Tuning for Fuel Economy

[covertrussian]

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.

 

Refresh my memory, how much AVCS are you running at highway RPM's? If your running 10* or more, try running 45* and see if it helps your MPG. But I also have a few other mods that might force me to hit MBT sooner.

 

I've hit 30mpg a few times with Stage 0, I've hit it more consistently with Stage 2 downpipe/tune, but that's probably because my tune has evolved a bunch since Stage 0. One of these days I might try running the stock downpipe again. Though I'm getting ready to swap in a Big 16g with an 8cm housing, which would make the stock downpipe irrelevant.

[Smithcraft]

I'm curious about one non-engine factor. With running that high of a tire pressure, how is your tread wear?

 

SC

[covertrussian]

That's one thing I was afraid off myself, what's the point of saving a few bugs on gas when you have center eaten bald tires needing to be replaced much sooner.

 

To my surprise 225's love higher pressures and are actually eating very evenly across the tread. This could be because of the design of the tires, or it could be that 225 tires are wide enough that extra pressure provides the needed support to keep them flat.

 

The only downside to higher pressures for me has been ride comfort and snow traction sucks.

[Smithcraft]

Thanks!

 

My Lincoln MoneyPit had 225s and it was a constant battle to keep them properly inflated to keep the treadwear even. But with my 89 Mustang, it was a battle to not blow the tires off. I miss that car.

 

SC

[covertrussian]

Just remember it's safer to overinflate then underinflate, tire blowouts happen from underinflation.

 

I might go back to 36/34psi for the spring/fall since it doesn't seem to help gas mileage as much as it helps in the winter. But that's another variable to test, and since I don't travel as much anymore, when I do travel I'm trying to test other mods/changes.

[Smithcraft]

Just trying to get better economy from my Subaru, I try to keep the tires inflated to the heavy load inflation level.

 

It would be better though if I just didn't press down so far on the pedal on the right.

 

SC

[Thinking out side box]

Been running Mike's break-in tune for two weeks now. At about 600 miles now and one oil change already. Street tuning it Thursday night, will let you know how it goes!

[Thinking out side box]

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.

[Thinking out side box]

Quote:

Originally Posted by 05legacygtr http://legacygt.com/forums/skynetim/buttons/viewpost.gif

Well then I have no idea. What did Cobb say? Does your AP have all its updates?

 

Sent from my SAMSUNG-SM-G920A using Tapatalk

 

Cobb didn't have too much to add and the unit was fully updated. It probably has something to do with the ECU being replaced (different model #) but I'm not 100% sure. Anyhow I ended up selling the Cobb and will probably just look into a custom tune down the road.

[Smithcraft]

Trying to get that other post to show, but maybe it was deleted...

 

SC

[covertrussian]

Which other post?

[Smithcraft]

According to vBulletin, there was another post. Sometimes vB hides a post until another post is made. I think maybe the poster deleted the post but it still showed a post in the list of subscribed posts...

 

SC

[solidxsnake]

According to vBulletin, there was another post. Sometimes vB hides a post until another post is made. I think maybe the poster deleted the post but it still showed a post in the list of subscribed posts...

 

SC

 

Sorry to continue the thread-jack, but if the poster was "thinking outside the box" or similar, I think it was a spam post that was deleted. Had the same problem in a bunch of my threads where they wouldn't mark themselves as read. My fix was to post in the threads then delete them (easier than getting the mods involved and it fixes it for everyone, I believe!).

 

But to keep it on topic, thanks for the thread, covert. When I get my exhaust all finished up, I'll probably try some of your tuning tips to get my highway economy up to snuff (right now I can about average 24-25mpg consistently purely on the highway).

 

Do you (or anyone else) know if/how it's possible to control the TGVs through tuning? I don't see any tables defined in my ECU definition and I don't think they've been defined, if possible. On the '07+ years, the TGVs don't stay open once the car's up to temp like the earlier ones, they actually stay closed whenever the load is low. I think this is causing me some knock issues (mainly because it's using an untouched AVCS table which I still haven't gotten around to fixing).

Edited April 2, 2016 by solidxsnake

[Smithcraft]

That was the user, so I guess it was eliminated.

 

SC

[covertrussian]

But to keep it on topic, thanks for the thread, covert. When I get my exhaust all finished up, I'll probably try some of your tuning tips to get my highway economy up to snuff (right now I can about average 24-25mpg consistently purely on the highway).

 

Do you (or anyone else) know if/how it's possible to control the TGVs through tuning? I don't see any tables defined in my ECU definition and I don't think they've been defined, if possible. On the '07+ years, the TGVs don't stay open once the car's up to temp like the earlier ones, they actually stay closed whenever the load is low. I think this is causing me some knock issues (mainly because it's using an untouched AVCS table which I still haven't gotten around to fixing).

 

I haven't seen a TGV table for 05's or 07's, but as you said 07+ actually have logic besides on/off so there should be a hidden table. Maybe the guys at RomRaider can help out with answering that for sure.

