Octane made easy: Do-it-yourself race fuel

[holeshot]

Originally posted by bclapham
sorry guys, i just read my post, i am beggining to sound like a pompus old fart!

Not at all. I think most people welcome a credible post. :thumb:

 

[bscottr]

Besides Bruce, you are MUCH to young to sound like an old fart. :)

 

[Studboy]

Rename this thread:

Screw-It-Yourself race fuel!!!

 

[Thumpitythumpity]

Tolulene is great if used as an emulsifier. In very low additions, it changes the vaporization characteristics of gasolene, making the fuel entering the combustion chamber a fine mist instead of droplets. A finer mist burns hotter and faster, and more evenly.
Most octane boosters are little more than diesel fuel.
I still don't know why we used to add mothballs to our gasolene for racing, but I was just the rider (twist grip/hang on), the real magicians were always the mechanics.

 

[oldfrt613]

Kind of strange to me to spend so much money on other stuff, and not spend a little coin on good fuel for something you love to do ( heck, it costs more to go to the movies, than a couple of gallons of race gas ). If nothing else, race fuel is consistant, where as pump gas can change from day to day. There are enough variables ( which you can identify ) in tuning without throwing in the pump fuel variable ( goodness only knows whats coming out of the pump today ) to boot.

 

[Thumpitythumpity]

I gotta agree with ya Oldfrt613, seems like the least a guy could do is stop by the local airport, head over to general aviation, and pick up some AVgas on the way out to the boonies, or to the track.
BTW, I meant DISPERSANT, not emulsifier...dadgum oldtimers disease kickin up again.
Pump gas is extremely iffy in these parts. My most used bike these days is my DR, so I ride it to the local store to gas up most of the time (great riding is just outside my front door). One of the worst feelings I know is that sickening sucking sound the pump makes as you get the trashy last dregs of fuel out of the tank. It's happened to me 3 times last year. Every time it does I'm tempted to pull my fuel line off and drain the gas/water/sludge out right there at the pumps. I'm only about a mile from our little airport, so I head over there most of the time unless I'm just lazy, or wanting to catch up on the gossip with the local truth and veracity league who meet at the store every day to stare at strangers who stop in.
The parts store has 5 gallon cans of racing fuel for sale, but it's so far over there I'd burn all 5 gallons out on the way home.
Anybody know what was supposed to be the advantage of putting mothballs in the gas? I never asked the knuckledraggers why they did it, it was hard enough just telling them what seemed to be wrong when it wasn't me. They usually had great insights on things...like if my complaint was that I was getting outrun to the first turn, they'd make helpful hints like "have you tried shifting gears?".

 

[Rich Rohrich]

Anybody know what was supposed to be the advantage of putting mothballs in the gas?

The mothball thing one has been around since before I was born.:yikes:

Like so many things, there is a SHRED of truth in here, but the "BS effect" has blown this totally out of proportion over the years.

REAL mothballs are made from Napthalene and some binders and has no oxygen molecule. Napthalene is used as a reference fuel in diesel fuel testing. Diesel Cetane ratings are the inverse of Octane ratings, the higher the cetane number the greater the tendency to knock. Napthalene in reference (reagent)form has a cetane rating rating = 0. Depending on who you ask this translates ROUGHLY to an MON octane rating about 90. Pump fuel in the US currently has an MON rating a couple of points lower than 90.
So there is the THREAD of truth I was referring to.

What the mothball proponents fail to realize is Napthalene has a boiling point of ~420 degrees F. That's anywhere from 100-200 degrees F higher than most gasoline components. If a component of gasoline fails to make the all important liquid to vapor transition then all it will do is pass through the combustion chamber leaching heat along the way. In simple terms it goes from the tank and back out the exhaust UNSCATHED. Even if you could vaporize the Napthalene and burn it, the energy available and the heat of combustion is too low to be of any use.

Naptha is just an early process component of gasoline. There are a lot of steps to go from Naptha to gasoline, so it's subject to essentially the same caveats as Napthalene.

Anyone who has been around manufacturing for more than a few days knows that when it comes to commodity products like Napthalene, Toluene. Xylene, Acetone etc , purity takes a back seat compared to "cost to manufacture". In a word these compounds are full of random junk.

So experiment away, but in the end it's just an excercise in chemical futlity.

 

[Thumpitythumpity]

Thanks for the education Rich!
I never knew exactly why they were so big on the mothball thing, I only knew that it was like a religion or something, and while I may not have been the smartest guy out there, I knew better than to ever question my crew chief.
One thing for sure though, I never had an engine eaten by moths.

