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Thread: Back with questions - RWD VE

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Posts: 31-40 of 49
2012-11-15 21:41:30
#31
- I thought we were talking about 12.5, why is 9.0 mentioned for N/A? Please post a link for the the 88mm 12.5 pistons. I asked multiple companies and none of them had them off the shelf. This was a over a year ago, and a few months back was the last time I checked. Maybe something has changed, but never heard of this size @ 12.5 being off the shelf.
Last edited by MR-4Door-SR20DET on 2012-11-16 at 19-07-51. Reason: Added compression ratio at the end of the sentence
2012-11-15 21:56:36
#32
Originally Posted by MR-4Door-SR20DET
- I thought we were talking about 12.5, why is 9.0 mentioned for N/A? Please post a link for the the 88mm 12.5 pistons. I asked multiple companies and none of them had them off the shelf. This was a over a year ago, and a few months back was the last time I checked. Maybe something has changed, but never heard of this size being off the shelf.


cp lists the 86,87.89.5 and 90mm in 12:5.1 off the self but the 88mm are only listed in 9:0.1. I just saw the 88mm in 12:5.1 on ebay 2 weeks ago. three to four listings as well which is why I took notice. cp ve piston part numbers for those interested.

SC7324V 3.386 86.00 STD 86 136.25 1.260 9.0 22 1.0 x 1.2 x 2.8mm 4
SC7325V 3.406 86.50 +0.5mm 86 136.25 1.260 9.0 22 1.0 x 1.2 x 2.8mm 4
SC73261V 3.465 88.00 +2.0mm 86 136.25 1.260 9.0 22 1.0 x 1.2 x 2.8mm 4
SC73264V 3.524 89.50 +3.5mm 86 136.25 1.260 9.0 22 1.0 x 1.2 x 2.8mm 4
SC7326V 3.425 87.00 +1.0mm 86 136.25 1.260 9.0 22 1.0 x 1.2 x 2.8mm 4
SC7329V 3.543 90.00 +4.0mm 86 136.25 1.260 9.0 22 1.0 x 1.2 x 2.8mm 4
SC7340V 3.386 86.00 STD 86 136.25 1.260 12.5 22 1.0 x 1.2 x 2.8mm 4
SC7341V 3.406 86.50 +0.5mm 86 136.25 1.260 12.5 22 1.0 x 1.2 x 2.8mm 4
SC7342V 3.425 87.00 +1.0mm 86 136.25 1.260 12.5 22 1.0 x 1.2 x 2.8mm 4
SC7343V 3.524 89.50 +3.5mm 86 136.25 1.260 12.5 22 1.0 x 1.2 x 2.8mm 4
SC7344V 3.543 90.00 +4.0mm 86 136.25 1.260 12.5 22 1.0 x 1.2 x 2.8mm 4
SC7329VS 3.543 90.00 +4.0mm 86 136.25 1.260 9.0 22 1.0 x 1.2 x 2.8mm 4*
Last edited by cortrim1 on 2012-11-16 at 01-52-56.
2012-11-16 17:57:07
#33
I'm starting a similar built on my RWD S15 SR20DET
You will find Gspec.com very useful for VE parts, and they have the Mazworx relocation + water hose.. kit plus the Xcessive intake manifold for a RWD conversion. Make sure you pick up the inlet runners with the VE head as that isn't supplied.
I am using an SR16VE head and keeping it all stock, re-furbing my bottom end but using standard parts, including standard DET pistons basically.

Where I am stuck is compression ratios. Please tell me where I am going wrong..
I will want a CR of about 9.0

SR20 bore and stroke 86mm
SR20DET piston crown volume 13cc (I believe)
SR16VE combustion chamber volume 41.7cc
Gasket thickness (I vary from 1.2 to 2mm)

and other info some calculators ask for - deck clearance volume 0.787cc

I'm getting really high ratios of 13+ and want much lower
2012-11-16 18:36:11
#34
Originally Posted by MaxS15
I'm starting a similar built on my RWD S15 SR20DET
You will find Gspec.com very useful for VE parts, and they have the Mazworx relocation + water hose.. kit plus the Xcessive intake manifold for a RWD conversion. Make sure you pick up the inlet runners with the VE head as that isn't supplied.
I am using an SR16VE head and keeping it all stock, re-furbing my bottom end but using standard parts, including standard DET pistons basically.

Where I am stuck is compression ratios. Please tell me where I am going wrong..
I will want a CR of about 9.0

SR20 bore and stroke 86mm
SR20DET piston crown volume 13cc (I believe)
SR16VE combustion chamber volume 41.7cc
Gasket thickness (I vary from 1.2 to 2mm)

and other info some calculators ask for - deck clearance volume 0.787cc

I'm getting really high ratios of 13+ and want much lower


which pistons det or ve? whats the sock compression on the pistons?
2012-11-16 19:43:03
#35
Originally Posted by MaxS15
I'm starting a similar built on my RWD S15 SR20DET
You will find Gspec.com very useful for VE parts, and they have the Mazworx relocation + water hose.. kit plus the Xcessive intake manifold for a RWD conversion. Make sure you pick up the inlet runners with the VE head as that isn't supplied.
I am using an SR16VE head and keeping it all stock, re-furbing my bottom end but using standard parts, including standard DET pistons basically.

Where I am stuck is compression ratios. Please tell me where I am going wrong..
I will want a CR of about 9.0

SR20 bore and stroke 86mm
SR20DET piston crown volume 13cc (I believe)
SR16VE combustion chamber volume 41.7cc
Gasket thickness (I vary from 1.2 to 2mm)

and other info some calculators ask for - deck clearance volume 0.787cc

I'm getting really high ratios of 13+ and want much lower


don't forget to upgrade the valve springs. The supertech 122lbs if your still going to be Turbo. I'm still gathering parts and waiting for more money before I move on my RWD VE+T build.
2012-11-17 04:23:16
#36
Only planning to rev to 8k for now, so I dont think new springs will be required yet... Or would you recommend them anyway?

DET pistons. I think the std comp ratio is 8.5:1 to 9:1 certainly no higher!!
2012-11-17 04:49:44
#37
Never measured myself, but lot's of knowledgeable members over the years have stated that DET 8.5:1 pistons with a VE head will give you a compression ratio of 9.3:1. The reason for this bump in compression is because of the smaller combustion chamber of the VE vs. the DE/DET.

If I was revving and boosting to 8K rpm on stock 20VE cams, I would definitely add stiffer valve springs into the mix. Most would recommend this; It is cheap insurance.
2012-11-17 04:54:47
#38
The springs on the sr16 are the same as the sr20ve. In na form 7500 on stock 2.0 cams is cool. 8k will result in valve. Turbo prob will be worse. If your running the Sr16ve cams then u might be fine. But with det pistons might have valve clearance on the high cams.
2012-11-17 10:17:45
#39
Thanks for the advice
Fortunately they are SR16VE cams, but I do think I may have clearance issues. Had better got some small valve reliefs cut like you say
I still can't get the sums right to give me the right CR numbers. If I run a slightly thicker Head gasket I should buy my self some clearance and lower CR
2012-11-17 13:55:00
#40
Originally Posted by MaxS15
Thanks for the advice
Fortunately they are SR16VE cams, but I do think I may have clearance issues. Had better got some small valve reliefs cut like you say
I still can't get the sums right to give me the right CR numbers. If I run a slightly thicker Head gasket I should buy my self some clearance and lower CR


Install valve springs. You will be pissed off if a valve contacts a piston. the det piston has no valve reliefs. you can have them added but I would still upgrade the valve springs. btw det 8:5.1 pistons with a ve head will be 9:3.1.
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