compression vs boost
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compression vs boost
why is it that people say to only run 12psi on stock head gaskets and internals which is around 350whp(right?) but if you get a thicker headgasket and lower your compression ratio you can run much more boost make up for the lower compression and then some. some guys get 500whp on stock internals but upgraded gasket. does this mean that if i got a stronger headgasket that i could be making 500whp with stock compression? im not planning on doing any of these builds just really curious.
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From: SLC, UT
Historically, high compression motors (such as the F20C/F22C) run hot because the more air is compressed, the closer the air molecules are to each other, the more they run into each other. This cause friction and creates heat.
With higher heat comes the risk that your fuel will ignite prior to entering the combustion chamber and being properly ignited by the spark from your spark plug. If this "pre-ignition" occurs in an area prior to entering the combustion chamber or prior to when the piston properly extended (like during the normal ignition process), engine damage can occur.
If you run lower compression, the engine will tend to run cooler and thus lessen the risk of pre-detonation. Lowering compression will mean a loss in performance. To offset this loss in performance, higher than 'normal' levels of cool air can be forced into the combustion chambers (through the intake manifold) and combined with increased fueling to create greater power levels. This is why forced induction motors can yield power outputs equal to or greater than motors that are much larger and naturally aspirated.
All this being said, for a number of reasons we have speculated about on this forum, it appears the F20C/F22C are able to withstand abnormally high boost levels without problems with pre-detonation. Why? It has to do with dynamic compression ratio as rpms increase rather than the static compression ratio we normally refer to. I cannot entirely explain this as I am not an engineer.
What I can say is that a handful of us FI guys have explored the limits of the dead stock S2000 engines with surprising success. As motors get high in mileage people will be more willing to toy with the real potential of this motor (cuz they'll be needing a rebuild at some point anyway).
As far as getting a "stronger" head gasket...it doesn't work that way. Stronger head gaskets don't really exist (it's not like a Mazda rotary). Instead, thicker head gaskets can lower compression and vice versa. Engine internals are what withstand levels of pre-detonation. Stronger internals would make more sense when building a motor, to withstand unexpected detonation that may occur for any number of reasons.
Basically, read this:
http://www.howstuffworks.com/engine.htm
Great site...it should explain the basics of an internal combustion engine...it will go into more detail than my post.
With higher heat comes the risk that your fuel will ignite prior to entering the combustion chamber and being properly ignited by the spark from your spark plug. If this "pre-ignition" occurs in an area prior to entering the combustion chamber or prior to when the piston properly extended (like during the normal ignition process), engine damage can occur.
If you run lower compression, the engine will tend to run cooler and thus lessen the risk of pre-detonation. Lowering compression will mean a loss in performance. To offset this loss in performance, higher than 'normal' levels of cool air can be forced into the combustion chambers (through the intake manifold) and combined with increased fueling to create greater power levels. This is why forced induction motors can yield power outputs equal to or greater than motors that are much larger and naturally aspirated.
All this being said, for a number of reasons we have speculated about on this forum, it appears the F20C/F22C are able to withstand abnormally high boost levels without problems with pre-detonation. Why? It has to do with dynamic compression ratio as rpms increase rather than the static compression ratio we normally refer to. I cannot entirely explain this as I am not an engineer.
What I can say is that a handful of us FI guys have explored the limits of the dead stock S2000 engines with surprising success. As motors get high in mileage people will be more willing to toy with the real potential of this motor (cuz they'll be needing a rebuild at some point anyway).
As far as getting a "stronger" head gasket...it doesn't work that way. Stronger head gaskets don't really exist (it's not like a Mazda rotary). Instead, thicker head gaskets can lower compression and vice versa. Engine internals are what withstand levels of pre-detonation. Stronger internals would make more sense when building a motor, to withstand unexpected detonation that may occur for any number of reasons.
Basically, read this:
http://www.howstuffworks.com/engine.htm
Great site...it should explain the basics of an internal combustion engine...it will go into more detail than my post.
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From: SLC, UT
By the way, don't take offense to the lack of responses...it's just that a lot of the guys on the forced induction forum are seasoned (NOT old) and have explained this kind of thing quite a bit.
Happy Motoring!
Happy Motoring!
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From: Skopje
well i will soon find out..
I will be going 11.5 CR JE pistons on my 14psi CTSC.
0.5cr more with the same boost.
And my motor was running quite cool with the stock CR ..no issues on heat and no mods done for it..
stefce
I will be going 11.5 CR JE pistons on my 14psi CTSC.
0.5cr more with the same boost.
