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03-25-09 

fullname: Charles Adams
comments: I've been told that av fuel has some anti-freeze agent of some type in
it. Does this play a significant role in the fuel.and could it harm the
performance of the engine?

Hello' Charles Adams,

AV-Gas doesn't have anti-freeze per say, like what you put in your Vehicle.  That stuff don't burn well {if at all}!  Have you tried to light any lately?  Av-Gas has a anti-freezing chemical that's added for very high altitude, hence the name "ANTI-FREEZE".  NOT WHAT'S PUT IN AUTOMOBILES.  THIS CHEMICAL ALSO SUPPORTS COMBUSTION.  A lot  of hot rodders put down Av-Gas.  The fact of the matter is, av-gas does very well in street/strip and some race type engines.  Do you really think race fuel is as consistent as av-gasoline?  I wouldn't put any race fuel in my air plane if I had one, would you?  And no, it won't harm your engine.  But remember, lead kills O'2 sensors and catalytic converters.  Hope I answered your question Charles.  Thanks for visiting the site and checking out Tech Tips. 

Rodney @ Tech Tips
info@kjbrothersracing.com

Hello Steven,

When it comes to selecting the right Octane, there is a lot to consider.  First of all, most street cars don't need high octane fuel.  That's why many camshaft's application notes include static compression ratio requirements.  Street strip cars with 11.0:1 compression and up will benefit from higher than 93 octane fuel.  Some race engines with camshafts making high compression with 9 or 10.0:1 compression (CYLINDER PRESSURE), not static compression, is done through valve timing, specifically the intake valve closing point.  If you're not using some kind of forced induction on the street or strip, and not running over 10lbs of boost, 93 octane will most likely be fine.  Also remember the more the compression, the less timing is required.  And there is always "TEST & TUNE" day. 

Hello' Ronnie King,     

Supercharging is one sure way to make good HORSEPOWER!!  Without knowing what the intended use of the vehicle is {STREET/STRIP OR RACE} I'll concentrate on street/strip use.  The key to maximizing performance and minimizing problems is to build a sensible street/strip engine.  Use common sense and select a CAMSHAFT that delivers strong low-speed and mid-range torque for everyday driving.  Don't forget changes to the FUEL, IGNITION & COMPRESSION OF THE ENGINE will have to be made, {ALTHOUGH THIS VARIES FROM APPLICATION TO APPLICATION}.          

Now on to the question, which is better Turbo's or Superchargers?  First I'll say Opinions vary as to which is better.  Turbochargers are essentially centrifugal blowers that are operated by exhaust gasses.  Turbo charged small blocks produce tremendous amounts of power, but on the street & strip they suffer from turbo lag, and can be hard to stage at the track while trying to build boost. They also suffer from heat sink.  Even with large intercoolers, after three or four consecutive runs, they will start to loose power because of the heat generated by the exhaust.  Although several years ago manufacturers tried to make a big push for after market Turbos, they never achieved widespread popularity. Complex installations and incompatibility with other types of performance equipment are only a few reasons turbos are not as popular as bolt on power boosters.     

You may or may not know that there are two types of Superchargers.  A positive displacement {ROOTS TYPE}, gives a constant level of boost making it easier to tune than a turbo car.  The other one is a Dynamic Compressor {Centrifugal Blowers}, which provides boost in proportion to engine R.P.M.        

Superchargers work by forcing increased volumes of air, mechanically into the Cylinders.  With a Supercharger you will have more control over the power and it will be more consistent on the street as well as the track.  Also, computer controlled cars respond very well to superchargers.  The big advantage is that superchargers produce additional power from much lower engine R.P.M. speeds {AND DON'T SUFFER FROM ANY LAG LIKE TURBOS} without any Loss of top end power.     

The disadvantage is, if to much boost is obtained it can effectively start creating a pull on the engine and can take as much as 30% of your engines horsepower.    

Centrifugal blowers use an impeller, rather than overlapping rotors to build boost, they are small and easily fit under the hood of just about any car, and are popular with Corvette, Camaro & Mustang owners.  The only drawback is it doesn't build boost as quickly as a roots type.  It builds boost at an exponential rate, by doubling rpm it increases boost by a factor of four to provide a particular boost level at a specific rpm.  At lower engine speeds boost drops off, this can be a blessing because limiting boost levels at lower rpm's creates fewer traction problems. 

P.S. for street use I would recommend a B&M Roots types 162 cid (Formerly called Forced Induction) 

Hope I answered your questions  (info@kjbrothersracing.com)  WE CAN GIVE YOU MORE INFO IF NEEDED or build your engine combo.