The Other 2.7 Car­rera

We ex­am­ine the com­mon be­lief that the 2.7 Car­rera bound for the US is an un­de­sir­able Porsche… ex­plod­ing a few myths along the way

Total 911 - - Contents - Writ­ten by Neill Watson Pho­tog­ra­phy by Daniel Pullen

How does the Us-spec 2.7 Car­rera dif­fer from the MFI ex­am­ple de­liv­ered to the rest of the world?

No­body likes a killjoy, es­pe­cially an au­to­mo­tive one. If you were a Porsche 911 driver in the mid-1970s, it must have felt as if ev­ery­one was want­ing to take all of your toys away and spoil all of your fun. A com­bi­na­tion of a global fuel cri­sis, soar­ing pump prices for petrol and oil em­bar­goes all com­bined with a sud­den at­tack of conscience as the world woke up to en­vi­ron­men­tal dam­age and ve­hi­cle ac­ci­dent safety. This ended up hav­ing a sig­nif­i­cant im­pact on the Porsche 911 that ev­ery­one loved.

Gone were the beau­ti­ful chromed bumpers, re­placed with what many saw as ugly ‘Fed­eral spec’ Im­pact Bumpers. Even the tra­di­tional Porsche whale­tail wasn’t spared, the Ger­man TÜV au­thor­i­ties de­cid­ing that the trail­ing edge was po­ten­tially dan­ger­ous, lead­ing Porsche to in­tro­duce the soft­rub­ber edg­ing that we know so well to­day.

In Europe, driv­ers were spared many of the en­gine mod­i­fi­ca­tions needed for Porsche to con­tinue to sell the 911 in the US. We re­mained safely en­joy­ing our me­chan­i­cal fuel in­jec­tion throt­tle re­sponse and looked smugly across the At­lantic at the Amer­i­cans and their Cal­i­for­nia law mak­ers, their poor 911 seem­ingly shack­led.

His­tory has not been kind to the Us-spec

Car­rera 2.7. If on­line fo­rums and hearsay were to be be­lieved, a Cal­i­for­nia-spec­i­fi­ca­tion Car­rera 2.7 would prob­a­bly have the up­hill per­for­mance of a Citroën 2CV. Ev­ery­where you could pos­si­bly look gives re­in­force­ment of the jaun­diced view that the 2.7 Car­rera with CIS is to be avoided. Noth­ing to see here… head over to Europe and seek out a 2.7 MFI.

How­ever, for one man, the chance to own a Usspec­i­fi­ca­tion 911 proved to be ir­re­sistible. “When a friend told me about a 2.7 US Car­rera he’d seen for sale, I wasn’t in­spired. Like ev­ery­one else it was some way down my list of Porsche I’d like to own. How­ever, my friend then said, ‘It’s a non-sun­roof Coupe’,” Robin Tit­ter­ing­ton says.

“That got me in­ter­ested. Af­ter all, I could al­ways swap out the en­gine, hot rod it, re­move the emis­sions gear. So I bought it with the ex­pec­ta­tion to change it, tune it, im­prove it.”

“But as I be­gan to put some miles on the car, the en­tire va­lid­ity of their tainted rep­u­ta­tion came into ques­tion. This was a stock en­gine and I was hav­ing fun. Some­thing doesn’t add up here! I’ve driven 1973 Car­rera RSS, nearly ev­ery year of early 911 T, E, and S mod­els and have owned a hot rod 2.5-litre 1971 911 for years – I’m not eas­ily swayed.”

Robin was ac­tu­ally en­joy­ing driv­ing the US

2.7 just as it was. The per­for­mance was cer­tainly dif­fer­ent, but a long way from be­ing un­ac­cept­able. And com­pared with other 911s he had owned, it was ac­tu­ally quite com­pa­ra­ble. Why should this stock Usspec 2.7 Car­rera with all of its al­leged shack­les and com­pro­mises be such fun to drive? Robin tried to find out more.

“I be­gan do­ing some quick re­search, but rather than an­swer my ques­tions it seemed to turn up lots of con­flict­ing per­for­mance data and in­for­ma­tion. Re­views of the 1974 US Car­rera from ‘back in the day’ were over­whelm­ingly pos­i­tive, although the per­for­mance num­bers were all over the map. More re­cent in­for­ma­tion and opin­ion seems pre­dom­i­nantly neg­a­tive. I soon had mag­a­zines and books scat­tered all over my desk­top and had to start writ­ing things down to keep it all straight.”

