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Fuel
Oct 11, 2004 15:57:45 GMT -5
Post by S33METEOR on Oct 11, 2004 15:57:45 GMT -5
I love gasoline. I find that in my Meteor with a 302 at 9.0:1, it runs stronger with 93-95 octane than on normal 87. This is also a summer blend. Anyone else agree?
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Fuel
Oct 13, 2004 9:27:02 GMT -5
Post by John C in Ark on Oct 13, 2004 9:27:02 GMT -5
Yes its going to run better on higher octane fuel. You can also run the timing with more advance on premium fuel.
The higher the octane the slower the burn. Yep just the opposite of wht we always think.
Anyhow, as the piston is going up on the compression stroke, the Octane rating is slowing the burn rate, until you get the spark. Then boom. Now if your timing is to advanced you will here the ping/knock/rattle of predet.
This is the fuel burning way to far in advance of the top dead center of the combustion stroke..
By retarding the timing, this set the spark to fire closer to the top of the combustion stroke. Getting a full burn just at or even after the top dead center, the piston is also being ing to travel down the cylinder on the power stroke.
(power becuase this is what and where the fuel burning is forcing the piston down)
With proper timing you dont get the predet knock, and the slower burn fuel is compressed tighter, thus producing a more complete burn in the smaller area at the top of the cylinder.
All this working together will add a few extra horsepower.
Then comes a cam more valve lift and the valves open for a longer time period, more fuel in the cylinder the more power you will make.
Now with all this in mind. We start dealing with cooler air and cooler fuel. These get smaller when they are chilled.
So now you have added more fuel and more oxidizer. The air and fuel is compressed tighter, in the same size bore. It burns and pushes the piston down faster on the power stroke.
This is also where higher compression pistons come in and even blowers forcing more fuel and air into the same sized chamber.
Then we have NO2 Laughing gass if you will. Its deadly to mamals including humans.
Its an Oxidizer, adding a lot more burnable air in the cylinder by fact the NO2 cools the air going into the cylinder. The draw bak to NO2 is it burns hot, reallu hot and really fast. It will knock a hole in a piston fast!!!! and even burns hot enough to melt the normal aluminum piston. This is why you need either ceramic coated pistons of forged when burning NO2. So adding fuel then cools the air producing even more power.
So after you have read this hopefully you can see whay 92-93 Octane worked better in many cars. BAck in the day we could get 100 octane and even 102-105. This really slows the burn down and allows higher compression yet. i.e. more power!!!
Many older engines had 10-1 or even higher compression from the factory.
389 Pontiacs came with 3- 2 barrels and 10.75 to 1 compression. This produce 360-375 HP, huge for back in the 1960- early 1970's. All the car makers had high HP engines.
Now take those with todays cam profiles and its easy to get 400-450 hp out of a 302 ford!!!
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Fuel
Oct 13, 2004 14:56:26 GMT -5
Post by w2zero on Oct 13, 2004 14:56:26 GMT -5
Modern heads are way better than the oldies too. They design in the quench area to control the flame front allowing higher compression with lower octane. With sufficient engine controls (computers and knock sensors) and a blower you can make more horsepower with regular than premium.......because it is a quicker burn. That couldn't be attempted without the computer controls because it makes adjustments in real time. Carbureted, you would err on the side of safety with less timing or higher octane and it might not make nearly as much power. This would be in a racing app only though where a narrow power band is actually easier to deal with than the myriad of compromises that allow us to use a carb on the street. Or something like that............ More caffiene.....
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