91 octane ?
Page 1 of 3 123 LastLast
Results 1 to 15 of 41

This is a discussion on 91 octane ? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I have used 87 octane in my 04 rex since purchasing it about 5 months ago. I was wondering if ...

  1. #1
    Registered User
    Join Date
    Apr 2004
    Location
    St. Louis
    Posts
    43

    91 octane ?

    I have used 87 octane in my 04 rex since purchasing it about 5 months ago. I was wondering if anyone had done the same and then reset the ECU to accomodate for changing to 91 or higher octane?

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Registered User
    Join Date
    Aug 2003
    Location
    Boyertown, Pa.
    Posts
    75
    Yikes
    I'm surprised no one else has jumped all over this.
    IIRC, the manual, the window sticker, and various other paperwork and labels clearly document that a WRX REQUIRES PREMIUM UNLEADED. The last time I looked, 87 octane was REGULAR.
    IF I were you, I'd get on the 91 octane right away, and do a reset. Your car must have "learned" all sorts of compromises to run that long on 87.

  4. #3
    Registered User soggynoodles's Avatar
    Join Date
    Jun 2004
    Location
    Palo Alto
    Posts
    495

    Re: 91 octane ?

    Originally posted by zillig04
    I have used 87 octane in my 04 rex since purchasing it about 5 months ago. I was wondering if anyone had done the same and then reset the ECU to accomodate for changing to 91 or higher octane?
    yea reset the ecu and get some 91 in the tank asap!
    Mine's a Stock-a-roo

  5. #4
    sss
    sss is offline
    Registered User
    Join Date
    Jul 2007
    Posts
    10

    91 octane?

    I'm a newb here, but I've read on a number of sites that the ECU will adjust to 87 octane, with a loss of power of course, but that there's no insidious long-term effects to those adjustments/compromises, other than the power.

    Of course, I've been told the 91 octane I get is too cheap and causing a little problem I have, so wtf do I know?

  6. #5
    Registered User WRX13oy's Avatar
    Join Date
    Jul 2003
    Location
    SOCAL!! 91752
    Posts
    6,979
    wow.
    SOCAL F4#02 OG member

    2002 PSM WRX stage 6
    2007 Kawasaki Ninja ZX6R

  7. #6
    Registered User wrxisthebest's Avatar
    Join Date
    Jun 2007
    Location
    Angels Camp, CA
    Posts
    0
    ouch ur engine must be hurtin!!!!

  8. #7
    UnBanned Sinister's Avatar
    Join Date
    Nov 2006
    Location
    Denver Metro Area
    Posts
    17,548
    I Support ClubWRX
    Quote Originally Posted by sss View Post
    I'm a newb here, but I've read on a number of sites that the ECU will adjust to 87 octane, with a loss of power of course, but that there's no insidious long-term effects to those adjustments/compromises, other than the power.

    Of course, I've been told the 91 octane I get is too cheap and causing a little problem I have, so wtf do I know?
    Quote Originally Posted by WRX13oy View Post
    wow.
    +1


    sss - B/c you're new, I'm not gonna say nothin mean, but check the thread dates buddy. You're helping someone out that had their issue in 2004. Thanks! Welcome to the site and feel free to introduce yourself in the New Member Hangout if you haven't already!
    Kevin
    Moderator
    Sinister's Blowoff Valve FAQ
    WRX Gas Mileage FAQ
    Sinister's Progress Thread - 430whp 429wtq - Sold
    Firearms Enthusiasts Thread

    The Sheriff's Star at the bottom left corner rates a user's reputation.
    If you found a user's post to be helpful or quite the opposite, please make it known to them by clicking the Star!

  9. #8
    Registered User D0WNxSH1FT's Avatar
    Join Date
    Oct 2004
    Location
    Westchester Cnty, NY
    Posts
    6,545
    Quote Originally Posted by sss View Post
    I'm a newb here, but I've read on a number of sites that the ECU will adjust to 87 octane, with a loss of power of course, but that there's no insidious long-term effects to those adjustments/compromises, other than the power.

    Of course, I've been told the 91 octane I get is too cheap and causing a little problem I have, so wtf do I know?
    DO NOT USE 87.

    You do not want to use low octane fuel with a turbocharged car. What you read is for Naturally Aspirated cars. Octane prevents knock which prevents your engine from detonating. You MUST use 91 or higher octane in a turbocharged car.

    Is your 91 oct bad? probably not. If you have a problem with you car please search your symptoms and then after if you still arent sure post in the Troubleshooting forum.
    2008 Satin White Pearl WRX Sedan w/ Navi
    2005 San Remo Red WRX Sedan w/ VF34 (traded)
    Pi Kappa Alpha | New England Flat 4

  10. #9
    sss
    sss is offline
    Registered User
    Join Date
    Jul 2007
    Posts
    10

    91 octane

    Well, I was really asking and not trying to help. Since the replies to the poster didn't really explain anything, I wasn't sure if they were correct or just talking smack. I'm wondering if that's really true, and if it is, what are the consequences of using 87 octane. And I've never put a drop of 87 octane in my car, I'm just curious what will happen.

