SPDFRK

Not a problem here, my car said it was 122 on the highway yesterday

i could use that!!

Farsyde

i would guess the spark plugs are ignited early/late (retard/advance) so they are ignited under lower/higher pressure, whichever the need may be

wakeech

yup... ignition retardation means that the ECU waits until after TDC to ignite the charge, so that the charge is under less compression... it'll almost never advance timing very far before TDC, as that would incur something extremely similar to detonation (pre-ignition)

anyways, this is so cool, i'ma sticky it.

*STICKY!!*

wakeech

just for future reference, there is a difference between "nitro" (which is NH4: nitromethane... big big big boom) and "nitrous" (NOx oxides of nitrogen)... one is a terribly high energy potential fuel, the other is an "oxygen substitute", and non-flammable.

TerenceT

btw TDC = top dead center of the piston

just called sherwin williams in so cal

5 gal jug @ 34.75
1 gal jug @ 7.95

i've to call out my buddy to see where he get his 1 gal jug at 4 something ??

Thanks wakeech for reminding the difference between nitro and nitrous

i don't want some of you pouring nitro (RC car gas) or Nitrous (nozzz) down your fuel tank and blame ME for it

btw, i am thinking of trying the xylene on my Nitro Rc first

it's a .12 2 stroke, any benefits? just want it to blow up far away if it does :D

Smoker

Hold on, I thought detonation is defined as the Air Fuel mixture combust by themselves BEFORE TDC. So how would igniting the Air Fuel mixture slightly after TDC helps this situations ??? I just don't understand how these fits together.

wakeech

well, i guess the lower tempurature (from the reduced compression) would slow the burn, preventing it from exploding??

feelthesweetbea

WHAT kind of effects would XYLENE have on the fuel system? Pumps, hoses, FPR, Exhaust fume collection?

TerenceT

supposely nothing cuz xylene and toulene is part of pump gas already

it would have the same effect as octane booster in a bottle, nothing.

plus you are dilluting it with gasoline, we are not running straight xylene...

plb

Would xylene help pass an emissions test? Or does it add chemicals in the exhaust that would cause it to fail the test?

If it works, a gallon of xylene seems like a better choice than a small bottle of emissions fuel additive.

wakeech

read it again... "it's already in the gasoline"...

whenever you combust a very pure oganic chemical, like if you had 100% toluene or whatever, you're going to get a very clean burn, as most everything is H or C.

Boozehound

I'm confused.

First things first - how can Xylene be a "high power" fuel? Aren't we talking about chemical engergy? And the chemical engergy would be greater for a given volume than other HC mixtures? I know it sounds like splitting hairs, but power is something way different.

As for increased performance on running Xylene - everything I've been taught goes along with what got said earlier (once you have enough "octane," there's no use for any more). So how does increasing the energy "density" of your fuel aid in completing useful work through the engine? So does a smaller amount of fuel output the same amount of work when running a high Xylene mixture? Does the new mixture effect efficiency or useful work when compared to a fuel that exceeds the standards set to prevent pre-ignition (octane requirement)?

I've always heard the conventional wisdom that you go with the lowest octane rating you can run without risking pre-ignition (or in most new engines - having the ECM step in and retard the timing). That's the same thing I learned in my thermodynamics classes, etc.

I guess I'm not following the basic idea here - what does the Xylene actually affect, and to what extent? Maybe I need to find me a ChemE to talk to... or maybe someone who will just explain things really slowly...

Farsyde

as was said before, it's not a "high power" fuel at all. It IS a component of all gasoline. It just happens to be a very pure form.

Think of it like Koolaid. Youve got some drink mix: like Tuelene, sugar like xylene, and a whole lotta water: like the remaining mix.

If you have all water and no mix or sugar, it's a crappy drink. Just like having all propane components makes a lesser octane or lesser quality "filler" for the gas. Now you add sugar and mix and the drink gets better and better. But it doesnt change the "power" of the fuel. Eventually there is a point where you cannot desolve anymore mix or sugar called saturation (octane limit).

Since Xylene and Tuelene are already in fuel, adding them only increases the octane to a cetain asymptotic point. All this does is help prevent detonation (pre ignition) which in a stock application may of may not help your car. But since the tuelene and xylene burn very cleanly there will be less carbon and other "junk" left behind. Imagine the boost levels you could reach that are normally octane limited!

Boozehound

Thanks Farsyde -

I suppose I asked for the Kool-Aid description now didn't I. However, I do understand that it's a component of gasoline (which is a pretty generic term in and of itself) and it's proportion relies heavily on process conditions at your local refinery. As for the power, that's what I was getting at - there's no power associated with fuels. Power deals with work and time, not chemical energy.

You did answer my question though - it's just used to improve octane. So I suppose the real advantage over a fuel with a similar octane rating is the cleaner emissions output.

