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-   -   Low Octane Fuel Economy Tune? (http://legacygt.com/forums/showthread.php?t=161061)

05COLEGGT 04-29-2011 09:04 AM

Low Octane Fuel Economy Tune?
 
Has anyone thought about developing a low boost low octane tune for the Accessport? With the rising cost of gasoline I know I'd appreciate having the option to run lower octane without fear of detonation. Wouldn't be too hard to use Cobb's economy map as a baseline and retard timing to keep detonation at bay. :)

bmx045 04-29-2011 09:21 AM

ummmmmm


well


you could just run wastegate boost with a slower throttle plate opening (much like si-drive). It would suck if you put in 87 octane with an economy map then if you want power, you can switch the map but then what? You have a tank of 87 in there lol...

BAC5.2 04-29-2011 09:33 AM

Sounds like you bought the wrong car.

bmx045 04-29-2011 09:36 AM

http://t2.gstatic.com/images?q=tbn:A...d_hn8e1Qaw&t=1

RabidWombat 04-29-2011 09:42 AM

Quote:

Originally Posted by 05COLEGGT (Post 3369575)
Has anyone thought about developing a low boost low octane tune for the Accessport? With the rising cost of gasoline I know I'd appreciate having the option to run lower octane without fear of detonation. Wouldn't be too hard to use Cobb's economy map as a baseline and retard timing to keep detonation at bay. :)

Heh, the rising gas prices around here have actually made me care less. Does it really matter when 87 is $4.27 and 91 $4.47?

bmx045 04-29-2011 09:42 AM

Quote:

Originally Posted by RabidWombat (Post 3369636)
Heh, the rising gas prices around here have actually made me care less. Does it really matter when 87 is $4.27 and 91 $4.47?


over here in new england 93 is $4.25 :lol:

cypher0117 04-29-2011 09:50 AM

guess it pays to live in the middle of nowhere sometimes... 93 octane is $3.85 by me

to the OP: you probably don't want to do that because likebmx045 said, you'd have to know you wanted power when you fill up your tank otherwise you'd have sub-par gas in there

BAC5.2 04-29-2011 09:53 AM

I think I paid $4.299 last time I filled up.

05COLEGGT 04-29-2011 10:09 AM

Ah come on guys. I expected more out of a Subie forum. Lets assume I'm not a newbie and have been tuning fuel injected cars for years and know the difference between 85 and 91-93 octane. My 'new to me' 05 Leggy is my new Daily Driver and I would really like to not have to fill up with premium every day. I understand I won't get max performance out of my engine by using lower octane but the cost savings would be nice considering my daily commute.
A nice safe tune could provide decent economy gains as well as allow a lower octane fuel especially given the super low compression ratio of the EJ255 motor. I find it hard to believe nobody else on this forum would be interested.

BAC5.2 04-29-2011 10:13 AM

Why'd you buy a car requiring premium fuel for a daily driver if you didn't want to put premium fuel in it?

bmx045 04-29-2011 10:14 AM

Quote:

Originally Posted by BAC5.2 (Post 3369673)
Why'd you buy a car requiring premium fuel for a daily driver if you didn't want to put premium fuel in it?




/thread

05COLEGGT 04-29-2011 10:27 AM

I bought the car because I like it, and it has decent power. I'm coming from a completely race built 400+whp Hyundai Tiburon running E85 and tuned by me, so I know what I'm doing and mostly what I'm talking about. lol
Mfrs base their octane rating on what gives the most safe and reliable peak performance. Most turbocharged engines can actually make power using lower octane fuel if built and tuned correctly. Actually most newer management systems can adapt and provide peak performance regardless of octane level. Look at the new Sonata Turbo for example. Its rated for regular (85-87) unleaded. Granted that it has direct injection but the concept is still the same. It can actually make more power on Premium due to increased knock threshold but its designed to run on regular.
If you guys aren't interested in a lower octane tune because all you care about is MAX POWA then that's your prerogative. I myself would like to have more options than just 91-93 octane fuel and with full ECU programmability that is a viable option.

BAC5.2 04-29-2011 10:34 AM

I guess I'm confused.

You bought a turbo car, with the intention of tuning it for fuel that will make it have almost as much power as a naturally aspirated version of the same car? Seems like you bought the wrong car to me. If you wanted the economy and power of a 2.5i, then why didn't you just get a 2.5i?

No one is questioning your tuning abilities, or whatever your talking about with the Hyundai. But go ahead and tune your LGT to run 87 octane. Let us know how it works out.

Keep in mind, you bought a car that has "decent power" and all you want to do with it, is make less power and get worse fuel economy.

bmx045 04-29-2011 10:35 AM

ask a fellow subaru tuner. Tuning for E85 wouldn't be a problem, that's pretty common amongst subaru performance lovers. You could tune it extremely conservative in terms of timing advance BUT with the nature of E85 itself, you're gunna go through more fuel than if you were to tune it for 87 or 91 specifically.

Typically E85 cars get worse mileage, though the fuel is cheaper. So I don't know why you'd go through the trouble of doing so.


aaaaand

what BAC said...

cypher0117 04-29-2011 10:44 AM

you/someone can probably tune the car to run on 87 octane. Probably reliably as well. I wouldn't do it though because I don't think the car has enough power stock on 91 octane. That and regardless of fuel prices, you'll only be spending ~$3 more per tank anyways. is $3 worth the power downgrade?


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