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Discussion Starter · #1 ·
I have a friend that wants to use alcohol injection in his sti and I am thinking about it to but he says he wants to get his car tuned with alcohol injection and 100 octane race gas. My understanding is that alcohol injection is like runing race gas there for not needing higher octane also that it cools down your motor. I keep trying to explane this to him but he says I dont know anything because I drive an evo. Can you gain more power by using 100 octane gas and alcohol injection?
 

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Well, running alky is LIKE race gas in that it raises the effective octane level, thus allowing you to run more boost, more timing, and more aggressive AFRs. However, it is not a substitute for straight race gas. You can make more power on alky+100oct than you can on alky+91oct, but that also depends on the setup you have and the turbo you're using. An STI with stock turbo can't make hardly any use out of alky+100oct, because their turbo is so small. With a bigger turbo, there's more to gain.

On the Evo, our turbo is big enough to make really good power up to 25-26psi, and we need alky (or race gas) to run that on a daily basis. Even 24psi is too high for someone on 91oct unless they have a IX with a non-aggressive tune. I run 91+alky and run 26psi daily up here in Colorado. I also have a separate map for 112+alky that I can use at the drag strip.
 

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Discussion Starter · #3 ·
How much psi can you run on the evo with stock turbo and 100 octane. My friend was going to run alohol injection with a gt35 turbo on his sti.
 

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Your question really just tells me you have a lot to learn about modding and tuning in general. There is no set amount of PSI that you can run on a stock turbo'd Evo with 100oct. It depends on many factors, such as your AFRs (lean or rich), your timing (weak or aggressive), your supporting mods (stock or all bolt-ons), your fuel system (upgraded fuel pump?), etc etc. Generally, if you know what you're doing, you can put in some 100oct on an empty tank and run 24-25psi at the track. I used to do that when I still used an SAFC with a few basic mods. I'd add 100-104 oct to my 93, re-tune the SAFC, and crank the boost to 24-25psi.
 

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I run 30 psi of boost on 93 octane with alcohol injection in my GT35R EVO on a daily basis. Now you can't do that on a stock block STi though if you want it to last... does he have a built block or is he still stock internals?

Keith
 
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