CalaisTurbo New Tags
User Name: Password:

Go Back   calaisturbo.com.au > Technical > Engines, Turbos, Exhausts, Intercoolers
Calais Turbo Advertising

Reply

 

Thread Tools
Old 01-05-03, 18:41   #1
carcrazy
Dont mess with Crazy
 
carcrazy's Avatar
 
Join Date: 20-05-02
Location: NSW, Sydney
Car: Imaginary one
Trader Rating: (12)
Pistons for RB25 / 30 head conversions, you can now buy them

I was reading an artical the other day and Arias pistons now makes a piston to suit the RB30 block to RB25 Head conversion, this is good news in regards to compression ratio problems with this swap, if your interested go to http://www.rocket.au.com for info, they are the distributors.

Carcrazy.
carcrazy is offline   Reply With Quote
Old 02-05-03, 02:07   #2
DVS 86
Player
 
DVS 86's Avatar
 
Join Date: 03-10-02
Location: Brisbane
Car:
Trader Rating: (0)
Wiseco has had these pistons on the market for over 6 months now. I thought everybody knew that.

Oh well. 8)
__________________
The definition of a STREET car is that you actually DRIVE the car to the track and back home again.
DVS 86 is offline   Reply With Quote
Old 02-05-03, 21:41   #3
RB30DEVL
Player
 
RB30DEVL's Avatar
 
Join Date: 30-08-02
Location: NSW, Newcastle
Car: VY SS Commodore
Trader Rating: (0)
re - compression problems

If you buy the whole RB25 engine and use the pistons out of that motor on the RB30 conrods then there's the compression problem solved.
Me,RB30-ZED and a few others around the place have fitted them to maintain a high compression ratio at 10.5:1,that ratio is not a problem to me,would probably be to someone who wants to use the crappy standard fuel but,even Shell Optimax may be marginal in my application as the R33 computer is programmed to run a far higher ignition advance than the cars here in Australia,I have heard of a 110 octane rating used over in Japan.
RB30DEVL is offline   Reply With Quote
Old 05-05-03, 10:58   #4
87calais
legend
 
87calais's Avatar
 
Join Date: 19-06-02
Location: NSW, Newcastle
Car: '87 VLCT Manual, '11 VE SS-V Manual
Trader Rating: (12)
Send a message via MSN to 87calais
yeah but while 10.5:1 is ok for an N/A engine , its way too high for a turbo application. Special Piston Services in Melbourne (i think) have pistons for RB30/25 head conversions or they will make a custom piston for you. I am using the RB26 head and i just need to supply them with the cc of the combustion chamber and the compression ratio i want to use and they will make a set of forgies for me. Most quotes i got for forgies were around $1800. SPS sell 6cyl piston sets, custom made for $1500. cant beat that for value for money. :mrgreen:
__________________
87calais
.
87calais is offline   Reply With Quote
Old 06-05-03, 00:49   #5
RB30DEVL
Player
 
RB30DEVL's Avatar
 
Join Date: 30-08-02
Location: NSW, Newcastle
Car: VY SS Commodore
Trader Rating: (0)
re- custom pistons

What about running VL turbo pistons in the conversion if going for high boost & big turbo,etc?
I suppose the only problem is running too lower compression as it will be at 7:1 thereabouts.
Another option I suppose would be to use the N/A RB30 pistons which work out to be 8.3:1,but I am told that anything over 15 PSI cannot be run with those pistons.
RB30DEVL is offline   Reply With Quote
Old 06-05-03, 03:19   #6
87calais
legend
 
87calais's Avatar
 
Join Date: 19-06-02
Location: NSW, Newcastle
Car: '87 VLCT Manual, '11 VE SS-V Manual
Trader Rating: (12)
Send a message via MSN to 87calais
Yeah VL turbo pistons make the compression ratio too low. It would be ok when on boost but very doughy off boost. Some people use the VL NA pistons and machine part of the crown off the piston to bring the compression ratio back to around 8:1.

