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MI-4
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im looking to put in some aftermarket pistons and rods..imlooking to raise compression to about 12:5 on pump gas 93 octane. Everywhere i look i only see pistons for turbo motors. Does anyone have a website where i can purchase some high compression pistons? But then i wonder if you change the compression on the motor i need to have the K-pro right? i couldnt run #4 with it and expect good gains, could I?
 

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www.todaracing.com

they have exactly what you're looking for, a High Compression Piston Kit and with their headgasket it'd be like 12.9:1,(12.5:1 with stock head gasket)

and i think the k-pro would be the best idea esp with the new head gasket if u got that too
 

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Rage With the Machines
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why would you want such a high ass compression??
wont it damage your engine more than normal...lol 11:1 is already crazy
 

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Rage With the Machines
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what other car comes with a compression as high as ours?
 

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RYU583 said:
what other car comes with a compression as high as ours?
Porsche GT3, Ferrari, Toyota Matrix(11.5:1 I think), VW TDI

You would really need to have good tuning for compression ratio that high. It's not impossible, just high maintenance.
 

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Actually 11:1 is quite high compared to most cars. The average gasoline injected engine runs between 8:1 and 10:1. The reason you are able to gain power out of such high compression, is because of the extra pressure in the combustion chamber. In order to burn such a highly compressed air/fuel mixture, you need a higher octane gasoline. That is why the Type S only runs on premium gasoline (91 octane recommended). If you are running an even higher compression, you must use a higher grade octane fuel to see any benefits of this compression (with a compression ratio of 12.5:1 may I recommend leaded 100 RON race gas) If you are tuning the ECU to run on this level of compression with lower grade fuel, the timing would have to be retarded drastically to avoid detonation. Therefore Hondata #4 could not be used at this compression, since the timing is advanced quite a bit.
Furthermore, without using a higher octane fuel to reap the benefits of this high compression, and with the timing retarded so much, you would probably lose more power if any thing. Seriously, only attempt this setup if you are building a race car.
 

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Chemical Soldier
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I have read in several places that a higher CR needs to be supplemented with bigger cams. But the reason as to why was never stated. Someone care to enlighten me on this?
 

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MI4K20 said:
im looking to put in some aftermarket pistons and rods..imlooking to raise compression to about 12:5 on pump gas 93 octane. Everywhere i look i only see pistons for turbo motors. Does anyone have a website where i can purchase some high compression pistons? But then i wonder if you change the compression on the motor i need to have the K-pro right? i couldnt run #4 with it and expect good gains, could I?
i have a brand new set of wiesco pistons for sale they are 12-1 cr and 1mm over size...they did not work for my motor so now iam stuck with them iam willing to take a big loss...make me offfers
 

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MI4K20 said:
im looking to put in some aftermarket pistons and rods..imlooking to raise compression to about 12:5 on pump gas 93 octane. Everywhere i look i only see pistons for turbo motors. Does anyone have a website where i can purchase some high compression pistons? But then i wonder if you change the compression on the motor i need to have the K-pro right? i couldnt run #4 with it and expect good gains, could I?
There are many K-series high compression pistons out there made by Wiseco. Point your browser to www.1mp0rtbu1lders.com (replace 1s with i, 0 with o, consider it a puzzle).
 

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ILikeFastCars&FastWomen
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RYU583 said:
what other car comes with a compression as high as ours?
The 1st Gen Toyota Prius has a 13:1 compression ratio and the 2nd Gen has 13.5:1. You'd have to read about it to understand it though because its effective ratio is less.
Anyways, 12:5 is about the highest OK cr that I myself would use, it just requires proper tuning, its not that big of a deal. Of course you'd want to get the K-Pro to extract the most power safely, and you could even have a couple different maps - one for 93 pump octane and one for higher octane/race gas. Just upload the desired program into the ecu to match the fuel being used.
 

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schuessler28 said:
I have read in several places that a higher CR needs to be supplemented with bigger cams. But the reason as to why was never stated. Someone care to enlighten me on this?
If you don't run a longer duration camshaft with high static compression, it will be easy for your engine to "over compress". The general rule is that the higher the static compression, the more duration is required, especially as the engine speeds increase.
 

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There is a lot more that goes into safely running a high compression ratio than just ecu tuning and octane. The shape of the combustion chamber (hemispherical, wedge shaped, etc) has a great effect on the level of compression that is possible.
Diesel engines run very high compression ratios (usually between 20:1 and 30:1) because of the way that the fuel is compressed and burned during the power stroke.
All I'm trying to say is maybe to pick up an old auto shop text book and read up on the specifics of everything in detail before you go ahead and purchase a whole bunch of parts that you possibly have no use for.
 

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mdoubilet said:
There is a lot more that goes into safely running a high compression ratio than just ecu tuning and octane. The shape of the combustion chamber (hemispherical, wedge shaped, etc) has a great effect on the level of compression that is possible.
Diesel engines run very high compression ratios (usually between 20:1 and 30:1) because of the way that the fuel is compressed and burned during the power stroke.
All I'm trying to say is maybe to pick up an old auto shop text book and read up on the specifics of everything in detail before you go ahead and purchase a whole bunch of parts that you possibly have no use for.
But diesel is a whole diffrent animal. For one thing the octane rating of diesel is much higher than most "race" fuels sold at the pumps, plus it uses compression to generate "controlled detonation".
 

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ILikeFastCars&FastWomen
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mdoubilet said:
There is a lot more that goes into safely running a high compression ratio than just ecu tuning and octane. The shape of the combustion chamber (hemispherical, wedge shaped, etc) has a great effect on the level of compression that is possible.
Diesel engines run very high compression ratios (usually between 20:1 and 30:1) because of the way that the fuel is compressed and burned during the power stroke.
All I'm trying to say is maybe to pick up an old auto shop text book and read up on the specifics of everything in detail before you go ahead and purchase a whole bunch of parts that you possibly have no use for.
Right, but we are talking about the K20 here specifically and I don't think 12.5:1 is too much. Yeah, not a bad idea to read up on the subject.
 

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isn't it just cheaper to shave the head a few thou "

You'll get the higher comp. without tearing down the short block.

If higher comp. is your goal.
 
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