Looking for the ultimate in per-formance for your Honda engine?If you want reliable horsepower forthe streets or record-setting horse-power for the strip, chances are thatforced induction will be a part ofthe equation. On the street, forcedinduction—by means of a turbo ors u p e r c h a rger—can deliver powerfigures that are in excess of mostfull-race, naturally aspirated pow-erplants. In full-race trim, boostedmotors can generate more powerthan even a well-built, bottle-fed(nitrous oxide) bullet. To ensurethat you buy the best system foryour needs the first time around,we’ve outlined the basics ofincreasing horsepower, the physicsbehind forced induction and thelatest information on the availableturbocharger and supercharger sys-tems for your Honda.

More PowerNo matter what anyone has told

you, the fact is there are only fourways to increase horsepower gen-erated by the engine at the fly-wheel. You can: reduce the amountof horsepower lost to friction,increase the engine’s displacement,

increase the rpm potential of theengine or increase the averagecylinder pressure by combustingmore air and fuel in the cylinder.Let’s take a look at the four meth-ods to see how we can apply themto a Honda powerplant.

As for reducing the amount ofhorsepower lost to friction, there’slittle that a tuner can do except useengine lubricants with frictionmodifiers. Since there are so manyof these on the market, it helps toheed the advice of people at tuningshops that have dyno- and field-tested the products. In any case,Honda engines are mechanicallyefficient, so don’t expect dramaticgains from switching to a differentoil or using an additive.

Speaking of additives, we allhave heard the V8 camp’s mantra"there’s no replacement for dis-placement." While this saying is

far from the truth—there are

many ways to add horsepowerwithout increasing an engine’s dis-placement—the fact is, all otherthings equal, a larger engine candigest more air and fuel so morepower will be made. Is increasingan engine’s displacement easy todo? With the exception of swap-ping the original engine for a big-ger one, increasing engine dis-placement in a Honda requiresoversized pistons and/or longer-stroke crankshafts. Either processrequires disassembling the engineand machine work which meansdown-time for your cruiser (thisa i n ’t no afternoon bolt-on).U n f o r t u n a t e l y, longer- s t r o k ecrankshafts will increase piston-to-wall side-loading, resulting inincreased engine wear and morestress on the connecting rods andcrankshaft. The longer stroke alsoresults in higher piston speeds thatmay result in a reduction of your

Supercharging vs. TurbochargingWhich is best for your Honda?By Michael Ferrara

1 Courtesy of HONDA TUNING / Summer 2000

maximum safe-level redline. Inany case, reliability is sacrificedunless the best parts available areused, and of course these parts arefar from being free.

High-quality internals are alsoon the "must-have" list for increas-ing the rpm potential of an engine.In very simplified terms, a 1.5-literengine spinning at 10,000 rpm cangenerate the same horsepower as a3.0-liter at 5000 rpm. Many otherfactors need to be taken intoaccount, but when the engine com-bination is optimized, more rpmmeans more horsepower. The criti-cal engine components that deter-mine the location and size (narrow,broad) of an engine’s powerbandare the camshaft(s) and cylinderhead.

On engines using a fixed camprofile, (non-VTEC), an enginewith cams designed for high-rpmpower generally loses some low-end torque. Although this may notbe a chief concern for a race car, astreet-driven car needs to havegood low-end torque for normaldriving. On VTEC motors, multi-ple cam profiles allow the engineto produce good low-end torquewithout sacrificing high-endpower.

Modifications made to increasethe average cylinder pressure in theengine also result in making morepower. How do you increase the

pressure within a cylinder that is afixed size? By getting more air andfuel to combust within the cylinder.Supercharged and turbo-equippedengines make more horsepower byforcing additional air into theengine that can be mixed withadditional fuel. Combusting moreair and fuel in the cylinder increas-es the average cylinder pressure inthe engine. With more pressure act-ing on the piston during the powerstroke, additional force drives thecrankshaft, generating more powerat the flywheel. Depending on thetype of supercharger or size ofturbo used, additional power canbe realized in all or part of theengine’s power band.

