Octane of E85

[ANDYS87]

Does anyone know the octane value of E85? I always thought it was a subpar fuel?????

 

[novaderrik]

it's officially rated at "over 100 octane" on all the pumps i've ever seen, but it can vary depending on the actual blend. E85 can be as low as 70% Ethanol and still be called E85.
sounds screwy, i know, but everything i've read says it averages about 105 octane, and only fluctuates a couple of numbers either way. so, as low as 103 and as high as 107.
try a half a tank in your turbocharged car, and you won't consider it "subpar"..

 

[GNVYUS 1]

E85 was told to me as being 105 octane ( Marathon engineer ).

Local turbo shop is saying it is acting like 110 octane minimum on forced induction cars. And I have heard that some turbo shops are seeing the same psi and timing as C16.

 

[ANDYS87]

I guess I was wrong. Sounds like a good thing!

Thanks for the replies

 

[the wrath]

so nova you are saying add a half a tark of e85 and i will notice a diffrence would i have to have 93 octane in it already? and what this all about with upgrading the fuel pump and injectors

 

[cstavro]

read up some more on e-85...even in this forum. 105 octane for the price of regular gas

you'll need 32% more fuel. use either 32% larger injectors, or 72.5 psig fuel pressure (assuming 43.5 psig baseline).

 

[novaderrik]

so nova you are saying add a half a tark of e85 and i will notice a diffrence would i have to have 93 octane in it already? and what this all about with upgrading the fuel pump and injectors

i always just run it with 87 octane to save some bucks- that's still 96 octane, which is enough for what i've got.
my car actually runs pretty good on straight 93 without any noticeable detonation- but with half 87/half E85, it feels like a 50 hp kick in the ass compared to straight 93- and gets the same mileage as straight 87. i've found that if i have more than about 50% E85, the mileage generally starts to suffer.

 

[GNVYUS 1]

No, don't even think of running that base fuel pressure Cstavro posted.

Please call any fuel injector shop and ask them why, one hint, fuel pump volume.

 

[cstavro]

No, don't even think of running that base fuel pressure Cstavro posted.

Please call any fuel injector shop and ask them why, one hint, fuel pump volume.

we don't even know what andy is running. he can certainly think about it...he just shouldn't proceed with a sub-par fueling system.

a bigger concern is whether the computer will think the engine is running lean and flood the motor (in closed loop). xfi has a fuel energy constant that takes care of that; i'm not sure about the stock pcm.

i mentioned in another thread that boost referenced fuel pressure regulators could put the fuel injectors into a dangerous operating zone (at 72.5 base psig).

my '99 buick has 33# injectors (@ 43.5 psig), but only 240 bhp stock. i have lots of head room. my injectors can also tolerate 100 psig.