So it ap­pears that all is not as it would seem with the 1974 US 2.7. Robin’s in­ves­ti­ga­tions ac­tu­ally posed more ques­tions than an­swers. “It seems that there were so many dif­fer­ent ways to record per­for­mance stats in the 1970s. Plus, many au­to­mo­tive mag­a­zines didn’t test with the same de­sire for ac­cu­racy that they do to­day.” Swap­ping be­tween power out­puts mea­sured at the fly­wheel and then also at the wheels seems to throw many fig­ures hope­lessly out of con­text. Robin’s study of the pe­riod data proves to be very in­ter­est­ing.

He con­tin­ues, “For in­stance, Car & Driver’s

Fe­bru­ary 1972 test of the new 2.4-litre Porsche used SAE gross horse­power num­bers, giv­ing the

911 S 210bhp, but in its 1974 test of the Car­rera they switched to the op­po­site ex­treme with SAE net horse­power, giv­ing it only 167hp! No won­der many have come to be­lieve these cars are un­der­pow­ered. In SAE gross units, the 1974 Car­rera US has 195bhp.”

In­deed, one of the big­gest is­sues is the Porsche fac­tory’s own record­ing of sta­tis­tics. Surely it would have the most ac­cu­rate and re­li­able set of data? Well, yes and no. The Ger­man gov­ern­ment re­quired auto man­u­fac­tur­ers to cer­tify pub­lished per­for­mance num­bers so they could be achieved by any sim­i­lar car off a dealer’s show­room floor. This means that

un­like cer­tain Ital­ian su­per­car man­u­fac­tur­ers of the pe­riod who would sup­ply a care­fully blueprinted and op­ti­mised car for test­ing, Porsche ac­tu­ally sub­mit­ted fig­ures that were at the lower end of what was pos­si­ble at the time.

The fac­tory tests also had to in­clude the kerb weight of the car, which was car weight plus a full fuel tank and half of the max­i­mum per­mis­si­ble load car­ry­ing ca­pac­ity of the car. The re­sult­ing num­bers re­flected what could be gen­er­ally ex­pected by the buy­ing pub­lic, not what was pos­si­ble with a blueprinted en­gine and a fac­tory race driver.

By now, Robin was be­com­ing ever more con­fused as his notes on the sub­ject grew and grew. So what was the US Car­rera ac­tu­ally ca­pa­ble of? What were the real dif­fer­ences be­tween a 2.7 Euro Car­rera and the 2.7 CIS? Robin ex­plains that in his view, that’s the wrong com­par­i­son.

“Many at­tempt to com­pare the 1974 Car­rera US to ei­ther the 1973 Car­rera RS or the 1974 Car­rera

Euro which had the RS MFI en­gine. This is not a fair com­par­i­son. The 1974 Car­rera US re­placed the 1973

911 S and Porsche’s goal was to main­tain or im­prove upon the per­for­mance of the 1973 911 S, not to pro­vide a Us-spec Euro Car­rera 2.7 MFI.”

While Robin’s view may be con­tentious to some, he has a very valid point. So when the com­par­i­son is made in that con­text, the rea­son for Robin’s sur­prise at his car’s per­for­mance be­comes ap­par­ent. Both the 911 S and the 2.7 US share the same kerb weight. This is pos­si­bly in­ac­cu­rate, how­ever, as the 1974 car had a larger fuel tank. Even so, the small dif­fer­ence is un­likely to af­fect per­for­mance.

Both cars use the same five-speed 915 gear­box with the same fi­nal drive ra­tio of 4.43:1. To take ad­van­tage of the torque of the larger 2.7-litre en­gine, the 1974 Car­rera US and the 1973 RS both used one­tooth longer forth and fifth gear sets than the 911 S.

In horse­power terms, the 2.7 is down 15bhp, 175 ver­sus 190bhp. How­ever, the 2.7’s ex­tra 20Nm of torque, de­liv­ered at a low rpm, prob­a­bly gives very use­ful per­for­mance in real-world driv­ing con­di­tions, which is ob­vi­ously where Robin is ex­pe­ri­enc­ing his car. Okay, so it’s not Euro Car­rera per­for­mance, but it is far from be­ing poor. In this con­text, Robin’s com­par­i­son makes sense.

