In which editor Steve Ben­nett gets be­hind the steer­ing wheels of a trio of Hartech's large-ca­pac­ity engine con­ver­sions, and finds their im­proved pulling power very much to his lik­ing. Stand by for Project Over­size… Pho­to­graphs by Antony Fraser

911 Porsche World - - Big-bore Engines -

When it comes to torque ver­sus revs I am def­i­nitely in the for­mer camp. High-revving en­gines do have a cer­tain ap­peal, par­tic­u­larly the small-ca­pac­ity scream­ers – like Honda's VTEC units – where all the power hap­pens at once, in a nar­row power band. But cru­cially they rarely seem that fast out in the real world, where a lin­ear power de­liv­ery feels just that. Or, to put it an­other way, they are rather flat as you wait for a dis­cernible peak in the power curve some­where near the red­line. Such en­gines work best in small, light­weight sports cars, but largely they have dis­ap­peared, killed off by emis­sions and the rise of tur­bocharg­ing in both diesel and petrol en­gines, plus emis­sions-friendly ‘tall’ gear­ing.

Not that Porsche en­gines have been lack­ing in torque in re­cent years. The most pop­u­lar sizes at 3.4, 3.6, 3.8 and 4.0 litres have suf­fi­cient ca­pac­ity to pro­duce that 'big' engine feel, which is what you no­tice in road driv­ing. They can be im­proved upon, too, but not sig­nif­i­cantly, un­less you start to play around with camshafts, throt­tle bod­ies, engine man­age­ment sys­tems, and so on. In­deed, take that route and you might see some sim­i­lar gains to Hartech's big-ca­pac­ity en­gines, as tested here. The dif­fer­ence is, though, that you will have spent a great deal more money, and you will have some­thing that feels raw, noisy and de­cid­edly non- fac­tory, which isn't what most peo­ple want. No, the beauty of Hartech's con­ver­sions, is that they feel and drive like stan­dard Porsches, which is surely the ul­ti­mate ac­co­lade for any mod­i­fied car.

Here at 911 & Porsche World we know this be­cause a few weeks ago we paid a visit, mob-handed, as it were, to Hartech’s labyrinthine but well-equipped premises in Bolton, Lan­cashire. While tech­ni­cal guru, Chris Hor­ton, was get­ting the low­down from Barry Hart, I was get­ting the seat-of-the-pants driv­ing ex­pe­ri­ence with the help of a num­ber of mod­i­fied-by-hartech ma­chines: a 996 Car­rera 2 3.7, up from its orig­i­nal 3.4 litres; a 996 Car­rera 2 3.9, in­creased from 3.6 litres; and a Cay­man ‘S’ 3.9, up from its orig­i­nal 3.4 litres. Cor­re­spond­ing stan­dard cars were on hand, too, with their own­ers, who also drove the Hartech cars. It was, as you can imag­ine, a fas­ci­nat­ing ex­er­cise. Just a shame about the sud­denly very au­tum­nal weather…

As a 3.4 996 Car­rera 2 owner my­self, I was in­trigued to try the 3.7 con­ver­sion first, against the stan­dard 3.4-litre 996 Cabri­o­let be­long­ing to Alex Yates. As ex­pected,

As a 3.4 owner my­self, I was in­trigued to try the 3.7 con­ver­sion first

Alex’s car felt more than fa­mil­iar, with the 3.4's typ­i­cally wide power band. For all its is­sues, it's a lovely, smooth, flex­i­ble unit. It’s not lack­ing in torque, ei­ther, but more of this valu­able com­mod­ity is never a bad thing, par­tic­u­larly if – as here – it is pro­duced lower down the rev range.

Hartech's demo 996 3.7 is a 1998 car, but it has weath­ered well, given that it’s now 20 years old. Pre­dictably it feels more like a gen 2, 3.6-litre 996, and com­pared to the stan­dard 3.4, the power builds ear­lier, be­com­ing mean­ing­ful from 2500rpm and mak­ing progress all the more ef­fort­lessly swift, with­out need­ing to run the engine into the higher rev range – un­less you want to, of course. And if you do, then it’s just as smooth as the stan­dard 3.4-litre, with peak power ar­riv­ing at much the same point. The dif­fer­ence is, as with the torque, there's more of it. In­deed, if you look at the graphs, the power and torque curves are re­mark­ably sim­i­lar in terms of shape, which is very much what you feel on the road. And for the record, the 3.7 con­ver­sion is mak­ing a max­i­mum of 325bhp be­tween 1500rpm and 7500rpm, an in­crease of nine per cent. But what you're re­ally feel­ing is the torque, which goes from 237lb ft be­tween 1500rpm to 7500rpm to 283lb ft, an in­crease of fully 20 per cent.