    So, what will happen?

  11. #10
    Registered User D0WNxSH1FT's Avatar
    Join Date
    Oct 2004
    Location
    Westchester Cnty, NY
    Posts
    6,545
    Quote Originally Posted by sss View Post
    Well, I was really asking and not trying to help. Since the replies to the poster didn't really explain anything, I wasn't sure if they were correct or just talking smack. I'm wondering if that's really true, and if it is, what are the consequences of using 87 octane. And I've never put a drop of 87 octane in my car, I'm just curious what will happen.

    So, what will happen?
    Your engine will knock and then detonate. Please search 87 octane for more information.
    2008 Satin White Pearl WRX Sedan w/ Navi
    2005 San Remo Red WRX Sedan w/ VF34 (traded)
    Pi Kappa Alpha | New England Flat 4

  12. #11
    Registered User WRX13oy's Avatar
    Join Date
    Jul 2003
    Location
    SOCAL!! 91752
    Posts
    6,979
    well. his engine is still running after 5 months of 87.

    probably has about 5 more months till its kaput
    SOCAL F4#02 OG member

    2002 PSM WRX stage 6
    2007 Kawasaki Ninja ZX6R

  13. #12
    UnBanned Sinister's Avatar
    Join Date
    Nov 2006
    Location
    Denver Metro Area
    Posts
    17,548
    I Support ClubWRX
    Quote Originally Posted by sss View Post
    Well, I was really asking and not trying to help. Since the replies to the poster didn't really explain anything, I wasn't sure if they were correct or just talking smack. I'm wondering if that's really true, and if it is, what are the consequences of using 87 octane. And I've never put a drop of 87 octane in my car, I'm just curious what will happen.

    So, what will happen?
    In extreme cases you can very possibly cause catastrophic engine failure. the use of 91 (93 is recommended in your manual) is to prevent detonation. Pressure, advanced timing, high heat, low octane, high compression, all cause detonation. Turbo engines use low compression, but have high pressure (from the turbo) high heat (1500-1600 EGTs) and therefore must use high octane to help prevent detonation.
    Kevin
    Moderator
    Sinister's Blowoff Valve FAQ
    WRX Gas Mileage FAQ
    Sinister's Progress Thread - 430whp 429wtq - Sold
    Firearms Enthusiasts Thread

    The Sheriff's Star at the bottom left corner rates a user's reputation.
    If you found a user's post to be helpful or quite the opposite, please make it known to them by clicking the Star!

  14. #13
    Registered User D0WNxSH1FT's Avatar
    Join Date
    Oct 2004
    Location
    Westchester Cnty, NY
    Posts
    6,545
    Quote Originally Posted by WRX13oy View Post
    well. his engine is still running after 5 months of 87.

    probably has about 5 more months till its kaput
    lol, well hes just asking a hypo, he doesnt actually use 87.

    Heres some info for SSS:

    "If you've read How Car Engines Work, you know that almost all cars use four-stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. (See How Car Engines Work for details.)

    The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

    The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more."
    2008 Satin White Pearl WRX Sedan w/ Navi
    2005 San Remo Red WRX Sedan w/ VF34 (traded)
    Pi Kappa Alpha | New England Flat 4

  15. #14
    UnBanned Sinister's Avatar
    Join Date
    Nov 2006
    Location
    Denver Metro Area
    Posts
    17,548
    I Support ClubWRX
    Quote Originally Posted by D0WNxSH1FT View Post
    lol, well hes just asking a hypo, he doesnt actually use 87.

    Heres some info for SSS:

    "If you've read How Car Engines Work, you know that almost all cars use four-stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. (See How Car Engines Work for details.)

    The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

    The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more."

    Good explanation.. Our engines are low compression by nature (8.2-8.4) But the introduction of forced induction increases cylinder pressure which doesn't increase the compression ratio, but rather increases the amount of fuel and air that are introduced into the cylinder during the cycle. This increases the cylinder pressure which also increases the chance for detonation. Same exact concept as DownXSh1ft explained, just in a turbo sense.

    (sorry if I stepped on your toes.. I was just adding! )
    Kevin
    Moderator
    Sinister's Blowoff Valve FAQ
    WRX Gas Mileage FAQ
    Sinister's Progress Thread - 430whp 429wtq - Sold
    Firearms Enthusiasts Thread

    The Sheriff's Star at the bottom left corner rates a user's reputation.
    If you found a user's post to be helpful or quite the opposite, please make it known to them by clicking the Star!

  16. #15
    Registered User D0WNxSH1FT's Avatar
    Join Date
    Oct 2004
    Location
    Westchester Cnty, NY
    Posts
    6,545
    Quote Originally Posted by Sinister View Post
    (sorry if I stepped on your toes.. I was just adding! )
    /banstick
    Very well said turning it around to work for a turbo engine.
    2008 Satin White Pearl WRX Sedan w/ Navi
    2005 San Remo Red WRX Sedan w/ VF34 (traded)
    Pi Kappa Alpha | New England Flat 4

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •