The E85 Mystery

NOBLE|370Z

Alright, so how come people can "safely" operate their Zs up to 600+WHP with E85 but for regular fuel of octane 91-93 it's only "safe" up to 550WHP?

Regardless of the type of fuel used if the resulting power is equal then the rods will be pushed just as hard (right?). VQ internals are supposedly good up to 550WHP so what's up with this physics defying e85 creating a double standard of limits of engine integrity?

Cheers


NOBLE

Cell

E85 is rated at a higher octane than the regular 91-93 that most people use.

This gives room for more timing without early detonation. Early detonation is the one thing you want to avoid.

Torque can be tuned to help reduce stress on the rods.

NOBLE|370Z

E85 is about 105octane equivalent? I understand the knocking limit but stress should be equivalent at the same torque (or HP). Therefore I may interpret that 500WHP on 93 octane is a limit mostly just due to "tuning" limits not engine rod mechanical strength...


NOBLE

1slow370

or it could be a relation to the flame speed of the two fuels, I'm not sure if there is a burn speed difference between e85 and 93 as in when the initial ignition takes place how long and how gradually does the cylinder come up to pressure. part of the problem with n2o is that end up a fuel mixture that burns very quickly once ignited so the rise in cylinder pressure is more rapid not just overall greater.

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synolimit

However you get more horsepower, more horsepower is worse than less horepsepower on all parts of a car. It's more stress and torque on everything. I hope that answers the question.

However not all HP is equal! A small turbo running 20psi making 400hp is more dangerous than a larger turbo running 15psi also at 400hp.

E85 scares me for a power adder because e85 greatly changes through the year. E85 friends carry an alcohol tester around for every fill up. If they're getting e70 then they back off because they lose their timing buffer. where if they knock at 25* so they run 23* on e85 but e70 would mean they'd knock at 24* or even 23*, it's now become a dangerous tune. With no buffer bad things can happen.

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NOBLE|370Z

I live in Canada and we don't have E85 available but we do have octane 94.

There are cases where guys are running their stock blocks at 640WHP (13psi) on E85 and they claim that their cars can handle it with out compromising their cars integrity. It seems to me like their tuners shouldn't be telling their customers that this is the case.



NOBLE

ElVee

Seems I need to watch my 370z browsing at work now, with that avatar not doing me favors when someone glances across my screen. Thanks.

SouthArk370Z

I'm not a Chemist or Combustion Engineer but I have been around some, uhhh, "unintended experiments" with both gasoline and EtOH explosions at atmospheric pressure. In my experience, gasoline makes a much louder boom than EtOH. I'm not sure if that holds up under the pressure of an engine.

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gomer_110

Given the same amount of gasoline and ethanol, the gasoline has more "energy". Simply put gasoline has a higher energy density. This is why ethanol fed cars require higher fuel flow rates.

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1slow370

what i mean is that it is possible that e85 takes longer to reach peak cylinder pressure from ignition, so that at the same pressure level it may be easier on the internals since the pressure build is more gradual an less sharp. so even at the same max pressure e85 may produce less shock load on the piston and rod.

Of course i don't know the burn speed of the two fuels so it could actually be more, especially since burn speed changes at elevated pressures.

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TopgunZ

A huge percentage of engine failure, maybe high 90s even, is due to detonation. E85s resistance to this is incredible. You could have a car pushing 350whp and detonating like crazy and the engine will let go. Or take the same car with 650whp and zero det and it will last years.

This is the benefit of E. You can turn up the boost and power and not pick up any detonation therefore creating more power safely. However, if it ever does detonate at those power levels then you have much more energy that needs to go somewhere, usually into the rod.

Ethanols latent heat of vaporization is also 2.5 times higher than that of gas. This means it pulls 2.5 times as much heat out of the intake charge therefore creating a safer environment for higher combustion.

Also, the 30% more fuel you dump into the cylinder washes the walls with more fuel and wards off hot spots.

It does have a much slower burn.



E85 is king in boosted applications.

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faceglide

Bad tuning to boot.

Limeybastard

Yep, that is what I learned in my boost life prior to my NA life.

synolimit

No matter what degree of peak timing a motor starts to knock, you still have to pull back some no matter the fuel. A motor knocking at 25* is much safer to run 20* where a e85 motor is in more danger to run 29* where it knocks at 30*. Fuel doesn't matter if you're running on the ragged edge. E85 is only as good as the tune. E85 still costs more, can eat your rubber lines and seals if not vitron or ethanol compatible and produces more harmful ozone.

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TopgunZ

Seriously bud where are you coming from? Your over on the other thread saying how you want to switch to e85 on an na application then your here dogging it.

Op... Its a way to make more power safely. Its cheaper and readily available race gas. Thats it.

Mods...Lock up the thread before more people become misinformed.

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