F I Ba - ELIMINATOR · 2018-10-23 · the air into the cylinders. This allows (and demands) a more dense fuel/air charge. Igniting a higher-pressure/more dense charge makes more power

10 APR-JUN 2012 engine professional AN AERA INTERNATIONAL QUARTERLY PUBLICATION

While this article may be a bit simplisticfor those familiar with forced induction,hopefully the information will be helpfulto those who are not as experienced withthis approach.

A naturally-aspirated engine usesavailable (ambient) air to enter theengine, mix with fuel and ignite in thecombustion chamber. A forced inductionsystem (supercharger or turbocharger)does just what the term implies…it forcesadditional air into the combustionchamber. When mixed with theappropriate ratio of fuel, you createhigher cylinder pressure, referred to asboost, which makes more power. Whilewe certainly don’t have the room here todelve into great detail, we’ll try to offer afew informational tidbits that willhopefully help you to better understandthe basics.

SUPERCHARGER BASICSSuperchargers (blowers) are offered inthree types, including the Roots type,centrifugal and the screw type. The Rootstype is the least complex, functioning asan air pump. Instead of compressing airinside the unit, pressurization takes placein the manifold and combustionchambers (referred to as external aircompression). Centrifugal and screw typesuperchargers compress air inside thesupercharger (internal compression),pushing the compressed air into theintake and combustion areas. Acentrifugal unit mechanically functionsmuch the same as a turbocharger, with aninternal impeller. Instead of being drivenby exhaust gas (as with a turbo), acentrifugal supercharger impeller isdriven mechanically by a drive belt. Thescrew type supercharger features two

Forced Induction BasicsBY MIKE MAVRIGIANPHOTOS BY MIKE MAVRIGIAN UNLESS OTHERWISE NOTED

Supercharging and turbocharging tidbits

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inter-meshing spiral rotors (if you’refamiliar with a twin-screw shop aircompressor, it’s easy to understand thisstyle). The two rotors progressivelycompress the air as they spin and as airpasses through the spiral “teeth.” Becauseof the precision tolerances required in themanufacturing process, screw typesuperchargers tend to be more expensive.Regardless of the style, a supercharger(and a turbocharger as well) packs moreair into the cylinders, effectively forcingthe air into the cylinders. This allows(and demands) a more dense fuel/aircharge. Igniting a higher-pressure/moredense charge makes more power.

SIZE AND SPEEDBoost is affected by both enginedisplacement and driven speed of theblower. If the blower is driven at aconstant speed ratio (between crank andblower), a larger-displacement blower willproduce more boost than a smallerblower on the same engine. As enginedisplacement increases (let’s say goingfrom a small block to a big block), boostis reduced if the blower is driven at thesame speed. If engine displacement isreduced (and the blower runs at the samespeed), boost is increased. If the blowerruns at a higher speed, boost is increased.At a lower blower speed, boost isreduced.

This is a very basic overview, buttypically you should choose a smallerblower size for smaller displacement anda larger blower size for biggerdisplacement engines. Drive pulleys can

be selected (larger or smaller diameter) tomake the blower run slower or faster, inorder to “tune” boost for the givenengine. For instance, running a largerblower on a smallblock can be tuned bydriving the blower at a slower speed inorder to keep the boost level down to apoint where you avoid detonation. But,running the blower too slow can reduceboost if the blower isn’t running fastenough to compress the air sufficiently. Ifyou run too-small a blower on a bigblockengine, the blower speed would need toincrease, possibly to the point ofbecoming inefficient (running at too higha speed can create excessively heatedintake air, which would ruin air density.In other words, you need to pay attentionboth to blower size and the speed atwhich it’s driven.

FUEL SYSTEMOften, customers tend to ignore the fuelsystem, which will typically need to beadjusted to accommodate the forcedinduction, in terms of delivery fuel linediameter and richening (via jets, injectors,ECM reprogramming, etc.). When usingforced induction (when boost is applied),you’ll need more fuel, since it alwaystakes more fuel to make more power.Plan on tuning with a richer mixture.Retarding ignition timing also allows theuse of more boost. We’re speaking inbroad generalities here, so talk to thesupercharger/ turbocharger manufacturerand plan to spend some time tuning bothfuel and spark.