And my motor was running quite cool with the stock CR ..no issues on heat and no mods done for it..
stefce
Joined: Oct 2000
Posts: 9,033
Likes: 21
From: South of the pier, Huntington Beach, CA
Originally Posted by stena,Sep 24 2009, 04:10 PM
well i will soon find out..
I will be going 11.5 CR JE pistons on my 14psi CTSC.
0.5cr more with the same boost.
And my motor was running quite cool with the stock CR ..no issues on heat and no mods done for it..
stefce
I will be going 11.5 CR JE pistons on my 14psi CTSC.
0.5cr more with the same boost.
And my motor was running quite cool with the stock CR ..no issues on heat and no mods done for it..
stefce
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great response courageoo7, i have searched but what i found was at an engineers level. your answer was much more clear. thanks to everyone elses reply and make a thread when your done your build stena cause id like to see the gains with a .5cr increase.
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From: South of the pier, Huntington Beach, CA
Originally Posted by 1999,Sep 24 2009, 11:18 PM
Even simpler the lower the compression the more space to dump more stuff in.
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From: Central NJ
Originally Posted by CourageOO7,Sep 24 2009, 07:07 PM
Historically, high compression motors (such as the F20C/F22C) run hot because the more air is compressed, the closer the air molecules are to each other, the more they run into each other. This cause friction and creates heat.
With higher heat comes the risk that your fuel will ignite prior to entering the combustion chamber and being properly ignited by the spark from your spark plug. If this "pre-ignition" occurs in an area prior to entering the combustion chamber or prior to when the piston properly extended (like during the normal ignition process), engine damage can occur.
If you run lower compression, the engine will tend to run cooler and thus lessen the risk of pre-detonation. Lowering compression will mean a loss in performance. To offset this loss in performance, higher than 'normal' levels of cool air can be forced into the combustion chambers (through the intake manifold) and combined with increased fueling to create greater power levels. This is why forced induction motors can yield power outputs equal to or greater than motors that are much larger and naturally aspirated.
All this being said, for a number of reasons we have speculated about on this forum, it appears the F20C/F22C are able to withstand abnormally high boost levels without problems with pre-detonation. Why? It has to do with dynamic compression ratio as rpms increase rather than the static compression ratio we normally refer to. I cannot entirely explain this as I am not an engineer.
What I can say is that a handful of us FI guys have explored the limits of the dead stock S2000 engines with surprising success. As motors get high in mileage people will be more willing to toy with the real potential of this motor (cuz they'll be needing a rebuild at some point anyway).
As far as getting a "stronger" head gasket...it doesn't work that way. Stronger head gaskets don't really exist (it's not like a Mazda rotary). Instead, thicker head gaskets can lower compression and vice versa. Engine internals are what withstand levels of pre-detonation. Stronger internals would make more sense when building a motor, to withstand unexpected detonation that may occur for any number of reasons.
Basically, read this:
http://www.howstuffworks.com/engine.htm
Great site...it should explain the basics of an internal combustion engine...it will go into more detail than my post.
With higher heat comes the risk that your fuel will ignite prior to entering the combustion chamber and being properly ignited by the spark from your spark plug. If this "pre-ignition" occurs in an area prior to entering the combustion chamber or prior to when the piston properly extended (like during the normal ignition process), engine damage can occur.
If you run lower compression, the engine will tend to run cooler and thus lessen the risk of pre-detonation. Lowering compression will mean a loss in performance. To offset this loss in performance, higher than 'normal' levels of cool air can be forced into the combustion chambers (through the intake manifold) and combined with increased fueling to create greater power levels. This is why forced induction motors can yield power outputs equal to or greater than motors that are much larger and naturally aspirated.
All this being said, for a number of reasons we have speculated about on this forum, it appears the F20C/F22C are able to withstand abnormally high boost levels without problems with pre-detonation. Why? It has to do with dynamic compression ratio as rpms increase rather than the static compression ratio we normally refer to. I cannot entirely explain this as I am not an engineer.
What I can say is that a handful of us FI guys have explored the limits of the dead stock S2000 engines with surprising success. As motors get high in mileage people will be more willing to toy with the real potential of this motor (cuz they'll be needing a rebuild at some point anyway).
As far as getting a "stronger" head gasket...it doesn't work that way. Stronger head gaskets don't really exist (it's not like a Mazda rotary). Instead, thicker head gaskets can lower compression and vice versa. Engine internals are what withstand levels of pre-detonation. Stronger internals would make more sense when building a motor, to withstand unexpected detonation that may occur for any number of reasons.
Basically, read this:
http://www.howstuffworks.com/engine.htm
Great site...it should explain the basics of an internal combustion engine...it will go into more detail than my post.
good write up. it explained a lot that i was confused on.