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Old 08-18-2005, 10:00 PM   #1
Davenow
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Default OK EM gurus. Riddle me this

A car.
An STI
Cruising at normal highway speeds
Light throttle, as normal cruising
17.5-1 a/f's
normal EGTS
better mpg




The million dollar question

1. Is this possible
2. What EM can do this
3. How did this person do it
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Old 08-18-2005, 10:08 PM   #2
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Informative link stolen from another thread.

http://www.avweb.com/news/columns/182084-1.html

My guesses are

1. Yes
2. Any tunable EM?
3. By tuning for "Economy", ie, lean to the point that power and EGT's drop, as described by the airplane guy
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Old 08-18-2005, 10:27 PM   #3
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Could also be the A/F was way off. I've never been able to run my car any leaner than about 15:1 cruising around town, 15.3:1 or so on the highway (low LOW load). After that it just starts missing and having all sorts of issues.

You'll need a standalone to make these changes though - hydra, aem... I don' think you can do it with a reflash, I seem to remember seeing "00" for 14.7 and that you couldn't go leaner than that.
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Old 08-18-2005, 10:41 PM   #4
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I've logged AFR's of 24 when off throttle with the stock ECU, maybe you are thinking of something else?
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Old 08-18-2005, 10:43 PM   #5
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you don't tune off throttle, thats fuel cut in most ECUs, including the stock ECU.
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Old 08-18-2005, 11:16 PM   #6
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Ah, I think I misunderstood your original statement, I didn't realize a reflash specifies a new target A/F to the stock control.
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Old 08-19-2005, 01:33 AM   #7
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1. Yes
2. TEC-3
3. Tec has RPM/LOAD AFR map. You can set any target for closed loop, as
long as it's measurable - so WB. 17.5 AFR at 3000 RPM - EGT are normal, but
I wouldn't go above 3500.

BobR
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Old 08-19-2005, 01:50 AM   #8
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You should be able to adjust part throttle a/f ratio with reflashes or standalones(access tuner, ecutek, hydra, aem, tec,...). From what i've heard, the stock ecu runs 14.7 to 1 for emissions purposes(so the cats work efficiently). If ya remove the cats, there's no real reason to run 14.7 to 1 at part throttle other then lack of a/f ratio control. 14 to 1 would create more power, and 16 to 1 would be better for fuel economy. One thing to think about in case you wanna run 19 to 1(or something really lean) is that there's a point where making the a/f ratio leaner hurts fuel economy. I've heard that 17.5 to 1 is leaner then the a/f ratio for best fuel economy, so there's really no reason to run so lean unless you want to hurt power output and hurt fuel economy.

peace
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Old 08-19-2005, 02:43 AM   #9
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except 14:1 (or higher) doesn't make more power. sure it saves gas and burns cleanest, but it doesn't make more power than a faster burning AFR (say 12.5:1). I say if you can run it that lean go for it, if MPG's is your goal.
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Old 08-19-2005, 09:22 AM   #10
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1) Yes
2) Utec
3) Thats for you to figure out.

TMS

hint wrxhackers
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Old 08-19-2005, 10:11 AM   #11
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with a utec, i guess if youre cruising on the highway and it requires more than 19% throttle (20% is the earliest you can enter OLF) you could just tune your 10 column for leaner than stoich AFRs. not that hard.

cant do it with a reflash eloquently...you could clamp the stock O2 sensor...or remap the OLF crossover and set it to 0% throttle, and just tune the car entirely in OLF...but you wouldnt get the benefits of automatically adjusting for fuel quality, etc...
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Old 08-19-2005, 10:17 AM   #12
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Quote:
Originally Posted by happasaiyan
with a utec, i guess if youre cruising on the highway and it requires more than 19% throttle (20% is the earliest you can enter OLF) you could just tune your 10 column for leaner than stoich AFRs. not that hard.
Check out my thread over on hackers on how to trick the Utec to go into OLF erlier than 20%TPS.

