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The Moto Morini 500 Turbo (prototype),
originally published
in "Bike" magazine, July 1982

presently also published by the British Morini Riders Club
(best screen resolution: 1024 x 768)

20 years after the presentation of the 500 Turbo, the Moto Morini factory website states on the Morini 500 Turbo:

"Morini innovation, one step too much forward".
500 Turbo, displayed at Milan Show in November 1981. The aim was to design a light and agile bike with comparable performance to 750cc. It was never produced for economic reasons (Moto Morini preferred investing in the 350cc off-road Kanguro).


"Bolognese Sauce"

Throughout last year (1981) the residents of a quiet Bologna suburb were regularly treated to the sight and sound of a scruffy black Morini V twin growling along their streets to and from nearby dual carriageways. It obviously wasn't just another 500cc prototype - it's motor appeared to breathe through a collection of washing machine parts, the steering head was loaded with dials and controls, and the tester riding it occasionally fiddled with various knobs on a small electronic control box. Had those same residents visited the Milan motorcycle show last November, it’s likely they'd have failed to make any connection between the slickly finished machine grabbing all the attention on the Morini stand and that ratty test bike tooling up and down the Via Alfredo Bergami back home in Bologna.

The actual development hack
500 Turbo - a far cry from the
beautiful vision of the designers
the dials and controls (6 !) another view

Except that both bikes had Turbo written on their side panels. Morini, the smallest of the Italian motorcycle manufacturers making it’s own motors, just had to be the least likely candidates for the title of First Non Japanese Production Turbo Makers. Committed to moderate production of a standard range of machines of no more than half litre capacity, using 72o V twin motors and a single-pot derivative, the little Bologna factory’s philosophy hardly included assaulting the problem-strewn heights of turbocharging - let alone turbocharging a V twin; something supposedly so difficult Honda only did it to show off. Yet the decisions which sent Morini down Turbo road were taken nearly 10 years ago. In 1974, soon after introduction of the 350cc Sport, Moto Morini began looking at what to do next.

testrider in the streets of Bologna

gabriella morini The Sport itself, designed by former Ferrari engineer and designer Franco Lambertini, was introduced in response to the changing world market for motorcycles. The Italian industry saw the writing go up on the wall in large Japanese characters during the late ‘60s. Morini, having been bombed out in 1943, built a steady base by meeting Europe's post-war demand for small motorcycles with a series of 98cc-25Occ four strokes. Convinced that they'd be unable to continue for long in the face of Oriental competition, Morini and the other Italian marques decided to move into areas where the Japs couldn't or hadn't the technology to compete - exclusivity and handling. Laverda went for super berserk mega muscle triples. Ducati brought out its refined and esoteric 90o V twins, Moto Guzzi did its best with its antiquated transverse V twin, shaft-driven motor. Only Benelli (under Alessandro de Tomaso) tried to take on the Japanese on their own ground with a never-very successful range of fours and sixes. Morini's founder, Alfonso Morini, died in 1969 and the business was taken over by his daughter Gabriella. Two years later the first Morini V twin prototype appeared. At the time, it was an ideal move. The company now had a sporty (read 'satisfyingly loud'), slim, nice handling machine with an instantly identifiable powerplant, production of which was easily within the capacity of its small factory. Add a 125cc single (effectively a V motor with one pot looped off), a 250cc twin for rich kids in the home market and a 500cc V for overseas and their short-term future was assured. So far so good. Morini's thinking from this point on was influenced by several factors. For one thing, three-quarters of its production goes to the home market where anything larger than 380cc has got to be pretty exciting to sell well because of Italy's infamous 35 per cent VAT loading on bikes over that capacity.
Gabriella Morini at her first public appearance in 1970, after she had taken over her fathers factory
Morini were determined to stick with the 72o motor which had become their trademark but at the same time it was clear that hogging Lambertini's design out to 500cc for the Maestro was pushing its ability to produce horsepower in the required amounts.

In any case, the company whose early 175cc four stroke sportsters gave Agostini a racing start in life harboured a deep rooted antipathy towards what the Italians quaintly term maxi motos. In Morini's view, increasing engine capacity and therefore mass to gain horsepower is a route which quickly runs into the law of diminishing returns; power to weight ratios improve sure enough, but rarely fast enough to match the weight increase, while the hassle of meeting noise and emission regulations is something a small factory can well do without.

