Octane Ratings

[infil]

Ok, quick simple breakdown, Octane is fuel's resistance to ignition.
Higher the octane, the harder hte fuel is to ignite, so no, 116 does NOT burn hotter than 91 octane, it takes a helluva lot more energy to ignite.

To get the most power out of your engine, run the LOWEST possible octane you can get away with, without detonating.
The reasons you would run a higher octane fuel are turbo/high compression engines due to the increased cylinder pressure.

As cylinder pressure increases, friction from the air/fuel charge being compressed increases and this raises the temperature. That temperature increasing will cause lower octane fuel to ignite before the spark plug actually fires. Preignition will absolutely destroy an engine. It puts tremendous pressure on the rod and rings, and extreme preignition is capable of shoving rods right through pistons.

Other reasons are in cases where extremely lean conditions will be seen, as in the case of nitrous. The way nitrous works, it adds extreme ammounts of oxygen to the mixture, tipping air fuel ratios well into the 15-16 range, and again, as that temperature increases so to do the chances for pre-ignition.

At the opposite end of the spectrum, too much octane means the car will run poorly, if at all. If you put c16(116 octane race fuel) into a stock neon, the chances that the car woudl even be able to fire the mixture are slim., however 100 octane is usually something that can be done, however it will still cause a loss of power that can be pretty detrimental.

All in all, mixing 93 and 100 in a 50/50 can be done and will generally help if you have a computer that pushes alot of timing, however it is again, a fine line that can only accurately be determined on a dyno. Injectors, pressure, pulse width, and valve/ignition timing will have a much more dramatic effect on power than overdoing it with too much octane.

[jamaicangrimreaper]

Great Post

[SuperGus]

My brothers 93 VR-4 has trouble with blowing out the spark at anything above 4500 rpms. He put 5 gallons of 110 race fuel in his tank, then filled the rest with 91 and the car ran better than it has since hes owned it. It was running so much better he could turn the boost up to 15 psi, now remember this is a stock motor with the exception of a Y pipe and HKS SSQV. Once all the race fuel was burned up his car ran like shit again so the boost had to go back down to 10. I will agree with infil, unless your motor is capable of handling the higher octanes, dont even bother.

[charger440neon2.0l]

infil great post as always! with a 3/S it typically means you need new plugs or you need to regap, when you blow out the spark. we run 14 psi and never fill up with anything but 91 octane in both of our stealths. I always reccomend changing them when a 3/S comes in with that issue since its a pain to change the rear three plugs.

[infil]

try irridiums in the stealths. I had zero fouling problems in the neon with a huge(.075) gap, including 2step time. by comparison i'll foul a set of regular resistors in 2 runs beyond the point of relighting hehe.

[charger440neon2.0l]

our shop puts NGK IFR6E11 laser iridium plugs they have a 0.044" gap in all tt stealths they are $9.98 ea. at advanced auto before the iridiums got down in price and became available we were putting ngk laser platinum plugs in, they are the same as factory and work great too, they just cost the same as the irridiums now.

[SuperGus]

Thanks for the info guys. He knows there was a gap problem and was just to lazy to pull them. Hes not worried about it now since the car is parked indefinatly.

[charger440neon2.0l]

since the car is parked indefinatly.

uhhh I don't like the sound of that. And I don't blame him for being to lazy to pull them the rears kinda suck.

[infil]

nah, rears on an 03+ 3.8L caravan suck.

[SuperGus]

Hes doing a full 99 conversion with wide body and building the motor.

[NeonTuning]

I always use 95 octane in my Neon. works fine.

Sometimes I put V-Power in it, should be a bit better for the engine..
Anyways, thats what a lot of ppl say.

[infil]

pump gas isn't going to really make a difference. Post was more directed at the guys who go to the track wiht a stock or mostly stock car and dump c16 in and wonder why they slow down.

With higher octane pump gas, you can actually create power and reliability problems, especially in cold weather. My wifes car runs like crap in winter with premium in it, same with our ford pickup.

All in all pump gas isn't going to make a dramatic difference unless you are running a very high oxygenation level in the fuel or its just bad gas. I try to stay with the major guys, BP, Hess, Conoco etc as opposed to the smaller stations as they usually have lower quality fuel, although with the standards now days, its pretty hard to get crappy gas, but not unheard of.

[racer12306]

I always use 95 octane in my Neon. works fine.

Sometimes I put V-Power in it, should be a bit better for the engine..
Anyways, thats what a lot of ppl say.

Is that 95 octane RON?

[NeonTuning]

yes Shell V-Power is octane 95.

In holland we only have 95 and 98 octane.

So I guess that's premium fuel.

if I put 98 in my Neon it runs like shit.

[racer12306]

I was just asking because in the states we have the (r+m)/2 method. Holland must be on the ron method.

Ron numbers are typically higher than (r+m)/2 numbers.