Compression ratio - 8th Generation Honda Civic Forum

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Old 09-21-2017, 07:21 PM   #1 (permalink)
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Compression ratio

I recently acquired a CTE stage 2 for a STEALLLL BNIB and I'm wondering if I were to build an engine on the side what would the ideal compression ratio be for 12psi of boost? I want to stay in the mid 300whp range. I've searched around quite a bit just mostly arguments. I came home to get facts and no bs. I just want to build a motor on the side that will take the abuse and punishment and still be reliable as this is my daily driver ATM thanks in advance guys

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Old 09-30-2017, 11:58 PM   #2 (permalink)
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At mid 300whp range you could probably save yourself a lot of money and just spend more on getting a really good tune and be just fine. The tune is everything. You could have a very expensive built motor and with a bad tune blow it. The tune is EVERYTHING I literally just finished installing my stage 2 CT kit and will be tuning it myself to ensure it is done properly.

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Old 10-02-2017, 12:21 AM   #3 (permalink)
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Just throw the cte on your current motor make sure you have full exhaust and flashpro and tune it you will be fine and hit your 300 number as stated it's all in the tune and supporting mods might want to add a after cooler and oil cooler if you did not get one
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Old 10-09-2017, 11:19 PM   #4 (permalink)
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Decreasing the compression ratio lowers the peak cylinder pressure and thus the temperature of the intake charge reducing the chance of engine knock. The ignition timing can then be advanced (particularly at low RPM) and boost can be increased. For heavily boosted motors the compression ratio should be decreased 1-2 points to ~8.5:1, where as for a mildly boosted motor the stock compression ratio (11:1) or 1 point decrease (10:1) should be sufficient.

However there are a lot of factors to take into account including fuel type (91, 93, E85), boost pressure, climate in the area you live, etc. For example I live in Arizona where the weather is nuclear hot, the fuel is oxygenated and only available in 91 octane. I'm building a similar set up (~14PSI) and reducing the compression ratio by 1 point (10:1).

Hope this helps!
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