E30 tune. Am I missing out?

[danbfree]

Yep, octane is just resistance to detonation. As I understand it, ethanol has a higher octane and a richer stoichiometric ratio than petrol, meaning that you can use more of it at higher boost/compression ratios to overcome the lower energy density.

But I'm probably just preaching to the choir here.

Right, that's why you get lower mileage running it as more is needed to reach power demand, there is no argument there... but my point is, and I thought everyone who really knows anything about cars knows this, that it's not just the fuels octane but also the environment it's put into, that lower environmental temp is absolutely a good part of how more power is made by being able to tune more aggressively, not just the fuel itself's octane.

 

[Ford ST]

I copied this.



The general consensus is ethanol burns “cooler” than*gas. Technically that is correct but what does that really mean? There’s a lot more to it and I’m throwing out my analysis (btw, this is not copied from any textbook or external resource--just my own back-of-the-envelope calcs so I make no assurances).*

The burning question in my mind has been how does*cooler*burning correlate to*cylinder*temps and power? That is, how can a fuel that burns “cooler” generate more power? How much “cooler” does it burn? Are the EGTs*cooler? To explain this, I did some calcs--the results seem reasonable so I thought I would post them here with explanation.*

If you take one mole (6.02 x 10^23 molecules) of octane (gasoline) and one mole of ethanol and combust them in air, octane would produce 5460 KJ of heat compared to 1368 KJ for ethanol (eqs 1 and 2). The heat given off from the combustion reaction can be experimentally measured to a very precise number. In this case, more heat is evolved from combusting one mole of octane than one mole of ethanol, in fact, about 4 times as much.*

C8H18 + 12.5O2 → 8CO2 + 9H2O DH (heat released) = -5460 KJ/mol [eq 1]
C2H5OH + 3O2 → 2CO2 + 3H2O DH = -1368 KJ/mol [eq 2]
(note: negative sign just means heat is released; more negative = more heat)

So in this sense, ethanol burns*cooler.*

Now, let’s take a look at what happens inside the*cylinder*when the oxygen content is the limiting factor. For this, we need to look at the combustion equations where the oxygen content is set as the limiting reagent (i.e. 12.5 moles). For every 12.5 moles of O2, you can*burn 1*mole of octane and 4.16 moles of ethanol. So you can see in this case, you actually get more heat from ethanol per unit oxygen (approximately 4.4% more) [eq 3].*

C8H18 + 12.5O2 → 8CO2 + 9H2O DH (heat released) = -5460 KJ/mol
4.16C2H5OH + 12.5O2 → 8.3 CO2 + 12.5 H2O DH = -5700 KJ/mol [eq 3]

If we scale down the last equation by 4.4% such that the thermal energy produced from burning ethanol equals that of octane, the equation becomes*

3.98 C2H5OH + 11.97 O2 → 7.95CO2 + 11.97 H2O DH = -5700/1.044 = -5460 KJ/mole [eq 4]

So how does ethanol burn*cooler, yet produce more power? Well, power is a result of*cylinderpressure. For that, we need to take into consideration the total number of moles of combustion products from octane and ethanol. For octane, you get a total of 17 moles of combustion products (eq. 1). For ethanol, you get a total of approximately 20 moles of combustion products (eq 4). That corresponds to approximately 18% more moles of*exhaustproducts from burning ethanol at the same thermal energy level as octane.*

Since P=nRT/V, pressure is proportional to not only T (temperature) but also n (# of moles of total*exhaust*products) at constant V. Well, if EtOH produces 18% more moles of*gas*at the same thermal energy level as octane, then the temp can drop by 18% to produce the same*cylinder*pressure. Hence,*ethanol can burn*cooler*to give the same pressure as burning octane because it produces a greater amount of combustion products.*

Here’s the rub--everyone wants max power, so you end up burning as much ethanol as there is O2 in the*cylinder*which thereby produces 4.4% more heat than octane with even greater*cylinder*pressures. So while ethanol can burn*cooler*and produce more power, in reality, we end up burning as much ethanol as possible to get max power. This results in higher*cylindertemps than*gas*(but more power too*[https://www]).



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[danbfree]

Not BURNS cooler, per se, but has engine cooling properties overall... From STRATIFIED, "As the airflow increases and temperatures start to climb the added ethanol really works to bring down cylinder temperatures and help keep knock away. Below are a few graphs which highlight the differences between E85 and gasoline tunes.The gains we see in these graphs come from the increased timing and boost we can push thanks to ethanol’s higher octane and increased cooling properties.

It's 2 things, period, we don't need to get anymore technical about it... and my tuning setup simply helps prove it, there is absolutely nothing to argue about or controversial... like I said I'll leave it alone now that I've quoted from the Stratified scriptures, LOL. Sorry things got intense a bit, but really this should be all known stuff for enthusiasts.

Here is the Stratified article, not too long and good reading: http://stratifiedauto.com/blog/e85-blends-in-the-mazda-disi-and-ford-ecoboost/

Very cool (literally), how it really helps in hotter weather, that also helps prove my point too.

 

[alexrex20]

I'm done here. We are getting lectured about basic tuning knowledge by someone that lacks basic tuning knowledge. LOL

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[Meowoosh]

Im still in for a debate on whether or not Ethanol is a good fuel for daily drivers in the first place. For a race car, sure. Empty the tank, teflon lined fuel lines, etc. But long term wear from E30 on a daily? Not sure if theres data out there for that aside from "bro ive had this tune for 30k miles and no issues yet".

If anyone has dug into two similar motors, with similar mileage and usage, but one ran gasoline and one ran gasahol at say e30? Wonder what differences could be seen, from the gas tank to the o2 sensor, and of course everything in between.

That said, i actually have 2 E30 maps, stratified and dizzy. But i find myself using them less and less now because of long term concerns (and short term valve train noises)

 

[danbfree]

I'm done here. We are getting lectured about basic tuning knowledge by someone that lacks basic tuning knowledge. LOL

So that's why I posted conclusive evidence of what I was simply trying to say all along? Dude, you have a funny way of stating the opposite, LOL... I was just trying to show you guys how this stuff works, it's a two-fold effect on how you get more power and especially for you guys in hot areas it really make a big difference!

 

[danbfree]

Im still in for a debate on whether or not Ethanol is a good fuel for daily drivers in the first place. For a race car, sure. Empty the tank, teflon lined fuel lines, etc. But long term wear from E30 on a daily? Not sure if theres data out there for that aside from "bro ive had this tune for 30k miles and no issues yet".

If anyone has dug into two similar motors, with similar mileage and usage, but one ran gasoline and one ran gasahol at say e30? Wonder what differences could be seen, from the gas tank to the o2 sensor, and of course everything in between.

That said, i actually have 2 E30 maps, stratified and dizzy. But i find myself using them less and less now because of long term concerns (and short term valve train noises)

Yeah, it does seem the valve have more chatter, I noticed that too... We also know that ethanol attracts water, you can't store a vehicle with pretty much ANY ethanol without fuel stabilizers, so part of it it also is the fact you need to be burning through this stuff fairly quickly and replacing it with fresh fuel on the regular... but yeah, I'm curious about long-term effects, but haven't heard of too many negatives...