Dragon

How is Germany these days? I was stationed there from Oct 90-Nov 93 up in the Bremen area at Garlstadt for a year and down by Frankfurt in Hanau for 2 years. I don't think a 13B will take very well to the autobahn and all that Wangan stuff...

rx7machine

Speaking of octane.. is there really any difference in the performance?

rotary_beetle

The higher the octane rating the slower the fuel burns. The slower it burns the less you will experience the effects of detonation. Detonation is when your fuel pre-ignites earlier in the power stroke then its supposed to. Causing colliding flame fronts and possible engine damage.



For example; an aggressive tune might be set right below the detonation threshhold at WOT and under full load with said octane rated fuel. Say that tune gets you 15psi boost on 91 octane fuel - Increase the fuel to 110 octane and you just raised your detonation threshold, now you can safely run 22psi of boost.. Detonation is usually your limit to how much boost you can run on a given set-up. Another factor that decreases your detonation threshold is inlet air temperature.



Thats why many people use intercoolers. A good intercooler lowers your air inlet temperature, this does two things. It increases the volume of air you can force into the engine (within the i/c's max flow rating) thus increasing the mass in each cylinder and with the proper fuel ratio increasing the potenial energy rating of each cylinder. Just as higher octane lets you run more boost so will an i/c. If i/c A cools your charge temp to 210 degrees and i/c B can only cool to 250 degrees then i/c B will detonate the engine first.



A cooler aircharge is going to keep pre-ignition cylinder temperatures lower, this helps prevent pre-ignition.



With higher octane if you do have pre-ignition, its effects will be minimized when compared to a lower octane with the same boost levels.



So with higher octane you can run more boost and thus get more power and performance.





I hope this helps answer your question.



--Paul

rx7machine

Ok, cool. Yea I've heard that the higher the octane rating the slower the fuel burns..