Dropping the compression?

[wunslowbrz]

I'm not too much of a genius when it comes down to motors but I know my way around one. Just need a little advice or help. Is there anyway I can drop the compression in my brz? 12.5 with like a max of 11 to 12 pounds isn't gonna cut it. I want to run atleast 10 to 1 ratio my friend was telling me about reverse dome Pistons ? I couldn't find any anywhere though. Can anyone shoot me in the right direction or any opinions on it? Has this been done yet ? And it's a 2013 brz btw thanks in advance

[JD001]

http://www.ft86club.com/forums/showt...ht=compression

See the link above as I think it also talks about the same subject.

[kch]

Originally Posted by wunslowbrz

I'm not too much of a genius when it comes down to motors but I know my way around one. Just need a little advice or help. Is there anyway I can drop the compression in my brz? 12.5 with like a max of 11 to 12 pounds isn't gonna cut it. I want to run atleast 10 to 1 ratio my friend was telling me about reverse dome Pistons ? I couldn't find any anywhere though. Can anyone shoot me in the right direction or any opinions on it? Has this been done yet ? And it's a 2013 brz btw thanks in advance

You'll need pistons. While you're in there, do rods, bearings, etc. But that means you're doing a full engine build, which is $$$$.

[Guff]

Effective compression matters more than just a static compression number. If you're building the motor, then do research on what type of setup you want to do. Just because you're adding boost, doesn't mean you have to drop compression. It does however, mean you should strengthen internal components. Once you open the motor, you really should go ahead and do a full build as you're going to regret it later on if you put pistons in and have a rod failure down the line. Take a look at people's builds with 10:1, 11:1, 12:1, etc. and what kind of powerbands they have and you'll get a better understanding of what you want.

[Spartarus]

First, Guff is right. There is a library of knowledge and experience here from which you can plan your build.

Second, from the way you posed your question I can tell you're not an expert, and neither is your friend.

It's ok, the forum is a place to learn. Take advice from friends with a huge grain of salt (like rock-salt sized) unless they are well qualified tuners.

Yes, the shape of the piston, and the height from wrist pin to dome determines the compression ratio. There are low-compression pistons available off-the-shelf for this engine.

You want to determine your power goals and budget before you start talking about compression.

Lowering compression will change the off-boost power characteristics of the engine.

Contrary to popular belief, lowering compression does not necessarily turn the engine into a sluggish turd off-boost.

Increased effective compression ratio is only part of the reason that boost makes more power.

In short, increasing effective compression raises the efficiency at which energy is extracted from the fuel-air mixture. Boosting the engine to an equivalent effective compression ratio increases the potential energy available, due to an increased mass of air and fuel, in addition to raising the efficiency at which that potential energy is converted to kinetic energy.

Many vendors sell the Pistons that you are looking for. I am encouraging you to do more research, or at least quantify your goals before you spend thousands of dollars on fancy pieces of metal.