They even produced a chart to back up the decision to opt for turbocharging. Claiming to show the general trend in maxi moto design from 1973 to this year (1982), it plots a rise in big bore output from around 70bhp to nearly 100, or a 30 per cent increase. At the same time big bikes have become about 16 per cent heavier as a rule, say Morini. The crunch comes when you do the sums and find power to weight ratios on the biggest multis have only improved by 11 per cent (not to mention the fact that Alfonso Morini would turn in his grave at the thought of a 550lb Morini hitting the streets. Looking at conventional solutions lead the company up blind alleys for three years. Until it considered turbocharging there didn't seem to be any way of making an acceptably fast yet light medium capacity machine without designing a new motor. And re-tooling to do that would have affected the whole range. In 1976 Morini finally decided to go for a turbo, aiming for 750cc performance from their existing 500cc powerplant with similar fuel consumption and little more weight than the standard bike. It was an ambitious project not least because the only turbos available at the time were almost useless on engines smaller than two litres but five years later they had their 500 Turbo. At least it looked as though they had. The pre-production model on show at Milan was strikingly different from any previous Morini, but so well hidden behind the bodywork was the rear of the motor that it really could have had a washing machine in there. Only clue to its internals was an incomprehensible full colour diagram laying bare the baffling complexities of the Moto Morini Turbo System.

Closer investigation was impossible with dozens of Milanese pressing in for a better look and the sensible thing to do seemed to go back to the factory some other time. Which is why I was crawling through Bologna a few months later, nursing a hired Fiat 127 through the traffic and mentally composing a book entitled: "101 Uses For A Dead Heathrow Baggage Handler". Yup, on strike again for an increased Smarties allowance or something.

The Morini factory is a surprisingly small concrete building hemmed in on all sides by apartment blocks. It's small entrance hall holds a display of racing machinery from the '50s and '60s plus examples of the current range of models. Design and admin offices occupy the main body of the building, and rolling road testing, final checking and dispatch are in the basement.

After being introduced to Morini's director Gianni Marchetti, Jim Forrest and I were shown round the works before being ushered into the Holy of Holies, the development workshop. If Honda allows two per cent of its annual budget to R&D, Morini allows about two percent of its space. The workshop was about the size of a Jap R&D department's executive washroom although it was obviously ample for the factory's needs, with a ramp leading down to a dyno room in the basement. The Milan Show turbo was on a bench in the centre of the room, stripped of its bodywork and turbo gear. Resting on the floor was a horrible battered object which was none other than the original prototype - now completely knackered after two years and 110,000 km of road testing round the city. If it hadn't been for Big Four interest in turbocharging, which undoubtedly preceded the introduction of really small turbines, the Morini project might still be waiting in the wings. Last November Morini still hoped to find a home grown item for production turbos but it hasn’t materialised and a Japanese IHI unit similar to those used in the Oriental boosters will sit behind the rear cylinder when the Italian turbo arrives in the showrooms.

Having found their turbocharger, Morini still had a bundle of problems to overcome. The two main ones were getting a turbo system to work adequately given the uneven exhaust pulses of a V twin, particularly at low rpm, and secondly Lambertini and his development engineers Paolo Zaghi and Luciano Negroni had to devise special methods of keeping the cylinders cool

while all those hot, compressed gases were being stuffed back into them. Honda, you'll remember, tackled the first of these problems with a complex system of electronic controls, fuel injection and a plenum chamber. Morini's solution was far simpler - simply cut the turbo out of the system at low revs and feed mixture directly from a single 36mm Dellorto carburettor into the inlets.
Simple though it sounds in principle, in practise the Morini system calls for a distributor between the turbine and inlets to direct the mixture flow. This was designed and placed at the end of an intercooler between the turbo and the cylinder heads. At low rpm the distributor closes the mouth of the intercooler and mixture flows across it into the motor. Exhaust gases still spin the turbine but the compressor on the other end of the shaft just pumps the same captive charge of air round inside the intercooler.

When the revs rise higher than a couple of thousand, sensors measuring depression in the inlet manifold tell the electronic control units it’s time to operate the distributor, which opens the intercooler.
Schematic diagram is Morini’s own, showing the importance of the intercooler

Mixture is diverted down its centre to the compressor, then pushed up the outside to the inlets. To avoid momentary fuel starvation as the air already in the intercooler is stuffed into the motor, a small injector nozzle working on pressure from the head of the fuel in the tank squirts juice into the compressor vanes.

