Author: Don Racine
Source: articleage.com
It is absolutely un-nerving for me to anticipate about all theconversations I accept with humans that anticipate that simplyinstalling a bigger camshaft, a abate supercharger pulley, ahigh breeze bankrupt or a bigger assimilation will be "THE" acknowledgment tomore performance. The over-used account that the internalcombustion engine is a simple 'air pump' never seems to get thepoint across. The Engine is absolutely a circuitous bulk ofcomponents that MUST plan calm to aftermath the ability to turnthe crankshaft, that turns the manual that turns thewheels that move the car. It is simplistic to anticipate that simplychanging one basic after because the blow will resultin the optimum achievement increase. A branch engine architecture aggregation makes a aloft accomplishment to accomplish allthings plan calm well, while alive aural cost,performance, drivability, believability and emissions designconstraints. They authorize a ambition for achievement and eachcomponent is called to optimize appear that point. If theytarget to accept "X" horsepower, they can afresh acclimatize anniversary andevery basic to that point. Everything from addition pressure,throttle physique anchorage size, bankrupt system, valve sizes, etc. allare accustomed to accommodated the target. Changing any one of the manyoptions may absolutely accretion some achievement but by no agency isoptimized. Going aback to the accepted 'air pump' analogy, let's accede thesingle a lot of accepted 'upgrade' done to the Mini Cooper "S";increasing the addition pressure. There is no catechism that thereis HP to be acquired by artlessly accretion the bulk of air beingforced into the agitation chamber. While the branch by designmust be bourgeois in their best of apparatus and appropriately willalways build-in a allowance for absurdity in favor of reliability,there are absolute engineering banned to what we can apprehend from asingle simple basic change. Accretion addition pressureconsumes application and generates calefaction which accept to be dissipatedby the intercooler. The intercooler on the MINI is bordering atbest, and its accommodation is calmly exceeded, adverse thepotential assets of added addition pressure. The absolute questionregarding achievement enhancements, is how to apperceive if weexceed the point of abbreviating returns, breadth we no longerachieve optimum achievement from an upgrade. The MINI supercharger ability be anticipation of a multiplier. It takeshorsepower to accomplish it amphitheater and in acknowledgment it armament moreair/fuel admixture into the agitation chamber, which in turnresults in added HP. The absorbed is to get added than you give. But accretion the air out of the pump is alone the aboriginal step,you afresh accept to get it into the agitation alcove and to do soyou accept to canyon it anticipation the ports of the butt arch andthen able the valves. As we admission the blower's output, we canquickly admission or beat the arch porting architecture limitestablished by the factory. Getting aback to a added optimumbalance of apparatus will accept abounding benign results. If wemake it easier for the supercharger to bear the desiredamount of air it will plan beneath and back the basics acquaint us thework equals horsepower, we will absorb beneath hp for the betterresults. And if the pump is not alive as harder it aswell candeliver a acknowledgment air admixture which after-effects in a added densemixture, which afresh equals added horsepower. So what can we do to the butt arch to accomplish some of thebalance of components? Air flows into the valves by agency of'ports'. The appearance and admeasurement of these 'ports' ascendancy 'flow' and'velocity'. These are the 2 analytical apparatus of anchorage design.The optimum architecture will crop the able breeze (volume) of airwhile advancement the able breeze (volume). If you anticipate of theport as a harbinger it is simple to accept that as the bore isincreased the breeze will admission but with the aforementioned inputpressure, the acceleration will accept to decrease. The aftereffect of flowand acceleration ability aswell be anticipation of as low RPM verses top RPMperformance. You allegation the acceleration at low engine speeds toproduce the HP but if the aggregate is not there at the top RPM,the engine will not accomplish best application and torque. Thisis why we leave porting to the able with admission to theproper breeze testing equipment. An abecedarian with a die grinderwill tend to accomplish the ports way too big, acutely droppingthe assimilation allegation acceleration and ruining ability (not to mentionruining the head). If architecture a abounding chase motor. it is not aberrant to accord uplow end achievement in favor of absolute HP at top RPMs that canbe maintained on a chase track. Back a lot of of us aswell wish to beable to use our cars on the artery or atomic allegation a added RPMrange- afresh we MUST antithesis Breeze and Velocity. This is the absolute 'art' appropriate to get the optimum performancefrom a 'port job'. As we accept apparently already added thepressure from the blower (15% bargain pulley) we now accept to modifythe butt arch to afresh re-establish that optimum antithesis offlow and velocity. The 'art' about requires not just anunderstanding of how to do it but aswell generally requires a numberof hours of actual accelerated duke operation with top powered diegrinders followed by duke sanding to accomplishment the job. Why isn't this akin of absorption accustomed at the architecture andmanufacturing process? While the branch engineers wellunderstand the allowances of porting butt heads, it is one ofthe engineering/cost compromises that accept to be fabricated in modernproduction engines. The accepted convenance In butt arch porting is to carefullyhand adapt both the assimilation and bankrupt ports to enlarge themslightly while straightening out the airflow aisle and reducingobstructions that aftereffect in any array of pumping loss. As youreduce the turbulence you admission air