ALFAGTV6.COM

[Jim K]

Hi guys, thought I'd show up to let you know the new 3liter 12v pistons are finally done and I received the first set yesterday. Though they skipped some of my specifications, the general quality is excellent and here is a brief description: 10.5:1 CR with std head, will accept giant valves (up to 48mm intake) they have anti friction skirt and anti-stick dome,they accept std Alfa rings (for convenience+cost) and they weigh ~488 gr vs ~590gr of the std ones (no rings). I understand they're also forged from some special JE alloy.
My biggest disappointment is I ordered a full skirt, cut back on the pin bosses and I got slippers! I guess I'll have to live with them.
Parts-wise, we now have new rods (THS) new pistons, new 46mm in. and 38mm ex. valves, new cams (they're already great performers as I hear...) and new headers (still working out the bugs). Please don't ask about the book...when I'm ready you'll know it.
Jim K.

[Micke]

I like the color.
Why don't you like the skirts? Prefer some MF/John Deere design...

[fedezyl]

Great pics Jim, any numbers on the cost of a set of these?

[Jim K]

The sale price will be determined by JE in a couple of days. I think Paul Spruell will carry these.
As for the skirt, I had specified the one shown here (which is what I have in my current 3liter JE set).
Jim K.

[Mats]

First time I've ever seen a radiused crown from JE, nice.
Not to sure about coating on the crown though, why did you opt for that? All I heard about it is that it makes the engine very sensitive to pre-ignition without any real gain in performance.

[MD]

I thought the whole idea was to minimise carbon build up on the crowns which historically IS one of the causes of pre-ignition?

[Jim K]

Well Mats, they tried to talk me out of the radius dome, arguing they've always seen more power with flat-tops. I insisted because I think all the angles in their other design are not very helpful for best flame propagation. Besides, its a very low dome that does not intrude into the chamber spoiling the shape; nothing like the old race Nords (that was half an orange, leaving a pitiful combustion space!)
I had mixed feelings about the thermal barrier. Just like we all do, I've read all the pros and cons and what tipped the scale is that its not an easy surface for residues to stick on (Tefal pan?). Then again, proper mapping shouldn't allow the engine to ping. People making these barriers claim lower engine temps, what can I say...
I'm sure if anyone ever wanted to order these pistons, they could ask for any number of changes like different ring grooves, no coating etc, as JE are very flexible with this sort of thing. Its not like they'll stock these in any quantity!
Jim K.

[Greg Gordon]

I think those look really great. I assume they will be offered in a slightly larger bore size so that users can re use liners.

Of course for my own purposes (that means forced induction) I tend to go the other way with compression.

I like the radius dome. That dome looks very similar to the 8.5:1 JEs in my dad's supercharged Nord.

Greg

[Jim K]

I may be jumping the gun here Greg, but I would think JE would have no problem making the same piston with the pin a couple of mm higher up for lower CR. If you're interested I could ask them (through P.Spruell). I think machining the pin boss higher is probably a lot simpler than altering piston diameter.
Jim K.

[Mats]

Interesting, what I meant was radiused edges, as in not knife-edges like they usually ship for some reason. The dome shape was a given success in my mind already instead of their usual "wall" in the middle of the piston.



Regarding the coating I think the problem is that it does not let heat into the piston and hence it can not be used as a "heat buffer" and the temp in the cc rise very rapidly. But I must say I'm only "parroting" what my boss has told me, he never use coating (on the crown) and he seems to do fine without it in his >200Hp/l 2-valve engines.

[Greg Gordon]

Hi Jim,

I think that piston design is great as is. For a normally aspirated car, they are exactly what I would want. I probably wouldn't move the wrist pin up to lower the compression ratio. I am sure that will work, but it will disturb the squish area, and I am always hesitant to do that. I would rather lower the compression by changing the dome's shape. In any case, that's forced induction stuff, and I don't want to change the topic of this thread.

Mats: I know exactly what you mean about that "wall" we see on a lot of forged pistons. I like the radius shape we see in this design a lot more, although I can't prove it's a lot more effective.

I can't comment intelligently on the coatings. I have no experience with them yet, although I do have a set of low compression JEs with that coating sitting here. However they are going in an unusual engine so I can't do a valid with and without coatings comparison.

[Zamani]

Wow nice pistons! I didn't know you liked more skirt, thought you would like less skirt

I think Barry said he had chambers in the heads and piston crowns applied with thermal barrier coating and it pings a lot. Baz?

Though I wish I had put the coating friction reducing on the skirts on my JEs. I think the 24Vs has 2 small square patches of teflon or whatever coating on the piston skirts (well at least on the 2.5 24V).

Are these the lower expansion type alloy? I have the Spruell JE pistons, and I don't hear them rattle during the cold mornings, but I was told the Venolias will rattle a little more when the engine is cold.

BTW JK, are you going to come up with newer 24V pistons? Maybe 24V heads will allow 11:1 pistons??

[Mats]

Are these the lower expansion type alloy? I have the Spruell JE pistons, and I don't hear them rattle during the cold mornings, but I was told the Venolias will rattle a little more when the engine is cold.

Is the wrist pin in the center or offset? offset pin will quiet down the engien a lot.

[MALDI]

From the http://www.jepistons.com, the brown coating is:

Thermal Barrier Crown (CC)
The thermal barrier crown coating is applied to the top of the piston and is designed to reflect heat into the combustion chamber, thereby increasing exhaust gas velocity and greatly improving scavenging potential. The .0015" thick coating can also assist in extending piston life by decreasing the rate of thermal transfer.

[Jim K]

The pin is centered Mats.
Z, I won't be 'developing' any more new parts, I think I've done my bit and at great financial cost too. We now have several new V6 parts as well as 24v big-valves (27mm). These last ones will only be tested for flow in a suitably modded 24v port and that's about it. About the piston material you''d be better off asking P.Spruell.
I now have to divert $$ resources to the 1.8T which is very...demanding so far. As for the V6, with some more tests and mapping it will be done and out of my way for good!
Jim K.