OST and JE Piston collaborate - New piston!

[oldeskewltoy]

I've been working with JE Piston now for about 3 months in developing a "new" piston for the 4AGE 16V. I sent them pistons, rods and this chamber casting



Why put new inside quote marks? Because the pistons crown isn't anything new... the "new" pistons crown design is actually rather olde... The crown of the new piston was derived from 13101-AE851.




So why a new piston?

Nearly every 4AGE piston out there has a significant dome because of 2 reasons....

1) Nearly every 4AGE piston is designed for O/S valves, either 1mm O/S or full on Atalntic... 2mm O/S. Accommodating O/S valves in your pistons lowers compression, and thus requires more crown to compensate.


2) This reason is far more subtle... the crown shape of the olde TRD piston extends to just past the valve reliefs, to a tapered edge that diverts/directs the "squish" up @ the spark plug. Because of this extended area, the crown can actually be LOWER.

Why is a lower crown better? Superior flame propagation.





So if the crown isn't new, then what is new?

The skirt...... JE Piston's Asymmetrical skirts



The original piston was designed with minimal skirt width... remember this had been designed as a high performance piston and low drag is a benefit. The problem with the 13101-AE851 wasn't the crown... but the VERY narrow skirt - about 41mm. That narrow works for a time, but it will not be long lived. The thrust side of the JE Asymmetrical is over 57mm providing a much more stable piston on the major thrust load side.


Availability:
cylinder bores - 81mm, 81.5mm, 82mm

wrist pins - 18mm, or 20mm

compression height - 30.5mm

crown volume - 2.5cc

Compression ratio range: 10.7 to 12.2*

10.7 - stock undecked block, stock head gasket, combustion chamber volume of 37cc
12.2 - decked block, stock head gasket, combustion chamber volume of 32.5cc

* 12.6 - zero deck, TRD .8mm gasket, combustion chamber volume of 32.5cc



Now.... the bad news... they aren't free

MSRP = $675.00 per set - this includes low tension rings. Options: Coated skirts + $70.00. Checking on crown coating costs at this time.

As always freight is extra.

The first set is tentatively sold at a partial discount.

[Bean]

Wondering how much they differ from my custom JEs

Sent from my Nexus 4 using Tapatalk

[oldeskewltoy]

(06-27-2014 10:42 PM)Bean Bandit Wrote:  Wondering how much they differ from my custom JEs

Sent from my Nexus 4 using Tapatalk

BB from his build Wrote:to my specifications...
CR=11.43; Piston Volume 3.5cc; valve reliefs: for stock diameter but more lift; compression height 30mm (instead of 30.5)

your crown volume 3.5cc, mine 2.5cc, your comp height 30mm, mine 30.5mm, your raised crown is just the center, my raised crown goes all the way out to the outer edges of the valve reliefs...

but I will admit your piston was part of the inspiration... but the AE851 piston was the inspiration for the actual crown design.


Here is what I mean about the difference in crown width... OEM 10.3 view on top

[oldeskewltoy]

It's no longer tentative... the first set is sold - 82mm bore 20mm wrist pin. Once they arrive I'll go through and take photos and get their actual mass

[oldeskewltoy]

UPDATE:

After in-depth consultation, the FSR skirt is being discarded in favor of a full skirted JE piston. The new dome will be retained, but the FSR /Asym skirts are NOT going to be used, I'm having the new piston retain JE Pistons full skirt.

WHY - ? Do to rod to stroke ratio, and engine speeds the FSR/Asym piston tends to "beat up" the 4AG cylinder bores. My whole intention with this piston is to supply a long lasting performance upgrade.

So... the new pistons will be fully skirted, and will carry the new crown.

[Project D]

So basicly back to that design:

Except the valves pockets and a lot better price I believe. (Tomei are pricey)

[oldeskewltoy]

(07-15-2014 05:27 PM)Project D Wrote:  So basicly back to that design:

Except the valves pockets and a lot better price I believe. (Tomei are pricey)

The Tomei slugs list for - ¥128000 - €928 - $1259.00. Sell for???

OST/JE - MSRP - $750.00, I'm selling them for $675.00.


the skirts will be closed.... like the piston skirt on the right in view below....



The mass will be VERY similar because the skirt walls are thinner, the closed skirt is for piston stability...


the crown is going to be very close to this.....

[harkes]

Hi Dan

This area look like a hotspot to me. Will this not cause problems with detonation?

[oldeskewltoy]

(07-16-2014 04:22 AM)harkes Wrote:  Hi Dan

This area look like a hotspot to me. Will this not cause problems with detonation?

I spoke to a few people about this and it might be an issue. I then spoke to JE and for JE Piston to set up the mill to "clip" those 4 corners(2 tiny peaks on the intake side similar to 2 on the exhaust side) on each piston would add over $200 to the price of a set... now the good news your machinist can do it prior to install!



The loss to the crown volume is about 1/10 of a cc total for all 4 "peaks"

edit - one thing to add to this... these still are a replacement forged piston... piston crowns typically need a bit of burnishing/sanding(or steel wool-ing) to knock the edges back anyway, in this case I'll show how.

[oldeskewltoy]

harkes Wrote:Hi Dan

This area look like a hotspot to me. Will this not cause problems with detonation?

OST Wrote:I spoke to a few people about this and it might be an issue. I then spoke to JE and for JE Piston to set up the mill to "clip" those 4 corners(2 tiny peaks on the intake side similar to 2 on the exhaust side) on each piston would add over $200 to the price of a set... now the good news your machinist can do it prior to install!



The loss to the crown volume is about 1/10 of a cc total for all 4 "peaks"

edit - one thing to add to this... these still are a replacement forged piston... piston crowns typically need a bit of burnishing/sanding(or steel wool-ing) to knock the edges back anyway, in this case I'll show how.

The new pistons arrive....




Using a diamond abrasive band I remove the 4 offending protrusions, and then using a 220 buff, I work the entire crown




A different perspective....



the arrows are pointing to where the 4 offenders were removed.... the "back" 2 arrows are pointing to the "worst" of the offenders... those by the exhaust valves.


this set of OST/JE pistons is ready for fitment



Pistons:
$675.00 (without crown re-shaping, or any coatings - straight from JE Piston)
Additions:
$40.00 - with OST re-shaped crowns
$75.00 - with slipper coating on the skirts
$75.00 - with ceramic crown coating - NOT available with OST crown work