Go Back   EcoModder Forum > EcoModding > Success Stories
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 01-31-2018, 11:52 AM   #1 (permalink)
EcoModding Lurker
 
Join Date: Dec 2008
Location: Western Canada
Posts: 46

2015 WRX - '15 Subaru WRX
90 day: 30.63 mpg (US)

2008 Suzuki SV650SA - '08 Suzuki SV650SA
90 day: 60.81 mpg (US)
Thanks: 1
Thanked 11 Times in 10 Posts
Lean Burn Success

I've been tuning my 2015 Subaru WRX to run in lean burn and I finally got around to doing some proper A-B-A testing. This car has a direct-injection turbo engine that is pretty knock-limited at moderate loads, so I wasn't sure how much of an effect a lean burn tune would have, but I'm pleased with the results.

In order to tune it, I used engine management software (Accesstuner Race), and re-calibrated the stock wideband oxygen sensor to trick the ECU into running lean. I'm currently running 17.5:1 AFRs at lower loads, which transitions to 16.3:1 at higher loads, and switches to normal AFRs at loads above 1.0g/rev of airflow (~40% of maximum load). The engine runs in full-time closed loop. Ignition timing is advanced up to 7.5 degrees over stock. Lean burn is active from 1200-2800rpm, and activates as soon as the oxygen sensor comes up to temperature, unless coolant temperatures are under -10C. I go into a lot more detail in This Post on NASIOC. I've also made a lot of changes that improve economy during engine warmup at the expense of emissions, which are detailed in that post (lower idle, disabled variable valve timing warmup settings, disabled stratified fueling idle mode, disabled post-start ignition timing tables).

I did some A-B-A testing to compare my tune with the stock map. Testing was done on a flat highway with the cruise set at 100km/hr in 6th gear with a warm car. There was a pretty steady cross wind that was more of a tail wind in the A-B direction, and more of a headwind in the B-A direction. Fuel consumption was determined by datalogging A/F ratio and mass airflow and then calculating the fuel flow in kg/hr. I also datalogged coolant, oil, and intake air temperatures to make sure they were consistent across all tests.

Average Fuel Consumption Results:
Stock Map:
A-B: 5.075 kg/hr
B-A: 5.587 kg/hr
Lean Burn: (17.0-17.1 AFRs)
A-B: 4.644 kg/hr
B-A: 5.274 kg/hr

Difference A-B: 8.5% less fuel with lean burn
Difference B-A: 5.6% less fuel with lean burn

The results were probably better on the A-B trip due to the lower engine load. (Edit: On the A-B trip, ignition timing was advanced an average of 6.1 degrees over stock. On the B-A trip, ignition timing was only advanced 3.2 degrees. At lower loads I can advance timing up to 7.5 degrees over stock). With a knock-limited engine like this, there is less to be gained by running lean at higher loads. I may do more testing at 40-80km/hr to determine if the results are even better at low engine loads.

__________________


Last edited by twj347; 02-23-2018 at 12:15 AM.. Reason: Ignition Timing Info
  Reply With Quote
The Following 2 Users Say Thank You to twj347 For This Useful Post:
mpg_numbers_guy (02-27-2018), pgfpro (02-01-2018)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 01-31-2018, 12:01 PM   #2 (permalink)
Master Novice
 
elhigh's Avatar
 
Join Date: Jan 2008
Location: SE USA - East Tennessee
Posts: 2,314

Josie - '87 Toyota Pickup
90 day: 40.02 mpg (US)

Felicia - '09 Toyota Prius Base
90 day: 49.01 mpg (US)
Thanks: 427
Thanked 616 Times in 450 Posts
Congrats!

I never got great mileage out of my Forester. In fact it seems to me that Subies in general are not mileage masters (in terms of fuel efficiency. In terms of longevity, all bets are off). If you can get this kind of result consistently, it could be worth a couple of MPG for you, not a bad result at all.

I haven't read your tech post (but it's nearly lunchtime and I will), did you include a periodic cookoff cycle to regenerate your catalytic converter?
__________________




Lead or follow. Either is fine.
  Reply With Quote
Old 01-31-2018, 12:45 PM   #3 (permalink)
EcoModding Lurker
 
Join Date: Dec 2008
Location: Western Canada
Posts: 46

2015 WRX - '15 Subaru WRX
90 day: 30.63 mpg (US)

2008 Suzuki SV650SA - '08 Suzuki SV650SA
90 day: 60.81 mpg (US)
Thanks: 1
Thanked 11 Times in 10 Posts
Quote:
Originally Posted by elhigh View Post
I haven't read your tech post (but it's nearly lunchtime and I will), did you include a periodic cookoff cycle to regenerate your catalytic converter?
No, I hadn't thought of doing that. Would this be purely to reduce emissions? The stock tune seems to cycle from lean to rich maybe once every few seconds or so. The logic for this is not accessible with my engine management software, so I don't think it would be possible to do that with my tune. The car still runs "clean", i.e. it passes the sniff test, but obviously NOx emissions will be higher with my lean burn tune. I live out in the boonies though, so reducing emissions is not a really high priority for me.
__________________

