Compression and Pistons????
12-07-2005, 06:11 PM
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Compression and Pistons???? I was wondering if somebody could explain to me or tell me where I can figure out, how compression affects the motor. I know when you mill a head that adds compression, but whats the purpose? Whats the difference in a -2cc piston and a -12cc piston? Thanks....
12-07-2005, 06:36 PM
#2
The negative cc of the piston is the amount of area that is removed from the piston head. When the piston travels up in it's stroke, it is compressing the air/fuel mixture that has been ingested into the cylinder. The more area that you remove from the piston, the more area you add for the pressure to go. Milling a head or having flat/domed pistons makes the area smaller, thus increasing pressure or compression. If you had 2 ballons, one barley filled with air, and one filled to the max. Which will pop harder? The harder the boom, the faster it pushes the air out. The diffrence between the 2 pistons you listed is that there is an extra 10 cc of material removed from the -12cc. more area removed, less compression. You could also get into flame travel and so on, but you should get the general idea from the above. 
12-07-2005, 10:39 PM
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Originally Posted by Beast96Z
The negative cc of the piston is the amount of area that is removed from the piston head. When the piston travels up in it's stroke, it is compressing the air/fuel mixture that has been ingested into the cylinder. The more area that you remove from the piston, the more area you add for the pressure to go. Milling a head or having flat/domed pistons makes the area smaller, thus increasing pressure or compression. If you had 2 ballons, one barley filled with air, and one filled to the max. Which will pop harder? The harder the boom, the faster it pushes the air out. The diffrence between the 2 pistons you listed is that there is an extra 10 cc of material removed from the -12cc. more area removed, less compression. You could also get into flame travel and so on, but you should get the general idea from the above.
So, the more you take out of a piston the less compression is created becasue the amount of increased area. This would be ideal for a FI motor versus a No2 motor. It would be pointless to run a milled head and a -12cc piston when setting up a motor. The two are cancelling each other, right? What would be a good combinatoin to run in a nitrous motor, a -2cc piston and a milled head?
12-07-2005, 11:12 PM
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If you building an all out race motor, you typically want the smaller chamber in the head and the dish to be in the piston. On most average everyday built motors, people go by what they have already. In most cases, you don't want to mill your heads because of the loss of Piston to valve clearence. Everytime you mill, you move the valves that much closer to the piston, which decreases the amount of camshaft you can run. If your setting up a No2 motor, you can keep the higher compression. To know what you would need, I would have to know what you are building. What size motor? What heads and so forth. These things play a part in determining a certain compression ratio, and figuring out which piston dish you'd need.
12-08-2005, 04:57 PM
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Originally Posted by Beast96Z
If you building an all out race motor, you typically want the smaller chamber in the head and the dish to be in the piston. On most average everyday built motors, people go by what they have already. In most cases, you don't want to mill your heads because of the loss of Piston to valve clearence. Everytime you mill, you move the valves that much closer to the piston, which decreases the amount of camshaft you can run. If your setting up a No2 motor, you can keep the higher compression. To know what you would need, I would have to know what you are building. What size motor? What heads and so forth. These things play a part in determining a certain compression ratio, and figuring out which piston dish you'd need.
What my plan to do is have a heads and cam motor that can handle a 200 shot. I really haven't decided on what heads to go with yet. I know it will either be AFR'S or the new edelbrock/LPE heads. I'm curenntly running the F-13 and still want to run that cam. Another thing is I don't know if I want to dish out the money for a 90/90 or run a LS6 intake on the car. All this on a stock cube LS1 with a forged lower end of course.. What do you think???
01-05-2006, 11:20 AM
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Originally Posted by A
What my plan to do is have a heads and cam motor that can handle a 200 shot. I really haven't decided on what heads to go with yet. I know it will either be AFR'S or the new edelbrock/LPE heads. I'm curenntly running the F-13 and still want to run that cam. Another thing is I don't know if I want to dish out the money for a 90/90 or run a LS6 intake on the car. All this on a stock cube LS1 with a forged lower end of course.. What do you think???