PRESSURE RELEASE VALVESInstalling a form of adjustable pressure-release valve (blow off/pop-off) offers asafety margin, allowing the release of apre-set amount of pressure to avoid over-boosting (again, lots of variables areinvolved here. Talk to your forcedinduction supplier for recommendationsbased on your specific setup). The twotypes of valves included here include awastegate (WG) and a blow-off valve(BOV). In the simplest of terms, a WGregulates pressure on the exhaust side,while a BOV regulates pressure at theintake side. The BOV is usuallypositioned on the feed pipe between theturbo and the intercooler. When you liftthrottle, the BOV prevents forced airfrom being packed into the engine whendecreasing RPM. The WG regulates theamount of boost from the turbo toprevent over-boosting. Both are required.

CAMSHAFTIn order to optimize the use of forcedinduction, ideally the engine will likelyprefer a lobe separation angle (LSA) inthe moderate-wide range, probablyaround 112 to 114 degrees. Generally,heavier valve springs are also required,depending on the amount of boost beingcreated. The exhaust is opening againstpressure, so this isn’t a huge concern, butwith regard to the intake side, you’lllikely need higher rate springs. We’re not

FORCED INDUCTION BASICSBY MIKE MAVRIGIAN

Especially for retro-fitting for closed-hood clearance,Edelbrock, as one example, offers a complete low-profilescrew-type supercharger kit (pictured left) that includeseverything needed except for the celebratory pizza oncethe job is finished. (Courtesy Edelbrock)

A thermal “blanket” (shown below) helps to reduceunderhood temperatures. (Courtesy DEI)


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trying to pass the buck here, but it’s bestto consult with a cam maker for arecommendation (you’ll need all of yourengine specs and forced induction infobefore you call).

SPARK PLUGSWhen running a supercharger, it’sgenerally recommended to run one heatrange colder than stock. According toKenne Bell Superchargers, a gap of0.035” is common.

COMPRESSION RATIOIf you’re building an engine specificallyfor forced induction, lowering thecompression ratio allows more boost withthe same octane.

Static compression ratio (CR) refers tothe compression ratio of your enginewithout forced induction. Finalcompression ratio (FCR) refers to thecompression that you’ll have when fullboost is applied.

The formula for calculating final CRis as follows:

(Boost divided by 14.7) + 1 X Static CR =Final Compression Ratio (FCR)

Shown above is a compression ratioreference chart that explains how staticcompression is affected by various forced

induction boost levels (courtesySilvolite/KB/United Engine & Machine).

Note that the higher your finalcompression ratio, the higher octane fuelyou’ll need to prevent detonation. Finalcompression ratios above 12.4:1 are notrecommended for use with premiumpump gasoline. Want more FCR? Thenprepare to pay for race fuel.


A twin-turboinstallation (duringfabrication). Note thelarge intercooler.



UPGRADING THE ENGINE TO ACCOMMODATE THE NEW-FOUND POWERConsider how your engine will handle theadded cylinder pressure. While “simply”installing a forced-air induction system(turbocharger or supercharger) onto anotherwise stock engine may seemtempting (and there are certainly systemsout there designed to work with stockengines), we really need to consider theneed for a few upgrades in order to allowthe engine to withstand the extra boost,in terms of component durability.Remember: any forced induction systemwill increase cylinder pressure. The extentof this increase may dictate the need toalso upgrade stress-related internalcomponents.

