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Turbo n/a ej20


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Hello i have a gf8 impreza wagon it has an n/a engine was wondering what would i be able to run boost wise on a stock bottom end i have a set of jdm wrx heads 1.6 mm mls head gaskets to put on it got equal length manifolds and made a 3 " up pipe and have a full 3" straight thought exhaust sti fuel pump and injectors and have a vf 34 non waste gated turbo or td05 20g turbo to choose from i have a gbd top mount intercooler it has a map sensor not a maf sensor was wondering what i would have to gap the rings for the piston to to stop ring land failer as had to stop building the engine that was going in the car due to 3rd child just wondering what i could run with what i got any help will be grateful  btw im an engineer and vehicle tech by trade so making parts and moding things wont be a problem thank you ben

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It is a turbo model but had an n/a engine put in as turbo engine was blown from previous owner using the thicker head gaskets and the import wrx heads lowers it to the same compression as the turbo models already worked it all out i have everything to turbo as it was a turbo model and i have wrx ecu power im not bothered with as i will finish my engine to put in it onces ive saved up to get the rest of the parts 

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I like to see things being done different but Tbh you'd probably be better off sourcing a 2nd hand turbo engine to drop in .

As by the time you've bought all the gaskets,head bolts ect and had the machine work done (hone ,faced ect) .

It would probably be cheaper, especially  in a scoob that is supposed to run a turbo lump in the first place. 

I've built a few ej20's but never a na motor ,so can't really help with the na spec or turbo conversion.

Im Unsure what type of materials the pistons and rods are made of too ? So have no idea if they're the same as wrx ones or whether they're made from weaker materials and whether they will handle standard boost (let alone once mapped).

Ring gaps would vary pending on piston material and target h.p . headgasket thickness would be needed to be calculated with knowing the piston bowl and head chamber cc to get the 8.5.1 compression ratio 

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I have a turbo motor i building atm but due to 3rd child had to put it on hold ive worked out with the 1.6 mm head gaskets and the jap import heads the compression ratios would be around 8.2-8.3 - 1 the pistion and con rods are cast simliar to the ej25 piston and con rods the blocks a sport bottom end the dimensions are the same as a turbo long block the heads are twin cam 16v heads the compression differents is due to the heads have a more shallow bowl which bumps up the compression i have everything to turbo with gaskes etc its more the ring gaps as with the stock ring gap with the stock heads can run around 8 - 10 psi before ring failure would run the stock wrx ecu and thats around the 12- 14 psi mark not going to map the engine as will just chuck in in my friends vw bug unless it blows up before hand i can do all the machine work myself so thats not a problem cheers for the reply

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Well sorry I can't help much more due to my lack of na spec knowledge, possible that turbo sized ring gaps and piston to bore clearances would work . But I generally don't like giving advice if I haven't done it myself (tried n tested) and I have no idea if the na pistons fail at lower boost levels because of the ring gaps or material they're made from ?

Most ej20 bottom ends are the same size on the outside,  but deck type ,crank thrust and internals differ quite a bit over the years on the turbo models alone. 

Just wanted to make you aware that the cost of gaskets ect wouldn't be much different from a na to turbo build. Especially if you can do the machine work yourself , I'd probably just build the turbo lump tbh .

Other than piston material I'd check that the oil galleries are the same from na to turbo , as although the turbo oil feed and return attach to the heads , I don't know if the na block galleries will feed the turbo heads correctly. 

Best of luck with it and feel free to start a build thread,  to keep us informed on your progress,  bud 

 

 

 

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