Which Pistons

[tm_r33]

my 25/30 is starting to be built this weekend. only part ive havnt yet got lined up is pistons. have read through so many pages on the forum and cant find a simply straight up answer. i need a decent comp ratio... obviously above 8.3 or thereabouts. will CP flat top pistons to suit RB30 give me a decent ratio. need a straight answer asap. what piston have ppl used to get decent comp ratio?

[tm_r33]

using standad rods and standard crank but balanced.

[tm_r33]

25det non neo head

[FineLine]

I would think any of the manufacturers 30 pistons should get you what you wantl

I use mahle for a comp ratio of around 8.5 to 1

[R32 Driver]

+2 Mahle 8.5:1 also

CP offer 8.5:1 or 9:1 also

wiseco only offers 7:1 i believe

[TiTAN]

CP

All compression ratios are based on zero deck height

1.2mm head gasket (7.13cc)

RB25 @ 62.5cc

RB26 @ 64.5cc

They assure me they have done alot of work to make sure the facts are correct.

p/n= CP-RB30/26-.20

Flat top with no valve pockets

8.2:1 COMPRESSION RATIO with RB25 head and bit less with RB26 head

21mm pin

1.280" compression height

Only stocked in 0.20 thou oversize but can be custom ordered in any size.

p/n= CP-RB30/26-.20-9.0

6.0cc dome top,

9.0:1 COMPRESSION RATIO with RB25 head and bit less with RB26 head

21mm pin

1.280" compression height

Only stocked in 0.20 thou oversize but can be custom ordered in any size.

*Care must be taken when using on RB26 with more than 11.5mm valve lift*

ARIAS

Suit RB30/26

p/n= AP332103

flat top

21mm pin

1.280" compression height

Only stocked in 0.20 thou oversize (86.5mm).

COMPRESSION RATIO 8.4-8.6

Suit RB30/26

p/n= AP332104

10.6cc dome top

21mm pin

1.280" compression height

Only stocked in 0.20 thou oversize (86.5mm).

COMPRESSION RATIO 9.2-9.4

Suit RB30/25

p/n= AP332105

13cc dome top

21mm pin

1.280" compression height

Only stocked in 0.20 thou oversize (86.5mm).

COMPRESSION RATIO 9.5-9.8

WISECO

Skyline RB30 w/ DOHC RB25det cylinder head

1.260" compresion height, 66.5cc head chamber, Dish top -11.3cc, 7.0:1 compression ratio, 21mm pin, 1mm gasket thickness, 1mm deck clearance.

K577M865 86.5mm

K577M87 87.00mm

[TiTAN]

my engine personally has the arias 9.2-9.4:1 pistons in it, little noisy on start up but i havent had any issues otherwise with them.

[works 510]

I also have the 8.5:1 Mahles in mine

[rockabilly]

cp,s in mine, 640bhp @ all 4 on a hub dyno,and if you search my threads they have had a beating, still going strong after chewing something up and spitting it out.lol bernie uk

[tm_r33]

Thanks guys. Especially titan. Extreamly helpful. Now know exactly what pistons will give me what comp ratios. As car is being built for circuit use, response is important, so a comp ratio of 9:1 would be excellent. Arias dome tops it is. 9.2 - 9.4 pending they in stock other wise dome top CP's

[bubba]

I've got the Wisecos (was originally built before all the others came out, I think they're pretty much 30ET pistons), still got plenty of off boost torque even with the 7:1 CR, we'll see what it does with the new turbo.. I imagine I'll be able to safely run heaps of boost and timing!

[tm_r33]

had a play around with some figures today and the 10.6cc dome top arias and the 6cc dome top CP both seem that they will get me where i need to be. The 13cc dome top arias will obviously give me a fairly high comp ratio and in turn will hinder the amount of boost i can wind into it. Im planning on running about 17 psi through a gt3582 at this stage.

The flat top pistons all seem to ofter a dramatically low CR and im not planning on throwing response out the window lol.

On a seperate note, i began removal of gearbox from the 33 this arvo. Clutch slave off... Tail shaft bolts off... So i started to remove bolts from block to box and got stuck on that annoying little f**ker right up the top. Any tips or suggestions or am i pulling the head off tomorrow???? Lol

[tm_r33]

I've got the Wisecos (was originally built before all the others came out, I think they're pretty much 30ET pistons), still got plenty of off boost torque even with the 7:1 CR, we'll see what it does with the new turbo.. I imagine I'll be able to safely run heaps of boost and timing!

I imagined it would of been a dog of a thing down low with that CR

[bubba]

On a seperate note, i began removal of gearbox from the 33 this arvo. Clutch slave off... Tail shaft bolts off... So i started to remove bolts from block to box and got stuck on that annoying little f**ker right up the top. Any tips or suggestions or am i pulling the head off tomorrow???? Lol

Lots of really long extensions... like a few feet worth.. that's how I get to the top bellhousing bolts on mine.

I imagined it would of been a dog of a thing down low with that CR

Nope, not as bad as you'd think. Small turbo and stock runners, so we'll see what it's like with the bigger turbo and a forward facing plenum once it's back together. I imagine if I was to run really big cams then it would probably be quite noticable but I'm only running stockers.

Edited July 14, 2010 by bubba

[FineLine]

had a play around with some figures today and the 10.6cc dome top arias and the 6cc dome top CP both seem that they will get me where i need to be. The 13cc dome top arias will obviously give me a fairly high comp ratio and in turn will hinder the amount of boost i can wind into it. Im planning on running about 17 psi through a gt3582 at this stage.

The flat top pistons all seem to ofter a dramatically low CR and im not planning on throwing response out the window lol.

On a seperate note, i began removal of gearbox from the 33 this arvo. Clutch slave off... Tail shaft bolts off... So i started to remove bolts from block to box and got stuck on that annoying little f**ker right up the top. Any tips or suggestions or am i pulling the head off tomorrow???? Lol

I have a metre long extension for that annoying bolt. works a treat.

[adamhr33]

I am using JE forged pistons

[tm_r33]

lol gearbox out... what a pain. would not wish that upon my enemies; as im very impatient i took to the stick with an angle grinder...

now i can rip the fly wheel out so i can get it balanced up with my rb30 crank and balancer

[JonnoHR31]

why didnt you just remove the whole motor and box together? or am i missing something here

[r33_racer]

Yeh weve learnt over the last 5 years of in/outs its just easier to disconnect everything and just take motor/gbox out in one hit. Do what you need to do, then chuck it back in!

Comment about your piston choice mate. Your going for higher comps to help response? Weve run both cp's flat top and domes and its makes bugger all difference. What does make the difference is manifold choices. Or so we found when at the track.

On a road car running 9:1 might be well and good, but for 95% of the time whilst on the race track you never fall off boost so much that you would really need that extra comp to help get you back on. Whilst racing you more then likely wont notice the difference. I couldnt.

[tm_r33]

Yeh weve learnt over the last 5 years of in/outs its just easier to disconnect everything and just take motor/gbox out in one hit. Do what you need to do, then chuck it back in! Comment about your piston choice mate. Your going for higher comps to help response? Weve run both cp's flat top and domes and its makes bugger all difference. What does make the difference is manifold choices. Or so we found when at the track. On a road car running 9:1 might be well and good, but for 95% of the time whilst on the race track you never fall off boost so much that you would really need that extra comp to help get you back on. Whilst racing you more then likely wont notice the difference. I couldnt.

point taken. i have done a lot of research and talking to people over past week including people who have rb30det with lower CR and i feel that staying close to the 9:1 ratio will suit my application. i guess time will soon tell. so you have played around with a few different exhaust manifolds to get the correct result?