In the last chapter, I reviewed some of the common bolt-on items owners can put on their C5s to improve power without disturbing the internals of their engines. Stock LS1s are rated at 345 or 350 hp (depending on year) at the crankshaft. What that means is that just the engines are bolted to a stationary dyno. During this type of test, the engine is not hooked to a transmission or differential. Putting a C5 on a rear-wheel chassis dyno is more real world. Rear-wheel dynos measure what the engine puts to the ground. They use large drum rollers turned by the rear wheels, and a computer measures RWHP and torque. For example, a stock LS1 rated at 345 hp usually produces between 292 to 297 rwhp. An LS6 rated at 405 hp at the crank produces 336 to 345 rwhp. Adding a good air-filter system, revised throttle body, and cat-back exhaust bumps a stock LS1 up to around 330 rwph. An LS6 with the same modifications usually produces around 355 to 365 rwhp. If you are searching for more horsepower, you must decide what to do to your car’s engine next. Each choice costs you money and time away from your car.
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In my view, the road to more horsepower in your Corvette leads down three different roads. I am going to attempt to discuss each of these three options to allow you to make an informed choice. The first is internal engine modifications, second is supercharging, and third is turbocharging. Selecting one of these choices should be made after carefully researching your driving requirements. Drag racing, road racing, Autocrossing, street driving, and weekend track events all require different kinds of engine performance and reliability. Each of these choices has benefits and drawbacks.
Internal Engine Modifications
Production road racers that use American cars like Corvette and Viper prefer internal engine modifications versus turbocharging or supercharging. Big-bore American street engines have a lot of untapped power potential that can be mined by modifying the heads and adding a better camshaft. These are called headand- cam packages. By changing the head and cam, the engine usually has a lot more power. This is particularly important coming out of a slow-speed corner where you need instant power. Usually, a head-and-cam package increases the rev range of the engine. Again, this might make the difference between being able to avoid making a shift in a corner to gain speed. Another common road-racing modification is increasing the engine’s cubic inches via boring or changing the entire block to a larger one. A road racer knows that minimizing complexity is a key to finishing a race. Turbochargers and superchargers add complexity and heat, which are enemies to engine endurance. Porsche is one of the few manufacturers that have successfully used turbochargers in their production racecars. Turbos are a great way to make small-displacement engines competitive against larger-bore engines like the Corvette or Viper.
The most common internal engine modification C5 owners can make to their cars is installing a head-and-cam package. They can opt to install polished and ported LS6 heads, which have bigger ports and flow more efficiently. Intake port volume on an LS6 head is 210 cubic centimeters (cc), compared to 200 cc on the LS1. The exhaust port volume for the LS1 is 70 cc, and 75 cc for the LS6. The combustion chamber on an LS6 is tighter at 64.45 cc, compared to 66.67 cc on the LS1 head. Both LS1 and LS6 heads use 2-inch intake and 1.55-inch exhaust valves. Some aftermarket suppliers prefer to port and polish the LS6 head because of its improved port flow and combustion chamber characteristics. Typically, they usually increase the valve size to 2.02 inches intake and 1.57 inches on the exhaust.
When tuners select a cam for a street head-and-cam package, they look for more lift and a mild increase in duration. This helps keep emissions levels low, while providing the customer with good driveability, a broader power band, and increased peak power. The LS6 cam has a duration approximately 0.050-inch lift of 204 degrees intake and 218 degrees exhaust. With the stock 1.7:1 rocker arm, it produces 0.555-inch intake lift and 0.551-inch exhaust lift at the valve. The lobe separation angle is 116 degrees. A good street camshaft should have duration at 0.50-inch valve lift of just under 220 degrees on the intake and 230 degrees exhaust. An ideal lift at the valve is around 0.600 inch (with proper valve-springs) and a lobe separation angle of 114 degrees. Prices vary for this upgrade, but plan on spending $10,000 to $15,000 for this modification. Depending on the extent of other modifications done to your car, such as free-flowing air inlets and exhaust systems, you can expect to add 70 to 80 hp. This moves an LS1 from 295 rwhp to around 375 to 385 rwhp. An LS6 should produce around 400 to 410 rwhp.