While today’s commonly-used OEhypereutectic pistons and powder-metalconnecting rods are certainly adequatefor daily and even spirited driving, whenwe’re talking about increasinghorsepower levels up to about the 450+HP range and beyond, we’re starting totake risks in terms of durability. If youplan to “boost” the induction system andpack-in a tighter air/fuel mix, you shouldseriously consider upgrading to forgedpistons that are designed to work withforced induction (possibly thicker domearea and a hardness treatment to protectring lands) and forged connecting rods.By the same token (and granted, this is adebatable area in terms of horsepowerlevel), consideration should also be givento upgrading to a forged crankshaft inplace of a stock cast crank.

When you’re asking, or expecting, theengine to produce a substantial increasein power, you’ll place added pressuresagainst the pistons, and you’re increasingthe forces/stresses that will be placed onthe rest of the rotating assembly (crankand rods). Again, depending on the levelof added power, the stock engine maynot be up to the task.

It boils down to how much poweryou plan to add and at what level youplan to abuse the engine. In some cases,you can get away with changing none ofthe engine internal components(depending on pressure levels anddepending on how the existing engine isalready configured), while in other caseswhere you plan to spit our some seriouspower, you simply must upgrade certaincomponents if you expect the engine tolive.

Yes, upgrading the engine (parts,machine shop labor) will add to the


A wastegate valve controlspressure on the exhaust (output)side of the turbo, controlling boostto the engine.

A blow-off valve (alsocalled a pop-off valve)“regulates” air on theintake side of theturbo, to preventcylinder packing whenengine RPM drops(deceleration, betweenshifts, etc.).

When plumbinga turbo system,flexible high-temp siliconeconnectionsallow for pipemovement(vibrations andduring thermalgrowth).




expense, but would you rather spend afraction of what the engine is worth forupgrading, or do nothing and experiencethe “thrill” of watching your stock enginehand-grenade, resulting in the expenseand hassle of replacing the entire longblock?

Let’s play devil’s advocate to helpillustrate a worst-case scenario. Let’s saythat the customer purchased a new“crate” engine (or let’s say that he’sdealing with the bone-stock originalproduction engine). Now, for the sake ofargument, let’s assume that this enginehas a static compression ratio of 10:1 andis equipped with hyper pistons, powder-metal connecting rods, stock production-line rod bolts, a cast iron crankshaft andpowdered-metal or cast iron main caps.Now, the vehicle owner decided to installa supercharger that will add, say, 12 lbsof boost (which can create a compressionratio at around 18:1 at full boost).

The engine fires up, the “tuner”adjusts fuel, spark and timing. Everythinglooks ultra-cool under the hood, and the

engine sounds downright nasty. He drivesthe car to a couple of local shows, smokethe tires now and then, and everybody’shappy. Then, the little horns pop out ofhis head and he nails the throttle on along stretch of country road, reallyhammering it through the gears and justplain winding it tight. All of a sudden, hehears a big bang, coinciding with a severeor total loss of power accompanied by anasty bunch of vibrations. There’s an oiltrail behind him, there’s lots of smoke,and he coasts to a dead stop, wonderingwhat just happened.

Let’s cut to the chase. The car getstowed, the engine gets pulled and torndown, and he’s horrified to find a nice bighole in the block, a loose/crooked crankdamper (busted crank snout), a couple ofbroken rods, busted pistons, bent valves,gouged combustion chambers and maybea busted cam (not to mention a chunky-soup slurry of metal particles throughoutthe oiling system).

At this point, the engine’s long blockis toast, and he’s looking at an expensive

rebuild (assuming the block can be saved)or a complete engine long-blockreplacement, not to mention the down-time of the car. All of this could havebeen avoided with a simple upgrade of afew key components. Suddenly, the catch-phrase “pay me now or pay me later”starts to make sense. Remember: when aforced induction engine blows, it canblow in a big way, since it’s still trying topack in a much higher pressure to thecylinders.

PLEASE NOTE: I’m certainly notsuggesting that the installation of anysupercharger or turbocharger system willdestroy an engine. That would be justplain dumb. The point that I’m trying tomake is to pay attention and consider thebig picture…the existing engine’slimitations and the potential need for afew component upgrades. Again, it boilsdown to the existing engine componentsand the level of power increase beingplanned.

