EFLEX - Anti-knock properties with different Ethanol concentrations

[trdee]

Gents,

Was having a discussion on the adaptronic forums regarding the change in anti-detonation properties of different ethanol concentrations in flex fuel and was linked to this fantastic paper. It's a thesis from MIT where they explain the anti-det/ethanol content relationship as well as describing the differences it makes in port injection and direct injection applications. It also goes over how much of the anti-knock properties are gained by the chemical structure of the ethanol and how much comes from the extra charge cooling effect you get from ethanol.

Link is here
https://www.google.com.au/url?sa=t&r...RDZq5t1bXSAhRA

If you are too lazy to read it all, the most important thing to take from the article is that they found that the anti-knock performance increases massively from 0% up to about 40% ethanol content, but after that, there is fuckall change to the detonation resistance (in a port-injection engine)

**THIS ISNT THE CASE FOR DIRECT INJECTION HOWEVER** Direct injection engines make better use of the charge cooling effect of ethanol, and the anti-detonation resistance increases linearly all the way to 100% ethanol

This sounds lineball with what I have seen in real world applications. Unigroup tested ethanol from E50 to E100 in one of their development cars and found that the max power they could get out of the fuel hardly changed at all.

REAL WORLD IMPLICATIONS
Everyone who has a song and dance that e-flex is really variable and bla bla bla is talking a bit of shit. yes it can vary from 60-something to 85 or whatever, but in this range the anti-knock properties of the fuel dont change by a significant amount at all. We're talking less than 1 octane number effectively.. yes you do need to have a flex fuel sensor so that your fuel mixtures are correct, but in terms of how much timing and boost you can run, it doesnt make any significant difference, at least not on port injection engines, which is what almost all of us have..

Comments?

[RONA]

Not really a huge surprise Dale from Castle Hill Exhaust has always said the difference between Eflex at E70 and say United E85 is 1-2kw max. Biggest difference will be you'll need a little more fuel. Eflex has a minimum ethanol content of E70 so if it is lower then that the site is dodgy.

[JustenGT8]

Yup, so all you ave to worry about (for those without fancy smancy e flex sensors) is a conservative enough AFR when you tune to keep you safe if you get a 'good' batch with a high ethanol %. Simple stuff really but good to see a MIT paper to back it up

[Celica RA45]

and the best part also is the caltex stuff is very good about E73 all the time as i test it and the bad news is the united e85 is all over the shop from being e90 down to crap the next moment

[andrew_mx83]

From my reading of the above, it would seem that after a certain point (say E50) you are better off with less ethanol in the fuel rather than more?
Ie E50 should give the same anti-knock properties and power potential as E90 but you would use less fuel, injector duty cycle etc?

[knightrous]

From my reading of the above, it would seem that after a certain point (say E50) you are better off with less ethanol in the fuel rather than more?
Ie E50 should give the same anti-knock properties and power potential as E90 but you would use less fuel, injector duty cycle etc?

That's how I was reading it. Then just use a Flex Fuel sensor to adjust for any potential swing in ethanol quality/quantity.

[dnegative]

Everyone who has a song and dance that e-flex is really variable and bla bla bla is talking a bit of shit. yes it can vary from 60-something to 85 or whatever, but in this range the anti-knock properties of the fuel dont change by a significant amount at all. We're talking less than 1 octane number effectively..

I thought that was pretty well known from all the GM tunes that have been looked at;

Anyway, any advantage with running low ethanol blends?

[JustenGT8]

From my reading of the above, it would seem that after a certain point (say E50) you are better off with less ethanol in the fuel rather than more?
Ie E50 should give the same anti-knock properties and power potential as E90 but you would use less fuel, injector duty cycle etc?

Nope not at all.

Anti det is only part of the benefit. As a more oxygenated fuel, it will make more power at stoich than petrol. Also, the charge cooling effect allows for better cylinder filling...so again more power. For performance it's simply a better fuel than petrol.

It also runs the engine much cooling and you can actual feel the engine having an easier life. At WP I could easily pick the difference of the car running E85 against 98.....it just did it all so much easier

[trdee]

Similar to what justen says above. You *could* run your car at e50 and enjoy most of the benefits without as bad a fuel consumption rate. But if you are using e85 then in reality you shouldnt be giving 2 fucks about fuel economy. The way I see it is you have a nice big safety margin instead

[andrew_mx83]

Thanks guys. Im building a motor fora guy at the moment that we want to run on e85 but its not available where he lives. He is fine to buy it in drums but if we can mix it with premium, or e10 that he can get locally the drums would last a lot longer. Its a high comp aspirated motor so we dont need the cooling quite as much as the turbo guys...

[Celica RA45]

well make sure the comp is at least over 14.5 to 1 then anything under that you will only pick up 1 or 2 kws in the mid range and it wasnt worth it so i went back to 98 on 13.5 to 1 comp

[maj]

Toyota 86 + turbo + stock hi-comp engine with DI + E100 = win?

[RONA]

Nope because E100 doesn't exist at any pump in Australia. Replace E100 with Eflex/E85 and you have win.

[aus jd 2703]

E100 does exhist but yeah not available from a fuel station, recently worked at the caltex refinery and they have E100 on site but it is mixed before it leaves as E-flex.
i believe E100 would require a uppercylinder lubricant as wont it "wash" the oil of the cylinder walls thus accelerating ring wear?
or is it like nitro methane and is extremely hard to ignite so in the case of nitro you use a small % of methanol (as little as 5 was common) to aid ignition of the nitro methane?

any way if i ever get my stuff together id love to run E85 and a flex sensor so it can account for left over fuel in the tank when i switch fuels on the refil. i personal would ad a drain to the return line that way i can drain the tank when i want fresh virgin E85 (ie track days)

[oldcorollas]

the 15 part of E85 has various petrol components to assist with vapourisation, depending on season.

I thought it was Caltex that was dropping E85 due to quality issues, and United was the consistent one?