So why would anyone pay between $5-10 a gallon to boost the octane for an unmodified NA car? If pump gas meets the requirement and you're not gung-ho green, then why switch? I understand the change if you want to run boost or mess with the compression ratio, but that's the heart of my question - is there something else achieved with Xylene?

wakeech

no one would really see any appreciable benefit from running this in the RX-8 right off the bat, but $5-$10 per gallon of really super (120 octane) unleaded gas is way the hell better than $6 or more per gallon for leaded race gas, eh??

unless you've really got a high performance vehicle and want to run your 22psi through your 66-1 Garrett turbo to make like 500 rwhp all the time, you really don't need to make the switch, yet.
if you, say, rebuild the engine, and Mazda offers like, i dunno, blank rotors so you can grind your own depression, and choose to go for like an 11:1 ratio, with a p-port and a 12k rpm redline, maybe you'd wanna do it. it just depends on the application.

rx7gslse

hey, I can add soemthing to this...

Several of the 3rd gen turbo guys here aroudn DFW are runninga tolulene mix on their cars and for the month or so have had no problems...

That being said, I don't really see the point of the extra expense on the Rx8s. While a boosted rotary will be able to run higher boost levels with a greater tolerance to detonation a normally aspirated rotary engine will see no power gains from running a higher octane due to the longer conmubustion burn...

And furthermore, the Rx8s for now are running some wicked rich a/f #s no there is no worry of detonation at all, and even if so, a NA engine can handle that pretty well..

That being said, with no gain from power, and no need for reduced detonation, I see no reason to run this on your Rx8s. It's just going to take extra effort and cost extra money...

FWIW the 787b race car ran it's lemans race on 85 or 87 octane and won... I figure they know what they're doing...

sleeepyhead

I read on a website that LOWER octane is best for NA rotary engines. Instead of explaining, i'll just give the link. I don't know what is the recommended octane is for the the RX-8, but if this is true for all NA rotaries like the article said, adding these expensive additives to your RX-8 would have a negative effect http://members.ij.net/mrmazda/cfaqtext.html#ROCTANE

Hymee

iTrader: (1)

There is a difference between the Octane rating, and the power potential. For instance, LPG can run at a higher comp. ratio because it has an Octane rating of about 110. But you get less power from it, as the calorific value is lower (the amount of energy available).

In Oz, we are recommended to use 95 RON fuel. Now I know I can increase the octane rating of my fuel by using some "go-go juice" such as toluene, but what I wan't to know is that going to give more available energy for combustion - hence more torque = more power??

It seemed like that is what the doc was talking about earlier on in this thread, but it has degenerated since then into arguments about whether the '8 needs higher octane fuel.

Cheers,
Hymee.

wakeech

let's revisit what has already been said:



...there you have it.

yes.

Turbo Matty P

BUMP for my question. My daily driver right now is a 95 Honda civic sedan with the D15B7 1.5L engine. I have added a true cold air intake, DC sports 4-2-1 header with 2.5" cat-less exhaust and an MSD 6A ignition and distributor. My car only has a 9 gallon tank. If I add 8 gallons of 93octane and 1 gallon of 115octane that only yields an approximate octane of 95.6. Is my math correct? If this is the case will this prove benneficial to my car? I also was able to buy 1 gallon cans of "pure" Xylene from Home Depot for $4.97/per. I've checked several variations on this and I'm stumped. If I mix 7gal 93o with 2 gal 115o I only get a mix of 86.7 octane?? Am I figuring this wrong? Please advice doc

TerenceT

((2x115) + (7x93)) / 9= 97.89

??

Turbo Matty P

I found my error. I was adding 2 gallons of 115octane as 130! not 230! I knew it just wasn't making any sense to me! Wow, who feels dumb right now? Take a step forward, not so fast everyone else, but me!
Anyway, now that my math is cleared up does anyone know if this octane will benefit my NA car with upgraded airflow and ignition mods? Any estimates on power??

3rdGen7

I use Toluene in my RX7 for race days. Also, over 30% you get a lot of smoke.. or so I was told by a lab I was dealing with on the topic.

Hymee

iTrader: (1)

I found a local supplier has an off the shelf 100% toluene product. Should I go for that? Or should I look out for Xylene?

I get the feeling from doc that theye are about as good as each other.

I'm going for more power, not more octane.

Cheers,
Hymee.

labrat

Hey Doctorr

Obviously you know your fuel. What do you have to say on adding ethanol to fuel? On my simple calculations, ethanol has a heat of combustion 33% lower than iso-octane (33kJ/g compared to 44kJ/g). Our federal government is in coalition with an agrarian party which is desperate to shore up support among their sugar cane growing constituents, who are going broke due to overseas competition, reduced sugar consumption, and of course inefficiencies. Oh, and the prime minister's mate has a couple of ethanol distilleries.

The news broke today that the government is sitting on a report which gives manufacturer's recommendations on which cars should not use ethanol-laced fuel. The government claims it is seeking more evidence. Government members claim that certain US states subsidize ethanol in fuel, and it does no harm to cars. They also say it can be added up to 20%. They say that the same oil companies who are against adding EtOH in Australia are praising it in the USA.

What's your take on this?