CPpistons ring gaps

[wrxG]

im planning to run a GT35r at 28psi with meth and C16 .. I need to know what size gaps i should run on the CP rings .. thanks

[mtcs]

I have a 2.5L CP piston install with my fresh pte6169 (35r)
Did mine like this:

Top: 0.017635 to 0.0196 did mine at 0.018
second: 0.018 to 0.0235 did mine at .022
oil: set at 0.020

been running the new motor for about 1000 miles so far. Did a compression check and it came out to be 122-130 accross the board. Looking really good.

[jaxscuby]

i'd follow CP's recommendation..

[smoky]

EJ257, stage 2 @ 19 PSI setup with CP 100mm piston. Did the ring following CP guide (bore x 0.005 for top and bore x 0.006 for second):
Top: 0.019
Second: 0.023
Oil ring (untouched), but verified at 0.015

[xilles]

Originally Posted by mtcs

I have a 2.5L CP piston install with my fresh pte6169 (35r)
Did mine like this:

Top: 0.017635 to 0.0196 did mine at 0.018
second: 0.018 to 0.0235 did mine at .022
oil: set at 0.020

been running the new motor for about 1000 miles so far. Did a compression check and it came out to be 122-130 accross the board. Looking really good.

++++1111111
if you run anything looser with your setup. the meth will run down and mix with your oil. ive seen it set at 22 and 24 for both top 2 rings and it ran pretty bad. DO NOT use CP specs UNLESS your car is completely setup for high wear IE ROAD RACE hot laps

CP gives looser specs to compensate for high psi under heavy load without meth. hot laps are great for there settings but horrible unless you run the car at 8k everywhere. they dont expand enough under normal driving conditions.

we set up all our built blocks with -1 from oem specs to compensate for engine wear. a little tighter clearance.

after blueprinting my motor
ive done 18 across top and 19 on hotter cyl 4
and 22 across second
i ran it looser on that one cyl to adjust for fine learn ecu parameters.

rule of thumb ecu trys and compensate for the cyl4 causing cyl 2 to break a ringland. this goes into tuning.

from subaru factory the motor runs this way.this was coming from master suby tech at the dealer where we built numurous motors.

hope this helps

[Zackbo]

Originally Posted by xilles

rule of thumb ecu trys and compensate for the cyl4 causing cyl 2 to break a ringland. this goes into tuning.

I've never heard anything like this. Please elaborate

[xilles]

cyl 4 runs lean with the stock intake manifold design causing it to run hotter.
ecu reads it as lean- compensates for that cyl 4 making it run right
which in turn causes the richest cyl 2 to have problems. does that make sense.or is that to vague.

can be fixed with a proper fuel table for each cylinder. or a better flowing intake manifold.

[jaxscuby]

injector compensation table..
its already in the stock ecu..

[wrxG]

never knew that about cylinder 4 running lean
thanks for the info guys!

[Wintershredder]

Originally Posted by mtcs

I have a 2.5L CP piston install with my fresh pte6169 (35r)
Did mine like this:

Top: 0.017635 to 0.0196 did mine at 0.018
second: 0.018 to 0.0235 did mine at .022
oil: set at 0.020

been running the new motor for about 1000 miles so far. Did a compression check and it came out to be 122-130 accross the board. Looking really good.

IMO this oil ring gap recommendation is a bit to big.
I would stay with 0.015

[xilles]

Originally Posted by jaxscuby

injector compensation table..
its already in the stock ecu..

if you analyze a stock ecu map
from the factory the PCM is programmed to perform the same in all aspects of country. there are to many variables to take into account.

would a stock car with the same gas same PCM run the same
in either at sea level compared to high altitudes of say Colorado.
no they will not. it will be better at sea level because of the denser air.

you get a tune because its deliberately manipulated for the environment its usually driving in. compared to a stock program that's made generalized for the whole country.

just because the fuel table compensates for it. it can only be limited to the stock parameters it has from factory = garbage.

not very cool just enough to get you by.

now if you build the motor and self tune. you can account for the changes you made. ie. ring clearances fuel trims etc.

[garboplateNY88]

Originally Posted by mtcs

I have a 2.5L CP piston install with my fresh pte6169 (35r)
Did mine like this:

Top: 0.017635 to 0.0196 did mine at 0.018
second: 0.018 to 0.0235 did mine at .022
oil: set at 0.020

been running the new motor for about 1000 miles so far. Did a compression check and it came out to be 122-130 accross the board. Looking really good.

O my block is same as yours and I got 125-133 4,000 miles very close amazed. Bottom ends looking good.

[mtcs]

Well...im going to hope for the best.
So far so good.

The .020 oil should be ok for now.

Car is basically away for the winter. It's snowing like hell outside now.
Going for a tune on saturday though...should be in the mid 50s that day.

Starting my build on my Sleeved Ej257 in 2 weeks. This block doesnt have to last too much longer anyways.
So I'll post up some questions about what ring gaps I should be using with my new 102mm pistons.

[CoolRex]

FYI Ron at Raw1 Performance runs .014 top ring .016 second ring .015 bottom oil rings.

Personally I'm running .018 top, .022 second, .015 oil control. My compression was rock solid 150 psi on a stone cold motor with only 30 miles on it (hybrid). Chasing other issues right now so the car is down at the moment (NOTHING piston/ring related).

[mtcs]

I actually have no idea what my compression should be.
Hybrid build will do that to you.
EJ257 DOHC bottom end with CP pistons, eagle rods, acl bearings
Ej251 SOHC Heads with port and polish, TWE Titanium retainers, TWE Dual springs, Delta cams 2000, SS nitrile valves.

So 122-130 accross the board....donno if that is good or bad.