Author Topic: Octane Question  (Read 4488 times)

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Offline Scoobum

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Octane Question
« on: March 10 2013, 07:46:09 AM »
If you let gas sit around...does the octane level drop. If so...how quickly.
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Offline Steve Wood

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Re: Octane Question
« Reply #1 on: March 10 2013, 11:00:22 AM »
down here, they say it is dropping within a month unless sealed air tight
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Offline daveismissing

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Offline earlbrown

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Re: Octane Question
« Reply #3 on: March 10 2013, 08:53:36 PM »
Yes, the aromatics are the first thing to flash off. Since those and the ethanol are the first thing to go, the octane does drop.

Keep in mind our fuel systems are sealed so it's not as big of a deal as it would be on a 60's car with a vented cap and vented float bowls (and expecting lead as an octane booster)
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Offline richmobj

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Re: Octane Question
« Reply #4 on: March 14 2013, 07:57:58 AM »
Speaking of octane... Is it true that if you install an alky system, you can run regular 87 octane gasoline and not have any problems as long as you don't go above stock boost levels?

Offline Steve Wood

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Re: Octane Question
« Reply #5 on: March 14 2013, 10:08:59 AM »
I think so but calculate how long it will cost to pay for the sytem and the methanol you are buying
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Offline earlbrown

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Re: Octane Question
« Reply #6 on: March 14 2013, 12:29:31 PM »
and then calculate how long you can leave the wastegate at the stock boost level.
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Offline larrym

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Re: Octane Question
« Reply #7 on: March 14 2013, 02:12:26 PM »
not long Earl  :P
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Offline daveismissing

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Re: Octane Question
« Reply #8 on: March 14 2013, 08:36:16 PM »
Stock boost should be within the limits of 87 octane without Alky- No?
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Offline TWIN86GNS

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Re: Octane Question
« Reply #9 on: March 14 2013, 10:48:23 PM »
Stock boost should be within the limits of 87 octane without Alky- No?

Depends on the chip and how much timing it has I would imagine.
 
If you are going to get an alcohol kit (most cars should) then bump the boost and the timing and enjoy the car!!   :rock:
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Offline earlbrown

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Re: Octane Question
« Reply #10 on: March 15 2013, 12:15:10 AM »
Stock boost should be within the limits of 87 octane without Alky- No?


I would guess the answer would be iffy. Oil control, outside temp and intercooler efficiency would be big factors.  12#'s would probably be doable on low octane ESP if the chip is burned for much higher boost.
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Offline SuperSix

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Re: Octane Question
« Reply #11 on: March 15 2013, 01:30:29 PM »
The ethanol doesn't evaporate - it sits there and absorbs a shit ton of moisture. Then the fuel separates. Especially in boat applications. Google it - ethanol is shit, and Stabil/etc don't work well.
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Offline daveismissing

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Re: Octane Question
« Reply #12 on: March 15 2013, 02:31:09 PM »
Checking back - 87 octane is roughly regular gas in 1987.
I can verify the car ran fine(street driven)  on regular gas stock chip- stock boost.
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Offline TWIN86GNS

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Re: Octane Question
« Reply #13 on: March 15 2013, 08:29:10 PM »
Checking back - 87 octane is roughly regular gas in 1987.
I can verify the car ran fine(street driven)  on regular gas stock chip- stock boost.
Original headgaskets
Dave,
 
The gas of 1987 - 1990 is MUCH different than the gas of today.  The gas back when our cars were new was decent compared to todays crap.  If you don't believe me than put 87 octane in the tank and lets go for a quick WOT blast to OD while running a stock chip.   :013:
Paul Beal
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1986 GN  #1,  11.38 @ 120.25 mph  with a 1.501 60'
1986 GN  #2,  13.25 @ 102.95 mph with a 2.086 60'

Offline motorhead

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Re: Octane Question
« Reply #14 on: March 16 2013, 09:35:46 AM »
Dave,
 
The gas of 1987 - 1990 is MUCH different than the gas of today.  The gas back when our cars were new was decent compared to todays crap.  If you don't believe me than put 87 octane in the tank and lets go for a quick WOT blast to OD while running a stock chip.   :013:

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