Austarion

Have been playing around recently putting the 2.6 motor from my US staz into my old GK sigma gsr to use as an autocross/track car. I had it out a couple of times with the asthmatic 350k astron in it and was going to put a webber or holley on to get a bit of extra grunt until common sense prevailed and I decided to be done with it and put in the turbo motor.

With all the wiring in place the time came to pull down the engine to fix suspected head gasket issue, (low compression in No 2 and 3) only to find shagged bores.

Anyway when I went to my engine builders to see what is available as expected the only starion listing he had was for 4g63.

What I need to know as a result is what else has pistons that will fit without bumping up the compression ratio too much and will handle boost?

Not wanting to run too much boost, ideally I would like to lift the c/r to maybe 8:1, 8.5:1 and keep boost to around 12psi mostly to keep cost down.

How will cast pistons handle this sort of setup?
Do I need to keep the c/r lower?

Search for starion on the us ebay they have cast and forged pistons for the turbo 2.6 off the shelf. As a bonus its cheaper even after factoring cost of postage.

yep done that ricethief, didn't turn up anything oversize in a cast job.
I have been offered a very good price on custom JE or CP forgies but am just too poor atm and have too many projects to spend un necessary money on a car that will be used on a monthly sort of basis.

I think sigma or triton slugs might be the go but want to make sure before buying.

How about these?

Forgies
http://cgi.ebay.com/ebaymotors/Mitsubis ... ccessories

Cast
http://cgi.ebay.com/ebaymotors/PISTON-R ... ccessories

if you want to run low boost then no problems running slightly higher C/R pistons - it will help off boost drivability lots too. Surely you could find a set of early Magna or GK/GN Sigma pistons somewhere in Aus?

Thanks for that ricey, didn't find/notice the cast set on ebay.

DG, finding them isn't really the issue I mostly wanted to make certain there were no major differences between US starion 2.6 and aust 2.6

Upon further research I have found there is a high comp sigma/low comp magna piston available which has a 1mm higher comp height.

How much will 1mm effect compression ratio?

They also have 0.5mm narrower compression ring grooves (1.5mm instead of 2mm) which could possibly mean thicker ring lands (0.5 to 1.0mm)depending on where they are located, a possible benefit since apparently this is where most starion pistons seem to give way.

Someone please correct me if this is not the case.

hrmm I'm not really up to it when it comes to 4G54s (try and avoid them haha) but I would find pistons which sit at the same deck height as yours, but perhaps don't have such a shallow dish (I think Magna ones are flat tops?)

Thicker ring lands would probably be better for boost applications, most modern turbo engines are running rings as thin as 1.2mm. In fact I don't think many engines these days run rings thicker than 1.5mm (other than heavy duty diesel engines)

if its any help a mate here runs a 2.6 turboed and wonted to make it simple cheap and to have power off the bottom even with out boost

a bit like you need for an autocross car

so he used std flat top pistons ( off the shelf duralights )
changed to a std M7 head with some double valve springs
the comp is around 8.8:1
he used a 31/79 grind cam
a modified magna EFI
a std turbo sigma ex manifold
intercooler

this made 136 Kw atw with 6 pound boost @ 5800 rev
but drives like a std N/A motor under boost

it hasn't been back to remap the system bvut that was going to be pumped up to 10 - 12 psi

Can anyone see any reason why standard pistons would be better than magna ones?

The bloke I will probably get to do the bottom end really seems more comfortable running stockers than hyper-eutectics regardless of C/R for some reason.

He really knows his shit from all reports, having built a heap of top level drag car engines I just don't really understand where he is coming from.

Can anybody shed some light on it for me?

Standard Starion 2.6 uses dished pistons and magna flat-tops. So you will increase the CR using magna pistons.
Alternatively look for some hyperuetectic GH sigma pistons. Similar dish to starion (I'm not sure if the ACLs are still available).

Also have a look on summitracing or dads engine machine shop (go via starquestclub.com) for what is available from the US. I suspect a decent set of turbo specific pistons will be cheaper than getting anything locally.

Fianlly have this sorted out thanks all.

First I bought the cast set Rice thief pointed out but the seller couldn't find them in oversize so lucked out there.

I got lucky and managed to track down a set of ACL dished pistons with 1mm taller deck height which according to my calculations will put the C/R at approx 7.6/1 up from 7.0/1 will run stock boost to be safe for now and raise to 10-12 PSi after fitting intercooler.

Everything else will be basicly standard, just out for a bit of fun :D

Toyota 22r pistons are pretty close in size... someone has ran them, they worked until they overboosted the motor and popped the headgasket.

We can't get ACL pistons here... it's lame.

-Robert

Can't really get ACL here anymore either nowadays.
They never actually made pistons in house to my knowledge, ACL pistons were made by Mahle if memory serves me correctly.

For what you are after i would be trying to run high 8's :1 as a minimum. With an intercooler there is no reason you cant run 14 psi and 9:1

Nosaki Faki wrote:Can't really get ACL here anymore either nowadays.
They never actually made pistons in house to my knowledge, ACL pistons were made by Mahle if memory serves me correctly.

Yep, that's pretty much spot on