engines jibber jabber

version 4 and version 5 are differnt in the phase 1/2 riff. head ports are redesigned, cams are milder, but electrionics are more advanced. some things changed on it - (redesign in all castings (head/block/transmission shell), make it a more modern day production animal (mechanically). just as GDB A/B are very differnt than GDB E/F, its a natural progression thing.

in summary:
ej20g and K are very similar dyna and response. arguably preferable to the ej207 gc8's, arguably not.

G and K differ in the way that a B18C1 and b18C5 differ. both can stand up to the same stress numbers, but one does a more outstanding job at it. both c1 and c5 can rev to 9K, and kick in vtec , but the C5 does it with more output because its simply more efficient. better head ports, bigger valves, titaninum stuff for crazy response attack, lightweight pistons to attack rpms more rapidly, thats the state of the tune. the K is much more sophisticated in a NA tune fashion than the g is. both at 1.5 bar will make you go crazy, the K will just carry more power under the curve getting there.

subaru went from 8.5:1 compression and 280ps to 8:1 compression and 280 ps without changing much. the turbines are changed for more response and torque under the curve, but the ultimate output is the same. in this sense, its the turbine that makes up for the lack of compresssion, but it can be further digressed in a more explicit mannter.

i.e. my car;

Ej20G sti RA car, ran 8.5:1 sti ver2 ra V-limited motor, then a 9:1 ej20H normal twin turbo legacy longmotor, and now is rockin a EJ20K ver3 sti- ra V-limited motor.

same turbine, same ecu, same exhaust setup, same intercooler setup.

to compare, the G ra motor and the H legacy motor drive almost identical. the .5 extra compression of the legacy has noticable improved off throttle response in the 10-20% throttle range. spool off throttle is advanced too, the compression reduces response time.
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the sti - RA motors had the same valves, springs, heads, cams, as the normal WRX ej20G's, but the differance of lighter weight (probbaly 15g or so lighter) pistons, and mechanically activated valvetrain compared to the hydrolic, but performance is negligable. the only differance is a slight accelleration in rotating mas movement, and more precise actulation of airflow at very high rpms - 7,500 rpm ++ where the turbine has already dropped out of ideal zone to be at (meaning you shouild have shifted already).

before you go hunting and asking me -"where can i get an RA", please note.

*ej20g- only "STi-RA" cars had mechanical valvetrain. i believe 800 total were made. rare even in japan.
*wrx ra is not the same.
*there is no point in wasting the extra money to have this particular setup. if you are bench racing, just buy the sticker and pretend like you spent 2x the money that you did.
*EJ20K is considerably better than the ver2 sti-ra head, and so you are just being silly by demanding the older version thats not as good.

so we move on to the EJ20K, as the wrx normal G and wrx-sti-ra G are basically the same thing with the H legacy being a very slight change (but preffered by me and arguably faster lap time).

the Ej20K in my car currently is paired exactally like all the previous EJ20's. Ej20G computer, intake manifold, side entry td05 turbine, stock exhaust, same catless downpipe, same boost map setting, everything. same gearbox, same car, same monkey behind the wheel.

my initial critizim before i drove it was if the drop in compression to 8:1 + the aggresive high rpm side vavetrain and port setup would make it a dog with the bigger, laggier td05. I was wrong.

to think, a 9:1 compression ej20K with flattop short skirts would be a mad setup...

the 8:1 lacks to the 9:! h in one area only. 10-20% throttle zone, the response is a little further away. it makes up in airflow completely from 20-25%, and as the rpms climb, it sucks in a lot more air.

why?
cams. valves, heads all more optimized and refined for air consumption.

it has a floaty feeling of surge to it:

rotating mass is 25g lighter in pistons, valvetrain components are lighter as well

the next progression in this setup witll be 9:1 compression with wrc short skirt flat tops and 2134cc stroker kit...