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    ACN91 really does suck

    Finally got all the extra ethanol out of the tank so I could start working on true ACN91 tuning and it's a little depressing. The flex fuel sensor shows 8-9% ethanol which makes sense. But unfortunately that means it's a pretty big step down from the 15-17% reading while at Tony's shop.

    Pulling a little more timing resulted in being able to do a relatively clean one gear pull at ~20psi under ideal conditions but as soon as you shift or anything isn't perfect it's knock all over the place. Pulled even more timing, only partly solves the problem. I don't have an EGT gauge but I imagine that's not pretty either. Bottom line, for a true daily driver under all conditions tune I don't think 20psi is compatible with ACN91. So I'll be pulling the boost down and looking for a compromise where I can run at least 6-7 degrees of advance by redline and at least 5 degrees at 5k. I'm guessing it will be somewhere between 16-18psi. I'm also guessing it will end up being about 400whp through the stock downpipes. Such is the life of a daily driver 3.0 liter.

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    One question on this topic, is anybody aware of an MHD accelerator pump function? I don't see any kind of short term enrichment based on throttle movement but I'm going leaner that target for 3-4 samples when I first hit the throttle and I'm noticing that I'm getting extra knock there independent of the timing map at that point.

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    ACN91 is the worst. My current (super conservative) pump gas tune for thrashing on hot Arizona days is probably under 400 whp. It may as well be 87 octane anywhere else.
    Chris - VTT Forum Representative
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    Click here to enlarge Originally Posted by Carl Morris Click here to enlarge
    Finally got all the extra ethanol out of the tank so I could start working on true ACN91 tuning and it's a little depressing. The flex fuel sensor shows 8-9% ethanol which makes sense. But unfortunately that means it's a pretty big step down from the 15-17% reading while at Tony's shop.

    Pulling a little more timing resulted in being able to do a relatively clean one gear pull at ~20psi under ideal conditions but as soon as you shift or anything isn't perfect it's knock all over the place. Pulled even more timing, only partly solves the problem. I don't have an EGT gauge but I imagine that's not pretty either. Bottom line, for a true daily driver under all conditions tune I don't think 20psi is compatible with ACN91. So I'll be pulling the boost down and looking for a compromise where I can run at least 6-7 degrees of advance by redline and at least 5 degrees at 5k. I'm guessing it will be somewhere between 16-18psi. I'm also guessing it will end up being about 400whp through the stock downpipes. Such is the life of a daily driver 3.0 liter.
    Which is what you would expect as pump gas is required to have under 10% Ethanol. The difference between 10 and 20% E85 is large enough to matter as you found out.

    If E85 is not easy to get run meth. It can be done VERY reliably and safely and will lower your AITs and bump up that octane while suppressing knock. You will get all of the power you lost on 20% ethanol in your dyno and more. I would get it if you plan on running 91 ACN more than say 30% of the time.

    You really want to do a 2-3 gear pull and not have bad corrections etc. Anyone can get a single gear pull(usually) to look decent.

    Are you on stock downpipes? At least gut them. I doubt the high EGTs are good for anyone or anything.

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    WMI is the perfect solution for no-E85 access 91 octane country. Click here to enlarge
    Burger Motorsports
    Home of the Worlds fastest N20s, N54s, N55s, N63s, S55s, and S63s!

    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please see http://www.burgertuning.com/emissions_info.html for more information on legal requirements related to use of BMS parts.

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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    If E85 is not easy to get run meth. It can be done VERY reliably and safely and will lower your AITs and bump up that octane while suppressing knock. You will get all of the power you lost on 20% ethanol in your dyno and more. I would get it if you plan on running 91 ACN more than say 30% of the time.

    You really want to do a 2-3 gear pull and not have bad corrections etc. Anyone can get a single gear pull(usually) to look decent.

