The ground-break­ing ro­tary still good enough to make heads spin

Wheels (Australia) - - Contents - PHO­TOS NATHAN JA­COBS

WHAT YOU are look­ing at here is a chimera; an alien shape that could never be repli­cated to­day. The low bon­net and cowl would never pass pedes­trian safety leg­is­la­tion now. Those would have to be raised, with fresh air over the top of the en­gine’s hard points. With it, the seat­ing po­si­tion would inch up by a com­men­su­rate amount and that would re­quire a higher roofline. Be­cause of that, the belt­line would have to be el­e­vated to prevent the glasshouse look­ing gawky. That, in turn, adds sheet­metal be­tween the belt­line and whee­larch tops, so the wheels need to get big­ger and heav­ier to main­tain pro­por­tion. And then you re­alise there’s no chance of repli­cat­ing the pu­rity and bal­ance of the beau­ti­ful FD RX-7. This mo­ment will never happen again.

It’s hard to know whether this pleases Wu-huang Chin or not. The Tai­wanese de­signer was part of the Mazda North Amer­i­can design team that won a shoot-out against a home team from Hiroshima. Many as­pects of the Ja­panese pro­posal would end up re­cy­cled into the MX-3, but the Amer­i­can design was some­thing very spe­cial.

“I first started work­ing on the third-gen­er­a­tion RX-7 in 1988,” says Chin. “Soft, or­ganic aero shapes were the trend of the time. Our goal was to de­velop a time­less design along the lines of the leg­endary Fer­rari and Jaguar sports/rac­ing cars from the 1960s. We pic­tured in our minds this car be­ing pre­sented at the Pebble Beach Con­cours 20 years later. How­ever, we did not want to bor­row any her­itage from oth­ers; in­stead we looked at the Cosmo Sport, the first- and sec­ond-gen­er­a­tion RX-7S and tried to continue this Mazda ro­tary her­itage.”

It’s hard to over­state how rad­i­cal the engi­neer­ing was here. The FD RX-7 and Cosmo shared a se­quen­tially tur­bocharged ro­tary en­gine, the first pro­duc­tion cars af­ter the Porsche 959 to of­fer this tech. The en­gine was pushed deep and low into a gap­ing trans­mis­sion cone for a sur­face-skim­ming centre of grav­ity. Long be­fore the com­pany’s ‘gram strat­egy’ on the MX-5, Mazda sought to slice weight out of ev­ery RX-7 com­po­nent. The brake pedal is a tiny alu­minium tile, drilled 12 times to fur­ther shave weight.

Even the spark plug leads were trimmed to save weight. The di­men­sions were kept com­pact; shorter, wider and lower than its pre­de­ces­sor with tighter over­hangs and 20 per­cent bet­ter tor­sional rigid­ity. For some sort of per­spec­tive, the 1230kg Type RZ model is a

yawn­ing 311kg lighter than a mod­ern Supra. As far as con­tem­po­rary bench­marks, the ini­tial power-to-weight ra­tio was within two per­cent of the Fer­rari 348 and two per­cent bet­ter than the alu­minium-bod­ied, and far more ex­pen­sive, Honda NSX.

The fun­da­men­tals were near per­fect. Light weight, a low centre of grav­ity, fully gal­vanised body, alu­minium dou­ble wish­bones front and rear, vented disc brakes all round and a clever Power Plant Frame (PPF) that used high-ten­sile steel to ef­fec­tively make the en­gine, gear­box, Torsen dif­fer­en­tial and rear axle into one unit. An al­lied ben­e­fit of the PPF was ad­di­tional crush re­sis­tance that then per­mit­ted the fit­ment of a larger 76-litre fuel tank with­out risk­ing it be­ing pierced by the diff hous­ing in the event of an ac­ci­dent. To­gether, the PPF, the ro­tary en­gine and gear­box to­talled a mere 374kg.

The twin Hi­tachi HT12 turbo set-up was fiendishly dif­fi­cult to cal­i­brate. It re­quired 67 vac­uum hoses to fi­nally en­sure that there was a smooth han­dover from one to the other, pres­sure bled off the pri­mary blower pre-spin­ning the sec­ondary tur­bocharger to 140,000rpm be­fore chim­ing in at an en­gine speed of just over 4000rpm. Stung by ac­cu­sa­tions of ro­tary en­gine un­re­li­a­bil­ity, Mazda pun­ished the 13BREW en­gine in test­ing, run­ning one unit at 8000rpm for six months while another was ac­cel­er­ated from tick­over to 7000rpm con­stantly for three months. Another test in­volved tak­ing the en­gine to its heat thresh­old and switch­ing it off to see if the tur­bocharg­ers would cre­mate them­selves, over and over again.

The car first launched world­wide in 1992 and there were three sub­gen­er­a­tions of the FD. The Se­ries 6 ran from 1992-1995, fol­lowed by a lightly mod­i­fied Se­ries 7 from 1995-1998. The Se­ries 8 was a Ja­pane­se­mar­ket-only swan­song from 1998-2002 but in­cluded the de­sir­able Type RZ and Spirit R mod­els. Wheels tested the RX-7 in Oc­to­ber 1992, putting it up against the BMW 325i, the Nis­san 300ZX and the Subaru SVX, but as far as dy­nam­ics were con­cerned, it was soon ap­par­ent that it was a mis­match. As Mike Mc­carthy said, “For sheer grunt and go, the RX-7 is streets ahead” and he noted that “the RX-7’S chas­sis dy­nam­ics are mind­bog­gling. Noth­ing here comes close.”

