-11

P# 6619

$5.19 each

 

 

Regular GND tip

Iridium OEM

SILFR6A

P# 7913

$8.90 each

 

 

 

Looks like we should buy the fanciest Ruthenium HX ones if you care about maximizing MPG, power, etc (due to cost mainly).

 

Or if you just want to keep the car running for "cheap", then get the tapered tip Iridium ones. save $11 per plug change. makes me wonder how much real world money you can save from MPG within 60k mile suggested replacement interval...

 

Lastly, what are people running for gap? NGK lists 0.030 for most of these OEM application plugs, with 2 listed at .032. Sprank told me many moons ago that he gaps to 0.026-0.028 (stated that it "...will make slightly more power and just works better"). Although it's probably best to double check that they're all gapped the same/correctly and leave them alone...

Edited January 13, 2020 by Flinkly

I've tried using those clips on my other cars and they were such a pita to install that I don't think I've ever even used them. IMO the gains are gonna be very tiny, if at all. Raise one of your wheels, see if you can rotate it (going to be limited amount of movement thanks to AWD). I can do it with one finger on my Legacy.

 

 

As for the plugs, those LFR6BHX seem WAY too cheap. Make sure you're not getting counterfeits: https://legacygt.com/forums/showthread.php/counterfeit-spark-plugs-281452.html

 

Finally, I've been doing a lot of testing in the background, but as usual the external factors have been really limiting me, so I have to swap in parts back and forth and it's just getting frustrating at this point.

 

Right now I'm testing a warmer T-Stat, hope to have some updates in coming weeks.

good info on the springs. i ordered some, but also looked at my calipers for a refresher on general construction. they don't appear easy to put on with our caliper style. assume it would be way easier on a fixed (vs. our floating) type.

 

ooooh, i'd love a warmer t-stat.

 

Crazy info on the fakes! i can't even see an appreciable difference between what they show as real and fake, except maybe the rougher edges to the threads and metal. i (probably wrongly) assume that Rock Auto is getting theirs from a legit source. my last set was from mSprank, so hopefully they're legit, although i'm hopefully changing them soon due mostly to age.

 

 

But similar pricing at some other places i think of as legit (although 30% higher cost than RA). Maybe all the plugs on RA for NGK are fakes and they just mirror the pricing of true parts -30%...

 

NGK.com

LFR6BHX $10.92 each (Ruthenium + fancy tips)

SILFR6B8 $16.13 each (Iridium + fancy tips)

 

Napa.com

LFR6BHX $11.99 each (Ruthenium + fancy tips)

SILFR6B8 $17.49 each (Iridium + fancy tips)

good info on the springs. i ordered some, but also looked at my calipers for a refresher on general construction. they don't appear easy to put on with our caliper style. assume it would be way easier on a fixed (vs. our floating) type.

 

Might be much easier on the Legacy, it does have much bigger brakes. Either way let us know how it goes!

 

 

ooooh, i'd love a warmer t-stat.

 

Lets just say my cruising water temp is 200F even at freezing temperatures. I'm not sure it will be good for summer though.

 

 

Crazy info on the fakes! i can't even see an appreciable difference between what they show as real and fake, except maybe the rougher edges to the threads and metal. i (probably wrongly) assume that Rock Auto is getting theirs from a legit source. my last set was from mSprank, so hopefully they're legit, although i'm hopefully changing them soon due mostly to age.

 

 

But similar pricing at some other places i think of as legit (although 30% higher cost than RA). Maybe all the plugs on RA for NGK are fakes and they just mirror the pricing of true parts -30%...

 

NGK.com

LFR6BHX $10.92 each (Ruthenium + fancy tips)

SILFR6B8 $16.13 each (Iridium + fancy tips)

 

Napa.com

LFR6BHX $11.99 each (Ruthenium + fancy tips)

SILFR6B8 $17.49 each (Iridium + fancy tips)

 

Last set I got was from RockAuto early last year, they were $8ish for Iridium SILFR6B8's, but the same ones are now $11ish at RockAuto. Makes me concerned that I got knockoffs and I didn't take any good pictures of them either, but the car is running fine, so I think it's all good.

 

I forgot your gap question, the more boost you run the smaller the gap you need to avoid spark blowout. You want the run the biggest gap you can without getting spark blowout, since it exposes more of the spark to the air and fuel mixture. If the car runs better with a smaller gap, that means your getting spark blowout with your boost levels, or your coils are getting weak.

 

I personally used to sidegap, old copper trick, so my gaps were bigger then normal. With B8's I'm running the upper end of factory spec (0.028-0.031).

200F when cruising? wow. Our 05 hoovers around 179F with OEM thermostat (78C marking on it). The 06, with the same thermostat, is more like 185F. The latter is lower if that makes any difference. Both got new radiators and new OEM tstats a couple of months ago.

200F when cruising? wow. Our 05 hoovers around 179F with OEM thermostat (78C marking on it). The 06, with the same thermostat, is more like 185F. The latter is lower if that makes any difference. Both got new radiators and new OEM tstats a couple of months ago.

 

It's a 192F thermostat, but as with all thermstats car always cruises 8-10F warmer then the stat it self (with fans off). I went with the higher end extreme to see if thermal efficiency goes up.