924Board.org

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

From what I gather from Racing's past threads, these are the pistons he's using with success-

http://www.bugauto.com/volkswagen/index.php?action=item&id=9724

I can't believe I've gone through two sets of $650/set JE's

With the VW pistons it looks like the rod bushings will need to be replaced with 22mm bushings (same as with the JE's), and you'll need to bore the cylinders out from the stock 86.5mm to 87mm. This is only .020" so no problems there. What you get are flat top forged Mahle pistons with something like 8:1 CR and a non-interference engine. All for $140 !!! Sounds pretty d*mn good to me.

-nick

Smoothie · Posted: Wed Oct 13, 2004 3:13 am Post subject:

Are you sure they're forged? I didn't see where they said that.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Ah, you're right. The forged set costs a whopping $60 extra!

There is a pull down menu to select them right after the "quantity" box.

-nick

924RACR · Posted: Wed Oct 13, 2004 3:44 am Post subject:

<drool>

I think I need that...

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Darin81T · Joined: 03 Sep 2003 Posts: 124 Location: Vader, WA

Do you have any more info on these pistons? Racing has used them? How much boost has he been running with them? I'm seriously considering getting those pistons, for that price you can't lose. I have the engine out of my car anyways and a bottom end rebuild probably wouldn't hurt.

Later,
Darin Flynn

jpab924 · Posted: Wed Oct 13, 2004 8:59 am Post subject:

-nick, I`ll wait and see how it works out for you, I am not even close to pulling the engine out yet, but it is on the future plans list. If it works for you, it works for me.

And for that price, I`ll order em up right away, seeing if it works for you.

Paul · Posted: Wed Oct 13, 2004 9:07 am Post subject:

Wonder how much you could get for just the cylinders on eBay?

wdb · Joined: 02 Nov 2002 Posts: 2024

I'm thinking the cylinders would look nice on the desk , pencil holder flower pot etc. maybe use them in the itake near the turbo to disapate heat before the IC . or a cup holder in the car . or thread the ends to make part/screw holder , or screw em together to make a shop lamp ! maybe an old ignition switch and key for the on/off knob with a break drum for the base and a headlight motor and headlight at thetop, so when you turn the key the headlight opens and shines down on the desk .

924RACR · Posted: Wed Oct 13, 2004 11:01 am Post subject:

LOL!

It's not something I plan on doing immediately, but I plan to rebuild the motor in my 81 before I put it on the track, and I expect that it'll have at least one piston in need of replacement, based on the experiences of those here. But there's plenty of work to be done between here and there...

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

924 turbo · Posted: Wed Oct 13, 2004 12:09 pm Post subject:

I'm planning on rebuilding the bottom end on my 931. If anyone has any information on what is required to use these pistons, I'd appreciate it. Are there modifications to the rods, any clearancing required at the crankshaft, etc? What compression ratio do you end up with?
_________________
Jon Furst

goturbo · Joined: 15 Jun 2004 Posts: 88 Location: Massillon Ohio, USA

If you guys check out the post 'engine rebuild tricks...I need some' on the 931 tech board, racing gave a good description on what I believe are the pistons in question. Seems like he has had good success with them.

...and then build the flip up light/vw jug desk light.

jamez · Joined: 03 Nov 2002 Posts: 401 Location: Chehalis, Wa

I don't get it, how can they be so cheap? plus they come with vdub cylinders?! buy the pistons and sell the cylinders on ebay.

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

hmm.. looking into this a little further. The CR might actually be much too high. If the numbers that have come up on the list before are correct:

931 head volume- 21.5cc (measured by cbass)
displacement for 87mm diameter- 501cc (calculated)
Racing's measurements on the pistons (sit 5.4mm below the deck) give a combustion chamber volume in the block as .54cm * pi * (8.7cm/2)^2 = 32.08cc
using a 2mm thick headgasket: .2cm * pi * (8.7cm/2)^2 = 11.88cc

CR formula: Volume at BDC / Volume at TDC

We get 8.66:1 with these pistons. This is not to mention that headgasket measurements have generally come out to be around 1.4-1.6mm, which would drive the CR up even further.

Verdict? Racing mentioned that he smoothed down the sharp edges in the combustion chamber of the head. Taking off just 2cc's would bring the CR just under 8.5:1. Again, this is with a 2mm gasket (which racing had made from copper). This process might be tricky to bring the CR under control. But still, for the price of a set of JE's, you could buy a copper gasket, o-ring the head, and smooth and cc the cylinders, without much $$ difference.

-nick

wdb · Joined: 02 Nov 2002 Posts: 2024

at this link http://not2fast.wryday.com/vw/stuff/vw_engines.shtml

they have the dementions of the VW/audi/vag engines and parts . I believe the 924 rod journals are 48 mm and wrist pin is 26 , since the prospective pistons wrist pin is 22 mm you may be able to use 1 of the vw rods that are shorter , in order to lower the compression ratio to whatever you prefer . see dementions for the details . no I dont know the 924 rods length .

jpab924 · Posted: Thu Oct 14, 2004 9:53 am Post subject:

Best way to figure things out would be to get in touch with him. I did some snooping and did find his photo albums, but do not want to intrude on his privacy by posting the pics here.

However, this is the site where his albums are stored and maybe if someone knows how to read-- is it Norweigan ?, maybe we can track him down.

http://www.winas.com/