The first prototype featured a fully adjustable distributor control on the steering head which allowed Morini to find the optimum revs for the change from normal to boosted breathing. Once they'd sorted this out, there was still the problem of greatly increased heat to overcome. In faint hope that the Universe still contains any sentient beings not already bored to tears by the theory of turbocharging, I’ll briefly re-iterate the sordid details.

A conventional internal combustion engine is both limited and fairly wasteful. It's limited by the ability of atmospheric pressure to fill its cylinders during the intake cycle, then it just pours about 35 per cent of the energy it produces during combustion away down the exhausts in the form of heat and gas momentum. The function of a turbocharger is to harness some of this wasted energy by making it spin a turbine which in turn spins a compressor which stuffs much more mixture into the pots than atmospheric pressure could manage. The result is, say, a 500cc motor which fills up with as much gas as a 750 or 900 and puts out equivalent power and torque. All you have to do is make sure it breathes properly and doesn't suffer from detonation, seizures, melted plugs or any other penalties of overheating.

Cooling the twin-pot mill presented Morini with a major headache, especially as the rear pot is partially masked by the front cylinder. Watercooling was out from the start: the prime reason for adopting turbocharging was to end up with a bike which made the maximum extra power for the minimum additional weight and bulk. So an intercooler was designed into the system from the outset. Made, like all the turbocharging hardware on the bike except for the turbine unit, by Morini, the intercooler is really a simple heat exchanger. Fresh (cool) mixture is ducted down the centre and the hot - around 700oC at max turbine revs - compressed mixture travels up the outside losing heat to the incoming mixture and through fins on the intercooler body. It’s a crude system compared to some of the latest car turbos which actually have a refridgeration unit, but it's the only intercooler on a turbo motorcycle. Cooling the charge also increases its density, making for better burning and less risk of detonation. The intercooler is hidden behind the sidepanels for the sake of neatness which begs the question of what cools the intercooler?
the intercooler below the leg of the testrider and on the left of it the turbocharger, hidden behind an improvised "sidepanel".

The answer is that the eight-piece glassfibre fairing/body unit isn't there just to make the Morini Turbo look decorative at garage parties. When Franco Marlenotti at RG Studies was given a design brief for the superstructure, it included a stipulation that the lower section must function as part of the cooling system by directing air over the cylinder heads and boosting bitz.
the airintakes location of the turbo, right above the centrestand; the intercooler above the rear cylinder

So twin scoops were placed either side of the single front downtube; the right one sending air over the front cylinder head, inlet manifold and intercooler and the other sending air over an oil cooler lying almost horizontally in the opening. A vent between the cylinders spills air on to the rear head while foils on the side panels turn a cooling breeze on to the rear barrel.

Yet more scoops on the side panels are supposed to cool the turbo and a large exhaust collector/silencer cradled in a frame extension under the tail. All this hot air exits through a slatted vent on the tail. Aerodynamic considerations also played a part in the fairing design. It's often said that your average, unfaired motorcycle is an aerodynamically perfect as a flying brick. Unfortunately, faired motorcycles are not necessarily much better. Parting the air in front of the machine is less than half the battle because it’s the drag and turbulence around the rear end and in the bike's wake which does most of the damage. As the airflow breaks up over the bike and rider it creates an area of low pressure holding the machine back, soaking up horsepower which ought to be making it go faster.

Morini's half-fairing is nowhere near perfect but they say the Suzuki RG500-style tail and through-flow of air reduce drag, while the blending of fairing and petrol tank at the front gets rid of unwanted turbulence behind the screen which, is where the air intake for the carb is situated. The crucial factor in top speed though is still weight.

There's still one more unique feature on the Morini turbo. A wastegate control. Lambertini was not content with a conventional springloaded wastegate which opens when exhaust pressure reaches a pre-set level and bleeds off the excess, thus limiting turbine speed and so preventing boost rising to dangerous levels. So yet another electromechanical control was added. Taking it’s instruction from pressure in the outlet side of the compressor venturi, the wastegate control lets boost pressure rise to nearly 18psi as the motor spins to 5,500 rpm before operating the wastegate, causing boost pressure to fall rapidly and level off at 12psi when 7,000 rpm is reached. From 2000 engine revolutions, cracking the throttle open spins the turbo to maximum boost in 1 1/2 seconds. Then the controlled opening of the wastegate cuts boost by 30 per cent.

