All of our Exxon/Shell/Chevron stations sell 93 E10. We also have a Red Dot that sells Ethenol free premium but is 91 octane. I'm currenty set at 18 PSI with the Alky off but occasionally run 23 PSI on Alky. Not fan of the E10 and would like to start using the Eth free. What boost will the 91 support safely.
Safest boost on 91 octane?
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6gunn
high on gas fumes
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Agreed with Boost231. I'm running 26psi on 91 with alky. No knock.
Sometimes I really wish boost gauges didn't have numbers on them. There is no magic number.
You car will run the safest with 2PSI less than whatever your functional knock indicator alerts knock.
Might be 14, might be 100. The number doesn't matter, just that you've got a cushion between where you're at and where the head gaskets spit out.
You car will run the safest with 2PSI less than whatever your functional knock indicator alerts knock.
Might be 14, might be 100. The number doesn't matter, just that you've got a cushion between where you're at and where the head gaskets spit out.
In my area 91 is good for about 14 # boost in general but of course exceptions do exist based on tune and conditions.
I was usually able to run 17 psi with a fresh tank of good 91 octane, but after a week or two on the same tank there would be some KR. I backed it down to 16 psi. I think the ambient air temperatures are probably lower here than SoCal most of the time.
Same reason some people 'manually' shift stock automatic transmissions.
Either that or they HATE having the fuel curve right.
Turbo6Smackdown
Well-Known Member
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"All of our Exxon/Shell/Chevron stations sell 93 E10. We also have a Red Dot that sells Ethenol free premium but is 91 octane. I'm currenty set at 18 PSI with the Alky off but occasionally run 23 PSI on Alky. Not fan of the E10 and would like to start using the Eth free. What boost will the 91 support safely."
Here's the other magic; what boost? That depends on what heads, what turbo, what fuel, air temps, etc etc. Boost actually doesn't mean a whole lot. If you had my EXACT same set up, but with a set of M&A race ported heads, boost would be really different for you than me. So yea, it's all about what cylinder pressure your engine's comfortable with. We usually (if were in to speed) just max it out so that it's about 2 psi below the KR threshold and be done with it, although you're going to need some big tires if you don't want to end up sideways every time you raise the TPS voltage lol.
Here's the other magic; what boost? That depends on what heads, what turbo, what fuel, air temps, etc etc. Boost actually doesn't mean a whole lot. If you had my EXACT same set up, but with a set of M&A race ported heads, boost would be really different for you than me. So yea, it's all about what cylinder pressure your engine's comfortable with. We usually (if were in to speed) just max it out so that it's about 2 psi below the KR threshold and be done with it, although you're going to need some big tires if you don't want to end up sideways every time you raise the TPS voltage lol.
with alky the 93 e10 stuff works great.
So running alky on say 16/18 psi is a bit overkill. I thought that might be a bit on the rich side, no?
Everything depends on set up and tune, your answer could be yes or no? I know I can't run anything over about 14 without the alky. I have ported aluminum heads TE63 FAST etc. About 600hp.
Change that number after the E to 85 and you'll not only become a fan,but you'll fall in love.
It does get horrible gas mileage. The most important number for you is 93. It's bigger than 91. Don't even think about the 10 percent of ethanol in the mixture. Stay focused on the number 93. The most common reason people use 91 is because they can't get 93. They would love to change places with you.
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