    Are you on stock downpipes? At least gut them. I doubt the high EGTs are good for anyone or anything.
    I understand. E85 is relatively easy to get in the Sacramento area so no issues there. But in the past I've run straight pump gas most of the time and had planned to continue that. For now I'll keep trying to see how much compromise is needed to do that safely before I make any more decisions. I've considered meth before but I hate to add additional complexity if I can avoid it. We'll see. I just noticed the spool maps might be contributing to my transition problems so I turned off spool mode to see if it cleans up any. Running about 17psi and low timing at the moment.

    Yeah, I'm still on stock downpipes. My concern is passing CA emissions. If I can pass without the cats I'd rather run new pipes than gutted stock pipes. One problem at a time, though. I'm actually pretty impressed with how much you can put through the stock pipes despite the lower power numbers. At least as you add boost on good gas the power continues to increase quickly so I wouldn't call it totally choked.

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    Click here to enlarge Originally Posted by Carl Morris Click here to enlarge
    I understand. E85 is relatively easy to get in the Sacramento area so no issues there. But in the past I've run straight pump gas most of the time and had planned to continue that. For now I'll keep trying to see how much compromise is needed to do that safely before I make any more decisions. I've considered meth before but I hate to add additional complexity if I can avoid it. We'll see. I just noticed the spool maps might be contributing to my transition problems so I turned off spool mode to see if it cleans up any. Running about 17psi and low timing at the moment.

    Yeah, I'm still on stock downpipes. My concern is passing CA emissions. If I can pass without the cats I'd rather run new pipes than gutted stock pipes. One problem at a time, though. I'm actually pretty impressed with how much you can put through the stock pipes despite the lower power numbers. At least as you add boost on good gas the power continues to increase quickly so I wouldn't call it totally choked.
    Meth is simple, tank in trunk. It only sprays when you hit a certain PSI or on WOT so it isn't on all the time only when you need it. 2 nozzles in your charge pipe. You check the tank once a month or so depending on how heavy you are on your foot. Meth is cheap enough and comes in a metal can. Just buy a 5 gallon jerry can with a push button to mix the water with the meth about 50:50. That means 1 pail is 10 gallons worth. Should last a while...also inexpensive all things considered...depending on what kit you get.

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    My opinion is that meth is simple...except the safety checks to make sure it's actually spraying when you think it's spraying. I'd rather not be dependent on that if I can do it a different way. Hence my flex fuel setup.

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    The easiest way to run 91 in these cars is to build and engine and drop the compression to have a bullet proof setup, these cars werent built to run such low octane fuel as BMW recommends a min of 95 ron for these cars.

    I'm with you on not running WMI as I have my own reasons for that..

    I carry a 2 gallon gas container of e85 or e98 where 93 is not available or just want to bump up the octane of 93 to have some fun with my car.

    I run around 600 to 618 rwhp on a daily basis using 93 @25psi and use a little e when needed to supress knock as octane varies a lot here from pump to pump.

    Using the VTT gc's was the only reason I could achieve the results I did, we tried a number of different turbo manufacturers on other cars but not the same setups and we cant even come close to these results.
    Bmw 1 series M 11.4@127mph

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    Click here to enlarge Originally Posted by Carl Morris Click here to enlarge
    My opinion is that meth is simple...except the safety checks to make sure it's actually spraying when you think it's spraying. I'd rather not be dependent on that if I can do it a different way. Hence my flex fuel setup.
    Back in the day I knew a tuner that would tune a car on pump gas to the edge of stupid. He'd then use meth to bring it back in to safe plus some. Never used it as a primary fuel source. It's not the best way to get max power but it stops it from being such a catastrophe if you run out/something goes sideways. A different perspective...


    Chris
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    That is the way I do it with 93, I tune it with a few minor corrections and smooth it out with a little e, that way if I cant get any I'm still safe.
    Bmw 1 series M 11.4@127mph

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    Click here to enlarge Originally Posted by Carl Morris Click here to enlarge
    My opinion is that meth is simple...except the safety checks to make sure it's actually spraying when you think it's spraying. I'd rather not be dependent on that if I can do it a different way. Hence my flex fuel setup.
    When mine is spraying the gauge tells me, it also tells me flow %, if the tank is low, etc. It has a little button on it to turn the meth off if I want. You always know when it is flowing, there is never a question of is it. If you use filters it is impossible to clog an injector. You have a FAV etc. It has multiple built in safeties if there ever was an issue which would open the waste gates worst case.

