AA Pistons Are Causing NightMares BOOM

[juki48]

[The Noof]

Something wierd about losing the wrist pin out the bottom of the pin boss: the forces to pull the piston down in the bore aren't really that great, and the hardest pull would be on the intake stroke.Compression stroke would offer the greatest load to the bottom of the pin boss .

[mharney]

If the material isn't strong enough for whatever reason (defect, gauge, whatever) I can see where enough spins would cause it to deform and then break, or if the material were too brittle, shear maybe.. but it just seems unlikely to me that an established company would have these problems showing up. I'd really like to hear what AA or Kona or some other representative/vendor has to say about it too.

[sszuch]

Noof,

With his combination, the highest piston accelerations occur at TDC and is 64615 ft/s^2 vs. 36500 ft/s^2 at 160*. I miscalculated earlier and the inertial load from the piston is 1266 lb. When the piston is on the compresion stroke, as well as through the power stroke, the pin is bearing on the top of the boss where there is more support (where "top" is the flat part of the piston for my clarification). It is at the top of the exhaust stroke / begining of the intake stroke where there is negligible pressure on the top of the piston lending the greatest stress at the bottom of the pin boss. Again, coupled with the effective bearing area at a reduction in cross-sectional area and a small radius (stress concentration) makes for a weak link at the bottom of the pin boss. It may not be a material issue since other manufacturers are using the same material, but there are many other factors that could cause failure. How the piston was treated post forging has a lot to do with performance, if it was not stress relieved properly or there could be surface defects in the material. Grain direction during the forging process also influences material properties as well as impurities in the base material. 2618-T6 is an aluminum / copper based alloy, and if not heat treated properly, the copper grain size can grow large making it brittle and reducing the strength of the material. It seems that maybe this is just a bad batch if it has only occured in the limited production runs posted earlier.

[The Noof]

You're right, bro. I had a brain cramp, I guess.Compression stroke loads the top of the wrist pin boss, rather than the bottom.Greatest load on the bottom of the wrist pin boss has to be on the intake stroke.

[2stroke]

Troy, im convinced you can break anything...and WILL...but you still wont see these cheapie pistons in any of my motors.

[TroyG]

Since this post has started I and the other guys running these AA pistons have been the ones answering all the questions. Now I have a few.

If these pistons are so great.
Were is Kona ?

Why don't we hear anything from him ?

Why was there a change in the piston from a grafite skirt to a non grafite skirt and back to a grafite skirt ?

Were are the published results that back up the statement ( They have been tested and are stronger as JE and Cheaper too..They are Forged from 2618 T6 Aluminum which is the same strength as the JE Pistons ) ??

If I do send my pistons to Kona, how do I know that they will be tested fairly & will the test results be published ?

Why did I get alot of support from alot of other supply houses and vendors across the country to help get my motor up and running except from Kona ?

Ask yourself this , If you had 2 pistons go bad & do the same thing ( Pull Rist Pins ) would you install a new set of AA's in your car ?

IS THERE ANYONE RUNNING A SET OF AA'S WITHOUT GRAFITE SKIRTS AT THIS TIME IN A DRAG CAR THAT HAS NOT HAD A PROBLEM ( bought between 10/06 & 7/07 ?

Were is Kona ? O I already asked that.

[mk-Zero]

You know, I *think* my friend was running AA pistons on his 2275 EFI/turbo that let go at moderate boost (maybe 12 psi) and moderate RPM's (maybe 5k or so). Can anyone identify these pistons? If they are not AA's then never mind...

_________________
Vintage Classic Specialist, Orange, CA
www.VCSresto.com
[email protected]
1952 VW Standard beetle
1955 VW Type 1, 231 hp daily driver
1956 VW Karmann Convertible Okrasa

[tree hugger]

I'd be keen to know if the problem exists outside of racing as well. I know that these are extreme failures in high performance applications but will these problems occur to a lesser degree in a daily???

[miniman82]

Why not just be on the safe side and use Mahles? Why would you even want to tempt fate?
_________________
Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747

[TroyG]

Troy Goodwin 1st motor failure Feb 07 #1 piston full set bought 11/06 ie VolksTalk Post
Troy Goodwin 2cd motor failure Aug 07 #4 piston single bought 3/07 ie The VolksTalk Post
Mike Chambers ie Here
Jason Lauffer at VW Paradise ie The Samba Post
Tom V. DRD Built Motor ie Here
Jason Fuller ie The Samba Post
SuperDave at Chassis Magic Race Cars Sorry Don’t know his full name ie The TVWDRA Post
Mauro Cattan 2332 N/A 12 to 1 Added 8/17

If I missed anyone let me know and I will ad you to the list. I’m sure the list will continue to grow, but I thought I would at least show that these motors are being built right by guys that do know how to tune and build motors.

Mauro Cattan
Im sorry we had to had you to the list, but thanks for posting........

If yall think its the nitrous doing this, yall have no clue.........
I am the only nitrous car on the list so go talk to the other guys for a while......

[url][/url]

[Eaallred]

The wrist pin area looks as thin as a Mahle. I can see how they would pull out. I don't care if they are the same grade of aluminum (or better) than a Wiseco or JE piston (which could be all they're going by if they say they're "just as good"), if the material is too thin, it just isn't going to hold.

It's not likley the intake draw itself that is causing enough restriction to pull the wrist pin out, rather the extremely harsh change of direction the piston is having to do. 5-6-7-8000 times a minute? That's brutal punishment.

