The best supercharged road engine?
If the craze for straight-eight engines was almost universally disastrous, as W. B. describes opposite, the story of the vee-eight configuration has been one of mighty success, especially in the USA. Out of that great well of multi-cylinder designs came the Rover SD1’s 3½-litre vee-eight, all-aluminium engine, prompted by Buick engineers and much redeveloped and refined in Solihull. The Editor’s great hero J. G. Parry Thomas, designer of the Leyland (straight) Eight, would doubtless have been surprised at the smooth and fuss-free performance of the current Leyland (vee) Eight. Had he been confronted by Janspeed’s twin-turbocharged Rover 3500, capable of hauling its luxurious five-seater, hatchback saloon at speeds approaching 140 m.p.h. – probably faster than his racing Leyland-Thomases – and with quite uncanny flexibility, effortlessness and quietness of delivery, Thomas would undoubtedly have been totally bemused.
Let me say here and now that this Janspeed turbocharged vee-eight is quite the best turbocharged road engine I have tried. In the February issue of Motor Sport I said in response to a reader’s letter that I was still sceptical about the use of turbochargers on road cars, even after trying recently the Saab and Porsche 924 Turbos. I also said that Jan Odor of Janspeed was about to convince me otherwise, and he has! The simple fact is that this torquey Rover engine is an ideal recipient for the turbocharger treatment and Odor has developed a genuinely “bolt on” kit which is both simple and efficient.
Other manufacturers claim that in addition to outstanding acceleration their turbocharged cars give better flexibility in the lower ranges and effectively as much performance when “off the turbo” as their normally aspirated equivalents. They have failed to totally convince me and while Saab and Porsche have managed to cut out most of the throttle lag which has been the Achilles heel of turbocharged engines, they still have a violent transition from comparatively gentle acceleration off boost to massive surge when the boost pressure builds up. This characteristic is particularly upsetting in conditions of poor traction: if the driving wheels lose grip, boost pressure builds up concurrently with suddenly increased engine revs and you are caught in a vicious circle. On the open road this is rarely encountered, but in town it was one feature of the front-wheel-drive Saab 99 Turbo which I disliked.
The Janspeed Rover Turbo scores so effectively because it has none of these faults, just incredible flexibility and a smooth transition from normal to turbo-boosted aspiration. It will actually start from rest on a level road in fifth gear, will pull about 250 r.p.m. in fifth (with the tachometer needle flicking off the zero stop), feet off the pedals, without stalling or juddering its transmission and then accept full throttle acceleration without a hiccup. In these respects it is a match for the manual XJ-S tested in Motor Sport, April 1976.
There is much more to this Rover’s finesse, but first of all let me say that I am not dealing here with a horrendously expensive conversion demanding a complete engine rebuild, new pistons, camshaft and the like. The engine itself is left totally alone save for drilling a couple of holes in the sump (with it removed, of course!) to accept oil drain pipes from the two American-made Rotomaster Turbosonic turbochargers. When Odor set about designing the conversion he expected to have to lower the compression ratio to at least the Range-Rover level by fitting new pistons, but in practice it turned out that the standard pistons and 9.35:1 compression ratio were perfectly amenable to 7 p.s.i. boost. This contradicts everybody else’s theories on lowering compression ratios – and it works, a tribute to the inherent strength of this vee-eight. As I write this, Odor is intent on screwing up the boost pressure to 9 p.s.i. as an experiment. The bang will probably carry from Salisbury to London!
The turbochargers are mounted one alongside each bank adjacent to the McPherson strut suspension housings. Each sucks through a forward-facing, 2 in. SU carburetter, the Rover’s original equipment fitted with BBW needles to weaken the mixture. The original air-cleaner and inlet air temperature regulator flap valve are cleverly utilised: cold air is fed from the front of the car into one side of the valve and hot air into the other side from a hot air box over the right hand turbo. Long, convoluted heater tubing feeds this air-mix from the air-cleaner to each carburetter. When one of these pipes fell off the air-cleaner it made no difference at all to the engine’s smooth running, so this air-temperature mixing can’t be all that critical. The air and fuel mixture is fed from the SUs directly into the compressor chambers of the turbochargers and thence through steel tubes, interlocked by a small pipe for pressure equalisation, over the top of each rocker box into the original inlet manifold in the middle of the vee. Throttles are linked and synchronised by a rose-jointed cross-shaft over the top of the engine and the manual choke is retained.
The original exhaust manifolds are dispensed with: in their place pipes from each exhaust port feed into collector boxes and thence into each turbo. The waste-gates (blow-off valves) are screwed into the bottom of each box and linked with sensor pipes to the turbo/inlet manifold connector pipes. An exhaust pipe from each turbo links into the standard Rover exhaust system via a Y-piece. Lubrication for the turbos is piped from a T-piece taken from the oil pressure switch and drains back via small pipes into each side of the sump. An oil cooler is included in the installation, as is heat protective material for the bonnet underside.
Ignition timing is reset to 6 degrees static and Champion N9Y plugs or equivalent replace the N12Ys.