We recently installed this Vortec supercharger setup onto a 5.0L Mustang. The installation was relatively simple, and after someminor re-arranging, underhood clearanceand fit was excellent.




UPGRADES TO CONSIDER FOR DURABILITY• Pistons (switch to forgedaluminum in place ofhypereutectic)

• Lower compression (where needed)to accommodate added amount ofboost

• Specialty coatings (thermal barrierand anti-friction)

• Moly-coated bearings (rods andmains)

• Connecting rods (switch to forgedin place of cast iron or powdered-metal cast)

• Connecting rod bolts (switching tohigher tensile strength aftermarketbolts is always a good idea)

• Crankshaft (switch to forged inplace of cast)

• Double-keyed crank snout• Steel/high performance crankdamper

• Converting to a keyeddamper/pulley on an LS press-fitpulley crank

• Cylinder head gaskets (switch toMLS in place of composite)

• Cylinder head studs (in place ofbolts)

• Main caps (billet steel in place ofcast iron or powdered metal)

• Main cap studs or bolts (usinghigher tensile strength)

• Main cap girdle (depending onengine)

• Valves (potential upgrade tohigher-quality stainless valvesand/or Inconel for exhaust valves)

• Higher-rate/more durable valvesprings

• Rocker arms (more durableaftermarket full-rollers)

• Cooling system (make sure theexisting cooling system is cleanand functions properly; andpotential need for more efficientwater pump and radiator,especially if using an intercooler)

Depending on the existing enginetype/age/condition, there’s muchmore to this subject than we haveroom to discuss in this brief article,but here, I’m pointing out theprimary areas of potential concern.

The turbocharger must besized for the engineapplication. For the street,cylinder heads typicallymay require smaller intakeports and larger exhaustports. A Borg-Warner T76turbo is shown here.

Here, a BOV(blow-off valve)is fitted betweenthe turbo andintercoolerduring a dynosetup at Koffel’sPlace in Huron,OH.

There’s no debate that a big ‘olRoots type blower adds a machomuscle flavor to any engine bay.




This twin-turbo drag enginefeatures Banks turbosystems and a meticulously-detailed dress-up. What athing of beauty.

Note the (costly) carbonfiber air intake feeding theturbos (right). This makesmy mouth water.


SPECIALTY COATINGENHANCEMENTSWhile some (primarily non-engine-builders) may scoff at the usefulness ofspecialty engine coatings, there aredistinct advantages that various coatingsoffer to improve either durability orperformance, or both.

While a wide range of specializedcoatings are available to suit a variety oftasks, with regard to coatings that suitforced induction setups, here we’refocusing on the following coatings:

• Thermal barrier coating for pistondomes

• Thermal barrier coating for combustionchambers

• Moly (anti-friction) coatings for pistonskirts and bearings

• Thermal barrier coatings for exhaustvalve faces and exhaust ports

• Thermal barrier coatings for exhaustmanifolds

Thermal barrier coatings (typicallyinvolving a ceramic formula) providewhat the term implies: a heat barrier.When applied to piston domes, this notonly helps to protect the piston fromexcessive heat (generated via forcedinduction, especially in turbo setups), butthis coating also helps to improvehorsepower. More specifically, it enhancescombustion efficiency, since the heat thatwould otherwise be soaked into thepiston and combustion chamber is nowbetter contained and aids in the moreefficient burning of the fuel/air mixture.The same holds true for thermal barriercoating applied to the faces of theexhaust valves and inside the cylinderhead exhaust ports. Instead of losing heat(via soak), the combustion heat is“contained” and scoots out instead ofhanging around and soaking into thepistons, valves and heads. Not only is thisa heat-protective coating, but because ofthe thermal efficiency, it may also

(depending on other factors) provide aslight increase in power.

