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12.4:1. this is your final or corrected compresssion ratio(FC). By that I mean adding in corrected altitude

FC- (altitude/1000)x.02

your cam selection (see Keith black pistons calculators for dynamic and static compression)

and if you are running a supercharger

(boost / 14.7+1) x compression ratio= FC

Piston companies list there compression ratios for a factory combination. Factory deck height, rod lengths, and head gasket thickness because they don't know what you are running. This calculator takes into account the things you can change and the closing event of your intake valve to give a true compression rating or dynamic.

I learned this from Blower Drive service Tech info on there web site.

Also I have a supercharged 2003 harley Davidson editon F-150. Stock static compression is 8.5:1. I am running 12 pounds of boost and I have run as high as 16lbs, on 91 octane.

That would put my static compression ratio over 15:1 on 91 octane.

(12lbs / 14.7 +1)=1.81x8.5(static compression)=15.44

(16lbs / 14.7 + 1)= 2.08 x 8.5=17.75

YES I did tune the computer for my changes, and it does remap the fuel and ignition, and aluminum heads help too.

If you do all the math and build it to the edge for where you live, don't go cruz the California beach from Denver because the altitude will change the air density and your compression ratio.

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Q: What is the maximum compression ratio to run on 93 octane?
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Congratulations you have just added to the Misinformation Superhighway. Stock specs for Hondas is about 10:1 COMPRESSION The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting. The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more


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Is plus gasoline better for your car?

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