Having concentrated its effort on the Formula 1 World Championship, the Renault Board had pretty much left it up to Peugeot to defend the French colours in the World rally championship.
It is in this way that the rally department (active at National level for many years), directed by Patrick Landon, unfortunately has a tendency to operate at a slow pace. This was a bit of a waste, because with a project leader as talented as Jean Ragnotti and a history of competing in rallies it is clear that the Board had all it needed to do as well as Peugeot with its 205 T16.
On the track (F1), they blew it in 1983; and a chance as good as that one might not happen along again.
Whilst the F1 Renault engines have a pretty good potential Lotus could well rescue their honour. This is the only bad thing we have to say about the (Renault) Board.
But lets get back to rallies and this astonishing Maxi 5 Turbo. Hybrid-engined, if it indeed is, the R5 Turbo had caused a sensation during its first public appearance in 1978 at the Paris Show.
At that time, it was only a demonstration mode. But you could see that they really might have something : A small, light R5 with an in-line mid-engine and transaxle gearbox and there you have it.…. something that was going to make ink run and mouths water.
With 160 Bhp for 970 kg, the production version already proved to be quick and well mannered. Its looks were radical for the time, and it out-performed pretty much anything else anywhere near its class. Not leaving an R5 Turbo 2 a leg to stand on the road is an exercise in acrobatics.
In the competition version, it has also demonstrated some amazing possibilities. First big victory in the Monte-Carlo Rally in 81, with Jean Ragnotti at the wheel, of course. The R5 Turbo would then regularly win the French Championship in 81 with Bruno Saby, in 82 with Jean-Luc Thérier and in 84 with Jean Ragnotti. And at the end of 84, Renault introduced us to its Maxi 5 Turbo, still with 2-wheel drive!
To the question that we were all asking: “Why?”, the Board, in its reply to the media, answered: “to make the Maxi 5 Turbo the quickest 2-wheel drive on tarmac”. To our critical mind, hyper-atrophied by professional distortion, we could not let a declaration of this kind pass without giggling. It is the same contest as the first of the “atmospherics” in F1 or the first to use tyres ” X " when in fact it is public knowledge that “Y”, are the best! In bringing home the Tour de Corse title, the Maxi 5 Turbo, after its difficult starts in the French Championship, has proved that it could triumph opposite 4-wheel drives! Bravo Renault Sport, bravo Jeannot! The statement to the media made us smile, but the victory in Corsica earned our respect… and our desire to drive this monster, which beat all that which seemed invincible.
A superb racing animal
In the absence of having the necessary means to proceed to 4-wheel drive, which, evidently, would have been desirable, the rally department at Renault therefore decided to appreciably develop its 5 Turbo “Tour de Corse” (well named!).
The work carried out is really impressive and merits a very detailed description. We’ll start with the engine.
From 1397 cm3 (the cubic capacity of the production car) the Maxi Turbo moves to 1527cm3. This slight increase in the cubic capacity was obtained through a greater internal diameter (77 mm instead of 76) and above all thanks to a new crankshaft with a slightly longer stroke (82mm instead of 77mm). Apart from the increase in the cubic capacity, we note that the new relationship of internal diameter-stroke was calculated to offer the maximum torque at the lowest speed.
The second important modification, is to the cam shaft, giving a much more aggressive profile with a higher lift and longer duration.
The Bosch K-Jetronlc has in effect been replaced by a mechanical injection, still Bosch, but with an ECU devised by Renault Sport and manufactured by Magnetti Marelli.
The turbo is a custom-made Garrett T4/T3 hybrid designed for a boost pressure which can vary between 1.6 and 1.85 bar actual (indicated boost is 2.6bar to 2.85 bar) and is regulated via a bleed control from the dash to the external wastegate.
To cool the air compressed in this way, Renault Sport has developed a splendid air/water cooler with a separate radiator located at the front with the engine water radiator. A water injection system linked to the boost pressure improves cooling and postpones the onset of detonation (the water is injected into the intake manifold).
Of course the engine is also dry-sumped, and forged pistons (containing an oil gallery inside the piston which is made in two halves and electron-beam welding together) which are cooled by oil internally and externally via an oil spray to their underside. The exhaust valves are sodium filled to withstand the extreme exhaust gas temps generated by a Turbo making this much boost. It’s not the F1 engine but we are not very far away from it!
