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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > JB+ 100% 91 octane 4200ft elevation



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      04-02-2009, 02:24 AM   #1
Noxious335
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JB+ 100% 91 octane 4200ft elevation

So I bought my 2007 white 335i Sedan 2 weeks ago. First BMW and I love it. The power upgrades are so cheap that I can't pass them up. I just installed the JB+ and I have it set at about 60% right now. The only fuel I can find around here that's not leaded is 91 octane. I know they BMS says not to go to 100% unless you can run at least 93 in it. However, I'm in Utah at an elevation of 4200 ft. I used to own a supercharged vehicle and the elevation and the outside temps played a big role in how likely you were to start pinging. I never had to worry about 91 octane fuel in the winter here because I didn't experience any warning signs. Does elevation and outside temp play a role with the amount of boost you can run?

A second question is regarding the octane boost in a can. Does anyone know if it legitimately works?
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      04-02-2009, 04:36 PM   #2
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No one has an opinion on the matter? I can't find a similar post and there has to be a lot of people running their JB+ at 100%. It's too tempting to not do it. I know altitude plays a role in NA engines, and with supercharged engines. A supercharged engine that pushes 9 psi at sea level will push 7.5 or 8 psi at 4200 ft. I don't know about turbos though because the waste gate is set to release at the same PSI regardless of elevation. I haven't turned it up yet and I was hoping to get some feedback before I did.
The other question about the Octane Boost in a bottle is relevant to the first question. Has anyone used it in place of 93 octane fuel successfully?
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      04-02-2009, 05:30 PM   #3
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I did research on octane boost and found inconclusive data.. I stay away from it, thought about trying it once but not in my N54
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      04-02-2009, 05:33 PM   #4
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At that elevation you llikely won't see near the gains others have reported, but you should be fine on 91. As for you question on octane boost in a bottle...Don't even bother. Too many tests have proven them ineffective at actually raising octane. The only exception I'm aware of is a Torco additive. I do know some who've had good results using that on other types of boosted setups. The other method is find someone who sells unleaded race fuel and mix it with your pump gas to the desired ratio.
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      04-02-2009, 10:06 PM   #5
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Originally Posted by RedDinan335i View Post
At that elevation you llikely won't see near the gains others have reported, but you should be fine on 91. As for you question on octane boost in a bottle...Don't even bother. Too many tests have proven them ineffective at actually raising octane. The only exception I'm aware of is a Torco additive. I do know some who've had good results using that on other types of boosted setups. The other method is find someone who sells unleaded race fuel and mix it with your pump gas to the desired ratio.
I started looking into this because I live in the southwest and because of regional agreements octane is capped at 91 here regardless of station. Living in Utah, I'm sure you're aware. I think your elevation is a little low, most gas stations don't start dropping the minimum octane rating to 85 until you reach the rockies at around 6-8000 feet.

I only purchase gasoline at Chevron or Shell, because of the nature of additives and detergents they use being slightly different from some other top tier gasolines. However, there has been at least two occasions when filling up I received a "bad tank of gas" where; for whatever reason, the gas was just shitty, when this happens the engine misses and chokes like it's octane starved.

I'm lucky enough to have a Rebel station just down the street that sells racing 100 (damn stuff is as blue as tidy bowl). The engine performs very well with one gallon mixed with 91. I made some inquiries with my local BMW dealership. A technician told me Lucas Octane works well with the N54. He explained this opinion was off the record because recommendations of this nature go against company policy.

So I tried the product and it performed better than the racing fuel. My drive from Vegas to Kingman was gravy. The engine performed so well that I was finding it quite difficult to stay anywhere within the 70 mile-an-hour speed limit. The local highway patrol was kind enough to remind me of this.

To address the contention that some of the studies find no real increase in octane values when added to a tank of gas is not something I would try to refute. Personally I don't care what it does to the octane values. All I know is the engine performs A LOT better with this stuff. The other benefit is one bottle treats about two full tanks at 8-10 dollars a bottle which makes it a little more economical that a gallon of racing fuel at $5.99. Lastly, it says on the side of the bottle that it's approved for turbos.

If you're concerned about performance at 91 octane I recommend trying this brand to see if you have the same luck I did with your application.

Last edited by Unky; 04-02-2009 at 10:27 PM.
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