 

[Vic]

Most octane boosters are little more than diesel fuel.

That's a new one.

 

[Thumpitythumpity]

Man Vic, I swear when I put my nose down close to the bottle of 104+, that's kerosene/diesel fuel/JP1 I'm smelling.
It says petroleum distillates on the lable, but I've not tasted any to be sure.
Unlike Rich I don't have any scientific background.
A friend of mine who works for Volvo was telling me that 104+ does not even burn, just takes up space and raises compression (which would seem like it would make a ping worse).
I run 104+ in my boat gas, my friend told me it was just diesel, but it never hurt anything, in fact, my outboard will do something pretty neat. If it's been running a while I can shut it off for 10 minutes, then turn the key on WITHOUT ENGAGING THE STARTER, and the S.O.B. will bust off instantly.
It's been doing this for more than three years, and I run it hard, so I know it's not hurting the engine.
104+ says petroleum distillates on the lable, but I've not tasted any to be sure.
Unlike Rich I don't have any scientific background, and so am always glad to be disabused of improper notions.

 

[Lokair]

I have asked this befor to a muscle car magazine tech ed and he assuered me that running diesel or kerosene mixed with Gas in my GTO (11:1)compression is a very bad idea. There is a very good article on Octane,power, and flame front tech in one of my back issues if I find it I will post it. There is a lot of science involved in octane that I am no expert on , but I willing to ask ?s and listen for answers.
Lok

 

[Thumpitythumpity]

I hear ya Lokair. I know running mostly diesel in a gasoline engine is a way big nono...some idiots siphoned some out of a school bus near where I live, somebody called in after seeing them...they were not hard to catch because the engine puked it's guts all over the road, and put them afoot.
Poetic justice....finest kind!

 

[Vic]

A friend of mine who works for Volvo was telling me that 104+ does not even burn, just takes up space and raises compression

Another new one. :)

As far as I know, all of the commercially available octane boosters are primarily tolulene.

 

[Thumpitythumpity]

LOL!!!!
Well I DID say he worked for Volvo.

 

[Rich Rohrich]

A friend of mine who works for Volvo was telling me that 104+ does not even burn, just takes up space and raises compression
.

You need to get a smarter group of friends :) or at least give serious consideration to NOT posting any more of their "chicken shed" wisdom in this thread. :bang:

 

[Thumpitythumpity]

Well Rich, the observation that 104+ smells like kerosene was entirely my own, and I stand by it.
There is a hell of a lot of difference between the way kerosene and tolulene, or acetone smell.
I may not know the engineering data, but I'll post whatever I want to post, since I consider my own real world experiences as valid as any.
Both acetone and tolulene in small quantities DO improve combustion characteristics, and not at the expense of throttle response.

 

[Okiewan]

See here's the thing. You post stuff that's inaccurate and or at best, wives tales, some will believe it. What you think you smell and what you actually smell, while I'm sure is relevant to octane and how well your bikes runs, can be verifiable by those pesky things called facts. The guy you just called-out is WAY into the chemistry of fuels and does what he feels is the right thing to squash silly mis-information being pushed on this forum. Sometimes it's better to read and learn before putting one's foot in one's mouth.

 

[Rich Rohrich]

Both acetone and tolulene in small quantities DO improve combustion characteristics, and not at the expense of throttle response.

You admit to a lack of understanding in terms of combustion chemistry and you still want to go down this road. :bang:

You're a new member so I tried to be nice as you were posting less than accurate information in this thread but it's clear that was a waste. It's a mistake I won't make again. ;)

 

[Thumpitythumpity]

Well, Have you done the entirely subjective sniff test yet?
Other peoples real world experience and some test data.
http://peswiki.com/index.php/Directory:Acetone_as_a_Fuel_Additive
I appreciate your trying to be nice.
I've read conflicting opinions by very qualified people, so what is the difference if two petrochemical engineers have a difference of OPINION, or you and I have a difference of OPINION?
Theory is not test data.

 

[oldfrt613]

Careful, you may wake the sleeping giant .....

 

[Thumpitythumpity]

LOL!!!
Arguing on the net is like participating in the special olympics.
You might win.
But your still retarded.

Ok. You win.