I know some people have 'dissed' the Wiseco pistons, but I love mine. VERY thick around the wrist pin area, and 9300rpm burnouts haven't shown any problems yet.
_________________
Eric Allred

You have to remember something: Everybody pities the weak; Jealousy you have to earn.

[TroyG]

OK Lets recap here for just a miniute. We have 2 nitrous , 2 turbos, 4 N/A motor having the exact same problem with the same end results. Look at the facts & pictures. We know there is no way in heck that all these motors did not suffer the same thing.

Detination
P/C Clearance
Pins Bending
Washing rings
Nitrous Stress

What we do know for a FACT is that these motors were running the exact same pistons.
We know the HP output from these motors were from 180 to 300.
We know that the pistons being called into question are the one made without grafite skirts.
We know all these motors let go at low RPM's.
We know that in all cases the pins pulled from the pistons.
We know that Kona has not responded to any of these post.

Now these questions still have not been answered yet, by anyone.

Were is Kona ?

Why don't we hear anything from him ?

Why was there a change in the piston from a grafite skirt to a non grafite skirt and back to a grafite skirt ?

Were are the published results that back up the statement ( They have been tested and are stronger as JE and Cheaper too..They are Forged from 2618 T6 Aluminum which is the same strength as the JE Pistons ) ??

If I do send my pistons to Kona, how do I know that they will be tested fairly & will the test results be published ?

Why did I get alot of support from alot of other supply houses and vendors across the country to help get my motor up and running except from Kona ?

Ask yourself this , If you had 2 pistons go bad & do the same thing ( Pull Rist Pins ) would you install a new set of AA's in your car ?

IS THERE ANYONE RUNNING A SET OF AA'S WITHOUT GRAFITE SKIRTS AT THIS TIME IN A DRAG CAR THAT HAS NOT HAD A PROBLEM ( bought between 10/06 & 7/07 ?

As you can see in this picture I was not running the motor to lean or washing the rings out.....
These are the plugs I was running during my tnt 3 weeks before the motor let go.

This is the plug that i removed from the car after it went boom.
Notice the timing mark on the ground strap and also notice there is NO detination and also notice it was not in a lean or rich condition to cause this problem..........

[RIS]

What was the skirt clearance on these engines, just out of curiousity?

Are all the cylinders used the AA 94mm long?

I've seen piston failures, but never soo much catastrophic cylinder failures in conjunction. All the cylinders seem to be coming apart in the same fashion too. I'd be questioning the cylinders as well.

I had 10K street miles and countless 12 second 1/4 mile passes on a standard (the $150 ones, not the ones touted as good as Wiseco) AA 94mm strokers and no problems. Cleaning them as we speak, will post pics if I find anything hairy. These were properly set-up for ring gap and skirt clearance.

The engine is going back together with the AA's as pictured, but with Mahle cylinders, again honed for proper skirt clearance and ring gaps set to spec. I had the AA longs and the skirt clearance was almost non existant, the Mahle cylinders were alot closer and only needed a little honing to get within spec. Fingers crossed.
_________________
Richard Sedoris - VW Performance & Machine - Youngstown, OH
http://rismachine.tumblr.com/
YouTube: https://m.youtube.com/channel/UCfTBCG4I61iVm_ROc8OAuOQ
Instagram: @rismachine

[TroyG]

Rich
Some were using mahle's, AA's & cima's. As you can tell looking through the pictures, yes all the motors look the same and the pins are pulling out of the pistons.

Most including myself were running .005 p/c wall clearance. I am not sure if everyone was running the same but i'm thinking so.

Best of luck to you.....

[The Noof]

It's hard NOT to be concerned by this thread.When so many people are having an issue with the same product, there HAS to be something to it.It would be nice to hear from Kona, and AA themselves.I hate to say it, but it wouldn't be the first time poor quality parts infiltrated the VW aftermarket.

[Alan_U]

Troy,

Get a high magnification lens and look at the porcelain area and the electrodes of the plug. You'll probably see melted small globs of aluminum either coming from the piston and maybe the head. You CANNOT see this with the naked eye. Alot of people "think" they dont have detonation but typically they do.

I'm currently using the non graphite "first" version of the AA's and they are holding together so far. I have .005 clearance with my AA cylinders. It was a tight biotch though when NIB.

When I hear things letting go I truly get that sick stomach feeling. Sorry to hear all this chaos is happening.

If your not fouling you may even consider a colder plug like a D9EA (if it exists) Sometimes you may even wonder if theres timing scatter from the distributor at high rpms (depending on what dist your using)

this post is getting long so I may have missed something but how did your conrod bearing (non cap side) look? Any indication of pounding?
_________________
11.92sec pump gas true daily driver. Who says it cant be done.

No more time for VW's.......

[TroyG]

lol
Hey Alan

I love those Clevite 77 rod bearings, and no the bearings look great..

As far as my plug reading go, I do cheet, I have a 8magapixel slr camera i take pictures of my plugs and you would be amazed at how much you can zoom in with good software.

My thoughts and preyers go out to you and your motor. Best of luck man.

[Terry Cloyd]

Troy do you think your nitrous delivery is equal in time and volume? If not one cylinder will lose.

[TroyG]

Hey Terry it's been a while........

Here is a pic of the motor and as you can see I am running 1 set of cheeter solinoids that are running the fuel and nitrous through 15 inch flex lines. All the line are the same. So yes the fuel and nitrous are hitting at the same time. I also run 2 fuel filters on the system as well as a filter on the nitrous.