Tuners are a secretive lot. They generally don’t like a “fender lizard” (someone looking over their shoulder) while they turn your Corvette into a rice rocket eater. Modifying a car correctly is an art, and every tuner thinks his approach is the best for making horsepower. I have always looked for opportunities to look behind the scenes at what it takes to transform a C5 into something special. After all, tuners are not inexpensive and if your performance goals are not met, getting them corrected is timely and costly. Before you decide to turn your keys and money over to a tuner, it is nice to know what to ask and what’s involved. While writing this book, I decided to shadow a Corvette tuner during the modification process on my Corvette. I searched for an experienced tuner willing to let me watch his operation.
As you know by now, I have a good relationship with MTI Racing, especially with owner Reese Cox. When I asked about shadowing him during a head-and-cam install, he agreed. We used my stock 2000 FRC to document MTI’s installation of their Stage I and II packages. Stage I includes: cold-air induction, air bridge, ported throttle body, ignition wires, Denso spark plugs, low-temp thermostat, X-pipe, and stainlesssteel exhaust. The Stage II LS1 package requires installation of the Stage I package. Stage II LS1 upgrade includes: modified cylinder heads, custom grind cam, custom pushrods, double roller timing chain, modified oil pump, underdrive pulley, new head gaskets, new belts, new engine bolt kit, and Stage II computer reflash. Reese recommended adding a set of his long-tube headers, SPEC 3 pressure plate, clutch, and Fidanza flywheel—I agreed.
My car was delivered to MTI Racing’s shop in Marietta, Georgia, to begin the transformation. There are several ways to complete this job. The head-and-cam package is installed by removing the hood and the engine accessories, including the radiator. This allows you to install the new parts from the top of the car. Another method is to remove just the engine and complete the project away from the car. The final way (the one MTI chose) is to remove the entire drivetrain from underneath and install the head and cam on the shop floor. Each has its advantages and disadvantages, and Reese chose the last method. Their first stop was putting the car on the dyno to get a baseline starting horsepower. The FRC produced 331.3 hp and 333.3 ftlbs of torque. This is higher than a stock LS1, because the car had a Stage I package. MTI started the project by first removing the FRC’s shifter.
Next, all of the chassis wiring was unplugged and the supporting attachments were removed. This included brake lines, shocks, water hoses, etc. Once everything was loose, the drivetrain was supported under the front and rear cradles with safety stands. Eight cradle bolts were removed, and the body was lifted clear of the drivetrain using a vertical lift. The front and rear cradles were left supporting the car’s drivetrain. This included the rear end, transmission, torque tube, engine, and front and rear suspension components. This process took MTI four hours. Now the engine was completely exposed, which allowed MTI to remove the engine accessories and the steering rack. Next, the lifters and lifter buckets were removed. The LS engine design allows a camshaft change without removing the heads; however, these heads were going to be modified.
A vacuum pump was used to remove any anti-freeze that might have seeped into the engine’s water passages and cylinders during disassembly. Next, a custom wrench was used to loosen the crankshaft pulley nut, which is torqued to 350 ft-lbs at the factory. Then the oil pump, timing chain, and pulley were removed. The engine was ready for cleanup and new parts. This completed day one of the project.
On day two the team removed the torque tube, transmission, and rear suspension from the engine. This was done to allow installation of a new flywheel, clutch, and pressure plate. Next, Reese and his team prepared the car for reassembly. First, he checked the new cylinder heads, to verify the size of the combustion chambers. He checked the volume of the combustion chamber on each head to calculate compression ratio. He installed the camshaft. Then the cam was degreed for two reasons—to verify the cam specs and to measure the opening and closing event of the engine’s intake cycle. This was done to get the phasing of the cam and crankshaft correct. Next, the deck height of the piston was checked to ensure correct compression ratio. The MTI Gen III cylinder heads are CNC ported and include a 2.02 intake and 1.60 exhaust valves. The intake and exhaust ports are hand blended to ensure optimum flow. After the heads were installed, the bolts were tightened to 37 ft-lbs. Next, MTI Racing’s long-tube headers were installed. The SPEC 3 pressure plate and clutch were mounted to the Fidanza lightweight flywheel that was bolted to the crankshaft. On day three the engine and driveline were completed and readied for reinstallation. MTI Racing utilized three sets of eyes during the reassembly process. After someone completed a task, two others reviewed the work to ensure proper completion and quality control. Slowly, the FRC was reunited with its drivetrain, and it took about two hours to complete. At the end of the day, the engine was started for the first time. It was allowed to sit overnight to seal the special head gaskets.
