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Going from 93 to 91 Octane


need bb

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Well I am moving and will no longer have access to 93 octane. I am tuned on 93 and I was wondering what changes I should make to my tune to accommodate 91 octane.

 

 

  • Should I run a little bit richer? I currently run between 10.8 - 11.0 AFR.
  • Should I run a little bit less boost at peak torque? With my 20G I currently peak around 21PSI.
  • I know that I will have to lower timing. Any insight on how much I should take out?

Thanks!

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I'd lower peak boost a little, maybe come down to 18 or 19psi. Pull 2* across the board and see how it likes that.

Don't touch fueling. 10.8 is already the edge of pig rich, and torque drops off very quickly below there.

 

Had you thought of adding meth injection to avoid detuning?

Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Are you moving to a higher elevation where you can only get 91? If so you may be ok doing nothing, but should still have the tune fixed as mentioned. I live at 7000' and have no problems unless I drive to a lower elevation on the 91 octane gas.

 

Jay

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Currently at sea level and new location is also at sea level. It looks like there is also E85 at some stations, but for now I want to make sure i am safe on 91.

 

I will lower boost and timing and see how things look.

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