Morini haven’t fully explained the reasons for this but it seems the wastegate control makes plenty of boost available in the mid-range for 60-70 mph cruising and rapid acceleration but reduces the pressure at high rpm before the volume of hot gas becomes too great for the elementary cooling arrangements to deal with. If the dyno charts I was given are to be believed this doesn't hurt power delivery, which climbs smoothly to its peak of a claimed 70bhp (at the gearbox sprocket) at 8,500rpm – 1,000rpm higher than the peak power point on the standard 500.
After five years’ development and two years’ road-testing, Morini appear to have come pretty close to the target they set themselves. If that 70bhp claim is the truth, they’ve extracted a 70 per cent power increase at the cost of only 10 per cent (This story is from 1982: the present Japanese Superbikes combine 180hp with an own weight of 180kg. It just shows the technical advance over the 20 years).
more weight – the 183kg (403lb) turbo is 16kg (35lb) heavier than the latest standard 500. Unfortunately Morini won't let anyone ride their turbo yet. In any case, when I visited the factory only two Morini turbos existed: one of those was utterly knackered and the other was in bits. It'll be interesting to see how well all the mechanical controls work. Can that complicated arrangement of valves diverting mixture round the
although the article suggests something else, the fancy and beautiful version of the 500 Turbo was not just a model, but was able to ride

system make the Morini as smooth and wellmannered on the road as Honda's computerised fuel injection? A bike which matches the Honda Turbo's smoothness and handling while giving its rider 120 fewer pounds to haul around would certainly be worth all that effort.

If it lives up to the manufacturer’s claims it’ll be at least as fast as the Honda Turbo at 210-215kph (130-133mph) flat out and purportedly infinitely less thirsty at 55mpg overall going up to 60mpg at steady round-town speeds. According to Negroni there's little noticeable ‘turbo lag’ because the intercooler distributor switch allows a head of pressure to build up and come in with a bang when it goes over to boost. When I was in Milan last year, however, Paolo Zaghi said the switch operated at 4,000rpm. If that's correct then you’d expect the motor to be struggling a little as the 8.6:1 compression pistons (as opposed to 11.2: 1 in the standard mill) sucked mixture through the single carb, long inlet manifold and round the sharp bends into the Heron heads.

Yet Morini's dyno charts claim a 10 per cent increase over power at four grand . . . some mistake here, surely. Or maybe it's my total ignorance of Italian. Most of the scepticism which has greeted the turbo stems from the few changes Morini have made to the 500's internals. It runs a stock crank but the low compression pistons are forged. Only other change specifically related to turbocharging is a beefed-up version of the two-plate dry clutch, though the factory has finally broken with tradition and linked the gear selector to a left foot lever. A sixth ratio has been added to the gearbox as well - both these mods appearing on the latest export versions of the 500 (the 500Sei).

To be fair turbocharging doesn't increase mechanical loads on the bottom half of the motor, in fact the softer compression reduces the hammering, though the whole transmission has to relay far more power to the rear wheel. Nor does moving the power peak 1000rpm higher come near the very high revs which racing Morini big ends were asked (but failed) to cope with in the Island some years back. Those forged pistons are there because thermal loads on the top half of the motor are so much higher than in a conventional motor and it's this problem of cooling which is more likely to cause failures than mechanical stresses.

Morini aroused scepticism as much by the way they quietly sprang the bike on a surprised world at the Milan Show as anything else. The Japanese have never bothered to explain just why they'd tackled turbocharging - Honda's attitude seemed to mirror the old Everest climbers’ answers: ‘Well, we did it because it was there’ and none of the machines so far offered to the l press come near to achieving the supposed target of markedly improved performance for minimum cost in weight and fuel consumption. The CX500T ended up weighing more than the 900 four it was supposed to make obsolete but couldn't better it on top speed, fuel consumption (even though the CB900 is appallingly thirsty anyway) or overall acceleration. This hasn't stopped the Oriental turbos receiving so much hype overkill it's hard to decide whether they're going to save to world or bring civilisation as we know it to an end. Then a little Italian factory whose fanatical devotees insist on light, easily serviceable, nimble motorcycles has the outrageous cheek to produce a neatly integrated turbo which, on paper at least, comes nearer to delivering the goods than any other save that developed by mighty Yamaha.
presentation at the Milan Motorshow in 1981 on this page you can see the 500 Turbo prototype, in the factory