Also on the subject of the engine, we note that the ignition is of an electronic map type “Microplex” (Marelli). When we look at the figures: this engine produces 350 Bhp at 6800 rpm instead of 300 Bhp at 6800 rpm on the previous version “Tour de Corse”. And, above all, it has remarkable torque: 310ft.lb at 5000 rpm (instead of 260 ft.lb at 5000 rpm ).
With a light weight of 905 kg (empty) the Maxi 5 Turbo therefore has a weight-power ratio of 390bhp per tonne. This figure is very respectable but, as the trial will confirm to us, it is the ratio weight/torque that makes your imagination run wild. With 310 ft.lb for 905 kg, we get a value of 350 ft.lb per tonne which is quite exceptional, and significantly more than the Audi, Peugeot & Lancias around it.
On the transmission side, the Maxi 5 has an axle-housing unit with five gears originating from the 5 Turbo. But the clutch and gearbox casings are made of magnesium. Moreover, the design of these casings has been modified with the aim of facilitating easier on-event servicing. Naturally, in this housing there is a reinforced gear train, special bearings and a conical couple of a greater diameter. Its no so easy to put 310 ft.lb down on the ground in a ”normal” gearbox. Three final drive ratios are possible: 9 X 35, 8 X 35 or 9 X 31. For this test, we had 9 X 35 which allows a top speed of 200 km/H at 7000 rpm in 5th. It is noted that the limited slip diff is generally regulated to 45% and the axle housing oil is cooled by a circuit comprising of an electric pump with thermostatic regulation and an aluminium radiator in one of the cars side-pods.
After the engine and the transmission, we will examine the “chassis”- bodywork unit. The aim, as always, was to reduce the weight while increasing the rigidity. According to Renault-Sport, the Maxi 5 gained 30% in rigidity while dropping from 930 to 905 kg. The shell is of steel with a roof panel in aluminium. The doors are also in aluminium while the wings, the tailgate the front panel and the fairing, integral to the pedestal, are in carbon-kevlar! This Renault 5 is not the most expensive car in the World Rally Championship but there was no haggling over the use of good materials.
The roll cage (Matter) and all the “framework fittings” are of course in aluminium. We also note in connection with the bodywork that the windscreen is heated by a micro resistors, the 100 litre fuel tank is a re-enforced rubber bag type, with optional carbon guards.
On this subject, when we mentioned a value of one million francs at the beginning of this article, we were “rounding up” a little, since the basic price is actually about FF 850,000 . But with some “options” and spare parts, it’s better to calculate “large”, knowing that four or five times the same sum will have to be spent to have a successful season in the French Championship with this monster.
With regard to suspension and brakes, the Maxi 5 was also the subject of some good development work. Indeed, drivers like François Chatriot, used to the R5 Turbo original and TdC, immediately noticed the differences between the Maxi and its predecessor were clear: one reacts like a real racing car while the other, less precise, is much more an “improved touring car”, resuming a formula which is a little nostalgic in style.
On a suspension level therefore, we note the adoption of new drawings, the appearance of rose-joints with stronger capacity, a rack and pinion steering gear assembled much more rigidly, anti-roll bars with rose-joints, two-stage springs (tender & main) much more scope for adjustment, in particular of castor). We also note that the shock absorbers are from Bilstein, and the progressive rubber axle bump stops are by Kleber. The brakes are 300mm by 28mm on the front and 280mm by 26mm on the rear. Alloy 4 pot callipers on front & rear. On the front, the discs are air-cooled by a flexible hose of 80mm ID, on the rear, this same cooling hose actually cools the rear wheel bearings !
Naturally, the distribution is adjustable at the front and back from the cockpit by means of a lever-driven proportioning valve near the hand brake, very useful in a rally for the hairpin bends, and is of course hydraulic.
We end the description with the wheels. Going from 1397 to 1527 cm, the R5 Turbo has actually, after application of the correction scale, gone from 1956 to 2136 cm. Crossing the 2 litre cubic capacity threshold, it benefits from the right to use broader rims. Not a negligible advantage if you have such power and you know that it was just this narrowness (everything is relative!) of the back wheels that constituted one of the problems of the previous R5 Turbo.
So, the Maxi got rims of 8 x 15 at the front and 11 x 15 at the rear (instead of 7 x 15 and 9 x 16.5). The, unchanged, front tyres are Michelins in 18/60 x 15, while the rear ones are from now on 29/61 x 15 (29 meaning 29cm in tyre cap width).
This assembly should however evolve to make room very soon for 20/59 X 15 at the front (a little broader and a lower size) and 29/64 X 15 at the rear (same width, but higher size, therefore better mobility and greater resistance to heating).
