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1G E85 Without a Tune (Theory)

Posted by 97egl, Nov 29, 2020

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  1. 97egl

    97egl Proven Member

    146
    26
    Joined Feb 6, 2014
    Brownsburg, Indiana
    So this is just theoretical and I'm looking for constructive criticism. ("Get a Turbo" is not constructive criticism nor possible for the class of car I am running)

    My theory is that since Gas stoich is 14.7:1 and E85 stoich is 9.7:1 an e85 engine requires 1.5 times the fuel that the same engine running regular gas needs. A 4g63 NT engine uses 240cc injectors so if I could find injectors with the correct impedance that are around 360cc or a little higher I believe I could possibly run E85 without any tuning required. Obviously I would need to upgrade the fuel pump to handle more fuel to at least a turbo pump.

    Is this Idea total garbage? Or does it just have some flaws that could possibly be worked out? Am I even correct in assuming that a 360cc injector would actually deliver 1.5 times more fuel than a 240cc injector?

    Thanks for any help guys.

    Figured I'd add an explanation of WHY I want to do this below


    I am making more power on an N/T circle track car by bumping compression up around 12:1 which I have to run 110 race which is not cheap and I go thru a lot of gas. Probably 60 gallons a season so I'd like to run e85 if I can do it cheap enough and save me from having to buy race gas at about 8 bucks a gallon. Car is supposed to be stock so I can't run an aftermarket ecu which they check for. They've never checked for compression or fuel type and for anyone to compete against guys running factory 200hp Sentra SE-R Spec-V cars you just have to cheat.
     

    205  3

    2002 Pontiac Grand Prix GTP 40th Anniversary
    fwd · automatic · Misc Vehicles

    Street Build 254  1

    1991 Plymouth Laser RS Turbo
    fwd · manual · 1G DSM
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  2. motomattx

    motomattx Proven Member

    3,221
    1,153
    Joined Dec 9, 2010
    wampum, Pennsylvania
    Yep, you should be able to do that, the thing is that you wont be able to change the ignition timing to take full advantage of the full potential of ethanol but you might not need to for what your actually doing with the car, its something you can try though and see how it works out, it shouldn't take much cash to give it a shot, the car might not run the perfect afr without you being able to tune it however you can technically tune it a little bit with fuel pressure and the mass air sensor screw if you knew what you are doing.
     

    Drag Race Build 4K  10  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  3. Canadian_CD9A

    Canadian_CD9A Proven Member

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    Joined Feb 10, 2012
    Winnipeg, MB, Canada
    Yes the idea is total garbage. It would require you to run in open loop all the time, since the stock ECU's closed loop maps work by targeting a 14.7:1 AFR and the narrowband either reads richer or leaner than that number. The ECU would flip out trying to adjust it back to that 14.7:1 (and failing), and you would have zero semblance of control over target AFR.
     
  4. motomattx

    motomattx Proven Member

    3,221
    1,153
    Joined Dec 9, 2010
    wampum, Pennsylvania
    Yeah, forgot about the factory narrowband getting involved, he would have to install a wideband and do narrowband simulation with it then it would be measuring Lambda and targeting stoich should be fine like that, op are you allowed to install a wideband sensor in your class? if not you could install a eprom ecu and have a chip burned set up for ethanol.
     

    Drag Race Build 4K  10  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  5. bastarddsm

    bastarddsm Proven Member

    5,319
    1,120
    Joined Aug 26, 2003
    Mendota, Illinois
    Wideband only reads stoich (lambda = 1), guys. It always reads .5v at lambda = 1 regardless of fuel. It'll be all good.

    I did this exact thing long ago, well a little different. I used stock 450's and like 55psi of fuel pressure on a 1g turbo. The stock afr maps are soo rich I did not quite want to be 1.5 times richer. That made it "lean" under closed loop. Another creative trick was to take my programmable output of my wideband so that like 16:1 gas afr was the switch point. In the end it all worked out. Car went like 105mph like that, and I'm 99% it would go faster now that I know more.
     

    Showcar Build 7K  1

    1991 Eagle Talon N/T
    9.805 @ 144.00 · 1G DSM
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    craracer05 and 97egl like this.
  6. 97egl

    97egl Proven Member

    146
    26
    Joined Feb 6, 2014
    Brownsburg, Indiana
    I can run a wideband sensor. I don't think the computer would cause problems trying to adjust tho. As @bastarddsm said the computer just tries to adjust the fuel mixture to lamda. Which we know is 9.7:1 but the o2 sensor is clueless as to anything except for how much voltage it's producing due to the level of o2 in the exhaust.

    As far as timing it is unfortunate that I can't take full advantage of that. I figured I will turn the CAS as far advanced as possible. Maybe die grind it to get a little more than factory but obviously without logging I don't want to go too crazy. May main thing is not actually making more power on E85. It's just to save money. If I can run e85 over 110 octane that saves me 6 dollars on 60 gallons a season. So 360 dollars savings a year for about 200 dollars of parts is a deal I'll take for sure. Availability is also a factor. Tracks are not reliable to have 110 available due to an empty tank or their pump is broken so I have to lug around an extra 20 gallons with me just in case. Got water in my fuel system once also due to them having an old tank that cracked and leaked. All that goes away with E85. There's also the advantage of it running cooler.

    Now I just have to figure out what injectors to run. It's a shame the 390cc from AT Turbo cars are low impedance or I could just swap those in and see if it'll work. They're probably a little too big tho anyways and I don't want to wire in a resistor just to find out they don't work right.

    Thanks for all your replies guys! If anyone has any other input on issues that may come up please keep posting
     

    205  3

    2002 Pontiac Grand Prix GTP 40th Anniversary
    fwd · automatic · Misc Vehicles

    Street Build 254  1

    1991 Plymouth Laser RS Turbo
    fwd · manual · 1G DSM
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