 

What I don't get is, if 07+ have higher compression and control the TGV's at low speeds much more, why on earth is the fuel economy still as bad as 05's?

 

While typing this I think I finally understand why 07+ AVCS map is so "aggressive" with TGV's closed airflow is greatly reduced thus you need to run more timing & AVCS to make up the lost power.

[l88m22vette]

I've read through this thread a couple of times and have built a stg 0 map for my OBXT based off your info in the RomRaider base map. The car is currently stock, I have only read the ECU and changed things based on your info. I'm planning a few bolt-ons soon, but do you have any advice for turning this map into a stage .5? Basically, keep the economy and safety of it with a bit more punch...

 

I am also adding some shots of the few small things I did myself in case it clashes with anything:

 

- Some mild acc pedal map smoothing (~10% removed from 7.1 and most of the 14.3 pedal angle)

- Dropped AVCS timing from 15.00 to 10.00 for 0.40 g/rev@2000rpm

- turned on the Wastegate Duty Ramping Fix, but left the Max Wastegate Duty Alternate Fix off

 

I turned down the timing for a bit of safety, and from what I read I have the correct settings for the wastegate settings, can anyone confirm those? I know it is only a 2005-06 issue...

 

http://i162.photobucket.com/albums/t279/l88m22vette/XT%20Tuning/v1-2%20Stg%200%20Safe%20OBXT%20acc%20pedal%20smoothing_zpsezggoxox.png

http://i162.photobucket.com/albums/t279/l88m22vette/XT%20Tuning/v1-3%20Stg%200%20Safe%20OBXT_zpsro0rfsmo.png

Edited May 29, 2016 by l88m22vette

[covertrussian]

For stage 0.5 you could play with timing for more power or increase boost to actually be 13.5psi since it seems like most factory legacy's run 10-11psi tops.

 

I'm technically at under stage 1 boost levels, but with downpipe and a few other mods, I'm running 14psi tops and putting down 230-250whp.

[Phillip J. Fry]

stock bpv has consistently given me better mileage than kompact or cobb.

 

after what i suspect as bad gas i went through 2 cans of bg44k and afterwards my mileage jumped up a few. was at 26 then went to 33 down the same stretch. using dyno tune.

 

so many parts get worn and used. op is right. you need to be mechanically sound.

 

coil packs get old after a while. i suspect #3 that sits just above the uppipe might see some extra abuse. i was running with a shield less stock pipe. many run cobb which has no shielding. i just changed out #3 out and havent fully tested mileage yet but its looking very good so far. will find out on my way to work tomorrow.

[covertrussian]

For what ever reason, my 100% day trips get much better gas mileage then the night trips. Case and point last week I got 29.88mpg during the day and tonight I got 28.19mpg going to the same city similar routes, even had less overall traffic, still got worse mpg though.

 

I've been racking my brain on why this is the case, so far have:

• Daytime seems to have more traffic, more traffic = more cars to break the wind infront of you = better aerodynamics.
  
• Day air is possibly less dense (assuming day temps are warmer), thus requires more throttle to maintain the same speed (less vacuum). Some say that keeping the throttle open more helps reduce pumping losses.
  
• Day air is possibly less dense thus less resistant/more aerodynamic
  
• Radiant light warms up the tires more, thus slightly less rolling resistance, but only on one side of the car.
  

 

Just a little frustrating, it's hard enough to get out, and now I need to take off work just to get consistent data?

Edited September 13, 2016 by covertrussian

[cryo]

Colder air will always produce more power thus less throttle needed to produce the same power. Its VERY odd you have observed this since most times sitting in daily traffic vs nightly traffic is just the opposite but I have no reason to question your results, just another interested subject in your tests.

 

the only way to truly test this is calculate *time spent idling, speed average, calculated fuel consumption over multiple tanks, miles traveled* to get a proper average etc..

 

I'm a geek when it comes to this stuff but at the same time NOTHING can be changed in the calibrations *especially the AVCS and CL tables* to find a norm..

 

Dave

[covertrussian]

Colder air will always produce more power thus less throttle needed to produce the same power.

 

Some say that's one of the main reasons why winter gas mileage is also down, the throttle being more closed reduces the engine efficiency and increases pumping losses.

 

One thing that I didn't really think about is lights. At night I'm powering two 65w low beam bulbs, two fog lights and tail lights, and that's on low beam only. I came across this interesting page, I haven't double checked his math, but it does make sense since electricity is not free. I might test this next time I go to the same city during the day and will have my lights on (like I would at night, since my DLR's are disabled).

 

Its VERY odd you have observed this since most times sitting in daily traffic vs nightly traffic is just the opposite but I have no reason to question your results, just another interested subject in your tests.

 

You live in a much more populated area, I have a ton of hills and mountains and most people are done traveling by 6pm it seems .

 

the only way to truly test this is calculate *time spent idling, speed average, calculated fuel consumption over multiple tanks, miles traveled* to get a proper average etc..

 

I'm a geek when it comes to this stuff but at the same time NOTHING can be changed in the calibrations *especially the AVCS and CL tables* to find a norm..

