POWER PLANT

NZ Performance Car - - Contents -

The for­mi­da­ble Honda K-se­ries en­gines are, without a doubt, one of the mas­ter­pieces of mod­ern au­to­mo­tive en­gi­neer­ing; even in their fac­tory straight-from-the-junk­yard Ac­cord, CR-V, or Odyssey form, they make many highly strung four-cylin­der race en­gines throw a rod try­ing to com­pete. The four-valve de­sign makes up­wards of 150kW in fac­tory form, and an off-the-shelf parts haul will see you able to ex­tract the likes of 340kW. How­ever, that is still not the limit, as Amer­i­can-based 4 Pis­ton Rac­ing has proven, ex­tract­ing an as­ton­ish­ing 387kW with noth­ing more than at­mo­spheric air pres­sure flow­ing into the Kinsler throt­tle bod­ies.

Luke Wil­son and Josh Klein have been in the Honda en­gine game for a very long time, con­stantly push­ing the bound­aries of what we all thought was pos­si­ble with these four-bangers. This 2.7-litre K24 is their cur­rent crown jewel. Built specif­i­cally for drag rac­ing, it makes the kind of num­bers that might seem like black magic, but, for the most part, this is the re­sult of 10 years of R&D poured into one fac­tory cast block.

The recipe to mak­ing big dyno fig­ures is a sim­ple one: make as much torque as pos­si­ble and spin the mo­tor as hard as pos­si­ble; the big horse­power num­bers will fol­low. Torque is achieved here through an in­creased 90mm (3mm over­sized) bore us­ing LA Sleeve duc­tile lin­ers, and an in­creased 106mm (7mm over­sized) stroke us­ing a Win­berg crank­shaft. With the use of Wiseco 2618 forged pis­tons, 155mm GRP Con­nect­ing Rods splay beam rods, and a 1.5mm Cometic head gas­ket spe­cially man­u­fac­tured for the boys, the com­pres­sion ra­tio sits at 16:1. The rpm side of the power equa­tion comes with the ability to spin the crank to 10,000rpm.

Achiev­ing this re­duced weight and fric­tion is the name of the game here. The gas-ported pis­tons have three coat­ings: first, a coat­ing of Wiseco’s Ar­morPlat­ing; then, hard an­odiz­ing; fi­nally, a fin­ish of Ar­morGlide skirt coat­ing. Fric­tion is also re­duced on the pis­tons by ditch­ing the cen­tre ring, run­ning only two in­stead of the com­mon three, which places ex­tra load on the oil-con­trol ring, re­quir­ing reg­u­lar re­place­ment. There­fore, these pis­tons are not some­thing you will find 4 Pis­ton putting into a cus­tomer en­gine. The Win­berg crank is also not an off-the-shelf item, hav­ing had 2.7kg of mass shaved from it, be­fore be­ing har­dened. It’s tricks of this type that add up to make the magic num­bers. We can all click ‘Buy now’ on an ar­ray of off-the-shelf parts, but don’t ex­pect to make more than 343–356kW.

The head is a fac­tory Honda cast­ing, and, as you’d ex­pect, it’s a work of art: CNC port­ing has achieved 430cfm flow, feed­ing the ti­ta­nium Ferro valves mea­sur­ing only 38mm (15⁄ inches). The springs are a 4 Pis­ton Pro Stock sin­gle valve-spring kit, while the rocker gear has shed half the fac­tory weight with the use of Fer­rea 4P RR8000 rocker arms. The cams are Skunk2 BMFxs. Feed­ing the head methanol are four 71mm Kinsler throt­tle bod­ies with 1600cc in­jec­tors.

Ex­ter­nally, the en­gine runs a Dai­ley dry sump, a Moroso dry-sump pan, and a set of My­ers Com­pe­ti­tion stepped 2.25-inch head­ers. On the en­gine dyno, the en­gine spun a best of 384kW at 9400 rpm and made 402Nm at 8600rpm, mak­ing 379Nm from as early as 6800rpm, which is an im­pres­sive power band.

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