who is using forged AA pistons? How much boost?

[shepherd]

I am collecting parts for a 2232 (84x92TW) efi/ turbo engine. The short block is pretty much there, and I am looking at the top end parts now. I have piston cooling nozzles installed, and will be running SL1 heads. Target boost is 16-20 psi but we all know more is better, so who knows..
That said, are the forged AA sets up to the task? I have used their Hypereutectic sets for a while now and am impressed at how well they perform. Stepping up to a JE or Weisco almost doubles the price, unless I'm looking in the wrong places.

[The Newf]

I built that exact config myself, including AA's.No issues with 24 psi on my setup.I use pump premium with meth injection starting @ 1 bar.This is street use though.You can't maintain 24 psi with a street bug for very long...lol.
P.S...I'm not encouraging anyone to do so...just sayin' what works for me.

[shepherd]

Thanks for the response, I had meant to post this in forced induction, maybe a moderator can move it for me?

[Piledriver]

Note that while the AA true forged slugs will slip right into a pair of out of the box Mahle jugs, they still require .005"-ish clearance... Just like forged Wisecos and JEs, same alloy.

They gained an undeservedly bad reputation with their pins pulling out and destroying engines at the top end of the quarter mile due to folks *overlooking this point, when the pistons seized in the bores when they got up to temperature.
(*~all of which should have known better)

One must measure things if you are building an engine, and get the jugs honed as required for clearance.

[The Newf]

Well said.Forged require more cold bore clearance than cast or hyper.I used .0045" as my blueprint spec.
I don't drive my Bug much anymore,but it sees 24 psi on the street,and I've run 32 psi on the track.Had a waste gate failure & the poor bastard hit 40 psi once,breaking a pile of head studs & lifting the heads.AA's were no worse for the wear.

[risk]

I am running the AA forged pistons, AA cylinders and total seal rings.. seems to be holding up good so far.

AA honed my cylinders to size (for .005" clearance) for $10 each..

[shepherd]

Good info on the clearance for forged pistons, thanks! I have an inquiry in to my supplier to see if they can check for me before shipping. On my 2161 I had the piston tops and chambers ceramic coated. Not because I felt it needed it, but to see how well it would hold up. So far it's spotless (stuck a bore scope down through the spark plug hole), and my heads run cooler than any other engine I've had a gauge on. I'm thinking this would be a good idea for a turbo engine as well?

[Piledriver]

Coatings are great but any detonation is likely to knock it off.

...Of course even the slightest detonation knocks tiny bits of aluminum off the piston and chamber.

[slowsixtyduece]

I had Set of 94mm AA forged pistons that had been in Mahle cylinders bored approx .004"-.005" ptw clearance. They had somewhere in the vacinity if 1000 turbo miles on them maybe? Visually they looked great, other than the graphite coating had worn off on the piston skirts. No issues whatsoever.

After reading the forums and all the horror stories from years ago (noted earlier), I decided to sell them. I'm sure they would have worked perfectly fine. At the time, for peace of mind, I sold them and bought some nos mahle 94s. I am sort of a nervous person when it comes to parts and I probably should have just ran the AAs but here I am!

[Chip Birks]

I had Set of 94mm AA forged pistons that had been in Mahle cylinders bored approx .004"-.005" ptw clearance. They had somewhere in the vacinity if 1000 turbo miles on them maybe? Visually they looked great, other than the graphite coating had worn off on the piston skirts. No issues whatsoever.

After reading the forums and all the horror stories from years ago (noted earlier), I decided to sell them. I'm sure they would have worked perfectly fine. At the time, for peace of mind, I sold them and bought some nos mahle 94s. I am sort of a nervous person when it comes to parts and I probably should have just ran the AAs but here I am!

I think you down graded dude. Mahle forged and AA forged are totally different animals. I'd say the AA parts are trying to copy the Wiseco level stuff. People run Wiseco instead of Mahle for a reason.

[Piledriver]

If he's not ridiculously boosted and has a good tune the Mahles are fine and will last a great deal longer.

The soft low silicon alloy most forged pistons are made from tend to have the ring grooves worn out before 10k miles, sometimes far less even in street use. (This includes all the forged pistons sold off the shelf for ACVWs)

Wiseco warns against 2813 aluminum pistons even for endurance racing on a NA engine due to ring seal issues.

The 4000 series alloys (higher silicon) forged pistons are commonly used and last like cast or hypers, and run similar clearances, but they are not available off the shelf for ACVWs. (TYPO 4032) is most common forged factory piston alloy)

Every significant piston mfr makes them, and they can be ordered for the same price as the softer forged pistons... but they last ~like stock, only much tougher.
They are not quite as forgiving of a bad tune as 2813, but nothing is safe from a bad tune anyway.

Subaru turbos run hypers from the factory, just designed for boost.
The STIs with forged pistons run 4000-series alloy pistons.

[seabeebuggy]

I hit 20 all the time on AA.

[gbaker770]

33 psi last week and then it took out the ringland.
Cylinder still looked perfect.

That was our maximum.
It took a few pulls to 30 as well.

[WickedWagens]

All of you running the AA's, Are you running their rings and wrist pins or are you using something else?

[WickedWagens]

I ran them last week at Bonneville in my land speed engine. I ran everywhere from 8-20 lbs. I guess time will tell how they will hold up.