supercharger effective compression

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.

http://www.wallaceracing.com/boost-compression-ratio-calc.php

effective-compression-ratio.jpg


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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



fincom.jpg

fincom1.jpg

related info
http://www.gtsparkplugs.com/EffectiveCo ... nCalc.html

http://www.rbracing-rsr.com/compression.htm

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

http://performancetrends.com/Calculator ... ulator.php

viewtopic.php?f=86&t=1330&p=2905#p2905

viewtopic.php?f=55&t=2718&p=12119&hilit=+octane+calculate#p12119

viewtopic.php?f=50&t=8960&p=31942&hilit=detonation+damage#p31942

viewtopic.php?f=86&t=1329&p=8354&hilit=water+alcohol+injection#p8354

viewtopic.php?f=50&t=8744&p=30912&hilit=detonation#p30912

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


READ SOME LINKS AND SUB LINKS
viewtopic.php?f=55&t=613&p=6025&hilit=toluene#p6025

viewtopic.php?f=86&t=7277&p=24725&hilit=ice%2Falcohol+inter+cooler#p24725

viewtopic.php?f=87&t=2141&p=25201&hilit=ethanol#p25201

viewtopic.php?f=86&t=1329&p=8354&hilit=water+alcohol+injection#p8354

viewtopic.php?f=86&t=4685&p=12676&hilit=ethanol#p12676

viewtopic.php?f=86&t=4484&p=11818&hilit=ethanol#p11818

viewtopic.php?f=55&t=59&p=72&hilit=nitrous#p72

viewtopic.php?f=53&t=3443&p=9118&hilit=+octane+calculate#p9118

http://www.superchargerusa.com/tech_comp_ratio.htm

GARRET TURBOS POSTED THIS
http://www.turbobygarrett.com/turbobyga ... ch_vs_lean
GARRETT said:
Why lean makes more power but is dangerous

When discussing engine tuning the 'Air/Fuel Ratio' (AFR) is one of the main topics. Proper AFR calibration is critical to performance and durability of the engine and it's components. The AFR defines the ratio of the amount of air consumed by the engine compared to the amount of fuel.

A 'Stoichiometric' AFR has the correct amount of air and fuel to produce a chemically complete combustion event. For gasoline engines, the stoichiometric, A/F ratio is 14.7:1, which means 14.7 parts of air to one part of fuel. The stoichiometric AFR depends on fuel type-- for alcohol it is 6.4:1 and 14.5:1 for diesel.

So what is meant by a rich or lean AFR? A lower AFR number contains less air than the 14.7:1 stoichiometric AFR, therefore it is a richer mixture. Conversely, a higher AFR number contains more air and therefore it is a leaner mixture.

For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich

Leaner AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition (SI) gasoline engines produce maximum power just slightly rich of stoichiometric. However, in practice it is kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load AFR on a normally-aspirated engine but can be dangerously lean with a highly-boosted engine.

Let's take a closer look. As the air-fuel mixture is ignited by the spark plug, a flame front propagates from the spark plug. The now-burning mixture raises the cylinder pressure and temperature, peaking at some point in the combustion process.

The turbocharger increases the density of the air resulting in a denser mixture. The denser mixture raises the peak cylinder pressure, therefore increasing the probability of knock. As the AFR is leaned out, the temperature of the burning gases increases, which also increases the probability of knock. This is why it is imperative to run richer AFR on a boosted engine at full load. Doing so will reduce the likelihood of knock, and will also keep temperatures under control.

There are actually three ways to reduce the probability of knock at full load on a turbocharged engine: reduce boost, adjust the AFR to richer mixture, and retard ignition timing. These three parameters need to be optimized together to yield the highest reliable power.
 
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Help with some air filter math
I am going to be putting a supercharger on my new car soon.

I can't seem to google the math for adding a supercharger to the car's air filter requirements.

I know that for a naturally aspirated car the formula is
Air filter square inches (A)= CID x RPM /20,839.

How do I add in the displacement of the supercharger to account for the engines total air requirement?

For example. My 6.2L is 376 CID x 6500=2,444,000/20839= 117.28 sq in of filter surface. If I add a 1.9L (116 CID) supercharger to it-- How much larger does my filter need to be.

Now what if I plan on running it at 18% over drive?

Help!


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.
https://www.onallcylinders.com/2013/11/27/match-air-filter-size-engine/

https://www.turbobygarrett.com/turbobygarrett/air_filter

http://www.wallaceracing.com/calc-cfm-head.php

http://www.wallaceracing.com/calc-epc.php

http://www.wallaceracing.com/hp-blower.php
volumetric.gif

exhaustpressure.jpg

EXFLOWZ4.jpg
 
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