See, nothing to it. :laugh:

 

[Thumpitythumpity]

I understand Okiewon, and I yield to Rich's greater understanding of chemistry, however, I have read conflicting opinions on this matter, written by "qualified" experts in the subject matter at hand.
My observation that 104+ smells like diesel fuel is simply that, my own observation. The observation that diesel smells different than tolulene is also a personal, subjective observation, and therefore entirely valid.
As far as chemistry experts go if they were so infallable, why was my sister born deformed after mom took thalidimide?
Now if I told people not to post their own opinions, would I be so self important as to think I were being nice?
Nope.
Am I being nice now?
Yep.

 

[Rich Rohrich]

Theory is not test data.

I just love it when someone calls me out apparently assuming I've never turned a wheel in anger on a race track. :rotfl:

My observation that 104+ smells like diesel fuel is simply that, my own observation. The observation that diesel smells different than tolulene is also a personal, subjective observation, and therefore entirely valid.

I never called THAT statement into question, but I did take issue with the following statement you seemed to be presenting as a fact:

A friend of mine who works for Volvo was telling me that 104+ does not even burn, just takes up space and raises compression (which would seem like it would make a ping worse).
I run 104+ in my boat gas, my friend told me it was just diesel,

or you presenting this as some sort of support of your claims:

Other peoples real world experience and some test data.
http://peswiki.com/index.php/Directory:Acetone_as_a_Fuel_Additive
.

I have to wonder how closely you read the page you linked to because it doesn't support your thoughts on acetone as an additive. Just a heads up. ;)

Opinions are fine (and welcomed) , when presented as such. When opinions get disguised as facts it just adds to the enormous body of misinformation already littering the internet, and we try hard to keep dirtrider.net from being just another storehouse of bad info like some many forums have turned into.

Unlike a lot of folks who post on internet forums and websites I've gone to great pains to test "accepted" theories in the real world of racing to hopefully separate the wheat from the chaff. A knowledge of chemistry without real world test data to back it up is of limited value at best. I think most of us can agree on that. We have a large group of very qualified members here who have gone to similar lengths to test ideas and theories on a variety of subjects. We are really fortunate to have such a quality membership base here.

If you look closely at the icon in my profile and you'll see my turbocharged dragbike from 1978 that ran on various gasoline blends including toluene as well as more exotic fuels. I learned a lot of what I know about fuels combustion chemistry over the past 30 years of racing the hard way, at the 1320 foot altar of engine destruction as well as various road race and MX tracks across the country. I didn't just pick up a Chem book one day and start spouting to kill time.

I'm bored with doing real work tonight and I haven't gone off on an insane rant in a while sooooooooooooo.......let's kill a few sacred cows once and for all.

Buckle up kids, this is going to be a bumpy and rambling ride:ohmy:

Sacred cow # 1 – Toluene is a magic fuel additive that adds power by just dumping it in gas tank.

Reference grade pure toluene vaporizes in the 240-250F range with a basically flat curve, but only lab guys with big checkbooks get that stuff. The commercially available stuff (Home Depot, paint store etc. ) has lots of distillation byproducts in it so like pump fuel it has a high temperature distillation curve that varies from load to load, so you'll see a curve with anything in the 280-400F range.

{This part is important} Anything in this range isn't likely to vaporize above 7000rpm in these engines so all it's doing is tweaking the distillation curve and the overall jetting.

There is no energy release value to it either as the gross combustion value for toluene is on par with everything else normally used in fuels.

Toluene is a decent additive if all you want to do is protect the engine from fragging itself due to detonation. It has reasonably high octane and it is relatively cheap. The downside is because additives like these are fairly reluctant to vaporize they make for sloppy throttle response, poor carb circuit transitions and poor high rpm running in engines like ours that have short intake tracts and run for sustained periods above 7000 rpm.

I’ve seen a number of instances of people on Internet automotive sites taking little chunks of info and using them out of context in an attempt to prove the efficacy of toluene in producing additional power by virtue of “heat of combustion” numbers. In doing they are are ignoring the fact that the maximum combustion heat produced by any fuel can be expressed as a function of its stoichiometric ratio and net heat of combustion. While fuels may have varying heats of combustion and stoichiometric ratios, when compared by their heat of combustion per pound of air, most aromatic hydrocarbons toluene included, and standard pump fuels are all pretty similar.

For those who haven't dozed off, here's how it works:

Reference grade toluene has a net heat of combustion = 17424 (btu/lb), and it's chemically correct (stoichiometric) A/F ratio is about 13.8:1 . This comes out to a heat of combustion per pound of air value of 1262. Average pump premium has net heat of combustion in the neighborhood of 19,000 (btu/lb) and the A/F ratio is about 15:1 which comes out to a heat of combustion per pound of air value of 1266 just a touch better but nothing we would notice. A good oxygenated race fuel like Phillips B35 (now sold as Firepower 324) has net heat of combustion of 18,747 (btu/lb) and the A/F ratio is 13.84 which comes out to a heat of combustion per pound of air value of 1355, an increase of about 9% over standard pump fuel.