In spite of the twin turbochargers this is essentially a very simple system, which any Rover owner with an ounce of engineering sense, or his garage mechanic, could fit. So though Janspeed will fit it at their Southampton Road, Salisbury premises (Salisbury 6955/6) for about £120, they can offer it as a fit-it-yourself kit. I did say “not horrendously expensive”, but it certainly isn’t cheap, either, at £889 plus VAT. Consider it this way: a new Rover 3500 manual so-equipped would cost about £9,000 and at that price there is nothing to compare in smooth, effortless high performance and low speed flexibility with this capacious hatchback. Much as I like the new Saab 900 Turbo, its 2-litre engine can’t be expected to match the 3½-litre’s torque. Odor had intended to offer a similar twin turbocharger conversion for the Range-Rover, but found an installation space problem which has forced him to resort to a single turbocharger system. He expects to try the twin-turbos on an automatic 3500 soon.
Odor claims a 40% improvement on the standard 3,528 c.c. engine’s 155 b.h.p. DIN at 5,250 r.p.m. and 198 lb. ft. at 2,500 r.p.m. This brings with it no deterioration of temperament whatsoever. Cold starting is reliable with the help of plenty of manual choke, continued use of which remains necessary for the first mile or two. The test car’s gearbox wasn’t a particularly good example of the breed, second gear objecting to cold oil for the first few miles. Hot starting is instantaneous and an inclination for the tickover speed to vary matches that of the normally-aspirated editorial 3500.
The retention of the standard compression ratio means that the engine performance unboosted is almost on a par with the standard car, perhaps losing a shade to more tortuous manifolding and leaner mixture. Thus performance remains excellent even on a light throttle. Boost, shown on a neatly-installed facia gauge, comes in progressively on full throttle from as low as 1,800 r.p.m., reaching its maximum as the needle rises to 2,500 r.p.m., when the high-geared Rover really begins to get into its stride. Past though it is, this Rover is not about standing start acceleration, more about mid-range acceleration, which is so superbly rapid and easy. In any case the weather stopped any ideas of serious standing start acceleration tests, as the photographs should make obvious. The 0-60 time is around 8 sec., which isn’t all that much superior to a good standard car, but above that the Turbo pulls off into the distance and there is no way a standard car can so much as look at this one in the mid ranges. Naturally, for best accelerative results it pays to keep the engine on the boil above 2,500-3,000 r.p.m., thus maintaining boost pressure, but on the other hand the flexibility is such that the Janspeed car can be driven like an automatic, using fourth or fifth and rarely is there a need to flick through all five gears consecutively. However hard the engine is punished at low speeds in the high gears there is no sign of pinking on four-star fuel; in fact Odor was forced to tank-up with two-star fuel for one long journey during the tanker drivers’ strike, even he being surprised that the pistons held up on that occasion. The Rover’s vee-eight is pretty hushed in standard form; the turbochargers silence it even more. The SD1’s vee-eight can safely rev. to 6,000 r.p.m., against 5,200 r.p.m. for the earlier Rover engines, but such high revolutions are unnecessary with the Turbo. The 140 m.p.h. maximum is a fairly safe estimate, equating to about 5,300 r.p.m. in fifth on the low profile, 205/60VR x 14 in. Dunlop SuperSports mounted on 7 in. rim alloy wheels. I managed to beat the elements to achieve a genuine 120 m.p.h. on a couple of occasions, reached from 60 m.p.h. in fifth with ridiculous ease, the surge of acceleration still continuing.
The wintry conditions ruined the consumption figures. What can be safely said is that if full throttle, and thus the turbocharger, is used considerably the consumption will be worse than standard; on a light throttle, off boost at steady cruising speeds, it should be better than standard.
I do wish Jan had left the suspension well alone on this particular car, for his modifications, not part of the turbo conversion package, had spoilt this Rover’s manners. His replacement of the self-levelling rear suspension with the 2300 SD1’s conventional type was probably a good idea for predictability on the limit, but the choice of rates for the Koni front strut inserts and Suspension Services modified rear dampers had gone awry. Worst of all were those wide wheels and tyres, the blame for which lies on my shoulders, for Jan, having learned from experience, suggested that the original wheels and CN36 Pirellis should be replaced. With so much snow around I settled for the better grip of the SuperSports, a mistake. Besides lowering the gearing slightly and throwing the speedometer readings way out this combination ruined the steering, ride and handling. I won’t go into full details, for this is not a suspension and tyre setup Jan is offering to the public, but I think it worth warning readers that the Rover does not take kindly to over-wide wheels and tyres, so they would be advised not to waste their money. As for the Turbo transfers down the test car’s flanks and across the screen, they are not compulsory.
Janspeed offer a wide range of turbocharger conversions for cars like the Datsun 260Z, RS2000 and Cortina o.h.c. I even drove a turbocharged 1.4 Mazda Hatchback from Salisbury station to Odor’s works. Jan Odor is obviously staking the future of his renowned and long-lived company on this means of force-fed aspiration and if this marvellous Rover Turbo is anything to go by he is very wise. – C. R.
As this page went to press I read of Sbarro’s Bugatti Royale replica announced at the Geneva Motor Show. This enormous device, described as a 7-litre vee-sixteen is powered by two Rover vee-eight engines linked together in line. Now, if they sent that along to Janspeed…! – C. R.