    The gauge is simple and gives you visual indicator when the Meth is flowing. Does not get much more simple. There is no question of if the meth is flowing. You also choose when it injects as to not waste the meth.

    You can also use the flexfuel logic for your meth set up. So it runs a 91/93 only map and then IF you are spraying meth, you can turn your meth off whenever or you run your tank dry, it will then switch to your correctly made meth map. This gives you the safety and power of being tuned correctly for the meth you are injecting, only when you are injecting.

    But if you are happy mixing at the pump or running full E85 as it is readily available go for it. If I had ACN I would run meth in a heart beat.

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    Reading the responses I can see how you could tune for "probably" safe and then add meth to make it safe but still survive if something went wrong. I'm not attracted to that just because with the flex fuel tune there's so much more power than that available with just a few gallons of E85 and it's easy for me to keep that in the garage all the time.

    Regarding all the safety strategies available for meth I know they exist and are pretty reliable. But they do add some complexity. And as an engineer that deals with failures all day every day I know even the safeties and backup safeties sometimes fail.

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    Update: Finally got the ACN91 knock issues under control, but it required going all the way down to 14-15psi and 4-6 degrees of timing. I still have a bit of issue with overboosting a bit after a redline shift and getting knock so I'll try to get that completely under control and then see if I can bring it back up a bit.

    More than one person has mentioned compression and I definitely think they are right. I forget that on my old GVR4 I was only running 7.8:1 compression...so yeah I could run 18psi on pump gas all day in Colorado no problem. But that's not the same as running 18psi of boost near sea level into 10.2:1 compression on worse gas.

  15. #15
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    Yes 91 fuel is pretty sad. The only worse fuel is that 94 octane up in Canada that sometimes logs like 93 and sometimes like 89 octane, lol.
    Burger Motorsports
    Home of the Worlds fastest N20s, N54s, N55s, N63s, S55s, and S63s!

    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please see http://www.burgertuning.com/emissions_info.html for more information on legal requirements related to use of BMS parts.

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    "Tank in trunk" is real safe for sure. So are invisible flames. Be sure to run plastic feed tubes through the cabin while you are at it and tell your insurance company about your new safety improvements too.

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    with 93 and a little e to smoothout timing corrections I run 25psi with 9.5 to 1 comp all day long.

    The comp is the real killer of unleaded fuel, with 10.2 comp i could never run any higher that 18psi with major corrections.

    Without the gc's I could have never achieved where I'am at today and them some.

    It comes down to the individual what they are trying to achieve and there is lots of different ways of getting there.

    Its up to you in the end if you want to do it properly or the cheap nasty way, there is no clear answer as everyone has their own opinion.
    Bmw 1 series M 11.4@127mph

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    Hey look I can post some here. So I'll contribute that ACN91 is to fuel like Natural light is to beer. Useful for games but you don't wanna drink it.

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    If you dont already know this guy ^^^ is the man to tune your car properly if you want it done right the first time.

    Without him I dont think I would have reached my goal period.
    Bmw 1 series M 11.4@127mph

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    Click here to enlarge Originally Posted by maxnix Click here to enlarge
    "Tank in trunk" is real safe for sure. So are invisible flames. Be sure to run plastic feed tubes through the cabin while you are at it and tell your insurance company about your new safety improvements too.
    Did someone wake up on the wrong side of the bed?

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    Click here to enlarge Originally Posted by martymil Click here to enlarge
    If you dont already know this guy ^^^ is the man to tune your car properly if you want it done right the first time.

    Without him I dont think I would have reached my goal period.
    Yeah, I know of @V8Bait :-). He's a busy guy...but hopefully we'll have a chance to work together a bit on this stuff eventually.

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