Jump to content

Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse

- - - - -

Turbo and octane requirements for '03 Baja

  • Please log in to reply
8 replies to this topic



    USMB Regular

  • Members
  • PipPipPip
  • 88 posts
  • Tennessee

Posted 13 September 2003 - 12:00 AM

I have requested information from three different turbo outfits referenced in this forum and have yet to receive any reply. My main question is : Is there a turbo set-up that allows the use of 87 octane unleaded fuel? I am thinking of purchasing either a turbo or supercharger set-up for my '03 Baja and would like to know what I am getting into. So far, I am like Schultz: I know Nothing!:banghead:

#2 applegump


    Eat, Live, Breath Subaru

  • Members
  • 316 posts
  • CH

Posted 13 September 2003 - 11:17 AM

Just a thought, wouldn't a factory baja turbo be cheaper than going custom?

#3 Strakes


    Kaboom? Kaboom?

  • Members
  • 520 posts
  • Knoxville

Posted 13 September 2003 - 01:48 PM

Some turbo-charging systems will allow you to run on 87 octane...but some will require premium fuel. My old Volvo and my friend's current Saab recommended 91 octane or better, but the computer can automatically adjust for a lower octane at the expense of performance...horsepower & torque. The owner's manual stated that 91 octane was recommended, but 87 can be used. Both mine and my friend's Saab were the "lower-pressure" turbos...not the fully blown "high-pressure" versions. I think the car's computer would adjust the timing via information from the knock sensor to compensate for lower octane...but I am not sure.

#4 wrxsubaru


    1000+ Super USER!

  • Members
  • 1,294 posts
  • Seattle Washington US

Posted 13 September 2003 - 05:01 PM

the stock turbo stup sould alow you to run 87 octane, but it may ping on hotter days, 89 seems like it would alow the car to run with out worry of detonation.



    USMB Regular

  • Members
  • PipPipPip
  • 88 posts
  • Tennessee

Posted 14 September 2003 - 05:19 AM

Applegump, I will bet you are right that a turbo system from Subaru would be all around cheaper than aftermarket and it would all be worked out. However, how much would the car cost over a na version and could I roll this one and not get burned at finance.

Thanks again for the good input, guys. Maybe you can tell me what is next in line for increasing torque out of this existing engine.

#6 calebz


    Andys Coupe killed my cat

  • Administrator
  • 7,547 posts
  • Tacoma

Posted 14 September 2003 - 08:28 AM

I have had all sorts of factory turbo cars.. Saabs, Volvos, Subarus, mitsubishis.. And even a couple of aftermarket turbos.. You really should run any turbo I have ever seen with the max octane you can get at the pump.. I have, both by experiment and by accident run 87 an 89 octane in my saabs and my subarus(the 2 turbo cars I have the most experience with) and I have had terrible results in relation to how well the car runs, Idles and performs.. If you have the money to spend on a turbo kit for a car, don't cheap out and put crappy gas in it.. I found some dyno results a few years ago, showed that an N/A honda got more power on 89 than 92 octane.. but the turbo Saab(95) got substantially more power with 92 octane.

Like I said above, I have never seen a turbo car that likes anything under 91 octane.. And since we have 93 down here, my soob is even happier.

#7 ScoobySchmitty


    I am The Stig.

  • Members
  • 475 posts
  • Kalamazoo

Posted 14 September 2003 - 11:01 AM

I think that with a turbo system, you will definitely want a higher octane. Higher octane fuel takes more energy to ignite than regular fuel, so it is used in HIGHER COMPRESSION engines. An engine set up for turbo has around an 8.0:1 compression ratio, WITHOUT the turbo charge. I'm not sure what the compression is with the turbo, but I am ASSUMING (keyword, so don't flame me experts!) that it is around 10.0-11.00:1 compression. When you compress the fuel/air mixture in the cylinder, the air heats up, and that heat ITSELF can ignite the fuel! However, the higher the octane, the smaller the chance that the fuel will prematurely ignite before the piston reaches full compression. A car's computer can compensate for this pre-ignition on lower octane fuels, but as Strakes and calebz said, your car will run horribly. Hope this helps out!


#8 wrxsubaru


    1000+ Super USER!

  • Members
  • 1,294 posts
  • Seattle Washington US

Posted 14 September 2003 - 11:37 PM

It realy depends on the design. When i had my 87 turbo supra it ran perfectly well on 87 octane in the summer. When i ran 89, or 91 which i normaly did I never noticed the diffrence, and i am pretty sensitive to diffrences in a car, but the supra was only runing 7 psi, but my frineds supra is running 12 psi (5 more than stock), and runs 89 octane, in a 89 supra, same engine as mine was, and has no problems.

#9 archemitis


    guy smiley

  • Members
  • 3,554 posts
  • the big minnie

Posted 15 September 2003 - 04:19 AM

12 psi and 89 octane=hole in piston
or the timing is so retarded because the knock sensor is going crazy from pings.
i would say run good gas, or do some testing, and get a good intercooler.

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users