Can EJ253 short block handle boost?

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07-14-2005, 04:43 AM

GrandpreRS

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Can EJ253 short block handle boost?

Going to replace lowerend of '99 ej253 shortblock and wondering if good idea to lower compression and boost or just upgrade to better block?

07-14-2005, 05:30 AM

cudaeh

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Car Info: 2000 impreza 2.5 rs

seems most have been having decent luck with 9psi... its an open deck so you wont want the 15-20 range... only issues I have read about is the connecting rods seem to be the weak point when it comes to turbo charging.. Most say that it is because of improper tuning, others insist that the reason the connecting rod breaks its because the turbo sits between the firewall and the back cylinder on the passingers side and that retains a bunch of heat right there... eather way forged connecting rods seem to be the cure

07-14-2005, 06:25 AM

GrandpreRS

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that is why im replacing bottom end. got bad rod. definitely getting forged pistons and rods. is it necessary to lower compression when boosted?

07-14-2005, 07:08 AM

GrandpreRS

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willl the original stage II crank be adiquate for the boost? could a stroker kit be helpful for the upgrade of the ej253 block?

07-14-2005, 07:31 AM

GrandpreRS

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anyone know what a JUN EJ25 stroker kit costs?

07-14-2005, 07:10 PM

CitySubie

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I'm not 100%, but I think the pistons have something to do with the air/fuel ratio's compression. For optimal BOOM for each piston, you need 14.7:1 air to fuel or fuel to air ratio. Adding boost will changed that ratio and changing piston to a lower compression sort of counteracts that.
I think.

07-15-2005, 04:19 PM

keggo

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14.7:1 seems REALLY high for a car. My gixxer has probably like 12:1

07-15-2005, 04:41 PM

cudaeh

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Quote:

Originally Posted by keggo

14.7:1 seems REALLY high for a car. My gixxer has probably like 12:1

are you getting air fule ratio confused with compression ratio? and yes 14.7:1 is ideal air fule, i dont know how acceviable that is.. but i know thats what is dieal..
the reason you want lower compression with forced induction systems is to counteract detination. because the air and fule mixture is entering the cylinders already pressurized you dont want to compress it too much. If you compress the mixture too much it will (because of the pressure) heat up to the burning point before the spark plug fires... This is known as detionation...
Now on the pratical non dictionary explanation of things...
i dont know...
no clue about the de-stroker kits, I know most after market systems are made to just bolt on. but if you want piece of mind i say forge every thing you can inturnaly and lower the compression... and keep us posted on how you went about that!!