On the final day, the car was computer tuned and road tested before going back on the Dyno. The MTI Racing headers and exhaust system fit nicely under the car. When the project was complete, the car was broken in and put back on the dyno. My best dyno run was 410 hp and 378.9 ft-lbs of torque versus the previous best run of 331.3 hp and 333.3 ft-lbs of torque at the rear wheels. That put this car close to 500 hp at the crank, pretty amazing for starting with a 345-hp car. As you read earlier, a Callaway Honker, a Callaway 78- mm throttle body, an MTI MAFS, and a Callaway cat-back exhaust were added after this project was completed. These changes brought the power up to 437 hp and 423.30 ft-lbs of torque. The car ran exceptionally well on the street and did not exhibit any bad behavior. Water temperatures remained stable with or without the air conditioning running. Because of its light weight (around 25 lbs compared to stock units’ 60 lbs), the SPEC required more revs to start, but the engine revved quickly to its 6,500-rpm redline. If you use the car for daily driving, I recommend installing a heavier SPEC 1 or 2 clutch and pressure plate. It is easier to drive day in and day out. What you sacrifice in performance is gained in comfort. On the road, I found that first gear pulls so hard that it overcomes the car’s traction control. First gear produces a lot of wheel spin even with 315/30 ZR17-inch tires mounted on 11-inch rims at the time of this project. The rumble of the cam and the sound of the exhaust made the price of admission very worthwhile. I punched the throttle while cruising and the car leapt forward and quickly headed toward its new redline.
With all this newfound power, I was glad my C5 was equipped with upgraded rotors and Hawk Plus HP brake pads. MTI not only improved my C5’s performance, but they exceeded all of my project goals.
Note: Prior to making this upgrade, LS1 owners should switch to an LS6 intake manifold.
LS2 Block Change
Horsepower, horsepower—can we ever get enough horsepower? Well by now you may have figured out that I am addicted to usable horsepower. Throughout my writing career in the Corvette hobby, I have only ridden in or driven four fast Corvettes. They are: 1969 L-88 Rebel Corvette roadster (finished fourth overall at the 1972 12 Hours of Sebring, naturally aspirated), 1988 Callaway Sledgehammer (254.6- mph street car, twin turbocharged), 1989 ZR-1 SnakeSkinner (640-hp, 2,700-lb GM Prototype test car, naturally aspirated), and Chuck Mallett’s 1996 One Lap of America Racer (1,050- hp, 250-mph street car, supercharged).
All of these cars had a common thread: not only were they blindingly fast in a straight line, they cornered and stopped with the best sports cars in the world. Each received their power from different methods, naturally aspirated, supercharged, or turbocharged. I enjoy watching single- purpose racecars like dragsters burn up the quarter mile, but I admire tuners who can make all of a car’s driving components (power, handling, and braking) work together in one package. The four cars that I mentioned above accomplished that goal.
As I have continued on the journey of modifying my own C5, I have kept that goal in mind. I wanted a fast car that had a suspension and braking system that could safely handle the power. When MTI completed my head-and-cam package, I upgraded my shocks and installed more aggressive brake pads in the car. But after driving the car awhile, I felt that the head-and-cam package lacked torque. When the LS2 engine was introduced in 2005, the engine was expanded from 5.7 liters (346 cubic inches) to 6 liters (360 cubic inches); I wondered if this engine might hold the answer to more torque. Shortly after the LS2 was introduced, tuners began offering engine packages that included a 4- inch stroke and a 4.010 bore. This translates into 6.6 liters or 404.1 cubic inches. During the installation of my head-and-cam package, Reese mentioned that he was going to offer this engine to his customers. I was very happy with the added horsepower, but I still felt it needed more torque. One thing led to another, and once again my C5 visited MTI Racing to get one of his LS2 engines installed.