The point of all this you ask? Usable energy values only really change when you go to specialty race fuels that contain oxygen bearing components or other voodoo components like isoprene. If you dump a load of any aromatic hydrocarbon in your fuel and you feel a difference it's likely only because you modified the fuel curve, which is something you could have done just as easily with brass aka JETTING.



A little more about Toluene and combustion chemistry.

The willingness of a hydrocarbon based fuel to ignite is essentially a function of it's ability to vaporize. Once it's vaporized they ALL light off pretty much the same. Pump fuel is adjusted throughout the year in an attempt to ensure that the fuel will vaporize quick enough for the lowest temperatures encountered but not so easily that you run into a vapor lock condition in warm temps.

If you pick a high octane race that has a vaporization curve that is poorly suited to your riding conditions you can effect it's starting behavior. Fuels that vaporize easily will tend to richen the jetting while fuels that take large amounts of heat to vaporize will in effect lean the mixture and force you to compensate with richer jetting.

Toluene, octane boosters, and combustion speed.

It’s common practice for people to summon the gods of combustion speed to try and explain the magic powers of toluene, acetone and any number of Home Depot speed secrets they are trying to foist off on an unknowing audience. They’ll tell you that these paint store solvents raise the octane of the fuel and as a result slow down combustion and fend off detonation as a result. It’s just more pseudo-science BS from people who would have done well to pay more attention in Chemistry 101 in high school. ;) Real combustion events follow the real laws of chemistry, and while it’s a pretty complex set of interactions there are a few things that are easy to explain and understand.

It's a commonly held misconception that higher Octane fuel slows down the flame speed, which keeps the engine from knocking. What a load of crap.
A fuel's laminar Flame speed (basically fuel burning without the influence of combustion swirl or tumble) is a function of fuel chemistry (specifically Hydrogen/Carbon ratio), not the Octane rating.

The Hydrogen/Carbon make up of the fuel will determine it’s flame speed and the energy release whether it's a high-octane fuel or not. You can have fast and slow burning high octane fuels, but in most cases the differences are so slight as to not be an issue.

The heat of combustion at a simple level is basically a function of combustion efficiency and the calorific (energy) value of a fuel. There isn't a lot of energy difference between most conventional fuels, but combustion efficiency can sometimes be improved with race fuels so a bit more heat release is possible. Overall it's pretty much a wash in most cases though.

In other words, you aren't going to change the energy release or the speed of combustion in any significant way by switching from 87 to 110 octane gasoline, or anything in between . If you lose or gain power by switching fuels there are other things at work.

The way octane influences knock has to do with the way fuel is burned (well it’s really REACTED in the chamber) in the combustion chamber. The components in higher-octane fuels are less likely to have weak molecular bonds that can break easily and form active radicals. Higher-octane fuel is just made up of components that are (for lack of a better term) stouter under high temperatures and high cylinder pressures. Things like our long lost friend lead and metallic additives like MMT (common in octane boosters) tend to work as an anti-catalyst and block the formation of the active radicals that lead to auto-ignition of the fuel and ultimately detonation. The longer it takes to react all the fuel the greater the chances are that heat will accelerate the reactions beyond what the fuel components can bear. The idea that purposely SLOWING things down in the chamber is somehow beneficial in light of the reactions taking place is pretty funny really

Heat , pressure, and time tend to be the driving force in all of this. The more heat and pressure you subject the fuel to and the longer you keep the temps elevated the better and more stable the fuel you need . That's why engines that run at high rpm and have small bores can run very low octane fuels even with high compression ratios.

It's just simple chemistry really. If you look at the chemistry of explosives you can see a lot of similar reactions taking place, and it can give you some real insights into what's happening inside the combustion chamber when things go wrong. It's a fine line between engine tuner and explosives engineer.

 

[Thumpitythumpity]

My point was about vaporization, and more thourough combustion.
Ok, friends?
Give us a hug. :yikes:

 

[Rich Rohrich]

The addition of acetone causes the mixture to burn more thoroughly.

In a gasoline burning engine (not a DIESEL) that is rarely the case.

Studying the combustion cycle will get you nowhere.

I give up. :bang: :bang: :bang: :bang: