LARGER THAN LIFE
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
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