Militarybuilt Posted July 17, 2022 Share Posted July 17, 2022 SO my 05 LGT is getting about 14.5-15.5 MPG. I have the typical bolt on mods, GS TMIC, cobb catted DP, Cobb intake, perrin tube, catless up-pipe, q300 catback. It's been tuned by Shinji with plenty of datalogs but that was last fall. The car sat for two months this spring and when I finally got back to driving it my mileage is bad, real bad. I emailed Shinji but I haven't heard back. Plugs were done last fall before tuning as well. Anywhere I should start? The car idles and runs fine, it's just got an appetite for fuel and at $5.85/gal it hurts. Link to comment Share on other sites More sharing options...
awfulwaffle Posted July 17, 2022 Share Posted July 17, 2022 What's your driving style like, to start? 14.5-15.5 MPG may be reasonable if you're ripping around everywhere, not so much if you're just cruising down the freeway at 70-80 mph and that's what you're averaging. Link to comment Share on other sites More sharing options...
Militarybuilt Posted July 17, 2022 Author Share Posted July 17, 2022 1 hour ago, awfulwaffle said: What's your driving style like, to start? 14.5-15.5 MPG may be reasonable if you're ripping around everywhere, not so much if you're just cruising down the freeway at 70-80 mph and that's what you're averaging. That's me trying to baby it back and forth to work and around town. Shifting at 2500, not going over 3700 and cruising at 60-70. Link to comment Share on other sites More sharing options...
awfulwaffle Posted July 17, 2022 Share Posted July 17, 2022 Yeah that's not right. How does your cruise AFR look? Driving steady, not accelerating. Link to comment Share on other sites More sharing options...
Militarybuilt Posted July 17, 2022 Author Share Posted July 17, 2022 1 minute ago, awfulwaffle said: Yeah that's not right. How does your cruise AFR look? Driving steady, not accelerating. I don't have a wideband but through the AP I think it's saying 15.5:1, which is a bit rich. Link to comment Share on other sites More sharing options...
awfulwaffle Posted July 17, 2022 Share Posted July 17, 2022 That's actually a bit lean. No way Shinji is targeting that, unless he was trying to make you a pretty extreme economy map. Next thing I'd look at is AF Learning 1, and AF Correction 1. With a steady 15.5 AFR at cruise, I'd expect these to be high positive. AF Learning 1 maxes out at 15%, and Correction at 25%. If these are pegged or close to it, your car has a large air leak and is dumping fuel to compensate. A 15.5 AFR means it's run out of room to adjust and still can't hit target, which should be in the 14.2-14.7 range. That, or one of the sensors (front O2 or MAF) responsible for closed loop fueling has gone bad. Hopefully that's all it is, because it's a simple fix. 1 Link to comment Share on other sites More sharing options...
Militarybuilt Posted July 17, 2022 Author Share Posted July 17, 2022 10 minutes ago, awfulwaffle said: That's actually a bit lean. No way Shinji is targeting that, unless he was trying to make you a pretty extreme economy map. Next thing I'd look at is AF Learning 1, and AF Correction 1. With a steady 15.5 AFR at cruise, I'd expect these to be high positive. AF Learning 1 maxes out at 15%, and Correction at 25%. If these are pegged or close to it, your car has a large air leak and is dumping fuel to compensate. A 15.5 AFR means it's run out of room to adjust and still can't hit target, which should be in the 14.2-14.7 range. That, or one of the sensors (front O2 or MAF) responsible for closed loop fueling has gone bad. Hopefully that's all it is, because it's a simple fix. I did a boost leak test the other day and it was solid no leaks. I'll have to get the laptop hooked up again and see what's it's reading for Learning and Correction, I should also get an actual wideband in the car like I should have a long time ago. I'm wondering if it has something to do with having the de-fouler in with the O2 to shut the engine light off? I have the datalog to send to Shinji as well whenever he responds, until then I just wont drive the car. My truck at 12.5mpg is cheaper to drive at this point... Link to comment Share on other sites More sharing options...
