Forced Induction Guide
So you've modified the intake, the exhaust, the suspension, the drivetrain, and everything else that you could possibly do. You're car is doing better than ever, and it's ready for that one "big" mod, the one that separates men from boys and winners from also-rans. You're ready for a supercharger or a turbocharger. But wait, you can't find any info anywhere online or in books--they all refer to V8 models. Fear not, that's what this page is here for. There are a lot of rumors and a lot of myths surrounding superchargers for V6s; we will attempt to clear some of these up. Read on and be inspired.
What does "forced induction" mean?
Forced induction is the process of using active mechanical force to push air into the intake of an engine. Ram air or cold air intake systems are not forced induction because they are passive--i.e. there are no mechanical parts moving to force the air into the engine. Superchargers and turbochargers are forced induction systems.
What is a supercharger?
A supercharger is really nothing more than a strong fan that bolts onto the car's intake and pushes air into the engine. They produce huge horsepower gains because the greatly increased amount of air coming into the engine can then be mixed with a greater amount of fuel, causing a stronger explosion within the combustion chambers (equals more power). There are three types of superchargers: roots, screw, and centrifugal. We will concentrate on centrifugal because they are the most popular for aftermarket applications and are the easiest to install on a V6 F-Body. All of the major aftermarket supercharger brands use centrifugal units: Vortech, ATI, Powerdyne, and Paxton. (It should be noted, however, that the Eaton supercharger used on the Grand Prix GTP is a roots type, not a centrifugal.)
Aftermarket centrifugal superchargers are metal snail-like units usually between 9" to 12" in diameter. A pulley mounted on the outside of the supercharger spins the gears within the supercharger, which then spin the impeller (the turbine's fan). The supercharger pulley is usually spun by the engine's serpentine belt, although some superchargers use a dedicated second belt, a cog belt, or a chain. It takes force to spin the supercharger pulley to the very high speeds required for the turbine to spin--this force comes from the engine's crankshaft (via the belt). It typically costs 100 hp to spin the turbine, but the engine will gain 200 hp from the extra air coming into the engine--thus the net gain is 100 hp (these numbers are only examples but they illustrate the concept).
What is a turbocharger?
A turbocharger is another form of forced induction. Turbos are very similar to centrifugal superchargers in operation, but instead of being powered by a belt running off the crankshaft, a turbo derives it's power from a fan within the engine's exhaust system. Exhaust gases spin this fan which then spins a variety of gears which spin the turbo's turbine, which pushes air through pipes and into the engine. Because turbos run off exhaust gases, at low rpm (where the force of exhaust gases exiting the engine is low) turbos do not spin fast. Turbos do not "wake up" until mid to high rpms, resulting in a condition known as "turbo lag". Generally speaking, a single turbo runs off a single exhaust header. In other words, an Eclipse with an inline 4-cylinder engine has a single turbo running off it's header, and a Supra with a V6 engine has twin turbos, each one running off a header. For a V6 or V8 F-Body a twin turbo system would probably be easier to design than a single turbo.
Why are superchargers more common on F-Bodies than turbochargers?
Turbocharging a car, particularly a fourth generation F-Body, is difficult. As of right now no company makes a turbo system for any V6 F-Body. The reason it is so difficult is that you have to mount the turbos somewhere and there is very little room to work in the back of the engine bay of a fourth generation V6 F-Body. In addition, you have to run hoses from the back of the engine to the throttle body and you have to mount the intercoolers somewhere. Thus, lack of space is the primary deterrant. In contrast, a supercharger bolts onto the front or top of the engine and does not require piping as involved as that of a turbo. But don't let a lack of popularity deter you--turbos still provide amazing power benefits, they are just more difficult to design and implement than bolt-on centrifugal superchargers.
What does "boost" mean?
When a supercharger spins, the turbine forces a large mass of air into a confined space (the space within the pipes leading from the supercharger to the throttle body). The volume of the air remains constant but the mass increases, and as a result the pressure of the air within that confined space increases. Boost is commonly measured in psi, or pounds of pressure per square inch. Most superchargers on V6 F-Bodies generate 6 psi to 12 psi. Generally speaking, 6 psi is considered a "safe" amount of boost for the L36, while 9 psi is usually regarded as the highest a stock L36 can handle. The L67 engine (the 3800 Series II found in the Pontiac Grand Prix GTP) comes stock with an Eaton supercharger that generates 8 psi. L67 owners typically increase their boost up to 12 psi or so, but higher numbers are possible (but dangerous). On cars with modified engines specifically designed to handle large amounts of boost, 15 psi, 18 psi, or numbers as high as 32 psi are not unheard of. The more boost you are running, the more power your engine will produce.
What is detonation?
