Tja
hadde en liten diskution med en polare förut angående effekt / komprition på en turbomotor.
jag hävdar STARKT att med lägre komp kan man uppnå högre effekt på en annars identisk motor bortsett från högre komp. innom rimliga grenser då såklart,
ja menar, ju mer plats du har att knö in soppa/luftblandningen desto kraftigare explotion.
han hävdar dock det motsatta, att det är bättre med ehn högre komp så länge man kan mappa ordentligt (vilket självklart gäller den andra motorn oxå).
så, kom med era resonumang nu, måste ju finnas en anledning till att folk köper lågkompskolvar o liknande =) knappast för att det inte finns nån som klarar av att mappa en motor för samma / mer effekt på högre komp.
vill ha så utförliga förklaringar som möjligt, gärna länkar som förklara (behöver överbevisa personen i fråga)
mvh Erik Jakobsson
effekt och komp-förhållande på en turbo motor
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effekt och komp-förhållande på en turbo motor
Enligt Haynse är man "Proffesionell mekaniker" =)
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Bmwandreas
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missade en grejj
självklar menar jag i mitt argument att man kan ha ett högre alddtryck o därigenom få in mer luft o soppa
så en lågkompad motor med högre laddtryck borde då enligt mej vara effektivare än en högkompad med ett lägre ladtryck
mvh Erik Jakobsson
självklar menar jag i mitt argument att man kan ha ett högre alddtryck o därigenom få in mer luft o soppa
så en lågkompad motor med högre laddtryck borde då enligt mej vara effektivare än en högkompad med ett lägre ladtryck
mvh Erik Jakobsson
Enligt Haynse är man "Proffesionell mekaniker" =)
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Bmwandreas
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Bmwandreas
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"What's better, low compression and more boost or high compression and less boost?"
There are certainly reasons to try to raise compression ratio, namely when off-boost performance matters, like on a street car, or when using a very small displacement motor. but when talking purely about on-boost power potential, compression just doesn't make any sense.
People have tested the power effects of raising compression for decades, and the most optimistic results are about 3% more power with an additional point of compression (going from 9:1 to 10:1, for example). All combinations will be limited by detonation at some boost and timing threshold, regardless of the fuel used. The decrease in compression allows you to run more boost, which introduces more oxygen into the cylinder. Raising the boost from 14psi to 15psi (just a 1psi increase) adds an additional 3.4% of oxygen. So right there, you are already past the break even mark of losing a point of compression. And obviously, lowering the compression a full point allows you to run much more than 1 additional psi of boost. In other words, you always pick up more power by adding boost and lowering compression, because power potential is based primarily on your ability to burn fuel, and that is directly proportional to the amount of oxygen that you have in the cylinder. Raising compression doesn't change the amount of oxygen/fuel in the cylinder, it just squeezes it a bit more.
So the big question becomes, how much boost do we gain for X amount of compression? The best method we have found is to calculate the effective compression ratio (ECR) with boost. The problem is that most people use an incorrect formula that says that 14.7psi of boost on a 8.5:1 motor is a 17:1 ECR. So how in the world do people get away with this combination on pump gas? You can't even idle down the street on pump gas on a true 17:1 compression motor. Here's the real formula to use:
sqrt((boost+14.7)/14.7) * CR = ECR
sqrt = square root
boost = psi of boost
CR = static compression ratio of the motor
ECR = effective compression ratio
So our above example gives an ECR of 12.0:1. This makes perfect sense, because 12:1 is considered to be the max safe limit with aluminum heads on pump gas, and 15psi is about as much boost as you can safely run before you at least start losing a significant amount of timing to knock. Of course every motor is different, and no formula is going to be perfect for all combinations, but this one is vastly better than the standard formula (which leaves out the square root).
So now we can target a certain ECR, say 12.0:1. We see that at 8.5:1 CR we can run 14.7psi of boost. But at 7.5:1 we can run 23psi of boost (and still maintain the 12.0:1 ECR). We only gave up 1 point of compression (3% max power) and yet we gained 28% more oxygen (28% more power potential). Suddenly it's quite obvious why top fuel is running 5:1 compression, that's where all the power is!!
There are certainly reasons to try to raise compression ratio, namely when off-boost performance matters, like on a street car, or when using a very small displacement motor. but when talking purely about on-boost power potential, compression just doesn't make any sense.
People have tested the power effects of raising compression for decades, and the most optimistic results are about 3% more power with an additional point of compression (going from 9:1 to 10:1, for example). All combinations will be limited by detonation at some boost and timing threshold, regardless of the fuel used. The decrease in compression allows you to run more boost, which introduces more oxygen into the cylinder. Raising the boost from 14psi to 15psi (just a 1psi increase) adds an additional 3.4% of oxygen. So right there, you are already past the break even mark of losing a point of compression. And obviously, lowering the compression a full point allows you to run much more than 1 additional psi of boost. In other words, you always pick up more power by adding boost and lowering compression, because power potential is based primarily on your ability to burn fuel, and that is directly proportional to the amount of oxygen that you have in the cylinder. Raising compression doesn't change the amount of oxygen/fuel in the cylinder, it just squeezes it a bit more.
So the big question becomes, how much boost do we gain for X amount of compression? The best method we have found is to calculate the effective compression ratio (ECR) with boost. The problem is that most people use an incorrect formula that says that 14.7psi of boost on a 8.5:1 motor is a 17:1 ECR. So how in the world do people get away with this combination on pump gas? You can't even idle down the street on pump gas on a true 17:1 compression motor. Here's the real formula to use:
sqrt((boost+14.7)/14.7) * CR = ECR
sqrt = square root
boost = psi of boost
CR = static compression ratio of the motor
ECR = effective compression ratio
So our above example gives an ECR of 12.0:1. This makes perfect sense, because 12:1 is considered to be the max safe limit with aluminum heads on pump gas, and 15psi is about as much boost as you can safely run before you at least start losing a significant amount of timing to knock. Of course every motor is different, and no formula is going to be perfect for all combinations, but this one is vastly better than the standard formula (which leaves out the square root).
So now we can target a certain ECR, say 12.0:1. We see that at 8.5:1 CR we can run 14.7psi of boost. But at 7.5:1 we can run 23psi of boost (and still maintain the 12.0:1 ECR). We only gave up 1 point of compression (3% max power) and yet we gained 28% more oxygen (28% more power potential). Suddenly it's quite obvious why top fuel is running 5:1 compression, that's where all the power is!!
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Bmwandreas
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Jaha...
Då undrar jag varför folk hackar på mig för att jag kör med runt 7,0:1 i komp?
Då undrar jag varför folk hackar på mig för att jag kör med runt 7,0:1 i komp?
http://www.garaget.org/Ticco-GBG" onclick="window.open(this.href);return false;
peppe wrote:Ticco wrote:Jaha...
Då undrar jag varför folk hackar på mig för att jag kör med runt 7,0:1 i komp?
För att dom kan?
http://www.garaget.org/Ticco-GBG" onclick="window.open(this.href);return false;
Flaxis wrote:Hela livet handlar väl inte om toppeffekt eller??
m.v.h//Flaxis
Asså, inte...?
http://www.garaget.org/Ticco-GBG" onclick="window.open(this.href);return false;
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Bmwandreas
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