Forced Induction BasicsAll mechanisms designed for

forced induction have the samegoal—to force a greater mass of airinto the engine so that when addi-tional fuel is added more horse-power can be made. The major dif-ference between a turbocharg e rand supercharger is the powersource of this mechanism. A super-charger uses horsepower from theengine’s crankshaft to spin its com-pressor while a turbo uses the ener-gy in the engine’s exhaust gas tospin its shaft.

Positive-DisplacementSupercharger

There are two basic styles ofs u p e r c h a rgers: positive displace-ment and centrifugal. Each typehas its own advantages and limita-tions. Also referred to as Roots-type units, positive-displacementsuperchargers are classified as suchsince every revolution of the blow-er pumps out a fixed volume of air,regardless of the blower’s rpm.

The result of this is that boostcomes on in an instant. With this

family of superchargers, theamount of boost is dependent onthe blower’s size, the engine size,percent of over-/underdrive, rotorclearances and the volumetric effi-ciency of the engine. As blowersize is increased, boost pressurealso increases. This results becausethe blower is pumping a greatervolume of air than the engine caningest, so the air not making itsway into the engine is put undermore pressure.

The size of the engine alsoaffects boost level. As an engine’ssize increases, boost pressure dropsbecause a greater percentage of theair displaced by the blower canmake its way into the larger engine.On positive-displacement blowers,boost can also be adjusted by vary-ing the pulley sizes on the engineand blower.

In addition to the already men-tioned factors, the breathing ability(volumetric efficiency) of theengine also affects the boost level.Engines with ported cylinderheads, healthy camshafts and after-market intakes will register a lowerboost level than a stock engine.This is because the modifiedengine breathes as if it were a larg-er stock engine—from what wealready know, a larger engine low-ers the boost level. In general, pos-itive-displacement supercharg e r sare unmatched in the area of boostresponse.

2 Courtesy of HONDA TUNING / Summer 2000

As for limitations, positive-dis-placement superchargers do notmatch the adiabatic efficiency of acentrifugal supercharger or tur-bocharger. As a result, charge airtemperatures for a particular boostlevel on an engine are typicallyhigher than the same engine with acentrifugal supercharg e r.A d d i t i o n a l l y, positive displace-ment superchargers are usuallyincompatible with intercooler sys-tems and the benefits that thesesystems can provide.

For Honda’s most popularengine platforms, Jackson Racingoffers a supercharger system. Thisbolt-on system uses an Eaton posi-tive-displacement supercharg e r.This Roots-type blower is the pre-ferred choice of many OEM vehi-cle manufacturers due to itsdurable design. Its durability is theresult of close-tolerance, CNC-machined rotors. These rotors areepoxy-coated for extended servicelife. The oiling system for thes u p e r c h a rger is self-contained,making installation straightfor-ward. A unique by-pass valvereduces the load on the supercharg-er under part-throttle. Making theauthorities happy, the systems fea-ture 50-state legal certification.

Centrifugal SuperchargerOriginally introduced byMcCullough (which is nowPaxton), centrifugal superchargersystems have become the backboneof the late-model (5.0 and beyond)movement. Today, Paxton, Vortechand ATI ProCharger dominate thecentrifugal blower market. Due tothe lack of complete centrifugalsupercharger systems for imports,finding a centrifugal superchargerunder the hood of a Honda is aboutas likely as finding all your tools

after someone borrows your tool-box.

Although both are classified assuperchargers, a centrifugal blowerhas a substantially different boostand performance curve than a pos-itive-displacement supercharg e r.Unlike positive-displacementunits, which provide the same air-flow regardless of rpm, centrifugalunits provide airflow proportionalto the supercharger’s speed. Theeffect is usually characterized bynot realizing full-boost redline. If acentrifugal supercharger uses apulley combination to generate 4psi of boost at 4000 rpm, it willproduce 8 psi of boost at 8000 rpm. Many consider this gradual boostcurve to be the biggest drawback orlimitation of a centrifugal super-charger. On traction-limited cars,this isn’t necessarily a problem—infact, it can be a solution to tire-spinning problems. In the realworld, the gradual boost curvecould translate into better tractionon traction-limited, front-wheeldrive street applications. On a pos-itive note, centrifugal supercharg-ers benefit from high adiabatic effi-ciencies and can be teamed with anintercooler system for additionalperformance and increased reliabil-ity.