Has anyone here used Special Piston Services forgies in an engine???. I was quite impressed with the price and service, just after peoples opinions on them.
Cheers
__________________
87calais
87calais is offline   Reply With Quote
Old 09-05-03, 11:16   #7
twinvl
Player
 
twinvl's Avatar
 
Join Date: 31-08-02
Location: VIC, Melb, East.
Car: R32 GTS-t 4 Door, TRX Bluebird SR20DET track car
Trader Rating: (1)
I rang Allan Engineering in Mallala a while back...
Can get Wiseco forgies machined to whatever comp ratio u like, they are a RB26 piston with a blank top so they machine it down to suit! $1600 with rings and gudgons.
I would have them already but i keep finding other stuff to spend all my $$$ on so can never afford them! 1 day!

BTW, this is a great thread!
__________________
Dam the under 2l class is quicker than the over 2l...
http://www.twinvl.driftshop.com.au
twinvl is offline   Reply With Quote
Old 09-05-03, 11:44   #8
darkstar
Silver Bullet
 
darkstar's Avatar
 
Join Date: 22-05-02
Location: Melbourne, MoTeC M800 :D
Car: 5spd Calais Turbo
Trader Rating: (21)
Send a message via ICQ to darkstar
1500 to 1800 is a good price for forgies, depending on what you get for it.

Friend recently got some rb25 pistons, standard forgies for 1500, might be SPS ones im not sure.

Truly an art work, i think that was wtih rings and gudgons, but they were albit incomplete.... needed to cross drill the gudgion pin housing for an oil squirter, but oitherwise great.
__________________
BACKYARD Performance
RB2630 T51 in the build...
darkstar is offline   Reply With Quote
Old 09-05-03, 13:33   #9
Guest
Guest
 
Location:
Car:
I have sps forgies, ringlands were machined 3 thou too wide, my engine builder wanted to throw them in the bin. :cry: I would have ordered CP's from the US if I had have known.
10:1 is sweet for aftermarket ecu and race type use, all the Honda turbo boys are 10:1 sometimes higher and with big boost.
  Reply With Quote
Old 13-05-03, 17:37   #10
HARRIS
Player
 
Join Date: 07-12-02
Location: VIC, Eastern Suburbs
Car:
Trader Rating: (0)
rb30 N/A pistons with RB25 Head = 8.3:1 compression ratio by memory, not 100% thou, i would of thought that to be a perfect balance for off-boost drivability
__________________
NA Engines are Not Applicable to Power
HARRIS is offline   Reply With Quote
Old 25-07-03, 14:04   #11
OldF@rt
Player
 
OldF@rt's Avatar
 
Join Date: 16-06-03
Location: Canberra, Fraser
Car: AR040 - '87 VL n/a
Trader Rating: (0)
Quote:
Originally Posted by HARRIS
rb30 N/A pistons with RB25 Head = 8.3:1 compression ratio by memory, not 100% thou, i would of thought that to be a perfect balance for off-boost drivability
Yep, it's 8.3:1 according to an article in a recent Zoom special.
__________________
Old age and treachery will always beat youth and skill...
OldF@rt is offline   Reply With Quote
Old 31-07-03, 22:44   #12
stimps
Player
 
stimps's Avatar
 
Join Date: 10-02-03
Location: Brisbane, Ipswich mate!
Car: 86 BT RB25DET twin turbo
Trader Rating: (0)
8.3 would be ideal wouldnt it? I have been driving around a standard rb25det (comp ratio is 9 i believe) and i managed 18psi with good cooler and constant fine tuning to keep it on the boil and had no problems (except the occasional pinging to let me know i had gone too close to the edge!)
I am considering the RB30DET motor soonish so i guess i might go that way...forgies of course.
stimps is offline   Reply With Quote
Old 08-08-03, 13:35   #13
Degree
Player
 