TMS
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Old 08-19-2005, 10:22 AM   #13
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you were averaging 10mpg??? yeah, thats bad.

nice trick- good job!
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Old 08-19-2005, 10:25 AM   #14
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tms- are you using ECU ignition advance while cruising? what are your ignition advance values like during cruising even if you arent?
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Old 08-19-2005, 10:27 AM   #15
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Right now I have started with the stg1 Utec base map. I changed the 10% colum to read ECU. So far no det.
Boost is set to 7psi. I am building a fuel economy map.

TMS
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Old 08-19-2005, 10:30 AM   #16
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i was just wondering if the stock ecu was advancing ignition (maybe why your EGTs were lowered)...and curious as to what they would put them at. hopefully the knock sensor sensitivity is high enough at lower rpms...but then again, knock is so much harder to even create at lower rpms.
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Old 08-19-2005, 10:43 AM   #17
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Quote:
Originally Posted by happasaiyan
i was just wondering if the stock ecu was advancing ignition (maybe why your EGTs were lowered)...and curious as to what they would put them at. hopefully the knock sensor sensitivity is high enough at lower rpms...but then again, knock is so much harder to even create at lower rpms.
My knock sensitivity is turned way up from the default settings. That was the first thing I tuned on this motor. 3 weeks to tune 6 numbers. I tuned the knock sens to be right at the noise floor of the motor. I know with ECU in the load colum I am running the Utec will not pull timing, but the CEL will flash letting me know something is not right.
The ECU is running ~ the same timing. I don't have a log yet but my SM3 timing display has not changed.

TMS
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Old 08-19-2005, 10:57 AM   #18
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cool, thanks for the info!
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Old 08-19-2005, 11:06 AM   #19
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1. yup
2. any EM that has closed loop and an reads a WIDEBAND SENSOR a narrow band won't work up there
3. dunno about it working well .. seems really lean
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Old 08-19-2005, 02:54 PM   #20
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What bugs me is that apparently there is a limitation with the stock ECU such that you can't target the fueling to go leaner than 14.7:1. Thus, StreetTUNER won't let you target leaner burns either. The cool thing is that the stock near-wideband sensor is capable of doing lean burns. You don't need a full wideband. It is accurate into the 16's.

t
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Old 08-19-2005, 03:28 PM   #21
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The stock o2 sensor might read a/f ratios richer and leaner then 14.7 to 1, but who knows how accurate it is when it's reading richer and leaner a/f ratios? From what I've heard, it was really only made to target 14.7 to 1. I know of a few people who checked the a/f ratio on the stock o2 sensor verse a wbo2 sensor while going a little richer then 13 to 1, and they weren't so close.......... I used to tell people that they could adjust the fueling of their lower load columns without a wbo2 since the stock o2 sensor could read downto 12.5 to 1(or whatever), but now I'm kinda leaning away from using the stock o2 sensor for any tuning purposes.

peace

Last edited by hippy; 08-19-2005 at 03:58 PM.
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Old 08-19-2005, 09:47 PM   #22
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Quote:
I used to tell people that they could adjust the fueling of their lower load columns without a wbo2 since the stock o2 sensor could read downto 12.5 to 1(or whatever), but now I'm kinda leaning away from using the stock o2 sensor for any tuning purposes.
I noticed this too when I was writing and testing my logging software. I had the program keeping the stock O2 readings and adding the WB data to the logs too, so you could compare them. Boy were they WAY off from each other, and my sensors weren't that far apart from each other, so I don't think much of the deviation is from sensor placement.

I would venture to say that the further from 14.7 the stock O2 sensor gets, it logarithmically gets more and more INaccurate. From what I've seen from data logs with both stock and wideband reading taken simultaneously, I wouldn't trust the stocker with anything richer than 13.5, and even then it's not completely accurate.

-jason
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