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iSooby has yet ANOTHER question involving EJ25 builds!!


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Ok... so lately I've been contemplating an ej25 and ej22 frankenmotor, high compression build. Ej25 block with ej22 crank, heads, etc etc... now I'm wondering about the electronic section of it. Will I still use all the same engine harness's??? And which Ecu would I use? I'd prefer to be able to get it tuned, and I know the ej25 has a locked Ecu... so is the ej22 Ecu locked as well or can I dyno tune it? And if I can... will it work for the build??

 

Thanks in advanced! I know I've been known to ask some dumb questions on here but this my first subi and I'm curious!=)

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using an EJ22 crank in an EJ25 block will lower your compression, not raise it. EJ22 has a 75mm stroke, EJ25 has a 79mm stroke. you will be effectively destroking the engine to 2.3l.

 

As for the 2.2 heads, if you leave the EJ25 crank/rods, you will raise the compression at the risk of detonation. you will likely have to run higher octane gas in that case. If you swap to EJ22 crank/rods you will still have lower compression and displacement, just slightly less of a drop. in any case, if you use 2.2 heads, i say stick with the 2.2 ECU, It should run your engine fine. however, keep in mind that raising the compression introduces its own issues with engine management.

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The frakenmotor has no issues running on the stock ecu. Run 89 octane and you will be okay. So far no. One. I have seen has broken this motor. Been in one with about 200chp in a 2200lbs brat. Snapa your neck
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I'm still learning what components I need to do the build. But yes I know I need higher octane gas. I was just wondering if dyno.tuning it would be worth the gains in power and how to do that with what Ecu. But what all parts go into a frankenbuild?
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Run the car with the manifold and harness you have.

 

using an EJ22 crank in an EJ25 block will lower your compression, not raise it. EJ22 has a 75mm stroke, EJ25 has a 79mm stroke. you will be effectively destroking the engine to 2.3l.

 

As for the 2.2 heads, if you leave the EJ25 crank/rods, you will raise the compression at the risk of detonation. you will likely have to run higher octane gas in that case. If you swap to EJ22 crank/rods you will still have lower compression and displacement, just slightly less of a drop. in any case, if you use 2.2 heads, i say stick with the 2.2 ECU, It should run your engine fine. however, keep in mind that raising the compression introduces its own issues with engine management.

 

He would just need +2mm rods which are available through a number of places these days. It increases VE and allows you to rev higher due to the reduced peak piston acceleration. This is becoming fairly popular with the turbo guys right now but to see meaningful differences you need a 4mm longer rod, which means custom pistons too. which means like $1500 just in rods and pistons.

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