Roddimus Prime

Tendo, 6 gallons of 93 octane + 1 gallon of 115octane Xylene (100% pure) = 7 gallons of 96.4octane.

7 gallons is about a half a tank so if you want less weight you could run 3 gallons of 93 + .5 gallon of Xylene. for the same 96 octane.

Never mix Xylene more than 6:1. It'll wash your cylinder walls. If you need anything higher than 96 octane you should just buy 100 octane race fuel from your local speed shop.

gotaphatprotege

lol true that my wallets quite happy runnin 87 and so is the car...lol

juddz

Octane is not a measure of a fuel's energy - fuel energy is measured in BTU. Octane is a measure of how quickly the fuel burns. The higher the octane, the slower the burn. You want a slower burn in cars with a higher compression ratio (or additional compression pressure as the result of a turbo or supercharger). The reason is, if the fuel burns too quickly, you'll get spontaneous combustion - commonly called "knock". Now, if your car has higher compression pressures than stock and you get knock, the knock sensor ( a piezo ceramic element) is going to sense the vibration and send an electrical signal to the ECU, which will retard spark timing, which will cost you power. But this will never happen if your car is stock, because it has been carefully calibrated by Mazda to have a wide margin against knock on 87 octane under full load conditions. Remember that running high octane fuel is really buying you additional margin against knock. If your Protege is essentially stock (or you haven't somehow increased in-cylinder pressures by shaving the head, adding higher compression pistons, or bolting on a turbo), you'll gain nothing by using a higher grade fuel. But if you order that Wagner turbo kit, better to invest in premium when you fill her up.

Roddimus Prime

wErd. I'm only using my home brew 96 octane when I'm on the spray.

juddz

And that's a good point that Roddimus makes. If you are using N2O, better go with higher octane fuel.

I was expecting that someone would correct me, and note that not all cars have knock sensors. This is true; and in such a case, there is nothing to detect knock and thus the ECU cannot compensate for it. But even if your car cannot detect knock, using the correct grade of fuel will prevent it.

Preventing knock from occurring is extremely important, because it causes in-cylinder temperatures to rise, which can lead to pre-ignition. Pre-ignition is ignition that occurs from a hot spot (such as a red hot exhaust valve) and it occurs independent of the spark event. This can lead to melted pistons, etc.

Roddimus Prime

technically, knocking and pinging IS pre-ignition. knock and ping are the two sounds people hear when pre-ignition occurs!

I know what you mean though.

gotaphatprotege

lol i dont know what he means...lol that plane went way over my head but hey you learn somthing new everyday

macdaddyslomo

that doesnt JUST occur from hot spots...I hate it when people make all inclusive statements...actually you are more likely to get detonation from higher cylinder pressures on lower octane gas than a hot spot....higher octane gas resists detonation in these higher cylinder pressures,ie,turbo,N20,high compression pistons...

juddz

Pre-ignition (surface ignition) occurs just from hot spots. Knock (spontaneous combustion) is the result of combustion pressure. There is a distinction between the two...

GNO

Me too!

Octane is simply a hydrocarbon chain. Octane just happens to be more resistant to detonation than heptane and many other hydrocarbon chains found in automotive fuel. The octane rating came about as a guide to how resistant a fuel is to combustion. The Octane rating is a measure of how resistant a fuel is to ignition, detonation resistance. There are two ratings used to form the Antiknock Index. The Antiknock Index (RON + MON/2) is the rating found on the pumps at gas stations.

"How quickly a fuel burns" is extremely vague. Typically "quick" is a term used to describe speed (scalar form of velocity), or a change in speed (acceleration). In which case, one measure would be Stoichiometric Flame Speed which is measured in m/s. I can see how you may be referring to the temperatures and pressures a fuel will autoignite, but using a term like "how quickly a fuel burns" is easily misleading.

hmmmm no. You want the fuel to burn at the same rate. Which is why certain hydrocarbons work better than others. If the fuel reaches its Autoignition Temperature for a given pressure, then the fuel will ignite. . . . commonly called "knock" or "detonation".


Pre-ignition is when the air/fuel mixture ignites prior to the spark plug firing and is usually but not always caused by hot spots. Detonation is the erratic combustion of the air/fuel mixture where multiple flame fronts collide instead of just one flame front expanding in a controlled manner. The collision between the flame fronts create an audible pressure wave. . . knock. Pre-ignition can contribute to detonation and vice versa.

juddz - I'm sorry if this post sounded like a flame. You have a lot of good information in your posts, but some of it was a bit misleading and I wanted to clear things up a bit.

Roddimus Prime

pwn3z

gotaphatprotege

jo0!!!!

gotaphatprotege

hahahaha lol

kcidmil

Word of warning to everyone. I live in SD, and they're really big on the new Ethanol. It's put into the 89 fuel around here, don't put any of it into your cars. They say it harmless to all vehicles, but it's a bunch of bull. I've kept my P5 away from it, but my maxima accidently got some in it. And then spent hours and lots of money replacing my injectors. Even my local Mazda dealer expressed doubts over the fuel for my P5. So if you ever travel this direction, don't get the ethanol.

Roddimus Prime

oh yeah "flex fuel"....cars should be specially designed to except it. The older taurus' could use flex fuel rather well but I know they underwent upgrades to allow them to use it.