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It is no secret that Honda Civics, Acuras, Mitsubishi Eclipses and other sport compact cars are a hot aftermerket upgrade opportunity. Most of these vehicles are four to 10 years old and are purchased by a second or third owner (typically male, age 18 to 28). Some of these owners are do-it-yourselfers, but most are not and need professional help to install anything more than simple bolt-on modifications. Consequently, a new breed of high-performance shop for sport compact performance work has emerged that caters to the owners of these cars.
The same kind of performance enthusiast who will fork over $1,000 for a set of custom 17-inch rims and low-profile street performance tires will also spend thousands more for spoilers, wings, vented and cross-drilled brake rotors, racing seats, gauges, audio equipment and performance engine accessories and modifications. We are talking everything from simple bolt-on items like exhaust headers, ram air/cold air intake plumbing, big bore throttle bodies and underdrive pulleys, to serious stuff like performance camshafts, pistons, connecting rods, reworked cylinder heads, trick computers, nitrous oxide systems, turbochargers and superchargers.
NO WAITING
Building performance engines and making performance engine modifications obviously requires two things: Experience and interest. If a repair shop is not into racing, has no firsthand experience modifying engines and has never gone through the learning curve of all the things that can go wrong when modifying an engine, it is not the shop to go to for performance engine work. You want a shop that knows what they are doing and has plenty of experience (and satisfied customers!).
WHAT TO LOOK FOR
If you plan to go beyond basic bolt-on modifications, you'll need a shop that has access to a good machine shop or who does their own machine work in-house. Equally important, they need experience in building sport compact engines, not just Chevy and Ford V8s. Can they cut heads to accept high compression O-rings? Can they do multi-angle valve jobs on multi-valve heads, replace valve guide liners, line bore overhead cam journals and straighten warped heads? Do they know the "weak points" of the various engines? Honda 1.5L engines, for example, tend to blow head gaskets because of a hot spot between the two center exhaust valves. The fix here is to replace the stock OEM head gasket with an aftermarket head gasket ( Fel-Pro brand). The Fel-Pro head gasket for these engines has a special reinforcement between the cylinders that will prevent a repeat head gasket failure.
A good machine shop should also know how to pressure test, weld and repair cracked aluminum cylinder heads. They should be able to plateau-hone cylinder blocks. They should also be able to polish and balance crankshafts. They should know how to check, recondition and shot peen connecting rods.
Building a reliable performance engine requires a lot of know-how to do the job right. It is not unusual for some of these modified Honda, Mitsubishi and other sport compact engines to put out over 400 horsepower with turbocharging and nitrous oxide. That's a lot of power from an engine that was never intended to produce that kind of power. Consequently, some things have to be beefed up such as pistons, rods, valve springs, head gaskets and so on. You can't transform a stock motor into a serious high-performance motor with external bolt-ons alone. You need to get inside the engine and do whatever it takes to make and handle the power.
PERFORMANCE CAMSHAFTS AND CYLINDER HEADS
One of the fastest and easiest ways to boost the power output of any small-displacement, naturally aspirated engine is to make it breathe big. This can be done by installing a higher-lift, longer-duration performance camshaft; by enlarging the head ports (which requires lots of grinding and test time on a flow bench to get it right); installing larger valves; replacing the stock intake manifold with a larger, higher-velocity manifold; or bolting on a forced-induction system like a supercharger or turbocharger.
Computer numeric controlled (CNC) machined heads have become popular in recent years because they are an affordable alternative to porting heads by hand. Once an engine builder develops a port profile that works well in a given engine, he can map it electronically and reproduce it with CNC milling equipment in head after head. There�s no guesswork, and each head turns out exactly the same. The trick here is getting the profile right the first time.
Hogging out the ports with a die grinder by hand can often hurt air flow more than it helps. Ports must be contoured to maximize air flow and velocity, and the only way to know if a change works or not is to test it on a flow bench.
Other head modifications may include narrowing the valve guide boss, shortening the amount of guide that protrudes into the port, and installing performance valves that have undercut stems just above the valve head. Removing metal in the combustion chamber to unshroud the valves also improves breathing, and polishing the chambers can minimize carbon buildup and the risk of detonation.
Additional gains in air flow can be found by carefully matching the intake and exhaust ports in the cylinder with the manifolds. Sharp edges obviously interfere with air flow, so carefully blending the area where these parts come together is a must.
Another performance trick that is usually done is equalizing the volume of the combustion chambers ("ccing" the head). This ensures the same compression in each cylinder and evens the power output, cylinder-to-cylinder.
Valve lift, duration and seat angles also play a big role in air flow. The combustion chambers in most Japanese four-valve heads are pretty cramped, so there�s not a lot of room to make changes. Even so, blending the bowl area to the seats and ports can improve air flow, as can using a three- or five-angle cut on the valves and seats.
For higher rpms, stiffer valve springs are a must, along with lightweight retainers. Titanium valves can also reduce valvetrain weight but are fairly pricey for most street engines.
The biggest gains in air flow will be realized by forcing more air into the engine. A number of aftermarket companies make fairly complete bolt-on supercharger and turbocharger kits for the more popular Honda, Acura and other Japanese applications. Most sell for around $3,000 to $4,000 dollars and don't require other internal engine modifications. Adding a blower or turbo to one of these engines can easily provide a 50 percent or more increase in horsepower. Add a nitrous oxide system to give the engine an extra boost for special occasions, and you can double the stock power output.