A few years ago, my race team rantwo cars with identically-prepared enginesin a 24-hour endurance race. Once enginefeatured thermal barrier coatings and theother engine did not. The coated-enginecar generated 7 additional horsepower atthe wheels (verified on a chassis dynoprior to the race). During the race, thecoated engine provided slightly faster laptimes and used slightly less fuel.Naturally, this isn’t a big factor for astreet engine, and my engines werenaturally aspirated, but my point is thatwe benefited from the ceramic coatings.

Anti-friction coatings (typically amoly-based formula) can be applied to avariety of surfaces, most specifically tocam, rod and main bearings and pistonskirts. While this won’t provideadditional power, it’s a protective filmthat helps reduce frictional losses and



An external oil feed connected to asupercharger housing. Individual lubrication

for the supercharger is critical.



SOURCES

SUPERCHARGERS• ACCELERATED RACING PRODUCTS

616-885-3626

• ALAN JOHNSON PERFORMANCEENGINEERINGwww.alanjohnsonperformance.com

• BILL MILLER ENGINEERINGwww.bmeltd.com

• BLOWER DRIVE SERVICEwww.blowerdriveservice.com

• DYERS SUPERCHARGERSwww.dyersblowers.com

• EATONwww.eaton.com

• EDELBROCK CORP.www.edelbrock.com

• KENNE BELLwww.kennebell.net

• LITTLEFIELD BLOWERSwww.littlefieldblowers.com

• MAGNUSON PRODUCTSwww.magnacharger.com

• MOONEYHAM BLOWERSwww.mooneyham-blowers.com

• PAXTONwww.paxtonauto.com

• PROCHARGERwww.procharger.com

• POWERDYNE

• THE BLOWER SHOPwww.theblowershop.com

• VORTECwww.vortecsuperchargers.com

• WEIAND AUTOMOTIVE INDUSTRIESwww.weiand.com

• WHIPPLE SUPERCHARGERSwww.whipplesuperchargers.com

TURBOCHARGERS• AFI TURBO

www.afiturbo.com

• BANKS POWERwww.bankspower.com

• BORG WARNER TURBO SYSTEMSwww.turbodriven.com

• EDELBROCK CORP.www.edelbrock.com

• FORCED PERFORMANCEwww.forcedperformance.net

• GARRETTwww.turbobygarrett.com

• INNOVATIVE TURBO SYSTEMS805-526-5400

• PRECISION TURBOwww.precisionturbo.net

• PROCHARGER/ATIwww.procharger.com

• TURBO ENGINEERINGwww.turboengineering.com

• TURBONETICSwww.turboneticsinc.com

extends component life, primarily duringcold startups and during high-temp/highstress environments (when you’re reallyhammering it).

Again, I’m not claiming that youabsolutely need these coatings. But, ifyou’re building an engine specifically withforced induction in mind, it certainlywon’t hurt, and just may extendcomponent life. Specialty coating services(such as Swain Tech Coatings, Polydyn,Calico and others) can provide any ofthese coatings to your existing parts, or(due to popularity of these coatings) youcan simply purchase already-coatedpistons and bearings. If you wantcombustion chambers, exhaust valves andexhaust ports coated, you will need tohave these services outsourced.

By the way, specialty coatings are alsoavailable for supercharger andturbocharger components, which mayprovide added efficiency as well as

extending durability. If you’re interestedin enhancing these units, contact both theforced induction maker and the coatingspecialists. They can advise you regardingavailability and benefits, and whatcoatings (if any) make the most sense foryour application.�

Mike Mavrigian has written thousands of technicalarticles over the past 30 years for a variety ofautomotive publications. In addition, Mike has writtenmany books for HP Books. Contact him at BirchwoodAutomotive Group, Creston, OH. Call (330) 435-6347 or e-mail: [email protected]: www.birchwoodautomotive.com.


The creative turbo pressurefeed plumbing passes

through the bulkhead andback through to the intake.


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F I Ba - ELIMINATOR · 2018-10-23 · the air into the cylinders. This allows (and demands) a more dense fuel/air charge. Igniting a higher-pressure/more dense charge makes more power