MTI Racing’s 6.6 package consists of an LS2 block with a 4.010-inch bore and 4.000-inch stroke that equals 404.1 cubic inches! It fits both C5 and C6 Corvettes. The heart of this new beast is a new, GM Performance LS2 short block, which received a 4.010- inch bore before assembly. The bottom end includes a Callies 4340 Racemaster forged crankshaft. The crank for this application weighs 52 lbs and has all forging lines removed to improve aerodynamic penetration through oil. The counter weights have an airfoil shape to also improve oil penetration. The engine uses Compstar 4340 forged IBeam connecting rods mounted to Mahle F1 Teflon skirted dished pistons.Each piston is coated with hardcoated aluminum for heat protection. These parts are held in place with H-11 lightweight, tapered wrist pins. These wrist pins weigh 103 grams each, compared to 147 grams for the stock pins. The engine is topped off with LS6 MTI modified heads and an MTI cam. This is a good camshaft for street and track use. With duration measured at 0.50- inch valve lift, the cam is just under 220 degrees on the intake and 230 degrees exhaust. Reese told us to expect a nice bump in torque.
You know the old saying: “There is no substitute for cubic inches!” Since our LS1 benefited from many MTI Racing upgrades, it was decided to reuse some of our previously installed parts on the new engine. This included the heads, Z06 intake, and 78-mm Callaway throttle body. The MTI Racing long-tube headers, Callaway exhaust system, Fidanza flywheel, and SPEC pressure plate and clutch were set aside during disassembly for reuse. MTI Racing elected to remove my old LS1 engine from the top rather than the bottom. Removal from the top allowed the car to be moved around the shop more easily. MTI quickly removed the usable parts from the old engine. The team installed a Callies 4340 Racemaster crank, Mahle F1 pistons, and Compstar connecting rods into the new LS2 block. Once the lower end was assembled, the pan and oil pump were installed.
Next, an MTI Racing spec hydraulic roller cam was installed, along with the timing chain and sprockets. The timing chain cover and external cam sensor wiring connector were also installed. Next, the cam buckets, intake valley pan, head bolt studs, and gaskets completed the short-block assembly. The heads, valvesprings, and crank pulley completed the engine. The team then mounted the Fidanza flywheel and SPEC pressure plate and clutch. The engine was now ready for installation.
During installation, it was discovered that the LS2 has one extra stud on the right side of the block that interferes with the C5 motor mount. Part of the stud had to be removed to clear the mount, but everything else fit perfectly. The two knock sensors located in the intake valley on the C5 were relocated to each side of the LS2 block. Also, the LS2 cam sensor is now located on the front instead of the back of the block. Reese built new wiring harnesses to accommodate these changes.
New, larger 32-mm injectors were installed to feed the increased cubic inches. The finishing touches included adding the headers, intake, radiator, cooling fans, and hood. The car was ready for its first startup. Reese checked the computer with his laptop and it started on the first try. After we completed a trouble-free, 500-mile break-in run, we returned to MTI Racing and hooked the car up to the dyno. Our best pull was 477 rwhp and 464 ft-lbs of torque. If you apply 16.5% for driveline losses, this rounds out to 556 hp at the crankshaft! The best thing about this 6.6 package is that it produces this power without adding turbos, superchargers, or nitrous to the engine.
On the road the car is very docile, almost a sleeper. The car lopes along with no stumbles or bad manners and it even has power in sixth gear. We no longer have to watch the tach to make sure the motor is turning above 3,500 rpm to get maximum performance. Now you can punch it at 2,500 rpm and have all the power you need. This is not a cam motor—it’s a torque motor. We averaged 27.6 mpg on a 7-hour trip with the air conditioning running. But the remarkable thing is that even at 2,000 rpm, the LS2 produces well over 350 ft-lbs of torque. When you punch it, hang on—it turns from a kitten into a tiger. The change in the car’s personality is pretty amazing. In its former life, the 2000 FRC was a quiet, comfortable cruiser. The added 40 hp and 50 ft-lbs of torque to the rear wheels over the head-and-cam package can really be felt. Before, the car came on really strong above 3,500 rpm; now, the power curve is very flat, which gives you power whenever you push the pedal. After the engine was installed, new front/rear springs, bigger sway bars, and Wilwood brakes were installed to cope with the increased power (see Chapters 3 and 5). Reese is a former Speedvision GT competitor and a very accomplished road racer. He arranged to compare my completed car to a stock 2006 Z06 at Road Atlanta’s 2.54-mile 12-turn road course. With Reese driving, my car lapped 1.1 seconds faster during its six-lap comparison. So the proof of all these changes is in the pudding!
