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Discussion Starter #1
Hello all,

I am trying to calculate my Final Comression Ration (FCR) with my future setup. I am shopping around for a good fuel match.

I will have a 76GTS turbo on my stock bottem end 2JZ-GTE. I have a street built PP head as well.

A formula to calculate different boost levels for FCR would be great.

Thanks!
 

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T88 YOU
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compression RATIO.... and compression PRESSURE are 2 different things, ratio stays constant whereas pressure increases as boost increases. im guessing you want a compression pressure formula?
 

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also, when you say fuel match, are you talking about fuel system, fuel quality, or fuel octane?
 

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Discussion Starter #5
When I meant fuel, I mean race gas. For example, VP C16 is good for engine with FCR of 17:1. So, Iam trying to figure out which fuel is right for me without being an overkill. So if I am boosting to 2bar with a 76GTS, will I fall under the 17:1 FCR and meet the C16 requirement or exceed it. However, I don't just want a "C16 " should be good. I want actual figures to prove this.
 

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T88 YOU
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VP is reffering to COMPRESSION RATIO when they rate their gas, compression PRESSURE would be a measurement in psi, not a RATIO. if you read the WHOLE description is says this "Used in turbocharged engines, blown engines and NITROUS APPLICATIONS WITH CRS UP TO 17:1. Recommended by the top nitrous oxide companies. Spec Fuel for NHRA Comp Eliminator." you are still on stock bottom end so you dont need to worry about compression, you need to worry about octane for boost, how much MAX boost are you planning to run?
 

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Discussion Starter #8
SupraDupaFlyBoy said:
VP is reffering to COMPRESSION RATIO when they rate their gas, compression PRESSURE would be a measurement in psi, not a RATIO. if you read the WHOLE description is says this "Used in turbocharged engines, blown engines and NITROUS APPLICATIONS WITH CRS UP TO 17:1. Recommended by the top nitrous oxide companies. Spec Fuel for NHRA Comp Eliminator." you are still on stock bottom end so you dont need to worry about compression, you need to worry about octane for boost, how much MAX boost are you planning to run?

Well, 2 bar for now. I keep a drum of Philips B33 in my garage but that was when I was only pushing 1.7bar with m HKS twins kit. I'm trying to make sure I have thr right fuel for my usage but without having to burn a whole in my pocket. I can get a 55gal drum of Phlips B33 delivered to my house for $365.
 

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donkeypunch said:
When I meant fuel, I mean race gas. For example, VP C16 is good for engine with FCR of 17:1. So, Iam trying to figure out which fuel is right for me without being an overkill. So if I am boosting to 2bar with a 76GTS, will I fall under the 17:1 FCR and meet the C16 requirement or exceed it. However, I don't just want a "C16 " should be good. I want actual figures to prove this.

I must be the only one who understands what your saying.

Im sure a formula does exist and I would LOVE to have the formula if someone has it. We know your on stock compression ratio, no big deal. 8.5:1 is the number. Now he runs 21lbs, it now turned into basically a 12.5:1 motor, because we are going to run some race gas. How much octane do we need is the question. 104 would be good, because we already know this.

Now..lets say we have a 12.5:1 motor running 21lbs of boost, what would the compression ratio be now? 15.5:1?

Please, some chime in if they are getting what Im saying.

-Corey
 

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SupraDupaFlyBoy said:
VP is reffering to COMPRESSION RATIO when they rate their gas, compression PRESSURE would be a measurement in psi, not a RATIO. if you read the WHOLE description is says this "Used in turbocharged engines, blown engines and NITROUS APPLICATIONS WITH CRS UP TO 17:1. Recommended by the top nitrous oxide companies. Spec Fuel for NHRA Comp Eliminator." you are still on stock bottom end so you dont need to worry about compression, you need to worry about octane for boost, how much MAX boost are you planning to run?
This tells him a whole lot. So this fuel will cover 12.5:1 and 30lbs of boost?

I know what your saying, obviously use c-16 up to 32lbs on stock compression. But this doesn't answer his first question.
 

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here is the thing guys, though you are measuring x amount of "boost pressure" in the intake manifold, i hate to brake it to ya but you are not getting x amount into the cylinder unless you have a volumetric efficiency of 100% which is damn hard! if you want to CALCULATE it and you know your volumetric efficiency you can do it this way with a formula i am just throwing out. xx boost / 14.7 X volumetric efficiency X compression ratio. now, this is ONLY a formula, formulas are not totally accurate due to other factors like, as i mentioned, VE... it is very difficult to measure VE and therefore difficult to precisely determine the amount of air getting into the cylinder.
 
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