Dashboard by Boeing !
Rally car dashboards have always impressed me, but I have to say that the one in the Maxi 5 has left me somewhat perplexed. While waiting for the track to dry and with François Chatriot as a guide, we visited “the office"...
On the left of the steering wheel there are four small dials: water temperature, oil pressure, oil temperature and battery charge. On both sides of the steering column: the speedo and the rev-counter then the four new dials, two of which are unused and the other two are assigned to the fuel gauge (100 L with graduations every 20 L) and to the clock. Further to the right we find the fuel pressure and the aircraft specification boost gauge showing both current atmospheric pressure and actual boost pressure. Next to the boost gauge is the famous small “miracle knob” which allows the driver to modify the boost whilst driving. This in turn makes the ECU deliver more fuel and therefore increase the power.
Above the boost gauge we find a light that indicates that the water injection is working (it starts at 2.2 bars) and a small dial which indicates the air intake temperature (generally in the neighbourhood of 30°).
Among the backlit dials we find, close to the rev-counter, an indicator showing the non-functioning of the water injection and an indicator for the gearbox oil temperature.
We also find of course the whole panoply of fuses and relays of all types, long-range controls, the electric fuel pump, the pump for the gear box cooling circuit, fans 1 and 2 etc... not forgetting the Jaeger electronic tripmaster and the Philips VHF radio.
Finally, during this test, the driver door seems to be lined with a precious materials ! After enquiries, it just turns out to be a spare ECU. So there you have it, we have told you everything about this Maxi 5 Turbo. We could add some thoughts with regard to aesthetics. The Maxi 5, although sometimes nicknamed “le break” by its drivers, in reference to the rear wing, is unquestionably aggressive, surprising and in spite of everything, is rather likeable. When you contemplate it face-on, with its monstrous integrated long-range lights you could ask yourself, what remains of the Renault 5? Just the two small main headlights lights with their oh-so-soft look.
For the rest, this R5 is just air valves, flaps, ailerons, wing expanders, rocker panels, etc. The car is certainly not aerodynamic, but the Maxi 5 has been carefully put through the wind tunnel in order to reduce negative lift front and increase rear downforce. Thanks to the splitter provided for this purpose on the front spoiler and on the gurney flap on the rear aileron. It is a very sophisticated aileron, by the way, since it directs a flow of air carefully and artfully towards the engine. Air is drawn down the rear-part of the tailgate (which is hollow) and is pressurized directly into the air-filter and from there onto the Turbo.
Clearly, the problems of cooling have been the object of splendid work. Unfortunately, this did not save François Chatriot from seeing his first Maxi Turbo perish in a fire at the Rally des Garrigues. But it is unfortunately obvious that, for rally cars with turbo engines, the risk of fire is great, notably when coming off the road.
THE TEST
The track still wasn’t dry, for the good reason that it was still raining on the Montihéry motor racing circuit, and so we were going to have to test the Maxi 5 in these conditions!
I must thank François Chatriot, as well as all his team, for their trust and even their courage: To entrust a racing car to a journalist for a test in the middle of the season, is a risk few teams would undertake. The road circuit at Montihéry in the rain with such an engine was at first not very engaging. But, all said and done, a rally car must adapt to all conditions… and the driver too! In order to get used to the monster a bit more, I decided to start with a quick installation-type drive with François Chatriot as co-pilot.
During these first few runs I could already note two things. First, the driver position was excellent, secondly, the engine showed itself to be powerful. Flexible, quiet... surprising! But, enough of beating about the bush, it was time to get serious. 350Bhp, 310 ft.lb and 900 kg : all this on a wet skating rink, this wasn’t going to be easy.
Luckily, the rain Michelins are very reliable and the engine proved itself to be extraordinarily flexible and docile. Unfortunately, being used to a lot more brutality with the engine of my Peugeot 505 turbo (more powerful, it’s true) I was literally dumbstruck by the flexibility of this little 4-pot atmospheric engine! From 3000 rpm its starting to come on cam. At around 4000 rpm, it already feels very strong and you have now reached the point of max torque on the old engine (TdC) with much more yet to come.
When you get to 5000rpm, its not necessary to consult the instructions to find out where max torque is ! I can assure you that you can feel it ! From 5000 to 7000 with its 310 ft.lb of torque, its short final drive and its light weight, the Maxi 5 literally flies from one bend to the other. It’s very impressive. Especially on a bevelled and soaked road circuit!