Detonation (also called engine knock) is when the air/fuel mixture within the cylinder ignites before the crankshaft has had time to rotate enough. This results in the crankshaft moving one direction and then suddenly one cylinder pushes it the opposite direction. Detonation is the primary cause of "engines blowing up" due to superchargers. The most common major disasters resulting from excessive detonation is a connecting rod snapping, a piston head cracking in two, the crankshaft breaking, or worse. Detonation is usually caused by excessively high temperatures within the combustion chamber--the high temperature causes the fuel to self-ignite before the spark plug fires. Detonation can also be caused by timing that is too far advanced.
How do I minimize the risk of detonation?
Detonation can be minimized in several ways. First, using high octane fuel is an absolute must for all supercharged cars. Octane resists burning, thus a high octane fuel will not self-ignite as easily as regular unleaded will. Second, timing retard is required on cars without intercoolers. Retarding the timing results in the spark plug firing later, which gives your crankshaft enough time to rotate into a position where the sudden very powerful explosion within the combustion chamber will rotate it in the correct direction. Third, because self-igniting fuel is caused by high cylinder temperatures, an intercooler or nitrous oxide will greatly reduce detonation.
What is an intercooler?
An intercooler is a wide, usually flat metal part that cools the air that passes through it. On many F-Body applications the intercooler mounts underneath the radiator. There are two major types of intercoolers: air-to-air and air-to-water. On a street driven car air-to-air intercoolers are usually more practical. For more information about intercoolers, check out Spearco Intercoolers.
How does an intercooler help a supercharged engine?
Engines follow the principles outlined by Boyle's Gas Laws. Cold air is more dense (has more oxygen molecules per unit volume) than warm air. The entire point of a supercharger is to get as many oxygen molecules as possible into the combustion chambers, where they can be mixed with fuel and the fuel can then burn. Thus, an engine that is getting cold air is getting more oxygen molecules and will in turn produce more power than an engine that is getting warm air. Air heats up when it is compressed. Superchargers, by their very nature as air compressors, generate a LOT of heat, and the air being forced through the intake pipes is typically as much as 75 degrees F hotter than ambient air. An intercooler cools this air down, resulting in an engine that gets a large mass of cold, dense air, resulting in a massive power increase. Intercooled forced induction systems are superior to non-intercooled systems in every respect. Although exact numbers are often disputed (and usually inaccurate) it is sometimes suggested that 9 psi of intercooled boost produces the same power gain that 13 psi of non-intercooled boost does. If you're spending over $4,000 to put a supercharger on your car it just doesn't make sense to NOT use an intercooler. Sadly, the automotive industry has been slow to realize this fact. While almost all car manufacturers provide intercoolers with their turbocharged cars, almost none provide intercoolers with their supercharged cars (most famous being the GM L67, non-intercooled). The reason car manufacturers do not intercool their supercharged cars from the factory is that they are designed for low-boost applications. If you are building a car for performance, however, things are different--and you want every horsepower you can get out of whatever boost level you're running. Indeed, the fastest Grand Prix GTPs are owned by people who saw the wisdom in adding an intercooler.
What are the most popular supercharger brands?
Although there are plenty of small no-name companies that make superchargers, by it's very nature a centrifugal supercharger takes a lot of work and time for engineers to design. Thus, it is always safest to stick with the big companies who have experience in the field and have reputations built on quality products. Here are four of the most popular brands:
What is involved in performing a custom install?
Installing a supercharger is not like adding an exhaust or changing a thermostat. It is a long, involved process that only professional mechanics or hardcore enthusiasts should attempt. Fortunately, the LT1 is very similar to the L36 and L32 in terms of the parts that supercharger kits use, as well as engine bay layout. Thus, if you were to attempt a custom install of, say a Vortech on an L36, ordering a Vortech LT1 kit and then going from there might be a good idea--because you never know exactly which LT1 kit parts will fit without trying.
Where can I get more information?
Read, study, and memorize all of these books:
3.4 and 3.8 V6 Supercharger Kits
Vector Performance/Powerdyne kit for 1995-2002 3.8
To this day the only official kit marketed by a company, the Vector supercharger provides dyno-proven gains. The kit uses a Powerdyne supercharger (non-intercooled) and was designed and put together by Vector Performance, a race shop in California. Vector buys the Powerdyne supercharger head units, puts all the parts you need for the kit into a box, and sends that box off to various distributors. Price is usually in the mid $3,500 range. It comes with a 6 psi pulley but a 9 psi upgrade can be purchased seperately. In order to fit the 3.8, Vector mounted the supercharger backwards and spin it's pulley off the flat side of the serpentine belt. There are two versions of this kit: one for 95-98 3.8 and one for the 99-02 models, the main difference being the way the intake pipes mount into the throttle body. Gains at 9 psi are dyno-proven to equal 90-100 rwhp on a stock engine. This kit is a great all-around setup providing a strong power gain at a reasonable price, with no guesswork about fitment. Unfortunately, Vector Performance has gone out of business and it is unknown if any new kits will ever be produced. There are, however, quite a few kits still floating around at various performance part distributors if you can find them. To read an article about this kit check out media.firebirdv6.com/vectorsupercharger.html.
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