Building an E85 Motor

[D's GS-T]

So Ive decided that since e85 is plentiful around here that id just build a higher compression motor for e85. I guess i was wondering if anyone has ever done this. I know most people usually just go bigger pump, injectors, e.c.t but has anyone run high compression pistons lik 10.0:1 or swapped heads e.c.t. I was thinking of going with the those magnus 10.0:1 pistons, and im not sure if anyone has tried anything else, or has any ideas. Thought it would be interesting to see what everyone else is doing.

 

[turboglenn]

Well, I gues if i had to say my engine was either "punp gas" or "e85" built, I would have to lean towards E85.

I only run 9:1 pistons, but on pump gas your knock sensor will act like it was 12:1 , this engine HATES pump gas with a passion (even with meth injection) but on e85 it's happy as can be.

Now I am no e85 expert and am still experimenting with it,and i'm not sure if i'd go 10:1 or not. In the scheme of things the 10:1 would give better off throttle response and more torque, but airflow is that al out ruler for maximum horse power and i think that you would suffer in the "max boost" department by going that high in CR. With that said we know that airflow (or boost) has the most power effect on the engine..... Second to that is timing (another factor that would be limited more by your 10:1's.. FOr exampe on my 7.8:1 engine i was running 26 - 28* of timing under boost, on this 9:1 motor is really doesn't like much above a 1g turbo OEM timing curve..maxing out in the 23-24* range up top and being more limited down low in the powerband where detoantion is more likely, so i have to run even less....with 10:1 you would have to run "X" amount less than that mose likely. Then the third factor in making power is the air fuel ratio... this is just like boost and timing and will be more limited by your engine specs....

Example is we're aready holding boost and timing lower for higher compression so we think we might get away with leaner AFR"s...well leaner AFR's bring on more heat and more heat brings on more detoantion which would then cause us to pull boost or timing back down.

What I'm getting at is that i think 10:1 has to be some wher near the point of diminishing return on our engines (but i could be wrong) I say 9:1 is good, but not the best if you can't get any E85 near you... If this was a pump gas only motor I would go back to 8:1 most liekly so i could push more air and compensate.

You also need to take into conideration if this is your daily driver or not because if it is and you go ot of town you might not be able to get any e85 (last time i went to kansas city i couldn't get any and had to use pump - thank god for a dual map w/ switch on the fly!

Now, e85 does knock, but not much and from some engine tear down pics i've seen recently it appears that although not detonating you can get things hot enough to melt pistons and other vital parts.

Good luck with your build and what ever CR you go with make sure to report back here with your results!

 

[DSM1G90]

E85 has a higher octane rating-being close to 100, yet the BTU's from E85 is much less than regular 93 pump gas, thus mileage and power is gonna suffer some on stock settings.

 

[MOTOR-RX]

Turbo Glen

what are you tuning wit?h

 

[turboglenn]

I"m running a haltech E6x ECU.. Just an average standalone system, but it allows you to fully extract your car's potential without having to please the Al'mighty DSM knock sensor...But it will let you blow your car up if you don't know what you're doing just as easily.

 

[e85_4g63]

10:1 is a good compression ratio for straight e85 cars. If your even thinking of running pump (gas, 93 oct, or 91 oct for the west coasters, I see your in MN so I wasn't sure what pump gas you get), lean more towards the 8 to 9 range (CR wise) in case you "have" to put some pump gas in it. There's a local guy here in PA that runs a 10:1 built motor with an evo III 16g on half 93 / half e85 tuned on Link. His car runs very very well. English (Lucas, from English Racing) has run pump gas (93 oct) on a 10:1 motor before. Be aware that the ethanol ratio's in e85 change through the year.

 

[D's GS-T]

ya around here its only 91, this car wont see pump gas since i wont ever be taking it that far, it will just see e85 and really nothing else. maybe i will go 9:1 though just incase I absolutely had to put in pump gas, with my luck thats what will happen .

 

[turboglenn]

RAcetek (a.k.a. sdsefi.com ) has a great lng article i read today about many of the reasons they would not advise a 10:1 engine build for anything turbo on the street... I'm not saying don't do it because i say so, ut i am saying don't do it because i truely feel you will be upset with yourself AFTER doing it. But either way, do post up your results as i'm very interested to see if the theories i've stated and read will be bent/broken by e85!!

 

[matthewdesigns]

There are a number of guys here running 10:1 or higher motors on e85. Check out this thread here by member mobythevan for his high compression build. My buddy Jason just built a 12:1 motor and is hopefully getting it in the car today. If you can do it, and have a steady flow of e85 in your area, then it's a good way to go.

 

[knochgoon24]

12:1 WTF

We built a little 5hp Briggs & Stratton motor in a high-mileage car club that ran 16:1 with a custom head. That thing ran iso-octane. (100 Octane) Several pistons were cracked from detonation while we were trying to tune it, but those were pistons from a 35cc weed eater.

 

[turboglenn]

My questioning still remains, as it seems yet to be tested that if the high compression is worth the trade off of lower boost and lower timing when it comes to really cranmking up the boost(haven't seen a report of high boost pulls in that thread yet). You would really have to do two damn near identical setups with the only change being compression ratio to find out though so go for it and let us know what youre restuls are...like i said, feel free. I'm not here to stop anyone, but it's not something i would advise still, even after reading the other thread it's still not something i would do for a car that i beat on daily.

 

[DSM1G90]

Truthfully, my guess would be to remain low compression to allow you to have the headroom for higher boost if needed - give yourself a good "buffer zone" to play with.

You tighten up that compression to the 12:1 as above mentioned and things could really go bad if one little slip occurs since the headroom buffer is really reduced.

Good luck in your search - DSM

 

[TastyTalon]

I would run lower compression to be safe rather than sorry. The thought of high compression is fun, but really if something goes wrong it won't be so forgiving. You can still make loads of power on a lower compression as you know. gl.