Degree's Avatar
 
Join Date: 20-06-02
Location: Brisbane, Northside
Car: Calais Turbo
Trader Rating: (1)
Arias are expensive and hard to get. Go Wisecos
Degree is offline   Reply With Quote
Old 14-08-03, 22:54   #14
dceptv
(. Y .)
 
dceptv's Avatar
 
Join Date: 22-11-02
Location: WA, Perth
Car: 2011 MN Triton GLXR T/D, 2010 Swift & 09 YZ250F
Trader Rating: (16)
Send a message via MSN to dceptv
Uhm...if you look at the standard vlt pistons you will see that they are multivalve pistons....
__________________
Autopro Bentley
1145 Albany Hwy, Bentley
92586644 or 0433393852
Like The Shop On Facebook :D
dceptv is offline   Reply With Quote
Old 15-08-03, 15:02   #15
twinvl
Player
 
twinvl's Avatar
 
Join Date: 31-08-02
Location: VIC, Melb, East.
Car: R32 GTS-t 4 Door, TRX Bluebird SR20DET track car
Trader Rating: (1)
There are 4 Valve reliefs in the RB30E pistons due to the valve arrangement in the single cam head. ie, cyc 1,2 and 3 inlet valves are on the front rh side and exhaust valves on the rear lh side. Then they swap fro cyc 4, 5 and 6. So instead of making 2 different pistons they made 1 with 4 reliefs!

Just saying they are not a multivalve piston but they are.......

It just so happends that the reliefs suit the twin cammer perfectly, no piston/valve contact possible! Atleast with a RB25DE VVT head anyway...
__________________
Dam the under 2l class is quicker than the over 2l...
http://www.twinvl.driftshop.com.au
twinvl is offline   Reply With Quote
Old 21-08-03, 03:46   #16
BLK-747
PUNISHER
 
BLK-747's Avatar
 
Join Date: 18-07-02
Location: Melbourne, AIRPORT
Car: BLK-747
Trader Rating: (14)
i think HSVSUX is onto something higher compression + lots of boost + good tunning = lots and lots of power
but this is very hard to accomplish and needs to be very fine tuned and a strong motor but can be done
__________________
PREPARING FOR TAKEOFF!!!
FASTEN YOUR SEATBELTS
BLK-747 is offline   Reply With Quote
Old 29-08-03, 01:06   #17
twinvl
Player
 
twinvl's Avatar
 
Join Date: 31-08-02
Location: VIC, Melb, East.
Car: R32 GTS-t 4 Door, TRX Bluebird SR20DET track car
Trader Rating: (1)
Just wanted to clear something up.
I did some chamber measuring and came up with a figure of 8.06:1 using the twincam head on a RB30E block, not 8.3:1...

The piston measured to be 1cc dished, turbo pistons 11cc dished.
For the compression ratio i want, 8.5:1, i need a 3cc domed piston!
I guess we shouldn't take whats in a mag as gospel! But then there can be alot of variation that throw the figure off too.
__________________
Dam the under 2l class is quicker than the over 2l...
http://www.twinvl.driftshop.com.au
twinvl is offline   Reply With Quote
Old 29-08-03, 16:01   #18
B15HOP
Player
 
B15HOP's Avatar
 
Join Date: 07-07-03
Location: Perth, NoR
Car: It's not just a car, n I don't just wanna "drive"! =)
Trader Rating: (0)
How do you measure the compression ratio anyway? Depends on the turbo but I was considering a smallish turbo 5 - 10psi with about 9:1 ratio?
__________________
"Never get out of the car!" - i'76

"The ecological crisis is a moral issue"
B15HOP is offline   Reply With Quote
Old 01-09-03, 11:56   #19
twinvl
Player
 
twinvl's Avatar
 
Join Date: 31-08-02
Location: VIC, Melb, East.
Car: R32 GTS-t 4 Door, TRX Bluebird SR20DET track car
Trader Rating: (1)
Quote:
Originally Posted by B15HOP
How do you measure the compression ratio anyway? Depends on the turbo but I was considering a smallish turbo 5 - 10psi with about 9:1 ratio?

