Cosworth Low Comp Pistons
#1
Cosworth Low Comp Pistons
Looking to build my motor and concerned that if I get 8.5:1 compression pistons that it may introduce to much lag. I'm not after top end hp numbers but a really nice solid drive on the street. The HKS low comps are 9:1 and the cosworth pistons are 8.8:1.
I'm thinking of getting the cosworths with tomei rods. Anyone used the cosworth pistons or have anything good/bad to say about them. I did search but everthing I found is based on other manufactures.
http://www.cosworth.com/shop_item.php?productid=403
My goals on my HKS ST is to run only about 10psi which should put me in range of around 440hp at the wheels from what I have seen from other installations with my lit.
If the low comps will introduce lag will a set of cams resolve this and if so which duration/lift would you recommend.
Michael
I'm thinking of getting the cosworths with tomei rods. Anyone used the cosworth pistons or have anything good/bad to say about them. I did search but everthing I found is based on other manufactures.
http://www.cosworth.com/shop_item.php?productid=403
My goals on my HKS ST is to run only about 10psi which should put me in range of around 440hp at the wheels from what I have seen from other installations with my lit.
If the low comps will introduce lag will a set of cams resolve this and if so which duration/lift would you recommend.
Michael
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Originally Posted by MR RIZK
Most of the above off the shelf are 8.5:1 and hence why I listed only the CW and HKS. I know CP's make custom pistons but was trying to get away of getting a set made if required.
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Originally Posted by thawk408
You will come hardpressed to notice a difference between 8.5 and 9.1. The size of the turbo is going to have more to do with lag then the CR of the engine. I believe the Wiseco's are 8.8 and the Arias extreme duty are 9.1.
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#9
Michael
I used the Arias 9.1 extreme duty in Andre's rebuild & custom 10.1 Arias ED's in Murrays motor. Both motors had no excesive noise when cold & represent excellent value at under a grand US. The Cosworth pistons come friction coated & will be excelent but expensive given that the rings are an extra cost.
IMHO the tomei rods are too expensive. The Eagle ARP2000 combo are great value and to date with 00's sold I have not heard of 1 complaint or failure in a VQ
Peter
I used the Arias 9.1 extreme duty in Andre's rebuild & custom 10.1 Arias ED's in Murrays motor. Both motors had no excesive noise when cold & represent excellent value at under a grand US. The Cosworth pistons come friction coated & will be excelent but expensive given that the rings are an extra cost.
IMHO the tomei rods are too expensive. The Eagle ARP2000 combo are great value and to date with 00's sold I have not heard of 1 complaint or failure in a VQ
Peter
Last edited by Nathan; 12-10-2007 at 02:01 PM.
#10
I thought the Arias are 8.6 but after checking forged internals website I can see that they get there own spec'd pistons made. The Arias site also state they can come pre-coated skirts which is good as I want to reduce the hassle to get it done later. My only concern is the required "Piston to cylinder block clearance" which may introduce slap/noise with Arias.
Last edited by MR RIZK; 12-10-2007 at 12:47 AM.
#11
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For tight piston to wall clearance and an 8.8:1 ratio, go with the Mahle pistons. The forging uses a 4032 alloy which does not expand as much as 2618.
The skirts are coated to reduce friction, and the rest of the piston is also coated in some other material. It is a beautiful forging; I was carefully examining them at PRI this past weekend.
remember that most of the "extreme" pistons on the market have pushed the rings down so much that the oil ring is in the pin area. This will almost certainly cause the engine to burn more oil than a piston that keeps the oil ring above the pin area.
Here's a couple pictures of the Mahles that one of their engineerings emailed to me.
The skirts are coated to reduce friction, and the rest of the piston is also coated in some other material. It is a beautiful forging; I was carefully examining them at PRI this past weekend.
remember that most of the "extreme" pistons on the market have pushed the rings down so much that the oil ring is in the pin area. This will almost certainly cause the engine to burn more oil than a piston that keeps the oil ring above the pin area.
Here's a couple pictures of the Mahles that one of their engineerings emailed to me.
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Originally Posted by QuadCam
For tight piston to wall clearance and an 8.8:1 ratio, go with the Mahle pistons. The forging uses a 4032 alloy which does not expand as much as 2618.
The skirts are coated to reduce friction, and the rest of the piston is also coated in some other material. It is a beautiful forging; I was carefully examining them at PRI this past weekend.
remember that most of the "extreme" pistons on the market have pushed the rings down so much that the oil ring is in the pin area. This will almost certainly cause the engine to burn more oil than a piston that keeps the oil ring above the pin area.
Here's a couple pictures of the Mahles that one of their engineerings emailed to me.
The skirts are coated to reduce friction, and the rest of the piston is also coated in some other material. It is a beautiful forging; I was carefully examining them at PRI this past weekend.
remember that most of the "extreme" pistons on the market have pushed the rings down so much that the oil ring is in the pin area. This will almost certainly cause the engine to burn more oil than a piston that keeps the oil ring above the pin area.
Here's a couple pictures of the Mahles that one of their engineerings emailed to me.
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Originally Posted by MR RIZK
got an email from cosworth for the fun of it and their piston to bore recomendation is 2.5 thou for their pistons
Sounds like they are using the 4032 alloy for their pistons.
manufacturers of 2618 alloy pistons for the VQ usually recommend .0035 to .004"
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