Intake and Exhaust CFM
Thread Starter
Pro
Joined: Jul 2007
Posts: 670
Likes: 0
From: Culver City California
Intake and Exhaust CFM
Ok folks I need some info........ I need to know the exact exhaust CFM and intake CFM of an '89 L98. I need this info to help me properly size the turbo on my new single turbo project. thanks
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
Is it a stock engine and are you going to run it stock? Stock cam?
You can use a dyno graph to get the numbers you need.
You don't need exact numbers as building a custom turbo engine is no exact sience.
You can use a dyno graph to get the numbers you need.
You don't need exact numbers as building a custom turbo engine is no exact sience.
Last edited by JoBy; Sep 2, 2007 at 02:27 AM.
Pro
Joined: May 2002
Posts: 518
Likes: 17
Stock 89 head and various manifolds @ 28" H20.
Stock cam and rocker:
I = 176 cfm @ .410"
E = 156 cfm @ .423"
Port stall:
I = 186 cfm @ .550"
E = 162 cfm @ .560"
Stock Manifold and Runner = 198 cfm
Accel Manifold and LTR = 232 cfm
Accel Manifold and SR = 240 cfm
Sad isn't it?
Stock cam and rocker:
I = 176 cfm @ .410"
E = 156 cfm @ .423"
Port stall:
I = 186 cfm @ .550"
E = 162 cfm @ .560"
Stock Manifold and Runner = 198 cfm
Accel Manifold and LTR = 232 cfm
Accel Manifold and SR = 240 cfm
Sad isn't it?
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
The CFM numbers in and out of the cylinder head is not important by itself. It is the total package with intake, cam and everything.
You get an estimate from engine hp: Engine HP X 1.6 = airflow in CFM.
250 hp x 1.6 = 400 CFM into the engine.
CFM out depends on exhaust back pressure and exhaust temperature, but the air in plus fuel in is what comes out of the exhaust.
You size the compressor of the turbo from the boost you are going to run and the CFM of the NA engine.
Then you want a large turbine housing to keep the exhaust pressure low and you want a small turbine housing to reduce lag.
You get an estimate from engine hp: Engine HP X 1.6 = airflow in CFM.
250 hp x 1.6 = 400 CFM into the engine.
CFM out depends on exhaust back pressure and exhaust temperature, but the air in plus fuel in is what comes out of the exhaust.
You size the compressor of the turbo from the boost you are going to run and the CFM of the NA engine.
Then you want a large turbine housing to keep the exhaust pressure low and you want a small turbine housing to reduce lag.
