Increase boost or compression ratio?
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Increase boost or compression ratio?

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    Senior Member Hass828's Avatar
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    Default Increase boost or compression ratio?

    Very good read on the subject.
    Increasing CR vs boost pressure
    "if we keep doing it the same way we always do..we will always get the same results"
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    LP-25.com Infomaniac's Avatar
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    Good reading. Apparently the original author found it. lol

    More boost less compression. Who would have thunk it.
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    gn7
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    Quote Originally Posted by Infomaniac View Post
    Good reading. Apparently the original author found it. lol

    More boost less compression. Who would have thunk it.
    I didn't read the whole thing. A little wordy for this time of day. But I sure hope that is what it says, or the guy is in lala land.

    It tookall that to exploain that more boost equals more air/fuel ina given space. This guy is wasting his time with this. He real calling is a NASA engineer.

    Went back and read a little more. If you read enough posts you get the idea that some of them would be lost on a blown alky deal including the OP. Things like
    "regardless of the fuel" when talking about a blown 11.5 to 1 deal.



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    Last edited by gn7; 07-16-2012 at 07:42 AM.

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    Quote Originally Posted by gn7 View Post
    I didn't read the whole thing. A little wordy for this time of day. But I sure hope that is what it says, or the guy is in lala land.

    It tookall that to exploain that more boost equals more air/fuel ina given space. This guy is wasting his time with this. He real calling is a NASA engineer.
    It boiled down to more mass airflow = more power.
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    gn7
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    Quote Originally Posted by Infomaniac View Post
    It boiled down to more mass airflow = more power.
    What concept!



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    I already knew all of that but still enjoyed the read. I love the part about mean effective pressure, that will open ones eyes as to why a turbocharged engine can make so much more power and yet retain some reliability as to compared to an equally powered high compression- NOS engine. The lower comp. turbocharged engine has a high very high break mean effective pressure, yet less max cylinder pressure.
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    gn7
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    Quote Originally Posted by Hass828 View Post
    I already knew all of that but still enjoyed the read. I love the part about mean effective pressure, that will open ones eyes as to why a turbocharged engine can make so much more power and yet retain some reliability as to compared to an equally powered high compression- NOS engine. The lower comp. turbocharged engine has a high very high break mean effective pressure, yet less max cylinder pressure.


    You say that like only turbo engines can have high break mean effective pressure. Like by some mysterious means a cylinder knows what created the bosst pressure. I might be a roots guy, but I AM alittle more open minded than that.

    But you are correct. 2 engines of equal size and equal HP with one on NOS and the other turbo'd, the NOS engine is never going to finish a 500 mile Indy race. If it even finishes a lap! They make power, but they are murder on parts getting it.

    But I didn't need a 3 page article to tell me that.



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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by gn7 View Post
    I didn't read the whole thing. A little wordy for this time of day...
    Holey crap! "Wordy" is understating it a bit. Don't ya think?

    Yeah, that certainly could have been summed up into "burn more fuel if you want more power, raise the C/R if you want more economy"

    Nice to see actual physics involved though. I eat that stuff up!
    Last edited by Budweiser; 07-16-2012 at 11:43 AM.

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    Quote Originally Posted by gn7 View Post


    You say that like only turbo engines can have high break mean effective pressure. Like by some mysterious means a cylinder knows what created the bosst pressure. I might be a roots guy, but I AM alittle more open minded than that.

    But you are correct. 2 engines of equal size and equal HP with one on NOS and the other turbo'd, the NOS engine is never going to finish a 500 mile Indy race. If it even finishes a lap! They make power, but they are murder on parts getting it.

    But I didn't need a 3 page article to tell me that.
    Hey you grouchy old fart! I didnt post this up specifically for you. If i had then I would have named the thread "Hey Bob, Get your grouchy old azz over here & read this so you can learn a thing or two".
    I am well of the fact that you have most of this stuff figured out. But even you are wrong from time to time and might need a little refresher course.

    Just thought that maybe some of the readers that arent quite the -expert- that you are might enjoy the read.
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    I didn't read the article and probably won't, but we can still argue. More fuel air = more power, but you need CR for the application. IE a fuel engine only needs 7 to1. An alcohol piece would be a turd no matter how much boost you put to it. So, ideal is not always less cr more fuel. Some alcohol guys think 12.5 is to much cr. Some run more. What is ideal? Does combustion chamber shape affect what ideal cr is per application.
    That ought to start something.
    Wags

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    i read the article and i enjoyed it. Learned something, again. I thought it was a good question and a fine answer...

    told you what and why, with theory, math, acutal data to support it. Guess that shows just how much i dont know, but i already knew that.

    and it begs another question: Supercharge or CID...when i think of that question it opens up the BIG





    just how much boost is worth how much CID?...how 'bout in terms of your valued air flow (fuel flow)...which one will be more efficient in hp/lb fuel or hp/lb engine?

    the answer without the theory, math and actual data would be suspect and without at least one of them would be sensless.





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    Quote Originally Posted by wagspe208 View Post
    I didn't read the article and probably won't, but we can still argue. More fuel air = more power, but you need CR for the application. IE a fuel engine only needs 7 to1. An alcohol piece would be a turd no matter how much boost you put to it. So, ideal is not always less cr more fuel. Some alcohol guys think 12.5 is to much cr. Some run more. What is ideal? Does combustion chamber shape affect what ideal cr is per application.
    That ought to start something.
    Wags
    Shame on you Wags.

    12.5 in a pinch head deal is quite a bit. 12.5 in a full out hemi head seems to be common. Blown alcohol.
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    Quote Originally Posted by wagspe208 View Post
    I didn't read the article and probably won't, but we can still argue. More fuel air = more power, but you need CR for the application. IE a fuel engine only needs 7 to1. An alcohol piece would be a turd no matter how much boost you put to it. So, ideal is not always less cr more fuel. Some alcohol guys think 12.5 is to much cr. Some run more. What is ideal? Does combustion chamber shape affect what ideal cr is per application.
    That ought to start something.
    Wags
    7 to 1 is not common for nitro without a blower. Unblown, its much higher. When you see 7 to 1 on a blown nitro deal, MORE FUEL is exactly the reason its that low. When that piston gets to TDC, the things are right at hydrostatic lock due to fuel. The running UNBOOSTED compression of a Top Fuel engine waaaaaay higher than the "static" compression due to the fuel charge in the thing.
    You simply can't have much higher compression when the A/F is 4 to 1. That fuel takes up alot of space.



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    Quote Originally Posted by Hass828 View Post
    Hey you grouchy old fart! I didnt post this up specifically for you. If i had then I would have named the thread "Hey Bob, Get your grouchy old azz over here & read this so you can learn a thing or two".
    I am well of the fact that you have most of this stuff figured out. But even you are wrong from time to time and might need a little refresher course.

    Just thought that maybe some of the readers that arent quite the -expert- that you are might enjoy the read.
    I agree Hass, it was good info. But I really never needed Einsteins theory to know that gravity exists.
    I guess experiencing gravity first hand did help come to that conclusion though.
    I guess learning through experience told me that there is a HUGE difference between a 8 to 1 motor with 24lbs of boost and a 10 to 1 with 16lbs. Not only will the 8 to 1 motor kick ass, but its easier on the engine, and easier on octane.



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