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highest octane i can run??


Guest ON3GO

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hey guys was wondering whats the highest race fuel i can run.

turbo L28ET motor.

upgraded EFI standalone system, turbo, injectors, etc.

is there a limit you can go?

thanks

 

mike

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Guest Nic-Rebel450CA

I'm just kind of curious why you are asking this. What you really want to be doing is trying to run the least amount of octane possible. Certainly you can run more octane if you want, and I am not sure there is really a limit other than the point at which it completely inhibits the fuel's ability to burn. What is it that you are trying to do?

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just trying to figure out whats the highest i can run.

my Z will never need race gas to hold its own as im building it so i wont need it to achive my goals, but i still wont mind using race gas to up the boost some more and see how much futher i can go.

also i can get any race gas i want for not alot.

so im just trying to find out whats the highest i can run without causing problems and or not gaining anymore performance.

thanks

 

mike

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Guest Nic-Rebel450CA

Ok, so your question is a little bit different then how I read it. What you want to know is basically what is the maximum amount of fuel you can force in there and get it to burn. There are a few things that you would need to know to figure that...

 

What is the maximum octane you want/have available?

What is the maximum boost your turbo can produce?

What is the maximum that the intake (including heads and valves) can support?

 

The first two questions are probably the easiest, but the hard one is going to be how much the intake can take in before there is just too much pressure. Assuming that the intake can handle whatever you force into it, that the engine will hold together as well, and that the injectors will flow enough fuel, you would simply need to find out what the maximum CR is that the octane rating will support, and then boost until that CR is reached. Of course, that is making 3 very big assumptions. The more detailed of an answer you want, the more specifics you need, and the less assumptions you can make.

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i can get any octane fuel, 110 to what the pro stock guys use... i think 123 or 126.

the turbo should push a good 26psi, maybe even more.

its a T04E 60-1 Stage 5 82a/r.

injectors will be 55lb o-rings and the intake manifold should flow pretty good... custom sheet metal unit.

head will have a good amount of port work also, thats all i can think of now...

reason asking is i wanna see how far i can push this car with the 100shot ill be using and max boost and some good tires... we are guessing 10's.

thanks

 

mike

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Guest Nic-Rebel450CA

Unfortunately that's a bit over my head, at least with how tired I am right now :D

 

If you throw NO into the equation, that makes a big difference itself if you want to find this out mathematically because NO is not air. Additionally I would assume that there are some other calculations you need to make with having NO and forced induction at the same time. I would find out for sure what you can get as far as octane, (I believe 126 is correct, so we can use that). A common estimate for octane is estimated octane requirement based on 11.5 times compression ratio, so we can turn that around backwards and say estimated max compression ratio based on octane amount. 126/11.5=10.95CR. This is conservative, so if you want to push it we will say 126/11=11.45CR. At sea level that is about 8PSI on a 7.5:1 standard compression (according to an online calculator I found, not sure how accurate that is). I believe that is figuring with 0deg of overlap, overlap will significantly change your max boost. Here is a more advanced calculator http://www.rbracing-rsr.com/comprAdvHD.htm

 

All of this should help you find out what you can run as a (relatively) safe setup. You can increase the AFM so you can add NO or higher boost, as long as the engine components can handle the force. (This is where the flow rate of the injectors comes in). Other than that, you are getting into some pretty detailed measurements and physics which I would have to scratch my head over for a lot longer than I have been in typing this. :wink:

 

BTW I am not making any claims as to the safety of my suggestions or the validity of the calculations. Any setup you choose to use is your own decision! :-D

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