supercharger effective compression

Discussion in 'Superchargers, Turbos, Nitrous' started by grumpyvette, May 5, 2013.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    I recently came across a centrifugal vortech supercharger (V2) for a carb'd motor.
    I would like to install it on my current 406 sbc.

    As we speak the engine consist of:
    Holley 4160 750 cfm
    Edelbrock Performer Intake
    Edelbrock Performer Rpm Heads
    10:5:1 forged pistons
    5.565 connecting rods
    Comp Cams 280 Magnum cam
    Lift: .490''
    Duration: 280°
    RPM Range: 2000-6000

    And if it is feasible I have a holley commander
    950 tbi setup I would like to use.

    Is this at all possible?

    you can physically bolt it on but with 10.5:1 compression your very likely to be building a combo that will get into detonation ,if you don,t use something like 115 octane race fuel.
    even 5 psi of boost would move your effective compression up well over 13:1

    related info ... nCalc.html

    viewtopic.php?f=86&t=4484&p=11815&hilit=water+alcohol+injection#p11815 ... ulator.php






    you have options, you might not have thought of and Ill just point out a few
    first theres ethanol/water injection kits that can be used in conjunction with nitrous plates, or super chargers ,theres also inter-coolers of various designs, and octane booster additives, and use of different fuel like toluene or E85 ,these lower the cylinder pressure peaks and heat levels allowing you to keep out of detonation while still producing a significant increase in power.then theres octane boosters like toluene that can be added to fuel top increase the octane and resistance to detonation









    GARRET TURBOS POSTED THIS ... ch_vs_lean
  2. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    the super charger itself , its internal displacement, has very little too do with the required math because you don,t know the engines boost curve, cam timing, exhaust scavenging efficiency, air temps, altitude,etc. or efficiency of that super charger or the boost level.
    a certain percentage of what passed through the air filter went out the exhaust during the valve over-lap, and cam timing and exhaust scavenging also effects the plenum boost pressure youll see on a gauge.
    but what you do know or at least should understand is that to boost performance your packing the cylinders with more air volume and effectively adding enough fuel to get the extra power.
    what you might know is that standard air pressure at sea level is close to 14.7 psi and if you know the peak boost (lets say it s 8 psi here ), that to get that 8 psi , thats roughly a 55% increase in air flow volume at 100% efficiency , so Id fudge and expect a small loss in that efficiency and Id expect and use a n increase of 65% in the original calc's as a reasonable base line, if your plenum boost reads 10 psi , you would be dealing with a 68% minimum increase so Id go to at least a 175% larger air filter area.
    remember some of that boost volume is forced out the exhaust during cylinder scavenging and as air is compressed the heat and pressure goes up rapidly and efficiency tends to drop as a result.
    IE Id suggest no less that a 165% surface area vs the original calcs.(so your safely in the ball park vs restricting potential flow.)
    obviously similar reasoning with a different displacement , boost level and super charger should work rather similarly, while surely not exact its also going to keep you out of trouble.
    another way too look at this if if you boosted power 30% you did so by using at least a bit more than 30% MORE fuel and AIR FLOW, so at a minimum Id suggest a 35% larger air filter

    info related links like usual.
    Last edited: Aug 6, 2018

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