How­ever, as we’ve only re­cently been writ­ing about the 2.7 Euro Car­rera in these pages, a di­rect com­par­i­son of the two cars does seem ap­pro­pri­ate. Some dif­fer­ences are ob­vi­ous, oth­ers less so.

Start­ing with the flat six, the ob­vi­ous dif­fer­ence is the much ma­ligned con­tin­u­ous in­jec­tion sys­tem. This dif­fers from MFI in that it fires fuel along each fuel rail ev­ery time the en­gine ro­tates, rather than se­quen­tially as in the case of MFI. Some­times de­scribed as Bosch K Jetronic, this sys­tem is still largely me­chan­i­cal in op­er­a­tion, though it did of­fer enough of an emis­sions ben­e­fit for the car to con­tinue to be sold in the US. To ac­com­mo­date the sys­tem the cam tim­ing needed to be al­tered, and so these en­gines also have dif­fer­ent camshafts. Robin says that throt­tle re­sponse doesn’t have quite the ‘hair-trig­ger’ feel of MFI, but is per­fectly fine once you’re used to it.

The much dis­cussed emis­sions kit fit­ted to these cars ac­tu­ally came in for the 1975 model year. So while Robin’s 1974 car does in­deed have an ‘emis­sions spec’ en­gine, the real penal­ties came in the sub­se­quent years.

Other in­ter­est­ing dif­fer­ences are the way the cars were spec­i­fied at the fac­tory with stan­dard equip­ment. In Europe, nearly all Euro Car­reras were five-speed man­ual as stan­dard, whereas in the US four-speed was stan­dard, with the five-speed be­ing op­tional. Elec­tric win­dows were stan­dard on US cars, to­gether with the rear duck­tail spoiler in 1974, both op­tional on the Euro Car­rera. Add in leather in­te­rior and the Car­rera script on the doors, all of which were al­most cer­tainly stan­dard on the US cars, and you can see that the two mod­els were ac­tu­ally pitched at dif­fer­ent buyer pro­files. The Euro Car­reras were de­signed to re­main ap­peal­ing to Euro­pean driv­ers, whereas the high-spec­i­fi­ca­tion US Car­reras all have a sig­nif­i­cantly higher stan­dard aimed at po­si­tion­ing the car at the top end of the range in 1974.

Robin’s ar­gu­ment that the US Car­rera 2.7 is ac­tu­ally not aimed at try­ing to make an ‘Amer­i­can’ Euro Car­rera is ac­tu­ally a very valid one. In fact, in some ways the US Car­rera is more for­ward-think­ing, Porsche ac­cept­ing the fact that emis­sions reg­u­la­tions were quickly be­com­ing the fu­ture of au­to­mo­tive tech­nol­ogy go­ing for­ward. In this re­gard the Euro Car­rera could be con­sid­ered to be stub­bornly stuck in the past, a le­gacy of a rapidly van­ish­ing time when 12 mpg was con­sid­ered per­fectly fine, ev­ery­one smoked 40 cig­a­rettes ev­ery day and the world just wasn’t con­cerned with safety, health or the en­vi­ron­ment.

Robin sums up the US Car­rera very well when he says, “There are no ex­cuses needed to jus­tify this car or its CIS in­jec­tion sys­tem – it was Porsche’s suc­cess­ful so­lu­tion to main­tain­ing the per­for­mance of the 1973 911 S while of­fer­ing im­proved emis­sion con­trol, bet­ter fuel econ­omy, re­duced main­te­nance and bet­ter re­li­a­bil­ity.”

None of us like reg­u­la­tions that en­croach on our plea­sure of en­joy­ing a flat six, but as the world con­stantly moves for­ward and we be­gin to see the end of the in­ter­nal com­bus­tion en­gine, it’s to

Porsche’s credit that it has man­aged to com­bine the stiff task of reg­u­la­tion com­pli­ance with the im­por­tant job of build­ing cars that we truly en­joy driv­ing for so many years. We all know that one day the end will come for our beloved flat six. The US Car­rera is an im­por­tant chap­ter in the life­time of the Porsche 911, and one that prob­a­bly de­serves more credit than it has his­tor­i­cally been given.

“There are no ex­cuses needed to jus­tify this car or its CIS in­jec­tion sys­tem – it was Porsche’s suc­cess­ful so­lu­tion to main­tain­ing the per­for­mance of the 1973 911 S”

BE­LOW Red Boge dampers were used on Us-spec Car­reras

ABOVE Stan­dard-spec wheels were 6 and 7x15-inch Fuchs

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