But Gianni Marchetti doesn't see arrival on the booster scene as having anything to do with muscle-flexing or joining the tailchase Honda started with their turbo. Morini has been at pains to point out that it started developing it’s turbo in 1976 and it’s possible that if the company had had the clout to persuade a European manufacturer to develop a suitably small turbocharger a few years ago it might have had the world's first production turbocharged motorcycle in the shops.

The Bologna factory decided long ago that there was sufficient demand for 120mph-plus machines to make it worth developing one of their own. Alongside the turbo, Lambertini drew up designs for a 650cc Maestro (the Misstro?) and experimented with different head designs - conceivably we might have been offered something like a 72o version of the Ducati Pantah - but those designs are still on the shelf. Look at it another way. Morini has neither the desire nor the resources to make large, heavy machines. In Marchetti's view, the cash spent on meeting increasingly restrictive noise and emission regulations, on the back-room political infighting leading up their introduction and promotion in the dwindling marketplace would be good money thrown after bad. Or: there's no way 116 Italians can beat Hondawayamzuki.

If and when a few Morini turbos are delivered into the hands of the press for evaluation it'll be clear once and for all how well the factory played its cards. Until then the cynics will continue to claim Morini is merely making a virtue out of a necessity, while more charitable individuals will no doubt reach for their paperback copies of Small Is Beautiful.

Talking of small, Morini decided several years ago that it needed to move out of the moped market. Now it’s not so sure. One project which is nearly ready to go should the moment arise is a 50cc four-stroke motor. It'd be one hell of a follow-up to a 130mph turbo.


cross section of a turbocharger
What does Turbo mean, how does it work?

The exhaust fumes, which leave an engine, still contain a lot of energy, which is usually lost. The turbo, or exhaust-fume-compressor uses this energy. The turbo unit has two separate chambers: The Turbine and the Compressor. The turbine which is placed in the exhaust system and the compressor, which is placed in the inlet manifold (or: on the inlet side). The turbine and compressor are fixed on the same shaft. As the hot exhaust gases stream through the turbine, it will rotate and the compressor will rotate with the same speed. This causes the mixture to reach the cylinder under pressure (turbo pressure). This system, with the exhaust gases as "source of energy", is called turbo-charging. The term "supercharging" is used when the compressor is driven mechanically. Turbo-charging has basically two advantages:
  • It is able to get extra power from a certain engine;
  • Or gets equal power from a smaller engine.
This second possibility is very interesting for motorbikes, because sizes and weight have a direct influence on handling, performance and fuel-economy. We will see weather or not these advantages can be realised on a production bike in the future.

Technical details Moto Morini 500 Turbo (prototype)
Engine Type:OHV, 4 stroke, turbocharged
Bore & Stroke:69 x 64 [x 2]
Displacement:478.cc
Carburation:Single Dellorto PHB36BS
Lubrication:Wet Sump 3 litre
Ignition:Electronic
Horsepower:70.5 at engine sprocket @ 8300 rpm
Torque:47.6 lb/ft @ 5600 rpm
Electrics:12V, 180W alternator
Starter:Electric
Primary Drive:Helical Gear
Clutch:Multi Plate dry
Suspension Front:Telehydraulic fork 5 1/2 inch travel
Suspension Rear:Adjustable gas charged shocks 4" travel
Brake Front:2 x 260mm disc
Brake Rear:1 x 260mm disc
Tire Front:100/90V18 Pirelli
Tire Rear:120/90v18 Pirelli
Weight:403 lbs
Length:89"
wheelbase:57.1"
Mileage:City 52.2 mpg
Max Speed:126 mph
Other nifty bits:
Modular bodywork with integrated fairing. Full instrumentation including speedometer, tachometer, electric clock, turbo boost meter and fuel gauge. Reinforced aluminum swing arm. Cartridge type oil filter (at last!). Oil cooler.
Triple beam halogen headlight.

Parts and/or photo's with a yellow background are comments added by Moto Morini Club Nederland and were not published in the original article. The original article was published in the (British) magazine "Bike" in June 1982.


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