There has been a bit of a confusion regarding sport pistons I was going to copy for my Sport project, I assumed that KW used 144mm rod, where in fact it does not.
So... looks like I am getting some pistons made and I am given 2 options:
1. Pay $1400+ for a 1 off set of 5 pieces
2. Pay $800 for a set of 5 pieces if I can meet the MOQ
Considering JE’s go for roughly $1200 to $1500 depending on the options I am going to go the Mahle Motorsport route.
Here are the stipulations:
• MOQ of 40 pieces – 8 sets of 5 cylinder pistons.
• Mahle 142 Alloy forging will be used ( a blend between 2618 & 4032 alloy)
• Lead time 4-6 weeks (Could be longer , could be shorter as it depends on when they will be cutting another group from that forging).
• Mahle proprietary Grafal coating applied as standard (no need to farm out for coated skirts and crowns like the JE’s)
• Fixed CC for Dish volume
• Fixed cut out for intake valve diameter – I would probably go with +2mm oversized on the cut outs for those running Ferrea/Supertech larger diameter valves
• Fixed Compression Height – so for those who want to use the 2.5L block will be forced to use a 160mm connecting rod.
• Fixed wrist pin diameter
The only variable will be the bore diameter.
These will be the specs for my set:
• Bore = 79.5mm
• Stroke = 86.4mm
• Block = 7A/AAN/ADU/3B @ 220mm Deck height
• Connecting Rod length = 144mm
• Compression Height = 220 – [(86.4/2) + 144] = 32.8mm
• Piston Dish CC = 12cc
• Wrist pin = 20mm
An Elring AAN 20V Turbo head gasket has a max bore of 82.2mm and a thickness when fully compressed of 1.6mm = 8.49cc
A Stock 7A cylinder head with flat Ferrea/Supertech Standard Size valves has a volume of 44cc in the valve pocket area.
Vc = 4cc + 44cc + 8.49cc = 56.49
79.5mm bore x 86.4mm stroke = 2144.4cc : Vh = 2144.4 / 5 = 428.88 cc / cylinder
81.0mm bore x 86.4mm stroke = 2226.1cc : Vh = 445.20 cc / cylinder
81.5mm bore x 86.4mm stroke = 2253.7cc : Vh = 450.74 cc / cylinder
82.5mm bore x 86.4mm stroke = 2309.3cc : Vh = 461.86 cc / cylinder
83.0mm bore x 86.4mm stroke = 2337.4cc : Vh = 467.44 cc / cylinder
Based on my math a 79.5mm bore piston (for me) will yield the following:
E (compression ratio) = (Vh + Vc) / Vc
= 428.88 + 56.49 / 56.49
= 8.6:1 CR
For sample if I went to an 83mm bore the CR would be:
= 467.44 + 56.49 / 56.49
= 9.27:1 CR
So the range of CR will be from 8.6:1 to 9.3:1 depending on the bore size chosen.
Now these are the possible combinations for the order:
(1) 79.5mm bore x 86.4mm stroke – Martin Pajak
(4) 81mm bore x 86.4mm stroke – for the AAN users with a good bore
(2) 82.5mm bore x 86.4mm stroke – for anyone that wants to overbore the block
(1) 83mm bore x 86.4mm stroke – for 2337cc
The remaining 7 sets can be any number of combinations for the bore size. Without meeting the MOQ this will be a custom order.
If you are interested, let me know
Martin Pajak
So... looks like I am getting some pistons made and I am given 2 options:
1. Pay $1400+ for a 1 off set of 5 pieces
2. Pay $800 for a set of 5 pieces if I can meet the MOQ
Considering JE’s go for roughly $1200 to $1500 depending on the options I am going to go the Mahle Motorsport route.
Here are the stipulations:
• MOQ of 40 pieces – 8 sets of 5 cylinder pistons.
• Mahle 142 Alloy forging will be used ( a blend between 2618 & 4032 alloy)
• Lead time 4-6 weeks (Could be longer , could be shorter as it depends on when they will be cutting another group from that forging).
• Mahle proprietary Grafal coating applied as standard (no need to farm out for coated skirts and crowns like the JE’s)
• Fixed CC for Dish volume
• Fixed cut out for intake valve diameter – I would probably go with +2mm oversized on the cut outs for those running Ferrea/Supertech larger diameter valves
• Fixed Compression Height – so for those who want to use the 2.5L block will be forced to use a 160mm connecting rod.
• Fixed wrist pin diameter
The only variable will be the bore diameter.
These will be the specs for my set:
• Bore = 79.5mm
• Stroke = 86.4mm
• Block = 7A/AAN/ADU/3B @ 220mm Deck height
• Connecting Rod length = 144mm
• Compression Height = 220 – [(86.4/2) + 144] = 32.8mm
• Piston Dish CC = 12cc
• Wrist pin = 20mm
An Elring AAN 20V Turbo head gasket has a max bore of 82.2mm and a thickness when fully compressed of 1.6mm = 8.49cc
A Stock 7A cylinder head with flat Ferrea/Supertech Standard Size valves has a volume of 44cc in the valve pocket area.
Vc = 4cc + 44cc + 8.49cc = 56.49
79.5mm bore x 86.4mm stroke = 2144.4cc : Vh = 2144.4 / 5 = 428.88 cc / cylinder
81.0mm bore x 86.4mm stroke = 2226.1cc : Vh = 445.20 cc / cylinder
81.5mm bore x 86.4mm stroke = 2253.7cc : Vh = 450.74 cc / cylinder
82.5mm bore x 86.4mm stroke = 2309.3cc : Vh = 461.86 cc / cylinder
83.0mm bore x 86.4mm stroke = 2337.4cc : Vh = 467.44 cc / cylinder
Based on my math a 79.5mm bore piston (for me) will yield the following:
E (compression ratio) = (Vh + Vc) / Vc
= 428.88 + 56.49 / 56.49
= 8.6:1 CR
For sample if I went to an 83mm bore the CR would be:
= 467.44 + 56.49 / 56.49
= 9.27:1 CR
So the range of CR will be from 8.6:1 to 9.3:1 depending on the bore size chosen.
Now these are the possible combinations for the order:
(1) 79.5mm bore x 86.4mm stroke – Martin Pajak
(4) 81mm bore x 86.4mm stroke – for the AAN users with a good bore
(2) 82.5mm bore x 86.4mm stroke – for anyone that wants to overbore the block
(1) 83mm bore x 86.4mm stroke – for 2337cc
The remaining 7 sets can be any number of combinations for the bore size. Without meeting the MOQ this will be a custom order.
If you are interested, let me know
Martin Pajak
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