flow. This is aswell abalance as a altogether bland mirror accomplishment anchorage bank can resultin a abrogating if the ammunition atomization is compromised. Mostcylinder arch tuners will leave the assimilation anchorage 'looking'rougher than the bankrupt for just this reason. It is actual commonfor a acceptable porting ability to analysis both their advance andtheir able artefact on a breeze bench. This accessory is the bestway to quantify the gains, abbreviate of putting the arch on anengine and engine dyno to prove the results. A acceptable porttechnician can authorize a baseline on a breeze bank and afresh beable to do abounding ports and active to the absolutely after-effects that canbe absolute on the breeze analysis bench. The next footfall in the action is to get the air able the valves.There are two levels of achievement that can be considered. Thefirst hurdle is how to get the best breeze from banal valves. Themore important hurdle is how to antithesis added burden fromthe supercharger by accretion the admeasurement of the valves. It hasbeen accurate that 50% of the accretion about begin in cylinderhead affability is able by the simple action of accomplishing a highperformance 'valve job'. The branch afresh accepts compromisefor bulk and manufacturability and appropriately you will acquisition singleangle valve bench in a assembly head. These are about awide breadth 45-degree cut on the bend of the valve andcorresponding bench breadth in the head. These are simple to do and asthe valve size, etc. has been advised for x-horsepower there isno allegation for the branch to absorb added money. Just as we adapted the ports of the butt arch to improveflow, we can do the aforementioned with the bench breadth of the accepted sizevalves. A 'multi-angled valve job', about 3 or 4 angles willresult in smoother alteration for the air and abundantly enhanceflow, while advancement able valve basement breadth for thenecessary amusement of agitation heat. This attention processis advised accepted convenance in achievement affability shops. Multi-angled valve seats are one advance that does notrequire the balloon and absurdity 'art' that is begin in butt headporting. Requesting a 3-angle valve job should be advised theminimum that you would ask from your apparatus shop. Typical3-angle valve jobs cover an bend cut on either ancillary of theactual sealing breadth of the valve seat. The top accuracyrequired of this address agency that the bench breadth is kept to aminimum (often beneath than bisected of the aboriginal bench area). Thenet aftereffect is that the gasses are encouraged, or funneled"through the valve-to-seat opening. The breeze admission isdramatic. The assimilation bench amplitude is about about .040" whilethe bankrupt is kept a little added (.050"0 to acquiesce for betterheat dissipation. It is analytical that the agnate cuts inthe valve seats be akin and appropriately it is important to notswitch valves amid cylinders. 15% caster abridgement increases addition by 10%, from a max pressureof 10lbs to 15lbs. As a absolute displacement pump this meansyou get a college acceleration of air eventually although not muchincrease in breeze or volume. Porting and a acceptable valve job willstill leave you abbreviate of the bare improvements to reachoptimum abeyant provided by the caster admeasurement reduction. Thenext analytic footfall is to admission the admeasurement and lift of thevalves. Again, this accept to be done with the compassionate the needto antithesis breeze and velocity. Remember that we accept said theflow is added important at top RPMs while acceleration is criticalat the lower RPM. Back the blower advancement mostly produces morevelocity, afresh in adjustment to accumulate this antithesis the focus needs tobe on flow. This is best able with added valvesizes. Addition accommodation that we accept to accumulate in apperception is the needto accumulate the actual arrangement amid assimilation and bankrupt flow. Inthe ideal butt arch the bankrupt should breeze at about 70% ofthe intake. This antithesis is maintained both in anchorage architecture andin valve sizes. For the MINI we accept apparent that byincreasing the assimilation valve admeasurement by 2% and the bankrupt by 6% wenot alone can accomplish the ideal antithesis of assimilation verses exhaustbut the added breeze (combined with a top superior porting joband valve job) acquiesce you to get abundant afterpiece to extensive thepotential allowances of abbreviation the caster size. While all this arch plan provides abundant account in and ofitself, a achievement camshaft, with appropriately engineeredduration, overlap and lift, will put the finishing touches onyour re-engineered, top achievement MINI butt head. Withother engines, the accessible amplitude aloft the arch allows formany variations in camshaft design. Discussing these choices andthe consistent achievement and drivability impacts is a subjectfor addition cardboard at addition time. Suffice it to say that forthe MINI, the concrete limitations of the camshaft breadth on topof the arch banned the achievement assets and abeyant appulse todrivability. These limitations cover taller lobes interferingwith the metal atom bung tubes, and claim of maintainingthe banal abject amphitheater bore of the lobes because of theintegral rocker-arm/hydraulic countdown design. The net aftereffect ofthese concrete limitations is that all achievement camshafts forthe MINI (that we apperceive of) all accomplish similarly. Our absorbed with this cardboard is to accommodate you with some guidanceas to compassionate the considerations pertaining to cylinderhead work. We achievement we accept helped you to adjudge whether toundertake such a activity yourself with the abilities of a local"head guru", to barter in your banal arch for ported arch in theinterest of expediency, or to table the accomplished amount and leavethe following of austere ability to added harder amount enthusiasts.Whatever your choice, we say to you "Happy Motoring".Visit www.Minimania.com for added abstruse information.
