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Old 11-07-2005, 11:39 AM   #1
StiPete
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'00 Impreza 2.5rs

Default Race gas info? (or higher octane)

I currently have a Protune map for 93 octane pump gas and I'm wondering if I'll see an increase in power if I run a higher octane gas?

I've heard the STi's ECU will only adjust itself up to 95 octane, any truth to this?

What would my best bet be if I wanted to give this a try?

I don't have any cats, so I don't know if I'd be better off using a leaded additive or if I should just keep it unleaded

I honestly don't have any real experience with trying to up the octane of my gas on this car.

Thanks for any help.

PS: I don't have a map made for race gas, I'll be using the Protune 93 octane map.
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Old 11-07-2005, 01:53 PM   #2
bboy
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You can likely increase power with octane, but you will have to alter the tuning to do so. The ECU will adjust "closed loop" fueling (it's a loop of optimization) but not "open loop". You are talking about power during WOT, and that is "open loop" fueling. There is some adjustment made by the ECU even during open loop, but that is usually in response to detonation (which hopefully you don't have going on right now).

If you are running the stock turbo and injectors, don't bother with race gas.
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Old 11-07-2005, 06:56 PM   #3
flycaster
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Quote:
Originally Posted by StiPete
I currently have a Protune map for 93 octane pump gas and I'm wondering if I'll see an increase in power if I run a higher octane gas?

I've heard the STi's ECU will only adjust itself up to 95 octane, any truth to this?
This has been debated for a while now, and the truth is I'm not sure anyone knows one way or the other. The ECU does adjust timing in small increments, and my tuners said there can be about a 3% increase. In my case, the car does feel like it makes more power...however, that could just as easily be a case of wishful thinking. I'll throw some in for track days, but for detonation safety, not additional power. If I get some, cool, but I'm not banking on it.

OTOH, if you're only talking about daily driving, I agree with bboy - you're simply wasting money.
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Old 11-07-2005, 07:11 PM   #4
nathansvt
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if you have a datalogger you can watch what the car is doing. There's a free datalogger out there that seems to work well. I'm using streettuner. My protuned map is a little on the aggressive side and so the car pulls some timing on pump gas. In my case I do see a benefit from race gas, but it takes about 8 long pulls for the ECU to learn it's safe to start ramping timing back up. Once it gets to the advance set in my maps, it stops advancing timing. Fueling seems to be unchanged.

Long story short, if your map is tuned to the ragged edge, you might see a benefit from higher octane gas. If not, it's of no benefit. If you want to know for sure, run some logs and look at the total advance or dynamic advance values.
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Old 11-07-2005, 08:47 PM   #5
Jon [in CT]
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Quote:
Originally Posted by nathansvt
Long story short, if your map is tuned to the ragged edge, you might see a benefit from higher octane gas.
ProTuners, almost without exception, claim to offer "conservative" or "safe" tunes. Such tunes should not be expected to show any increase in power with race gas.
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Old 11-08-2005, 05:21 PM   #6
OMEGA SUPREME
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Well ive run race gas on my TurboXS dynomap that was tuned on 93 and i swear your car just feels smoother (prob in my head) Plus race gas smells good
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Old 11-08-2005, 05:59 PM   #7
bboy
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Quote:
Originally Posted by OMEGA SUPREME
Plus race gas smells good
Now I understand.
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Old 11-09-2005, 11:27 AM   #8
kevin2.5rs
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I use Sunoco 94 with 93 oct map.
I noticed a difference when I started using the 94 vs 93
The power delivery feels a lot smoother with it
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