The E85 Mystery
 

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

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.

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

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.

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.

The E85 Mystery
 

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

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.

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.

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.

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.

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.

:iagree:

Bad tuning to boot.

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

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.

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.

Octane, tuning, and other in-cylinder transient factors aside, unless we're talking same set-up, same (type of) dyno, etc, I would take that claim with a pinch of salt.

Even if it can be achieved and verified, how long is the motor holding together as torque levels climb past mechanical tolerances? You can crack a ringland if combustion pressures get high enough, even without evidence of autoignition/knock events.

I said over there I'd run e85 only as needed. Only at the track. Not sure if you saw that or not.

It's not cheaper. Saving a few cents per gallon doesn't make up the 30% faster burn rate. It's no where near cheaper!!

Ill admit that the more power your making, in every revolution, the motor weakens. Rods, pistons, rings, everything.

However, you can make that power with less chance of it letting go due to predet. Also you can stretch out the lifetime of that motor if you are running less boost by using more timing, which is safer to do with E.

You also said "Id be scared to use E85 as a power adder". Now you want to run it on the track.

Again where the hell are you coming from? I said it was cheap RACE GAS. So "a few cents per gallon"? Please show me where I can get race gas for $2.89.

Nobody runs E85 for its amazing cost saving benefits. We run it because its race gas for 1/3 the price.

Ask yourself why they make race gas.

Would anybody not want to run race gas if you could all the time?

If you're going to quote me do it right. You left off the important part. I said scared because it changes THROUGH THE YEAR!!. I don't run at the track in December with a foot of snow, do you??? Plus even in summer it may not be e85, more like e80-75-70 etc. like my friends before a fill up I'll check the etoh content. If its low ill retune before a track day and not just blindly put it in like a dumb *** and go.

Lol I think VP racing fuel would disagree with you there. And I know why they run RACE gas! Its 100% controlled and perfect everytime and not some different street gas that's always changing and never the same from the multitude of companies that produce it. You thinking its race gas and used as such is like me saying I run a re11, rs3, z1 yok, etc etc on different wheels at different times and it doesn't matter because they're all "race tires."

That's why you tune off of E70 then you can only get better quality from there on up. I agree that the fact they differ the content can be a pain.

However, E85 has only been proven to be a far superior fuel to run vs. pump gas by every tuner in the world. You talk about subi guys all the time. Well subi guys love this stuff for a reason. They all are boosted.

Why do you think there are guys that drive 50 miles out of there way with two 5 gallon tanks in their hatch just to run this stuff?

This shouldn't be a "should I run it" discussion. It should be a " Am I boosted and do I have availability"? Then its a no brainer.

If quenching hotspots are the only issue, then, yes, that follows.

Also, if E85 has a lower stoichiometric ratio than regular petrol I believe that translates into more potential energy (i.e., combustion pressure) to get out of it, so that could be contributing too.

I have no idea what the actual mechanical tolerances are on a stock VQ37HR longblock, tho...

Are there any confirmed breaks from overpower as opposed to detonation?

Ethanol has significantly less potential energy than gasoline. That's why it takes significantly more of it (think huge injectors) to make lots of power. But it's excellent for knock resistance.

Per Wiki: Gasoline has 114K BTU/gal to Ethanol's 76K/gal.

Not that I know of. I'm sure mine will go eventually. I flog the hell out of it at the track pretty regularly. And that's 600+ whp on stock internals. But of course that's one of the main reasons I went with e85.

I'm just treating it as an experiment at the point. How long can I beat on it at these power levels at the track before it fails? We'll see!

I think the key value here is latent heat of vaporization vs. amount of fuel needed to achieve peak torque, which is a factor related to stoichiometry -- check out p. 117 on down at this link.

http://martysgarage.info/manuals/bell2ttuning.pdf

It's from A.G. Bell's book on fueling 2-stroke engines, but he has the exact same formulas/rationale in his 4-stroke supercharged tuning book.

Anyway, in theory, less efficient, but more energy ultimately produced as a consequence.