What goes in must also come out, so a performance engine also needs a free-flowing exhaust system that creates minimal backpressure. Bolt-on, four-tube exhaust headers that dump into a large bore converter, oversized exhaust pipes and a straight-through muffler will allow the engine to exhale. Sorry, but those big sewer pipe tailpipe extensions you see on so many Japanese cars today just don't do much for performance, unless the entire exhaust system has been opened up to flow more fumes.
POWER VERSUS RELIABILITY
As power goes up, reliability goes down. Force-feeding an otherwise stock engine with a blower or turbo, or boosting power with a shot of nitrous, increases combustion temperatures and pressures to the point where detonation and pre-ignition become a serious concern. If there is too much spark advance or the fuel mixture goes lean at high rpm, the engine will probably fry a piston. The stock head gasket may also be unable to contain the additional pressure, and may have to be replaced with a high-performance gasket or copper head gasket.
Higher combustion pressures also increase the load on the pistons, connecting rods, crankshafts, bearings and block. Stronger forged or hypereutectic pistons may have to be substituted for stock cast pistons. Stronger chrome moly steel rods may have to be substituted for stock cast-iron rods. Bearing clearances may have to be changed to improve oil pressure and lubrication. The crankshaft may have to be balanced and polished for higher rpm durability.
Additional modifications will certainly be needed with the clutch to handle the higher power output of the engine. And so it goes, all through the driveline until the weak links have all been identified and strengthened to handle the power. Unfortunately, the way many people do this is to push the envelope until something breaks. That's where experience comes in. If you know what the weak points are, you can eliminate a lot of potential problems by making the necessary modifications before they fail.
ENGINE ASSEMBLY TRICKS
With any performance engine, clearances are the key to survival. We are talking crankshaft and rod bearing clearances, piston-to-wall clearances, and even spring clearances.
When installing performance valve springs, pay close attention to the installed height. This ensures that the springs have the required pressure to keep the valves shut. Height is checked by measuring the distance between the spring seat in the head and the retainer on the valve stem. Most performance valve springs are closely matched but, if adjustments are needed, it can be done by shimming the valves to equalize pressures. Shims are made of hardened steel, come in various thicknesses and are usually serrated on one side to prevent rotation (the serrated side faces the head). The thicker the shim, the more it increases spring pressure. Don't overshim, though, because doing so may lead to coil bind with a high-lift cam or rocker arms.
The spacing between the spring coils must also be checked with the valves at full lift to make sure the springs do not bind. High lift cams and/or rocker arms push the valves open more, so it is important to make sure there is still some room between the coils at maximum lift. This can be done by inserting a feeler gauge between the coils. A minimum clearance of .060 inch is usually recommended.
With piston clearances, stock dimensions may not apply. Many aftermarket performance pistons have a moly coating on the skirt to protect the piston and cylinder from scuffing. Note: The assembly clearances on most of these are very tight, and may actually be zero or a slight interference fit on some applications! Follow the piston manufacturers recommendations here.
Oil pressure is important, too. Most performance engines need at least 10 lbs. of oil pressure for every 1,000 rpm. If the motor is built to turn 7,000 rpm, for example, it will need an oil pump that can maintain 70 lbs. of oil pressure at that rpm.
To maintain the oil film between the bearing and journal, the clearance between the bearings and their journals needs to be large enough to allow good oil flow and cooling, but tight enough to retain the oil and maintain good oil pressure. Most stock engine rod and main bearings require about .00075 to .001 inch of bearing clearance for every inch of crank journal. For performance engines, opinions differ as to how much clearance works best. Some engine builders add a little extra clearance, while others reduce clearances slightly. You have to figure out what works best in which types of applications - and that takes experience.
DON'T FORGET COOLING
Increasing an engine's power output also produces more waste heat that must be disposed of by the cooling system. This may overload a stock radiator, so a larger or more efficient radiator and cooling fan may be needed to manage the heat.
On turbocharged engines, routing incoming air through a hot turbo compressor increases the temperature of the gas. This, in turn, makes the air less dense than it could be. Therefore, to maximize power, the air needs to be routed through an intercooler. The intercooler is nothing more than an air-to-air heat exchanger mounted somewhere in front of the radiator. Sizing is very important because you want high efficiency and air flow without adding too much volume. That misstep would add to turbo lag when the throttle is punched wide open. Some of the more tricked-out setups use a water spray to increase intercooler cooling.
Recently featured in the movie "2Fast 2Furious," the EVO sells for a cool $30,000. Conservatively rated at 271 horsepower, the turbocharged and intercooled 2.0L four- cylinder pumps nonstop torque to all four wheels via a five-speed, all-wheel-drive system. The car comes on strong at any speed and in any gear. I recently had the opportunity to drive the "EVO" at the Road America race track in Elkart Lake, WI. Let me tell you, this was one car I wanted to drive over and over again. Part of the Evolution's power secret is its two-stage turbocharger, which virtually eliminates any turbo lag. The big intercooler in the front also keeps the mixture cool enough to prevent detonation when the engine is under boost. While there were plenty of other cars to choose from that day (Porsches, Nissans, Mercedes-Benz, Corvettes and Mustangs),the EVO was, by far, my favorite. |
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