CR for procharged LS1
Thread Starter
Teching In
Joined: Nov 2014
Posts: 17
Likes: 0
From: arkansas
CR for procharged LS1 First build for me, and I am trying to figure out compression ratio before I pick new Pistons/rods. I have read in a lot of posts that you want some where in the 9.7-10:1 CR for a procharge build. Here is what I got.
Wiseco 3.903, -3.2 reliefs
LS9 gasket 4.100, .051 thickness
PRC 215 68cc
Stroke 3.622
CR: 9.64
Getting 9.92 with same stuff except a .041 gasket 4.0 size. Also thought about using Trick flow 220 that have a 64cc chamber, same piston and LS9 gasket. I am getting CR:10.08. I used the Wallace racing calculator and just wanted to know if those are correct CR numbers. Any advice on the Pistons or which head to go with would be great.
Thanks
Wiseco 3.903, -3.2 reliefs
LS9 gasket 4.100, .051 thickness
PRC 215 68cc
Stroke 3.622
CR: 9.64
Getting 9.92 with same stuff except a .041 gasket 4.0 size. Also thought about using Trick flow 220 that have a 64cc chamber, same piston and LS9 gasket. I am getting CR:10.08. I used the Wallace racing calculator and just wanted to know if those are correct CR numbers. Any advice on the Pistons or which head to go with would be great.
Thanks
I have been reading threads about this also. It seems a lot of guys are going with high boost and low compression and having to spin the pro charger beyond its safe rpm speeds. There for to compete with a turbo build boost wise is not the way to go.
There are calculators that will take your horse power plus psi and give you a result. I was amazed to see a 550hp motor @ 7psi went to 800hp more or less. This made me think that a pro charger could last forever compared to turbos while making great power with better air temps and higher compression. Should be great out of the hole and at 1/8 mile tracks.
I also found that even a high compression engine to around 12:1 camed correctly bleeding off cylinder psi @ the right amount (overlap/lobe separation) is good. Pro chargers are ideal for stock cr's (11:1-10.5:1)and cams.
There are calculators that will take your horse power plus psi and give you a result. I was amazed to see a 550hp motor @ 7psi went to 800hp more or less. This made me think that a pro charger could last forever compared to turbos while making great power with better air temps and higher compression. Should be great out of the hole and at 1/8 mile tracks.
I also found that even a high compression engine to around 12:1 camed correctly bleeding off cylinder psi @ the right amount (overlap/lobe separation) is good. Pro chargers are ideal for stock cr's (11:1-10.5:1)and cams.
Thread Starter
Teching In
Joined: Nov 2014
Posts: 17
Likes: 0
From: arkansas
Used diamond racing calculator and got a 10.15:1 with:
Wiseco 3.903, -3.2 Pistons
Scat I beam with arp 8740, 6.125", .927 pin
PRC 225 heads 62cc small bore chamber
LS9 head gasket
Any suggestions or changed I should look into?
Wiseco 3.903, -3.2 Pistons
Scat I beam with arp 8740, 6.125", .927 pin
PRC 225 heads 62cc small bore chamber
LS9 head gasket
Any suggestions or changed I should look into?
Staging Lane
Joined: Feb 2005
Posts: 97
Likes: 2
From: Lynbrook, NY
correctly bleeding off cylinder psi @ the right amount (overlap/lobe separation)
Neither of those affect DCR directly. The determinant is intake valve closing point.
Some of those computers are using this:
New HP = old HP X (boost + ATM)/ATM
Example: HP = 100 HP X (14.7 + 14.7)/14.7 = 200 HP
This is nonsense, and comes close only by accident.
Neither of those affect DCR directly. The determinant is intake valve closing point.
Some of those computers are using this:
New HP = old HP X (boost + ATM)/ATM
Example: HP = 100 HP X (14.7 + 14.7)/14.7 = 200 HP
This is nonsense, and comes close only by accident.
Last edited by panic; May 24, 2016 at 06:54 PM.
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Teching In
Joined: Nov 2014
Posts: 17
Likes: 0
From: arkansas
I must be getting something wrong with my numbers. I see people posting getting 9.6-9.8 CR with -10 cc piston and 72cc heads. Am I doing something wrong? Have been using Wallace racing and diamond racing calculators. Also plan on using brute speed blower cam.
Last edited by Firehawk173; May 24, 2016 at 07:05 PM.
Thread Starter
Teching In
Joined: Nov 2014
Posts: 17
Likes: 0
From: arkansas
Thread Starter
Teching In
Joined: Nov 2014
Posts: 17
Likes: 0
From: arkansas
Thanks for the Info. I have decided on the scat I beams and Wiseco 3.905,-3.2 dish, LS9 gasket and prc 225 cc head with a 62cc chamber. Used diamond racing and Wallace racing calculator and got 10.2-10.3 CR with that setup.
That will be nice to drive around out of boost and part throttle. D1 head unit ?