Time to try the 3.9-litre 996 now. Again it's a C2, but a 3.6 gen 2, which this time be­longs to Hartech di­rec­tor and ser­vice man­ager To­bias Hig­gins. It's a Tip­tronic, and we have a 996 C4S Tip on hand for the stan­dard com­par­i­son, which from the seat of my pants feels, well, stan­dard. That is to say that over the gen 1 3.4-litre 996, there is ap­pre­cia­bly more torque, which is what you would ex­pect from an­other 200cc. And the 3.9 Hartech engine? Well, the ba­sic facts are these: power is up from 320bhp to 347bhp, while torque in­creases from 273lb ft to 313lb ft be­tween 1500rpm and 7000rpm. Put into a dif­fer­ent per­spec­tive, and per­haps a more real-world one, for both power and torque that's a 14 per cent in­crease be­tween 3000rpm and 6000rpm.

And how does it feel? Mus­cu­lar! Us­ing the Tip­tronic in man­ual mode in third and fourth gears high­lights the engine’s power curve,

Us­ing the Tip­tronic in man­ual high­lights the engine’s power curve

and again the ex­pe­ri­ence is mir­rored by the num­bers. Af­ter all, you're not go­ing to mis­take an ex­tra 14 per cent of power in that real-world sweet spot. It's there, you can feel it and you can ex­ploit it, but with­out hav­ing to work the engine's up­per rev range. Again, that's power from ca­pac­ity and torque, rather than power from revs.

And so to the Cay­man ‘S’, which Barry Hart reck­ons to be the most in­ter­est­ing and ap­peal­ing con­ver­sion here, be­cause un­like the other two it has jumped an ex­tra 500cc (as op­posed to 300cc for the two 996s), which has re­sulted in a mas­sive im­prove­ment in breath­ing at low revs, com­pared to the 3.7-litre engine, with which it shares the same stroke. Dig­ging into this fur­ther and at 2000rpm both torque and bhp are some 48 per cent higher. Yes, that's worth a dou­ble take! This tails off to 20 per cent at 5000rpm and 16 per cent at 7000rpm, but who's com­plain­ing? In terms of power the 3.4-litre to 3.9-litre con­ver­sion goes from 303bhp to nearly 352bhp, be­tween 1500rpm to 7000rpm, while torque – as you would ex­pect from the above fig­ures – jumps from 250lb ft at 4500rpm to 320lb ft at roughly the same rpm.

Study the graph for the full low­down, but those dif­fer­ences be­tween the stan­dard and mod­i­fied power and torque curves are repli­cated on the road. Be­tween the stan­dard Cay­man ‘S’ on hand and the mod­i­fied 3.9, the dif­fer­ence was all too clear, aided by the fact that each car was a man­ual, giv­ing max­i­mum con­trol over the two en­gines. The 3.9 has power ev­ery­where, start­ing with that mas­sive surge from low rpm, which feels like an elec­tric mo­tor has joined the party or, as Barry de­scribes it, rather like com­bin­ing a low­pres­sure and a high-pres­sure turbo.

Cer­tainly the Cay­man hits the sweet spot, thanks to that ca­pac­i­tyver­sus-stroke com­bi­na­tion. Yes, it's fast, but it's the way that it pro­duces the power that makes it so suit­able as a road-car engine. The same ap­plies to all the con­ver­sions, but more so with the Cay­man. Its broad spread of power and its in­cred­i­ble flex­i­bil­ity give you op­tions. Over­rid­ing mem­ory? A long, straight, up­hill drag and, even in sixth gear, the Cay­man sim­ply de­mol­ish­ing it.

An ab­so­lutely fas­ci­nat­ing ex­pe­ri­ence, then. And a po­ten­tial cherry on the cake for any­body pon­der­ing an engine re­build. I mean, why wouldn't you? Right now, I just can’t get out of mind the prospect of that 3.9-litre engine sit­ting in the back of my gen 1, 3.4-litre 996. How about it, Barry? PW

Ben­nett at the wheel of Hartech’s ca­pac­i­tyen­hanced, 352bhp Cay­man ‘S’. Both power and torque have been in­creased by 48 per cent, with torque at 320lb ft at 4500rpm

Us­ing a gen 2 3.6litre 996 as a start­ing point, ca­pac­ity in­creases to 3.9 litres and power to 347bhp, with torque in­creas­ing from 273lb ft to 313lb ft

Hartech’s 3.7-litre con­ver­sion as fit­ted to a lovely, early 996 makes 325bhp, and 283lb ft of torque, which is an in­crease of 20 per cent

Rolling-road graph for the Cay­man 3.9 con­ver­sion clearly demon­strates a 48 per cent in­crease in both power and torque. Note how the curves have es­sen­tially the same pro­file for both stan­dard and mod­i­fied en­gines

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