C5-R Block Change
The basic LS1 engine block architecture is used in the LS2, LS-7, LS-9, C5-R, and C6-R engines. The C5-R and C6-R blocks feature stronger webbing, but unless you are adding serious horsepower (+800 to 1,500 hp), the LS-7 or LS-9 blocks should be adequate for your needs. Many tuners offer packages with 427 cubic inches, and so far I have resisted the temptation to put one of these motors into my car. Again, these engines do produce more torque and serve as an excellent foundation for turbocharged and supercharged engines. But so far, I am happy with my car’s total performance. Maybe I will change my mind if I sell one million copies of this book!
Turbochargers have been used as a performance enhancement on many different kinds of vehicles for years. Their popularity really got a big boost during World War II, when they were added to Allied fighter planes and bombers as a way of allowing them to fly at much higher altitudes. The war helped advance the turbocharger technology, and today they are fitted to many different kinds of vehicles, airplanes, trucks, and small-displacement cars. Indy cars have used turbos to boost power in their engines for many years, and Porsche is a heavy user of turbos in their racecars. Reeves Callaway broke new ground with Chevrolet in 1986 when he offered a twin-turbo package for the C4 Corvette. The twin turbos boosted the L-98’s output from 230 hp to 345 hp. That was a big number in 1986.
Turbos lost favor with GM with the introduction of the 375-hp LT-5, the 405-hp LS6, the 505-hp LS-7, and the 650-hp supercharged LS-9. Corvette has relied on making horsepower with naturally aspirated and supercharged engines. Naturally aspirated Corvette engines with large displacement and high compression can muscle their way to the top of the hill. This is why Corvettes and Vipers trounce competitors with great big engines under their hoods.
However, some tuners love turbocharging. In the Corvette community, Callaway and Lingenfelter are well known for their turbocharging experience. Callaway’s 254.6- mph Sledgehammer was powered with a twin-turbocharged, 990-hp small-block. Lingenfelter Performance Engineering (LPE) is a multiple winner of Car & Driver’s Supertuner shootout with a twin-turbo C5.
Turbos use wasted exhaust gases to turn the turbine located inside the turbo unit. The effect is not unlike a water wheel. When using a water wheel to power a wheat-grinding mill, no water gets into the mill because it is separate. The same goes for a turbocharger. No exhaust gas bleeds to the intake charge because the power source is separate. The exhaust gases enter and exit turbine enclosures— exhaust gas goes in radially, turns a wheel, and exits axially. On the other side of the turbo, work gets done in the opposite direction. The rotating impeller shaft powered by the exhaust moves air, which enters the center (axially) and exits the side (radially). So, a turbocharger simply uses leftover power in the exhaust to pump more air directly into the engine for increased boost or power. Boost controls determine the right amount of boost sent to the engine.
More boost produces more power, but reduces engine life and durability. Because turbos are powered by exhaust, they become very hot under extreme use. Heat is the enemy of a car and the downside of turbos is that they must be carefully protected from a car’s vital operating parts. Anything that is located near a turbo tends to overheat, fail, or melt. My advice is that if you want to add turbos to your car, have it modified by an experienced vendor like Lingenfelter or Callaway.
Let’s start with the similarities between turbochargers and superchargers. Both use forced-induction systems to compress the air flowing into the engine. The advantage of compressing the air is that it stuffs more into the cylinders. More air means more fuel can be added, so you get more power from each cylinder explosion. A turbo or supercharged engine produces more power overall than does the same engine without the charging. Typical boost provided by a supercharger is 6 to 8 lbs per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50% more air into the engine. Therefore, expect to get 50% more power. However, it’s not perfectly efficient, so an improvement of 30% to 40% is more likely.
The key difference between a turbocharger and a supercharger is the power supply. Something has to supply the power to run the air compressor. In a supercharger, a belt connects directly to the engine. It gets its power the same way that the water pump or alternator does. A turbocharger, as we discussed above, gets its power from the exhaust system. Both systems have tradeoffs. In theory, a turbocharger is more efficient because it is using the “wasted” energy in the exhaust stream for its power source. On the other hand, a turbocharger causes some amount of backpressure in the exhaust system and tends to provide less boost until the engine is running at higher RPM. This is known as turbo lag.
