from mr2oc.com rsrace
Ok so Ive gotten several questions and concerns about pistons and compression ratios with the 3sgte pistons on the market and I wanted to make a post to clarify everything.
CP, JE, and SRP all have 9.0:1 pistons. Its the only compression ratio they offer, and I often get customers who just prefer 8.5:1.
Arias and Ross both list a 8.5:1 piston but heres the part to pay attention to.
CP/JE/SRP all list their compression ratios assuming an aftermarket .040" (1mm) thickness headgasket.
Ross/Arias both list their compression ratios assuming a factory .056" (1.4224mm) thick headgasket.
Well, if you measure the compression ratio with the CP/JE/SRP pistons using a factory headgasket thickness like Ross/Arias do, you get an 8.5:1 piston, and likewise, if you measure the compression ratio with a Ross/Arias piston using a 1mm aftermarket headgasket thickness, you get a 9.0:1 piston.
So, all of these pistons are the same compression ratio, just listed in different ways. I got with my guy at JE and we used their high tech fancy shmancy inhouse software to get the compression ratios using different thickness headgaskets and this is what we came up with...
Here are the headgaskets we worked with that are available for the 3sgte:
TRD: 0.8mm
Cometic: 1mm
HKS: 1mm & 1.6mm
Apexi: 1.1mm & 1.5mm & 1.8mm & 2.1mm
(CP/JE/SRP/Ross/Arias Pistons)+(TRD 0.8mm Headgasket)=(9.2:1)
(CP/JE/SRP/Ross/Arias Pistons)+(Cometic/HKS 1mm Headgasket)=(9.0:1)
(CP/JE/SRP/Ross/Arias Pistons)+(Apexi 1.1mm Headgasket)=(8.8:1)
(CP/JE/SRP/Ross/Arias Pistons)+(Factory 1.4224mm or Apexi 1.5mm or HKS 1.6mm Headgasket)=(~8.5:1)
(CP/JE/SRP/Ross/Arias Pistons)+(Apexi 1.8mm Headgasket)=(8.375:1)
(CP/JE/SRP/Ross/Arias Pistons)+(Apexi 2.1mm Headgasket)=(8.1:1)
Wiseco's 9.0:1 piston however is 9.0:1 with a factory .056" (1.4224mm) headgasket, so it truely is a 9.0:1 at the same headgasket thickness where the rest of them are 8.5:1
If you want to get close to an 8.5:1 compression ratio with a Wiseco Piston you will need to use the Apexi 1.8mm Headgasket. That combo will put you right around 8.6:1 compression. or you can use the Apexi 2.1mm headgasket to get to 8.4:1 ... more clearly illustrated below:
(Wiseco Pistons)+(TRD .8mm Headgasket)=(9.4:1)
(Wiseco Pistons)+(Cometic/HKS 1mm Headgasket)=(9.2:1)
(Wiseco Pistons)+(Apexi 1.1mm Headgasket)=(9.1:1)
(Wiseco Pistons)+(Factory 1.4224mm or Apexi 1.5mm or HKS 1.6mm Headgasket)=(~9.0:1)
note: i put the "~" because all of my calculations come up saying the wiseco piston is 8.8:1 with a factory headgasket thickness, but they advertise 9.0:1 so its about 9.0:1
(Wiseco Pistons)+(Apexi 1.8mm Headgasket)=(8.6:1)
(Wiseco Pistons)+(Apexi 2.1mm Headgasket)=(8.4:1)
disclaimer: this is slightly simplified, in order for it to be exact, you would have to do this for every bore size as well and go out a couple more decimal places on the compression ratio but for the purpose us car guys are using it for, this is as accurate as we need.
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Now for the sake of saving time and making things easier for you guys, I will go ahead and list the part numbers for everything ive talked about in this post.
Cometic 1mm 87mm Headgasket: C4314-040
HKS 1mm 87.5mm Headgasket: 2301-RT034
HKS 1.6mm 87.5mm Headgasket: 2301-RT035
Apexi 1.1mm 88mm Headgasket: 814-T201
Apexi 1.5mm 88mm Headgasket: 814-T202
Apexi 1.8mm 88mm Headgasket: 814-T203
Apexi 2.1mm 88mm Headgasket: 814-T204
Wiseco Pistons:
K615M86 // 3sgte // Bore: 86.00mm (Standard Bore)
K615M865 // 3sgte // Bore: 86.50mm (+.020" Overbore)
K615M87 // 3sgte // Bore: 87.00mm (+.040" Overbore)
CP Pistons:
252061 // 3SGTE // Bore: 86.50mm (.020" 0.5mm overbore)
252062 // 3SGTE // Bore: 87.00mm (.040" 1.0mm overbore)
JE Pistons:
SC7449 // 3SGTE // Bore: 86.00mm (Standard Bore)
SC7450 // 3SGTE // Bore: 86.50mm (+.020" Overbore)
SC7453 // 3SGTE // Bore: 87.00mm (+.040" Overbore)
SRP Professional Pistons:
283458 // 3SGTE // Bore: 86.00mm (Standard Bore)
282309 // 3SGTE // Bore: 86.50mm (+.020" Overbore)
Arias Pistons:
3710101 // 3SGTE // Bore: 87.00mm (+1mm [+0.040"] Overbore)
Since this isnt a "for sale" post Im not going to post any prices that would clutter this up, but if you are interested in purchasing any of these items, or just wondering how much they cost, please check out our sale post in the vendor section here:
http://www.mr2oc.com/showthread.php...065#post4017065
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Last edited by RSRACEcom : September 29th, 2009 at 08:13.