Now, if E85 ends up breaking about even, then it's just less efficient, but has a higher auto ignition threshold and higher octane, in which case never mind my other point :p

Those are great books BTW!

The E85 Mystery
 

Some great discussion taking place here.

It would be nice if VQ owners knew whether our cars are power limited at 550WHP due to engine internal strength or if it's based solely on detonation. This is important to distinguish because guys with stock motors and FI should know what the limiting factor really is.

If a tuner could get 700WHP out of my stock engin, regardless of fuel, would I really feel comfortable keeping it there (even if there are no signs if detonation)? Definitely not lol

I'm getting my car tuned in a couple weeks and I want to be prepared so I think I'll play it safe. I'll have two maps. 1 for 91 and another for 94 octane. Regardless of the amount of power he can get with the 94 I will make sure to use a boost setting that maintains no more power than 550WHP. When someone can produce information indicating it's 600WHP then I'll change it at that point. For the long haul I think that's the best approach - IMO


NOBLE

One BIG issue that doesn't come up is the fuel pressure drop associated with a stock fuel pump assembly AND keeping it returnless. Over time the drop can get worse leaning out the AFRs. I HIGHLY, and I stress HIGHLY, recommend forced inducted 370Zs run a return style fuel system. From what we've gathered, fuel pressure drops become apparent near and around 450 whp.

There are quite a few of us running 600+ for some time now. But admittedly no one with 20k miles or so. Just give it time :)

I'm convinced 600 with proper fuel, cooling, and tune is well within limits. Proof is in the pudding

Can't you just upgrade to a higher output pump?

Between that and bigger injectors I'm surprised there would be much drop off unless we're talking a lot of boost pressure.

What lph and injectors are the high horsepower Z's running vs. OEM specs?

Doesn't matter how big of a pump you put in the oem return less setup. You'll never avoid that pressure drop at the big end. Everyone will see it if they measure fuel pressure at the rail.

And like seb said, they're seeing it at 450hp, so pretty low flow.

This is interesting since phunk and I both made 500+ on E85 which we know requires even more flow.

didn't phunk have his return setup? I know the drop is there. Maybe just not bad enough to cause problems until you get up into the higher end, but you could see the pressure drop even at low boost

He was returnless. It may drop well over desired. But if afrs are in check .......

Not running E85 but I put a fuel pressure gauge in using Phunk's multi-adapter. I'm running aero340 fuel pump at about 9-9.5 lbs boost. I'm definitely seeing the pressure drop Seb is referring to. AFRs are solid and the venturi restriction at the pump is holding much higher fuel pressure than stock but I'm definitely dropping 10lbs under boost. Next time I drop the turbo I'll definitely be installing Phunk's S1 return system and drilling the venturi out to get pressure reading to expected 52 psi of a stock VQ.

So stock pump, stock setup with bigger injectors and e85 on a NA is ok or no?

I did make 586rwhp @9psi returnless with E85. I had a mild feed line upgrade, but I did not have the return portion. I do have the CJM S2SE return system now, but not when I was on the dyno. When I was running returnless, I did have pressure drop. I cannot remember now how much it was, but it was clearly there as indicated by the gauge in the engine bay, which we could see on the dyno. Since I watch my A/Fs like a hawk and have the ability to readjust my tune as required, pending changes in weather, etc... I just dealt with the pressure drop and accommodated it as required.

edit: I should stress/imply that it is not recommended to run it how i did. those of us in the industry are often willing to take greater risks with our personal cars. i will run my own car in a state that i would never give back to a customer.

My car runs more boost on the street than it does on the dyno... tuned at 9 psi. but more often than not, on the street, my boost is 10-10.5, sometimes even hits 11. once i hit 13! lol. Its funny how the boost sounds so low if you talk to guys with 4 cylinders running around with 30-40 psi to make our power!

So Im guessing you could get past 600whp running pump gas on this stock fuel system if were seeing it getting close on a fuel requiring 25% more flow.