Superchargers have become popular in recent years for several reasons, including cost, efficiency, reliability, and performance. Supercharging an engine often results in power increases in the range of 50% to 100%. Although superchargers are expensive, nothing provides more horsepower for your dollar. They provide power only when the engine is under full throttle or under load, not under normal cruising conditions. This means that the supercharger does not affect the engine’s reliability, longevity, or fuel economy under normal driving conditions.
Most superchargers sold today are centrifugal style. This means they are internal-compression superchargers. This style creates boost (compresses the air) inside the supercharger head unit (blower) before discharging it into the engine’s air intake. External compression superchargers (roots or screw-type superchargers such as those offered by Whipple, Kenne Bell, Jackson Racing, Eaton) have become less popular as centrifugal superchargers have evolved. Centrifugal superchargers (Vortech, Paxton, Powerdyne, ATI ProCharger) are more reliable, especially at higher boost levels. They are capable of creating more boost than external compression superchargers while creating a much cooler intake charge. Boost is created when the supercharger’s internal impeller pushes air through the blower. This push overcomes the vacuum force naturally created by the engine’s air intake. This allows air to be forced, rather than pulled, into the air intake. Boost is measured in pounds per square inch, or PSI. More boost equates to a denser air charge into the engine’s combustion chamber. This allows the engine to burn more air and fuel and create more horsepower. Most street superchargers produce somewhere in the range of 6 to 9 psi, meaning they produce 6 to 9 additional pounds of pressure over the atmospheric pressure at that elevation (at sea level, atmospheric pressure is 14.7 psi).Supercharger impellers on centrifugal superchargers are spun via an external pulley that is normally driven from the engine’s accessory belt. Because the supercharger pulley needs to spin at very high RPM, an internal step-up causes the impeller to run at substantially higher speeds than the input pulley. The speed that the impeller spins determines how much boost the supercharger develops. Changing the input pulley size can have a large effect on the amount of boost put out by the supercharger. Smaller pulleys produce more boost. This is why having a selection of pulleys is so popular with supercharger owners. This selection allows owners the ability to squeeze every bit of power from the engine. Because pulleys only cost around $70, they are an inexpensive way to test and tune your supercharger at different boost levels.
Many people assume that running a supercharger, and hence added intake boost, puts added strain on an engine’s parts. This is not necessarily true, because engine damage is almost always caused by high RPM. Because a supercharger helps the engine produce more power at lower RPM, a supercharged engine makes the same horsepower as its naturally aspirated counterpart at substantially lower engine RPM. Many of today’s street engines are designed to run up to 6,000 rpm. Some people think that a supercharger increases the engine’s compression to the point of detonation. Detonation exists when the combustion pressure is so high that the inlet charge ignites before the spark plug fires. When this happens, combustion takes place while the piston is still traveling up the cylinder bore. This puts tremendous loads on the piston, rod, and crank. Most supercharger kits include a boost timing retard chip that retards the engine’s ignition timing to prevent detonation.
Because superchargers spin at such high speeds, they often create a substantial amount of heat and require lubrication to keep friction to a minimum. Different supercharger companies have combated heat and friction in different ways. While no single method is the best, each has advantages and disadvantages. Powerdyne uses an internal belt to spin internal gears (step-up drive), which minimizes heat, is very quiet, and lasts for over 50,000 miles. This internal belt never slips, and does not require your engine’s oil supply for lubrication. It is one of the easiest superchargers to install. Vortech, Paxton, and ATI (except ATI’s self-contained systems) use engine oil to lubricate the step-up gears and keep heat and friction to a minimum.
While this lubrication is the most common and works well, it does require the engine’s oil pan to be tapped so the supercharger can draw engine oil from the engine. The ATI self-contained systems use oil to provide lubrication, but they use proprietary oil that stays inside the supercharger head unit and never requires changing. This system is efficient and does not require the engine’s oil pan to be tapped, but it is noisier than Powerdyne’s belt drive system. Typical superchargers bolted onto a stock LS1 or LS2 engine add about 120 hp to the rear wheels.
Both turbochargers and superchargers can utilize intercoolers to improve performance. Intercoolers cool the air after it has been discharged from the turbo or supercharger before it enters the intake manifold. The cooler air provides a denser air charge, which can make added horsepower, especially under higher boost conditions. Intercoolers are popular for racing applications, but are not normally needed for street drivers running 6 to 9 psi of boost.
Written by Walt Thurn and Posted with Permission of CarTechBooks