BMW i8 ROAD­STER

BMW has taken its cut­ting gear to the roof of the i8 coupe to cre­ate a car even more strik­ing than the orig­i­nal. But is it as elec­tri­fy­ing to drive as it looks?

Evo - - CONTENTS - Stu­art Gal­lagher (@stu­artg917)

B MW HAD NO IN­TEN­TION OF of­fer­ing its i8 as a road­ster, but such was cus­tomer de­mand that the com­pany’s engi­neers lit­er­ally took a saw to the car­bon­fi­bre roof of an i8 coupe to see what would hap­pen when they cut it off. Un­sur­pris­ingly, the car­bon tub didn’t fold in on it­self like a ’70s Bri­tish sports car at its first MOT, and so the i8 Road­ster was born.

What fol­lowed was a de­vel­op­ment process never en­vis­aged when BMW launched its plug-in hy­brid coupe four years and 13,000 ex­am­ples ago. While re­mov­ing the roof was rel­a­tively straight­for­ward, it did present a hand­ful of new is­sues to over­come. Chief amongst these was air­flow. The i8 coupe ex­pels the hot air from its front-mounted ra­di­a­tors through a vent in the front bon­net, the air then flow­ing over and along the roof of the car and across the rear deck. With­out a roof, that 70deg C air now headed straight over the header rail and into the pas­sen­gers’ laps; great in the win­ter, less so in sunny Cal­i­for­nia. So, the vent was plugged and the warm air redi­rected to exit through the whee­larches and un­der the car, pro­vid­ing a so­lu­tion, but cre­at­ing a new prob­lem at the same time.

The com­bi­na­tion of the redi­rected air un­der the car and the re­moval of the fixed roof played havoc with the air­flow. The aero team sug­gested a fixed rear wing, but the de­sign­ers sent them back to their draw­ing boards to think again. They re­turned with a re­vised rear dif­fuser and, at the front, po­si­tioned low be­hind the front bumper, a new spoiler, which com­bine to solve the prob­lem.

Very lit­tle ad­di­tional brac­ing was re­quired for the tub, bar a few ad­di­tional lay­ers of car­bon in the A-pil­lars and the wind­screen header, while a plate was se­cured to the outer cor­ners of the un­der­side of the i8 to guar­an­tee stiff­ness. The but­ter­fly doors are also new, de­spite look­ing pretty much iden­ti­cal to the coupe’s orig­i­nals mi­nus the win­dow frames. Yet this al­ter­ation brought a need for new hinges and amended weight dis­tri­bu­tion in or­der for the doors to stay open. Then there is the roof. Nei­ther BMW nor its cus­tomers wanted a metal fold­ing roof or a lift-out targa-style panel. The for­mer was ve­toed be­cause it would re­move all lug­gage space (not that there’s a great deal to start with), the lat­ter be­cause stor­ing it in the car would be an is­sue and leav­ing it at home not an op­tion. Nat­u­rally, the soft-top that was set­tled upon is elec­tric. It can open or close in 15 sec­onds and be op­er­ated at road speeds of up to 31mph, but it does mean the small, 911-style rear seats of

the coupe have gone, re­placed with a fur­ther 100 litres of lug­gage space.

Vis­ually the i8 Road­ster is ar­guably more strik­ing than the coupe, up­ping the kerb­side ap­peal as it de­liv­ers a hit of genuine de­sign fresh­ness, with the in­te­gra­tion of the open roof harm­ing not a sin­gle line on the car.

Co­in­cid­ing with the Road­ster’s ar­rival is BMW’S lat­est edrive tech­nol­ogy, which will be fit­ted to the i8 coupe, too. The sig­nif­i­cant change is to the bat­tery pack, which re­mains the same phys­i­cal size but with cell ca­pac­ity in­creased and its en­ergy ca­pac­ity up from 7.1 to 11.6kwh. Pri­mar­ily this is to im­prove the i8’s elec­tric-only driv­ing range (now up to 33 miles, from 20) and the speeds at which you can drive with­out the help of the (un­changed) 1.5-litre three-cylin­der turbo petrol en­gine. But there’s also a mild, 12bhp power in­crease to 141bhp for the elec­tric mo­tor, which com­bines with the three-pot’s 228bhp to give a to­tal of 369bhp. Torque re­mains at a strong 420lb ft.

De­spite an ad­di­tional 60kg to move along com­pared with the coupe’s 1535kg, there’s lit­tle no­tice­able per­for­mance dis­ad­van­tage. The abil­ity to drive for longer and faster – up to 70mph – un­der elec­tric power is wel­come, and with the roof open the sen­sa­tions are height­ened as a new wave of sounds that would nor­mally be drowned out by an en­gine, ex­haust note and tyre noise (the i8 still runs a nar­row front and rear tyre) now wash over you. There’s a hint of For­mula E about it, which petrol-power purists will most likely hate.

Se­lect Sport mode, awaken the in­ter­nal com­bus­tion en­gine, and it and the ex­haust note add a layer of char­ac­ter that brings the sports car out of the i8. The gruff­ness of the en­gine is more small-ca­pac­ity ’60s sports car than large-lunged ’90s be­he­moth, but add in the tur­bocharger’s chuff and puff and the i8 au­di­bly en­cour­ages you to push harder than the coupe ever does.

With new spring and damper rates the Road­ster grips, steers and changes di­rec­tion bet­ter than the orig­i­nal coupe, too. There’s still lit­tle feel from the steer­ing, but the front tyres work much harder be­fore fall­ing into un­der­steer, and with the trac­tion systems off, all four cor­ners flow as one.

It’s no M-car, and it’s cer­tainly no 911, but it is a fine road­ster that de­liv­ers a unique and en­gag­ing thrill that few, if any, can match.

‘With the roof open, sen­sa­tions are height­ened as a new wave of sounds wash over you’

Above: but­ter­fly doors, now frame­less to match the open top, re­quired re­design­ing for the road­ster

Above: there’s lit­tle buf­fet­ing with the roof open and only a slight in­crease in wind noise when it’s closed. Left and be­low: E- Cop­per metal­lic and Don­ing­ton Grey metal­lic are new colour op­tions

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