Infosecdad Posted July 17, 2022 Share Posted July 17, 2022 (edited) What was your MPG before parking it for a number of months? Edited July 17, 2022 by Infosecdad Link to comment Share on other sites More sharing options...
Militarybuilt Posted July 17, 2022 Author Share Posted July 17, 2022 15 minutes ago, Infosecdad said: What was your MPG before parking it for a number of months? 17-18mpg-ish. Still not great. Link to comment Share on other sites More sharing options...
awfulwaffle Posted July 17, 2022 Share Posted July 17, 2022 Even if the rear O2 is entirely absent, the car should be targeting around a 13.8 AFR assuming the baseline target is 14.7ish in the tables. That'll drop your mileage to 18-20 in my experience. That said, any tuner worth their salt should be able to shut off the rear O2 compensation in your car because those tables have been known for a long time. You shouldn't even need the de-fouler, or even the rear O2 sensor to be plugged in, and still hit the proper 14.7 target and get decent gas mileage. If you have no air leaks, I'd still be taking a look at those fuel trims. That will help us see if there's something wrong in the closed loop fueling calculations. 1 Link to comment Share on other sites More sharing options...
Infosecdad Posted July 17, 2022 Share Posted July 17, 2022 6 minutes ago, Militarybuilt said: 17-18mpg-ish. Still not great. Is that mostly in-town driving or hwy or a mix? I get 17-18mpg in town, and 25-26mpg at 75-80 or ~28mpg at 60-65mpg. Link to comment Share on other sites More sharing options...
Militarybuilt Posted July 17, 2022 Author Share Posted July 17, 2022 15 minutes ago, awfulwaffle said: Even if the rear O2 is entirely absent, the car should be targeting around a 13.8 AFR assuming the baseline target is 14.7ish in the tables. That'll drop your mileage to 18-20 in my experience. That said, any tuner worth their salt should be able to shut off the rear O2 compensation in your car because those tables have been known for a long time. You shouldn't even need the de-fouler, or even the rear O2 sensor to be plugged in, and still hit the proper 14.7 target and get decent gas mileage. If you have no air leaks, I'd still be taking a look at those fuel trims. That will help us see if there's something wrong in the closed loop fueling calculations. Makes sense. Hopefully he can figure it out, if not I'll be looking for another tuner or sack up and get an actual dyno tune. Downside is I;ll have to drive three hours south to Green Bay as that's the closest Subaru tuner/dyno. Link to comment Share on other sites More sharing options...
awfulwaffle Posted July 17, 2022 Share Posted July 17, 2022 For sure, good luck. Let us know how it goes. I just realized, the defouler may be necessary these days. I keep forgetting about the Cobb Green Speed stuff - that rear O2 comp table is probably no longer available if you're tuning via Cobb. Link to comment Share on other sites More sharing options...
Militarybuilt Posted July 17, 2022 Author Share Posted July 17, 2022 Just now, awfulwaffle said: For sure, good luck. Let us know how it goes. I just realized, the defouler may be necessary these days. I keep forgetting about the Cobb Green Speed stuff - that rear O2 comp table is probably no longer available if you're tuning via Cobb. Yea I don't know what program he is using. But I do have a local source that uses an open source program via a tuner in the UK, that may be the ticket too. Link to comment Share on other sites More sharing options...
Enlight Posted July 23, 2022 Share Posted July 23, 2022 I'm not knowledgeable about AFR's, but have you check whether your MAF is clean? I was dumping extra fuel and found that my MAF was filthy. muFreight.co A JDM Container Sharing Service from Japan to NYC Website | Instagram | Email Bessie II's Thread Link to comment Share on other sites More sharing options...
Militarybuilt Posted July 23, 2022 Author Share Posted July 23, 2022 1 hour ago, Enlight said: I'm not knowledgeable about AFR's, but have you check whether your MAF is clean? I was dumping extra fuel and found that my MAF was filthy. Yea I definitely thought about that, so I cleaned it haha. But unfortunately it didn't help. 1 Link to comment Share on other sites More sharing options...
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