U measure the volume of the combustion chamber in the head, and cyclinder with the piston down a little, by sealing around the piston/valves ect with grease, then place a piece of glass over the opening and fill with oil using a syringe to measure the volume!

Measurements i got were
63cc for twin cam head
55cc for single cam head
21.3cc for 86mm bore, piston 3.5mm from TDC, cyc vol,
and head gasket 87mm bore, 1mm thick.

With these figures i got 20.33cc displacment of piston from 3.5mm down to TDC with measured at 21.3cc the piston is 0.97cc dished.
Head gasket makes up 5.94cc.
So add the head volume, 63cc with the piston @TDC volume and gasket volume together to get a total combustion chamber of 69.91cc.
Then the compression ratio is the cyclinder volume at BDC compared to volume at TDC, BDCcc/TDCcc.
BDC volume is for 86mm bore and 85mm stroke is 493.7cc piston displacment + CC of 69.91cc = 563.61cc.
and 563.61cc / 69.91cc = 8.06
8.06:1 comp ratio.

If you do all the same calculations with a 55cc head volume (SOHC head) you get 8.98:1, which verifies the results/measurements!
__________________
Dam the under 2l class is quicker than the over 2l...
http://www.twinvl.driftshop.com.au
twinvl is offline   Reply With Quote
Old 03-09-03, 21:50   #20
B15HOP
Player
 
B15HOP's Avatar
 
Join Date: 07-07-03
Location: Perth, NoR
Car: It's not just a car, n I don't just wanna "drive"! =)
Trader Rating: (0)
Hey I found the equation:

((boost psi / 14.7) + 1) x motor compression = effective compression

That would explain why a BMW is soo @#$kn powerfull while still being n/a. The M3 has something like 12:1 compression ratio which equivelent of running 6psi of boost with a 9:1 compression ratio. This is why before it made me wonder why the BMW had such high compretion ratio and produced soo much power only n/a. The M3 with 3.3L vvti and high compression produces almost 250kW.

Racing cars have an "effective compression ratio" of 22:1, thats a crap load. Due to laws of compression though that kind of ratio would kinda fry your standard engine. Cooling becomes a problem and day to day driving becomes unreliable. Forged pistons are a must in these situations because of heat and pressure differences.

Changing to dohc should be worth it in the long run due to better cooling the head provides as well as the increased flow at higher rpm. With forced induction like turbo or supercharger and 15 psi, your effective compression would be more like 18:1 which is over double the ammount of air traveling through the engine.
__________________
"Never get out of the car!" - i'76

"The ecological crisis is a moral issue"

Last edited by B15HOP; 03-09-03 at 21:56.
B15HOP is offline   Reply With Quote
Old 12-11-03, 16:10   #21
sr20trx
Player
 
sr20trx's Avatar
 
Join Date: 12-06-02
Location: Perth, Atwell
Car: R31 Skyline GTSII - 340rwHP
Trader Rating: (0)
Few quick questions guys, as I am planning this conversion soon

1. I will be retaining my current RB30 NA bottom end (8.3:1), with Hiflo'd VLT T3/4, decent cooler....what rwHP realistically acheivable...i'm doing 280rwHP atm with Turbo'd NA RB30.

