LS2 FAST 90 or 102?
10-05-2012, 08:17 PM
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LS2 FAST 90 or 102? Ok I am having a forged LS2 built for spray and I am debating on which intake to go with. It will be a weekend street warrior. I am going with AI 226cc 243s and I custom spec'd cam from them also just not sure on the specs yet. It will be a full potential cam because I want every last HP out of this motor as possible. Not really worried about great drivability just want it to be wicked on spray and off of spray. I would like to make somewhere around 500 N/A and about 700-750 on spray. Whichever intake I choose will be direct ported at some point. Thanks for the help.
Ross
Ross
10-24-2012, 01:25 PM
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Well obviously a bigger inlet and bigger plenum means a greater volume of air the manifold can move. That being said, the flow through the bigger manifold will be hampered compared to the smaller one if engine speed is not fast enough. It sounds like you are not concerned with low speed efficiency and will probably be revving this motor out well above 6k rpm, so that begs the next question: how big is the cam and how big is the motor?
A large cubic inch engine will need greater air volume to feed it, especially at high rpm, and a cam that holds the intake valve open and with a lot of overlap will need that too to be taken advantage of. So assuming the CID is large and the cam specs are as well (also assuming your header primary size is correct and your head port volume is big) then the intake manifold is the last restriction to VE.
That being said, the N2O brings air with it to increase the density of the incoming charge, so running on spray you're not as concerned with N/A efficiency because the spray will make up for that.
Bottom line: If this is a 400 CID+ motor I'd go with the 102mm intake, if its near stock CID i'd stick with the 90mm for driveability and the spray will more than make up for it. IMHO
A large cubic inch engine will need greater air volume to feed it, especially at high rpm, and a cam that holds the intake valve open and with a lot of overlap will need that too to be taken advantage of. So assuming the CID is large and the cam specs are as well (also assuming your header primary size is correct and your head port volume is big) then the intake manifold is the last restriction to VE.
That being said, the N2O brings air with it to increase the density of the incoming charge, so running on spray you're not as concerned with N/A efficiency because the spray will make up for that.
Bottom line: If this is a 400 CID+ motor I'd go with the 102mm intake, if its near stock CID i'd stick with the 90mm for driveability and the spray will more than make up for it. IMHO
