Arias Pistons

[Tektrader69]

Any opinions on the ACL/MAHL forgies?

[Fitzpatrick Speed Works]

If you can get Mahle pistons for an rb26 or even rb25 I would really like to know those part numbers, Mahle are the best no questions... I have been trying to get them for the rb for the best part of this year but with no success, another thing to remember is alot of mahle designs have really short sides or skirts more or less none they are just the crowns this is aweseome for power but not really longevity as they arent as stable in the bore. They are good though... ACL are just replacement type pistons they are good but dont offer high end forgies made from good materials like some of the other companies, but again they serve there purposes!!!!

[Cubes]

I thought I will post a few pics that I've gathered around abouts.

[180bfj20det]

What are the brands of forgies available and what is order of pricing?

Arent ALL forged pistons as good as one another because they are forged or are there different types of manufacture, composition and therefore durability?

I here a lot about wiesco, arias and JE but I would really love to know, as stated in my first question what all the brands that are available and the pricing of each.

Also it would be nice to know what piston you chose and why you chose it?

I have put together chat I can from this forum but I am still confused.

Cheers

[R32-GTS]

Stay away from the ACL / ROSS forgies as they are noisy as and recommend a 6 thou clearance which seemed acceptable maybe 10 years ago.

[180bfj20det]

Stay away from the ACL / ROSS forgies as they are noisy as and recommend a 6 thou clearance which seemed acceptable maybe 10 years ago.

OK so what do you guys recommend then if you can, answer the questions I put foward before it would be great... cause I just dont know what to get :confused:

Cheers

[proengines]

I think I've posted something before about this, We've used Arias, CP, ACL/Ross, JE, Venolia, Wiseco and SPS pistons in RB engines and never had any of them fail because of piston design or material problems.

Some have advantages and disadvantages, from my experience Arias are a nice piston, well finished but the rings supplied are a little ordinary. CP are a very nice piston, the same sort of quality as JE and both run fairly tight clearances. Ross makes most of ACL's forged "sport compact" style pistons, these are solid, great sizes, really good rings but do run a little extra cold clearance because of a lower silicone content which does make the piston a little tougher. They are also a bit heavier than others. Venolia pistons are tough as nails but run big clearances, a little more than ACL/Ross. Venolias are supplied without rings and there are some pretty ordinary ring sets being sold with them, some even with a cast top ring. Wiseco pistons are excellent all round, well finished, good balance, great ring pack with narrow 1.2mm steel top rings, round wire clips, most have coated skirts and small cold clearances. SPS make great pistons, they are a little dearer than most but they will make exactly what you want, whatever ring style you want, weight etc..

With the cold noise issue, as a rule of thumb, the lower the silicone content of the alloy used the tougher the piston will be, as the silicone content increases, the clearance decreases but the piston becomes slightly more brittle. There are other advantages/disadvantages of different silicone contents and people will argue until they're out of breath what is better but really it depends on the application. For a street engine that is driven regularly and doesnt get a proper warm up something with a slightly higher silicone content will work better as the piston is more stable in the bore even when cold. For a race car this doesnt matter as much as the engine is warmed up before it is driven.

Materials are improving, most of Mahles range now are extremely strong and run tiny clearances, their Subaru pistons are only running .0025" clearance which was pretty unheard of a few years ago for a forged piston. Eventually they will be available for most models but currently their market is dictated by what sells in america, so Subaru, Mitsubishi, Honda and Toyota are well catered for. They will make custom pistons for anything but it's a slow process as their production is dictated by Nascar customers as that's their biggest market so custom orders can take a while.

[Gav]

Nice write-up Greg.

A question - does anyone know who manufactures the HKS pistons? How good are these and is the option of nickel coating worthwhile?

[BOOSTD]

No. 3 piston is reading 30psi down and is majorly oil soaked. Will let you know were the failure is on inspection/pull down. =*(

[Cubes]

Thats bad, I think I would walk around the house majorly depressed if that happened to my freshly built motor.

Have you got a gut feeling on what it may be? Tuning, Machine work/assembly or support system failure?

[discopotato03]

I got JE VG30 Pistons and the gapless rings for mine , I wanted 87.5mm and 22mm gudgeon pins but mainly the higher compression ratio ie up round 8.8 - 9 to 1 . I don't know what clearence is recommended for these as the build is not too soon . Fingers crossed those Sealed Power rings will pay off .

Cheers A .

[Tektrader69]

Thats interesting, I have a set of ACL forged VG30 pistons ready to go here as well. What are the advantages of the gapless rings over normal ones?

I always assumed the ACL pistons where Mahle, after reading all the posts here maybe they are made by Ross.

Sorry to ask for an education on this, but I would like to know.

[discopotato03]

I believe its to do with very little blow by ie keeping the expanding gasses in the cylinder rather than escaping into the crank case . If they reduce oil contamination in the cylinder it can help maintain the fuels octane rating .

Cheers A .

[BOOSTD]

Thats bad, I think I would walk around the house majorly depressed if that happened to my freshly built motor.

 

Have you got a gut feeling on what it may be? Tuning, Machine work/assembly or support system failure?

not sure what the cause is yet. The car was running 0.4bar and rich. The failure seems to be heat related tho as it was on my first 30min+ long drive. Don't you hate it when the machine shop decides to use closer clearances then you asked for and then you get the "warrenty covers oil leaks only mate"

[BU5TER]

you sure its not the venolia pistons they are well known now to have a fault and crack?

[DoughBoy]

I've ended up buying some Venolia's from CRD.

Forsooth.

[BOOSTD]

you sure its not the venolia pistons they are well known now to have a fault and crack?

Will let you know when I do. Tell me more about this fault ?

[Blitz]

Its a well known fault Matt

Venolias are a very poorly designed piston. Did you have a good look at the underside and skirt design of them before you bought them?

The skirts are very thin, too thin in fact and there is a groove machined around the outside of the piston that even further reduces the overall skirt thickness leaving a weakspot. This is where I have seen them crack.

The last piston that I looked at which was pulled out of a freshly built RB26 was cracked in such a way around the skirt that a peice the size of a 20c peice was ready to fall off

[Mik]

What Piston to bore clearance was it running? Sounds like the skirt may have picked up on the bore.

[B33st]

Here is a photo of the Venolia piston from my current RB25 Build, hope they cause me no problems.