  Reply With Quote
Old 02-01-2018, 07:47 AM   #4 (permalink)
Master Novice
 
elhigh's Avatar
 
Join Date: Jan 2008
Location: SE USA - East Tennessee
Posts: 2,314

Josie - '87 Toyota Pickup
90 day: 40.02 mpg (US)

Felicia - '09 Toyota Prius Base
90 day: 49.01 mpg (US)
Thanks: 427
Thanked 616 Times in 450 Posts
I think the regen cycle is partly about emissions but also partly about extending the life of the cat. Hopefully someone will weigh in on this to clear up any misconceptions, but my understanding is that the regen cycle briefly drops the car back into stoich to heat the cat back up and keep it operating normally, and to burn off anything that has accumulated within it while it was running cool under lean burn.

I don't live in the sticks (maybe I do - small town of about 1600) but the metro area doesn't have annual inspections here either. As long as your lights work and the wheels don't come off, you're good.
__________________




Lead or follow. Either is fine.
  Reply With Quote
Old 02-02-2018, 01:05 PM   #5 (permalink)
EcoModding Lurker
 
Join Date: Dec 2008
Location: Western Canada
Posts: 46

2015 WRX - '15 Subaru WRX
90 day: 30.63 mpg (US)

2008 Suzuki SV650SA - '08 Suzuki SV650SA
90 day: 60.81 mpg (US)
Thanks: 1
Thanked 11 Times in 10 Posts
According to user Oil Pan 4 in This Thread, running lean doesn't seem to damage the cat. He seems to have quite a bit of experience running lean, so I took his word for it.
__________________

  Reply With Quote
Old 02-19-2018, 09:54 AM   #6 (permalink)
EcoModding Lurker
 
Join Date: Jun 2015
Location: Syracuse, NY
Posts: 11

Subi - '15 Subaru Impreza Premium
Thanks: 0
Thanked 0 Times in 0 Posts
I have been trying to get this done in my 2015 Impreza premium for a while! Do you think this method would work on a n/a Impreza like mine?
  Reply With Quote
Old 02-19-2018, 07:30 PM   #7 (permalink)
EcoModding Lurker
 
Join Date: Dec 2008
Location: Western Canada
Posts: 46

2015 WRX - '15 Subaru WRX
90 day: 30.63 mpg (US)

2008 Suzuki SV650SA - '08 Suzuki SV650SA
90 day: 60.81 mpg (US)
Thanks: 1
Thanked 11 Times in 10 Posts
Quote:
Originally Posted by quagss View Post
I have been trying to get this done in my 2015 Impreza premium for a while! Do you think this method would work on a n/a Impreza like mine?
I don't see why it wouldn't work well, but I don't think COBB engine management is an option for the NA Imprezas. You might want to see if RomRaider works for your engine.
__________________

  Reply With Quote
Old 02-19-2018, 07:40 PM   #8 (permalink)
Master EcoModder
 
Join Date: Jun 2016
Location: KY
Posts: 1,346

IGL - '04 Saturn Ion
Team Saturn
90 day: 56.19 mpg (US)
Thanks: 63
Thanked 364 Times in 268 Posts
I’m just a little envious of you guys which have aftermarket tuning support on factory PCM, lol... I want lean burn so bad, because the engine is at relatively low load at a decent cruising speed, so I imagine lean burn would help lots, but the only thing I can do is use a SAFC or go standalone...
__________________
My current Ecotec project...


My last Ecotec project...
  Reply With Quote
Old 02-20-2018, 02:23 PM   #9 (permalink)
home of the odd vehicles
 
rmay635703's Avatar
 
Join Date: Jun 2008
Location: Somewhere in WI
Posts: 3,874

Silver - '10 Chevy Cobalt XFE
Thanks: 495
Thanked 863 Times in 650 Posts
Quote:
Originally Posted by 19bonestock88 View Post
I’m just a little envious of you guys which have aftermarket tuning support on factory PCM, lol... I want lean burn so bad, because the engine is at relatively low load at a decent cruising speed, so I imagine lean burn would help lots, but the only thing I can do is use a SAFC or go standalone...
A dual EFIE will give you up to 15.2:1 which is better than nothing
  Reply With Quote
Old 02-27-2018, 02:47 AM   #10 (permalink)
Master EcoModder
 
Join Date: Jun 2016
Location: KY
Posts: 1,346

IGL - '04 Saturn Ion
Team Saturn
90 day: 56.19 mpg (US)
Thanks: 63
Thanked 364 Times in 268 Posts
Quote:
Originally Posted by rmay635703 View Post
A dual EFIE will give you up to 15.2:1 which is better than nothing
Dual EFIE? I don’t follow...

__________________
My current Ecotec project...


My last Ecotec project...
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com