 

Dave

 

Agreed, to get perfect numbers that would be the way to go, but it's just too hard to do for us regular folks paying out of pocket . It looks like EPA tests (or at least used to) the cars on a dyno and they don't monitor how much gas is consumed by seeing how much gas was used, instead they capture the exhaust and measure/calculate gas consumption based on molecules.

 

I personally started setting up baselines for all surrounding cities, they have to be more then 120miles round trip, because gas pump fillup inconsistencies get high when you fillup less then 3.5 gallons. I try to keep my within city destinations to be the same, I note down traffic amounts and now started noting down day/night/headlight usage too.

 

I know it's better to do full tank, but unless you want to travel 500 miles in one go, your adding too many inconsistencies (fuel evaporates into gas as the car sits, cold starts, etc.). As long as your comparing the same city trip and same amount of miles your results should be accurate enough.

[covertrussian]

I installed a Big 16G earlier this year, I was expecting pretty nice MPG gains from a better flowing laggier turbo. On the contrary I got worse gas mileage then before. This really killed my motivation to do any more testing on this car, especially since we got the 2012 Outback 2.5i, which gets 30-32mpg highway and is much more kid friendly (but is slooooowwww ).

 

Just a refresher on terminology before I proceed:

A-B Trip = Starting in one city, ending (filling up) in another

A-B-A Tip = Starting in one city, going to another, going back to starting city and filling up there.

(B)TDC = (Before)Top Dead Center

 

Anyway, couple weeks ago I was on a work trip (A-B trip), going there I got 28.94mpg which was down from 30.0mpg from previous time with a VF46. Then it finally hit me, bigger turbo is similar to a better flowing Intake & Exhaust (in one) and that less timing is needed since the engine can fill the cylinders with more oxygen (less heat from bigger turbo = cooler denser oxygen charge). With more oxygen in the cylinders and the same ignition advance the mixture finishes burning well before TDC creating extra pressure in the cylinders, this creates drag inside the engine that other cylinders have to waste power to overcome. Optimally you want the mixture to finish burning right as the cylinder gets to TDC, this is a magical and mystical amount of ignition advance BTDC that changes by a lot of factors.

 

To test this theory, I proceeded with changing the timing from 45* at 2800-3200 to be 40*. This got me an impressive 30.98mpg on the return leg of the trip, with plenty of stop and go traffic.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/ECU/Timing/16G/16G%2040IGN2.8-3.2k.png~original

 

I didn't want to make this post until I got a chance to test this more and get more data under the belt first, I think I have enough data now to conclude that 45* is indeed too much timing now. Here are some numbers from A-B-A Trip to the same City. Day = Headlights are off.

3/11/2016 - 100% Day - 66-77F - 45* 2.8-3.2k - 29.45MPG

7/19/2016 - 50% Day - 72-80F - 45* 2.8-3.2k - 27.15MPG

9/02/2016 - 100% Day - 70-80F - 40* 2.8-3.2k - 29.88MPG

9/12/2016 - 50% Day - 68-82F - 40* 2.8-3.2k - 28.19MPG

 

Looks like the timing reduction helped a good bit more on 1/2 night trips, not exactly sure on why, temps are within the similar ranges so I don't think air density had much play in this.

 

I'm testing even less timing to see if it going below 40* is needed. So far I only have 4 A-B style trips from this weekend, sadly to places I've never been to thus I don't have base numbers. These kind of trips are good to test new changes but then I still need to verify them with an A-B-A style trip:

Anyway, I tried running even less timing, 35* 2.8-3.2k, this got me 28.94mpg during the day, I expected a bit higher for this road. For the next fillup I tried running 38*, that got me 29.50mpg with part of it being in pretty heavy traffic (no standing though).

 

I decided to keep 38* or the return back home trip. First leg with no traffic, 2/3 at night and 1/3 in morning with low beams & fogs on 100% of the trip got me 28.69mpg, second leg with low traffic in the morning and headlights off got me 31.26mpg. I think 38* might be the winning combo for my current setup, guess I wont know until I go do another A-B-A trip, I'm glad gas is still cheapish for me to be able to play with this .

 

UPDATE: I did an A-B-A trip test with the 38* highway map and got 30.85mpg during the day, which is in top 3 best MPG's to this city to date!

Edited May 15, 2017 by covertrussian

[solidxsnake]

Do you run base timing all the time, and zero out your dynamic advance?

[covertrussian]

Nope, my dynamic advance is set to 6* for most of the map. I simply set the initial IAM to be 1.0, thus every reset/flash starts at full advance right of way. I've proven that this doesn't eliminate any stock function, my IAM still goes down on a lot of knock.

[solidxsnake]

Nope, my dynamic advance is set to 6* for most of the map. I simply set the initial IAM to be 1.0, thus every reset/flash starts at full advance right of way. I've proven that this doesn't eliminate any stock function, my IAM still goes down on a lot of knock.

 

The reason I asked was because that means your timing is actually ~6° earlier than that table (for most of your map), correct?