If you’re interested in buildinga custom supercharger systemaround a centrifugal supercharger,give the manufacturer a call to seewhich supercharger is needed togenerate your target horsepower.Also, you need to let the super-charger manufacturer know whichway the supercharger will spinwhen mounted on the engine sincethe rotation direction of a Hondaengine is unconventional (counter-clockwise). As more and more tra-ditional companies address the

import market, we expect to see

centrifugal supercharger systemsfor Hondas in the future.

The TurbochargerIf there is one alternative to dis-

placement that V8 owners fearmost, it’s the turbocharg e r.Essentially two machines in one, aturbocharger is both a compressorand a turbine. Like a supercharger,a turbo has a compressor element.Rather than drive the compressorwith a belt, a turbo drives the com-pressor with its second component:a turbine.

What’s a turbine? Long beforesteam engines, people harnessedMother Nature’s energy resourcesto help do the work. By placing apaddle wheel in a flowing river, thewheel could be used to spin a shaftconnected to other mechanisms tomill grain. A turbine works thesame way as a paddle wheel. Infact, think of a turbine as a paddlewheel for hot gases instead of aflowing river. Instead of flowingw a t e r, a turbine uses the hotexhaust gases that flow out of yourengine.

The hot gases are channeledthrough a turbine housing whichspeeds up the flow by acting like anozzle, and shooting gases againstblades of the turbine wheel. Thiscauses the mounting shaft of theturbine wheel to spin. Since thesame shaft mounts the turbine andcompressor wheels, the compres-sor wheel spins at the same speedon the compressor side. Ratherthan pulleys controlling the speedof the compressor, modern tur-bocharger systems use a wastegateto regulate boost pressure. T h ewastegate reads the boost pressureat the intake manifold and opens itsvalve to maintain boost at a con-stant level. The valve channelsexhaust flow away from the turbine3 Courtesy of HONDA TUNING / Summer 2000

wheel to regulate the shaft andcompressor speeds.

How does a turbocharg e r’sboost response curve compare to apositive-displacement and a cen-trifugal supercharger? A t u r-b o c h a rg e r’s boost curve fallssomewhere in between the two.The sizing of the turbocharger hasa dramatic effect on how early orlate in the powerband the turboreaches its peak boost level. Oncethe engine reaches the rpm wherethe turbocharger produces peakboost, its boost curve performs likea positive-displacement super-c h a rger keeping boost constantuntil redline.

As for efficiency, the compres-sor on most turbos edge out bothcentrifugal and positive-displace-ment superchargers. Turbochargersare easy to team with an intercool-er, and "intercooled-boost" is theultimate in performance and relia-bility.

What Is Boost?In forced induction applica-

tions, boost is a measure of thepressure of the air in the engine’sintake manifold. As this pressure isincreased, a greater volume of airwill be pushed into the cylinderwhen the intake valves open.Increasing the boost level of as u p e r c h a rger while adding addi-tional fuel will produce morepower—to a point. As with mostthings in life, including publichighways, there are limits—whenpressure increases, temperaturealso increases. When temperatureincreases, the density of the air(mass of air found in a given vol-ume) decreases.

Usually, moderately raising theboost level (going from 6- to 9-psiin a street application supercharg-

er) increases the volume of air sub-stantially more than it reduces thedensity of the air, so more power ismade when the appropriate amountof additional fuel is added.Basically, we get a higher quantity(volume) of air while losing a bit ofquality (density) in the air.Therefore, the total mass of airinduced into the engine is more, somore fuel can be added and morepower can be made.

When boost levels are too high,there is a higher volume of airbeing pushed into the engine at alower density. Although we areincreasing the quantity, the qualityis so poor that the value of the air isless than at a lower boost-level.The result is that the total mass ofair being pumped into the engineremains the same or is actuallyreduced, causing horsepower toremain the same or drop off. Thisphenomenon occurs when super-chargers are driven to run at highboost levels where they are ineffi-cient or when the compressor of aturbo is beyond its normal operat-ing range. The equation that relatesmass, density, and volume is as fol-lows:

Mass (kg) = Density (kg/m^3) xVolume (m^3)

In summary, more power ismade when the mass of air and fuelpumped into the engine isincreased. Raising boost levelsincreases the volume of air, whilethe resulting increase in air temper-ature decreases the density of theair. The returns are beneficial (as inmore horsepower) only when theincrease in volume outweighs thedecrease in density.