Aus­tralia re­ceived the very spe­cial RX-7 SP in 1995, pro­duced to ho­molo­gate ve­hi­cles for the Aus­tralian GT Pro­duc­tion Car Se­ries and the Bathurst 12 Hour. Only 35 were built in 204kw/357nm guise, and for many, this is still the ul­ti­mate pro­duc­tion FD. Sell­ing here for $99,790, it

was around half the price of the $189,450 BMW E36 M3R and $218,000 Porsche 993 Car­rera RS Club­sport and was a bet­ter road car than both the Ger­mans. With a carbon air­box, a lower diff ra­tio, Kevlar-shelled Re­caros, a huge in­ter­cooler with manual spray function, big­ger brakes and stick­ier rub­ber. That and a 120-litre race-spec fuel tank, a mod­i­fied nose cone and spoiler, 17-inch wheels, a freer breathing ex­haust and a re-flashed ECU. The re­sult was a win at the 1995 Bathurst 12 hour (held at East­ern Creek in that year, with John Bowe and Dick John­son de­liv­er­ing Mazda vic­tory for the fourth year in suc­ces­sion). The car pic­tured here is the Ja­panese mar­ket Bathurst R spun off the back of the wins in 2001.

While the likes of the SP, the Spirit R and the Type RZ are easy rec­om­men­da­tions, vir­tu­ally any manual RX-7 is worth seek­ing out. The Tour­ing X auto is some­what lame, and later Se­ries 8 im­ports with au­to­matic gear­boxes are down 10-15 horses com­pared to their manual equiv­a­lents. Usu­ally the dif­fi­culty is find­ing a rel­a­tively un­mo­lested car. In the FD RX-7’S case, that’s vir­tu­ally im­pos­si­ble. Most own­ers un­der­stand­ably freshen the look of their car with new al­loy wheel de­signs, and switch­ing the twin­turbo setup for an eas­ier to man­age sin­gle turbo in­stal­la­tion is a pop­u­lar con­ver­sion. This helps get rid of the so-called rat’s nest of vac­uum hoses that can spring al­most im­pos­si­ble-to-di­ag­nose leaks.

The en­gine it­self is tougher than the in­ter­net hor­ror sto­ries sug­gest, es­pe­cially if pre­vi­ous keep­ers have been dili­gent with cor­rect-grade non-syn­thetic oil. The oil needs to burn in a ro­tary and syn­thet­ics don’t do this bril­liantly, leav­ing de­posits and var­nishes in the com­bus­tion cham­ber that will wear the apex seals. A high-zinc con­tent min­eral oil that’s changed ev­ery 5000km is the way to go. Get­ting a spe­cial­ist to per­form a com­pres­sion test is also key. The fac­tory ser­vice manual reck­ons on 100psi for each cham­ber, and should you see a re­sult lower than 85psi, you could well be on the road to a re­build.

The RX-7 is broadly heat-in­tol­er­ant, and hot cli­mates can see the rat’s nest and wiring loom be­come brittle and un­re­li­able. Same goes for the en­gine mount rub­bers. Re­plac­ing the fan switch is rec­om­mended for Aus­tralia, as the fan kicks in at 124° Cel­sius, which can be too late to prevent the en­gine swel­ter­ing. Re­plac­ing it with an FC switch causes the fans to run at medium speed from a lower tem­per­a­ture. Coolant should also be dili­gently changed as old, acidic coolant will de­te­ri­o­rate the apex seals.

A good sec­ondary health test of the en­gine is to con­nect a boost gauge to the in­take man­i­fold and have a mate rev the en­gine slowly and cleanly. Check that the tur­bocharger isn’t reg­is­ter­ing more than 10psi un­til around 4500rpm. From there, charge pres­sure will mo­men­tar­ily dip to around 8psi as the sec­ond tur­bocharger spools up and then blip back up to a steady 10psi. Crank­ing up the boost on an FD RX-7 re­quires a lot of ad­di­tional and ex­pen­sive work on cooling. Some have tried go­ing down this route be­fore de­cid­ing that it’s eas­ier to fit a small-block V8 than try to get an FD run­ning high boost re­li­ably. Many RX-7 en­thu­si­asts view this as a par­tic­u­lar sac­ri­lege.

Get a well-sorted car and all of the things that made the RX-7 great back in the day still ap­ply to­day. There’s a fun­da­men­tal right­ness about the de­ci­sions made about the car’s dy­nam­ics that haven’t aged at all. The qual­i­ties of light weight, a charis­matic en­gine, great steer­ing, adjustable han­dling and a cleanly de­signed, driver-fo­cused cabin tran­scend the quar­ter of a cen­tury since the FD RX-7 de­buted.

The years have done noth­ing to erode the appeal of this, the most sen­su­ous of all the Ja­panese bubble-era su­per coupes. The FD rep­re­sents a spe­cific mo­ment in time, but in this in­stance one that seems to have per­pet­u­ally sidesteppe­d the undig­ni­fied rav­ages of the ageing process. It’s a jewel-like exotic which rep­re­sents the last of an ex­cep­tional line.

Model Mazda FD RX-7 (’92 Aus spec) En­gine 1308cc twin ro­tor, twin-turbo Max power 176kw @ 6500rpm Max torque 294Nm @ 5000rpm Trans­mis­sion 5-speed manual Weight 1310kg 0-100km/h 6.5sec (as tested) Price $73,000 then, from $35,000 now

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