2. What cams do people use with the head....the standard NA items?

3. Injectors....RB25DET's?.....& what rwHP would they max at?

4. Will my VLT bolt straight up to the RB25DET Manifold?

5. Or, If there is a thread on this already do you have a link

Cheers

Lindsay
__________________
http://www.pbase.com/psi_gtsii
http://www.pbase.com/gts2turbo
http://www.pbase.com/gts2turbo2
sr20trx is offline   Reply With Quote
Old 19-11-03, 16:45   #22
CyberCrim
Player
 
Join Date: 21-10-03
Location: NSW, St Marys
Car:
Trader Rating: (0)
If fitting the RB25 head to a RB30 block can you still run the power steering without any fouling problems?
CyberCrim is offline   Reply With Quote
Old 23-11-03, 16:14   #23
calaistur
Player
 
Join Date: 22-10-03
Location: QLD, North Queensland
Car: 1987 Calaist Turbo
Trader Rating: (0)
Hey TwinVL, can you do that calc for an RB25 head on an RB30 with standard RB30ET pistons. I have read it is about 7.3:1.
calaistur is offline   Reply With Quote
Old 25-11-03, 13:39   #24
twinvl
Player
 
twinvl's Avatar
 
Join Date: 31-08-02
Location: VIC, Melb, East.
Car: R32 GTS-t 4 Door, TRX Bluebird SR20DET track car
Trader Rating: (1)
Hey,

Yeah can do no probs!

If you work it out from the standard comp ratios of 9.0:1 and 7.8:1 and use all the same figures it can be done.

0.97cc n/a piston + 5.94cc headgasket + 55cc sohc head = 61.91cc
493.7cc piston displacement + 61.91cc total @tdc = 555.61cc @ bdc
555.61cc / 61.91cc = 8.97 8.97:1 comp ratio for na

So if i make the ratio = 7.8 and the piston volume = PV, i can work it out.

493.7+PV / PV = 7.8

493.7+PV = 7.8PV
493.7 = 7.8PV - PV
493.7 = 6.8PV

PV = 72.6cc

piston dish = 72.6cc - 5.94cc head gasket - 55cc head = 11.66cc piston dish

So no if i add up the piston volume 11.66cc with the head gasket 5.94cc and the twincam head of 63cc = 80.6cc volume @tdc

And again add displacement of 493.7cc and tdc vol of 80.6cc = 574.3cc voulme @bdc
Comp ratio is
574.3 / 80.6 = 7.13 7.13:1 comp ratio, RB30ET pistons with RB25DE head!

I think thats too low, it would be ok if u wanted to pump in about 2bar of boost but then the standard pistons wouldn't cope with that for to long....


Cheers.
__________________
Dam the under 2l class is quicker than the over 2l...
http://www.twinvl.driftshop.com.au
twinvl is offline   Reply With Quote
Old 14-01-04, 21:18   #25
Krieger
Player
 
Krieger's Avatar
 
Join Date: 05-01-04
Location: SA, Adelaide
Car: VL, Audi 100
Trader Rating: (0)
hey people, sorry to ressurect a bit of an old thread,

BI5HOP, higher compression is a much better thing that high boost. a high compression engine will probably (in most cases) make more power than a low compression engine with high boost.

kinda puzzles me why people go for low compression pistons like 7:1 and such, makes the car a pig off boost, and will make your support systems work much harder(intercooler etc., because you using higher boost to make the same power) maybe they are still used to old engines with poor head clamping and poor cylinder sealing... you shouldn't have any of those probs with the RB's, so long as you use good fuel.

compression is your friend, boost is not.
the reason why the stocker has low compression,. no intercooler, poor fuel, simple as that.

am into racing nitro r/c cars,, 20:1+ CR, 35000 rpm...
-jimmy
Krieger is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads

Thread Thread Starter Forum Replies Last Post
RB25 Head conversion wit RB30ET pistons?? TroyVK Engines, Turbos, Exhausts, Intercoolers 3 10-05-03 18:55
Help!! Head gasket has blown and head cracked, what do l do? whiteshadow VL Non-Turbo Discussion 15 29-01-03 09:44
Refreshening motor- what pistons brad Engines, Turbos, Exhausts, Intercoolers 6 17-11-02 15:06


All times are GMT +10. The time now is 05:55.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Ad Management plugin by RedTyger