04-17-2013, 08:42 AM | #1 |
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E85 and Detonation
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I was having an issue with my car under the following conditions - 6th gear, 50-60 mph (so figure below 2,500 RPM), 2/3 - 3/4 throttle, Comfort or EcoPro modes, ambient temperatures ranging from 55 to 75 degrees. The car would shudder pretty hard and it felt to me like it was detonating and the ECU was pulling boost, timing, etc until the detonation stopped. Then it was advancing everything back to max, detonating, pulling everything...and so on. No warning lights or limp mode, but I could envision the car going into limp mode if I allowed it to go on (which I didn't out of fear of hurting the motor). The issue was easy to duplicate so I was confident it wasn't a fluke. To test the theory I filled my tank with 1/2 91 octane and 1/2 E85. Before doing so, I went searching for spark plugs that are 1 heat range cooler than the stock plugs. I found something interesting - looking at RealOem, there is a reference to spark plugs for cars without flex fuel preparation. Hhhmmm...ok. I'm not aware of the N20 being sold anywhere in the world as a flex-fuel vehicle. Could that imply that the car is already setup that way? Anyway I couldn't find any plugs available except for the OEM parts so I quit looking. I also consulted with a friend who is a BMW Master Tech (and outstanding BMW race car builder) to see if E85 would hurt the car. He said he didn't think so and that I should give it a shot. Now on to the E85 - WOW! The shudder described above is completely gone. My car feels so quick it is amazing. Even the idle has smoothed out a touch. Maybe it is all my imagination but there is a perceptible difference. Our cars should be the right configuration to take advantage of E85 - DI and Turbo with very sophisticated engine management. So perhaps the extra octane really is helping out. On the downside, my fuel economy has taken a serious hit. Usually I average between 26 and 29 on my daily 22 mile commute in LA traffic. Since filling-up I am having trouble getting above 19. Some of that might have been due to my playing around trying to get the car to shudder. Some of it might be the result of spending less time on the freeway since the fill-up. Next tank I will attempt to more closely duplicate my routine commute. But I am expecting 20-25% reduction in economy. Time will tell. If only there were more E85 stations around So Cal. Thus far it appears to be a reasonable substitute to $9/gallon race gas, which is (shockingly) easier to find at the pump than E85 is. But the lack of infrastructure makes using E85 very challenging. Thanks for reading. |
04-17-2013, 11:06 AM | #2 |
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Sooo I'm little confused.. have you had your car tuned for e85 fuel? Or just mixing it and hoping the ecu will make adjustments on its own? Don't think ill ever run e85 without proper tune. If you did get a tune, where?
Mpg drop is always expected with e85.. since you need to pump in more fuel. |
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04-17-2013, 01:41 PM | #3 | |
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I feel you man. I accidentally pumped a complete tank of e85, as I was reading blogs on forums I didn't know you should only put about 4 gallons, and oh man it does make a difference. Idk but the turbo is a little louder now. I feel like it has more power and torque. My car is automatic and when driving in sport mode it kinda peels out when it goes into 2nd gear. At first I thought it was my imagination but it wasn't. My fuel economy went from 25 to 18mpg. But we'll worth it. Now I just mix the gas as Im trying to get better mpg.
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04-17-2013, 01:53 PM | #4 | |
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The only benefit of an e85 specific tune is if it runs more boost and timing to take advantage of e85's knock resistance. But there is no reason why a stock tune can't also take advantage of that knock resistance by allowing the car to run max boost/timing maps. The gains would not be as significant as with a dedicated e85 tune for sure. But there is no potential harm from running e85 on a stock tune. |
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04-17-2013, 02:59 PM | #5 | |
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04-17-2013, 10:52 PM | #7 |
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04-18-2013, 12:38 PM | #8 | |
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04-18-2013, 12:55 PM | #9 |
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04-18-2013, 02:09 PM | #10 |
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04-18-2013, 05:04 PM | #11 |
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04-20-2013, 11:27 AM | #13 |
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Car went in for service which was due anyhow. No issues found that would lead to detonation. The one CEL I got was caused by an exhaust flap error. There were other error codes stored but they mostly related to non-mechanical issues. Three of the codes were logged from before the car was delivered to me at the BMW Welt.
But here's an interesting note - the tech printed and gave me the reports on my fuel quality! That was pretty interesting. I only use Chevron Premium 91 (the best we can get here) and almost always fill at the same two stations. Despite my use of Tier 1 premium, the car was reflecting almost all of my fill-ups as level 2 gas (0 being worst, 3 being best). I was told that measurement is from the amount of detonation detected by the ECU. Something like 41 fill-ups were level 2, 5 were level 3 (I would wager those were during my euro delivery) and one was level 1. Maybe there really is something valid in the complaints about crappy CA gas. The take-away is that this motor detonates quite a bit and people should really consider higher grade fuel if contemplating a tune. |
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04-20-2013, 11:30 AM | #14 | |
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I used 93, usually Shell before I was tuned, and continue to do so.
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04-21-2013, 10:49 AM | #15 |
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04-23-2013, 07:38 PM | #16 |
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E85
What I don't understand is why we are getting all excited about using E85?? I can use it in my work car, but my mileage really goes down. Plus, a lot of people on this forum get excited about using ethanol blended fuels saying how bad they are for your car. Then we use a fuel that by it's nature has to be at least 70 percent ethanol in our vehicles. I personally don't mind using ethanol blended fuels. I've gone through six squad cars and have used ethanol blended fuels in everyone of them. You know how many engine failures I have had. Zero. If it gives you any idea of miles driven. I just got a new car about a month ago. My old one had just short of 215,000.
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04-23-2013, 08:42 PM | #17 | |
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NO hardware changes, just the tune for E85 showed 300whp/350wtq. That is a DRASTIC increase for something so small.
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04-24-2013, 02:47 PM | #18 | |
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Last edited by Rick4345; 04-24-2013 at 02:48 PM.. Reason: corrected spelling |
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04-24-2013, 02:57 PM | #19 | |
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04-24-2013, 03:06 PM | #20 |
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I think it's very reliable. I would just like to see the ablility to use it without a tune.
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04-24-2013, 03:21 PM | #21 |
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You CAN use it without a tune. The only reason to use it if you have a tune is because the tune makes the car run closer to the edge of detonation. E85 helps prevent the detonation so you can maximize the benefit of the tune.
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04-24-2013, 03:35 PM | #22 |
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What is the amount of E85 that you would recommend to use for a full tank? I have a 328i, so we are dealing with the 2.0 turbo. The only mechanical modifications I have are a K&N filter and M Performance exhaust. I want to keep everything as stock as possible.
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