Always a positive addition to aforced-induction system, intercool-ers add both power and reliability.

How do they work? Intercoolers

reject some of the heat built up bythe pressure increase of the air.This provides the engine with ahigher quality (higher density)charge of intake air. Since the airtemperature is reduced, the boostpressure is also reduced when anintercooler is added to a system.Although intercoolers do impose arestriction to airflow affecting thequantity (volume) of the airflowinto the engine, the increase in thequality (density) of the air morethan makes up for this.

Important ConsiderationsNo matter how much addition-

al air is forced into the engine, noadditional horsepower will bemade unless additional fuel is alsoadded. Remember the energy thatmakes horsepower in an enginecomes from the fuel, not the air. Ingeneral, every 2 hp producedrequires 1 lb of fuel per hour (or .5pound per horsepower). W h e nmodifications are performed thatincrease airflow into the engine,more air is available for the com-bustion of fuel. The combustion ofthe additional fuel is what trans-lates into additional horsepower.

Supercharger and turbochargersystem manufacturers spend agreat deal of time making sure theirsystems offer reliable performance.Reliability can be questionablewhen modifications are made toboost levels. Raising the boostlevel increases the chance ofengine-damaging detonation. Fuelquality, the engine’s compressionratio, and total ignition timing limitthe amount of boost that can be runwithout detonation; exceeding thelimit can result in a piston-melting,lean-fuel condition or in detonation(where the fuel uncontrollablyexplodes in the cylinder causingpossible engine damage). 4 Courtesy of HONDA TUNING / Summer 2000

5 Courtesy of HONDA TUNING / Summer 2000

R e m e m b e r, supercharger andt u r b o c h a rger systems from themajor manufacturers are engi-neered to provide reliable perform-ance when used as directed. Whenconsidering raising boost levels(which may not be emission legalin some states) always contact thesystem manufacturer for their rec-ommendations. Talking to theexperts will provide an extra meas-ure of reliability to ensure your ridedoesn’t take an extended vacationfrom the streets.

The SourceVortech Engineering, Inc.

1650 Pacific Ave.Channel Islands, CA 93033

(805) 247-0669www.vortechsuperchargers.com

ApplicationsKits:

V-5 G-Trim Supercharger Kit1999 Honda Si

$3,800

Units:V-5 D-Trim Supercharger

1.5-3.0-liter engines$2,200

RevHard Manufacturing7407 1/2 Fulton Ave.North Hollywood Ave.

North Hollywood, CA 91606(818) 764-4312

www.revhard.com

ApplicationsKits:

RH18KIT (turbo)’94-’97 Acura Integra

$3,600

RH16KIT (turbo)’93-’97 Honda Civic

$3,550

V-9 F- and G-Trim Supercharger1.5-3.0-liter engines

$2,200

Jackson Racing440 Rutherford St.Goleta, CA 93117

(888) 888-4079www.jacksonracing.com

Acura989-510

94-98 Acura Integra GS, LS, RSDOHC NON VTEC 1.8L B181B

989-500 94-99 Acura Integra GS-RDOHC VTEC 1.8L B18C1

Honda989-000

88-91 CRX, Civic, EX, SISOHC NON VTEC 1.6L D16A6

989-100 92-95 Civic, EX, SI

SOHC VTEC 1.6L D16Z6

989-200 96-99 Civic EX

SOHC VTEC 1.6L D16Y8

989-600 97-98 Acura Integra Type-RDOHC VTEC 1.8L B18C5

Units:RHRTBO

Hybrid T3/T4 Turbo$775

RHBTBORevHard Hypo Turbo

$850

989-210 96-99 Civic DX, LX, CX

SOHC VTEC 1.6L D16Y7

989-250 99-00 Civic Si

DOHC VTEC 1.6L B16A2

Mazda Miata999-000

90-93 MiataDOHC 1.6L B6E

999-100 94-97 Miata

DOHC 1.8L BP

999-105 94-97 Miata

DOHC 1.8L BP

999-110 94-97 Miata

DOHC 1.8L BP

999-130 94-97 Miata

DOHC 1.8L BP

999-20099 Miata

DOHC 1.8L

*all superchargers run from $2495-2995