ROTAX KART LINEUP TEST

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sodi kart celesta

42 Vroom international magazine

track testROTAX MAX RANGE

praga speedy birel ry 30

what a treat

sodi kart celesta mach 1 a03 haase edox

43Vroom international magazine

VROOM INTERNATIONAL N.141

We tried all the karts that

were protagonists of the

Rotax Finals in Portimao, on

the same track that

saw the finals of the

international Grand

Finals; from the Praga

Micro to the Haase DD2

Masters, going through

Birel Junior, Sodi Max and the

Mach1 DD2. report: m. Voltini - photos: a. bonaga



sodi kart celestapraga speedy birel ry 30




does not let down: 28.5 horse power for the basic “barycentral” version FR Max (because the DD2 has another 4 more) guarantee such a thrust that you won’t miss the other classes or craving better performance on the track.

IN ALGARVE NEXT TO THE AUTODROME Before looking at the karts we tried out one by one, let’s say a few words about the track where the test was carried out: The track at the Kartodromo Internacional do Algarve (KIA) is in Portimao next to the well-known car racing circuit. So, just like the car circuit and the bike circuit also, the karting circuit has some very interesting characteristics. You start with the starting straight which connects to the various parts; it’s really long and “conditions” drive ratios to be used. Then there is a strong braking point with a double turn; with two alternating hairpins and fast turns for accelerating, till you

get to a very narrow part that precedes the two 90° turns before the finishing line. It is quite a technical circuit, where you need long ratios that need great care, also being careful not to let the engine drop too much in revs in the more technical parts. Another article, a more complete one on the track, its turns and general characteristics has already been published in Vroom International, the September 2012 issue. For this test, four other drivers who had just raced the final gave us a hand:

FOUR PLUS ONE - At the Kartodromo do Algarve in Portimao there are four Rotax Grand Finals protagonists to help our tester: Alejandro Jurado (right) with the Praga Micro, Bruno Borlido, Louie Pagano and Alan Rudolph testing the Junior, Max and DD2 respectively.

his year too the international Rotax Max Challenge Grand Finals have been galactic as far as karting is concerned, more than 270 drivers (plus about thirty kids from the Micro class, which has raced

a national race) who came to the track of Algarve in Portimao. This is a top level event that has been going since 2000 (first edition), that you can read about it in the previous issue. Here we want to underline that Vroom was present at this meeting too, but not just as a spectator: we took advantage of the situation and tested the karts used for the event, so that we could give you an idea of the material used and the differences between the various classes, not just the difference in regulations and mechanics but also in drive style.

ONE FOR ALL AND ALL FOR ONE A brief introduction is needed to follow this topic better: thanks to the collaboration with some chassis manufacturers, in the final it’s the organisation that supplies karts for all the drivers! Each class is allocated to a specific brand so karts are the same for each driver: another thing that balances and underlines the drivers’ skill, one of the many reasons why this program is much appreciated. So, on this occasion, the karts for various classes present were divided as follows: Praga chassis for the Micro class, Birel for the Junior, Sodi Kart for Max, Mach1 for DD2 and Haase for DD2 Masters. We will look at and deal with each class in an appropriate space dedicated to the test for each kart, but in the meantime don’t forget that in each case they use a Rotax FR Max engine. It is the same group of

engines, the same displacement of a 125 cc for all the classes present, from the Micro to the Max. Only the DD2 is different because the base has a gear box with two ratios and drive is without a chain, the axle gets motion directly from gearbox through which it passes. But in all the other cases the drive unit is practically the same: only a few details change, that is, the presence or not of a pneumatic valve on the exhaust, restricting flanges on the induction and exhaust for reducing power in the smaller classes and so on. However, the basic structure is the same as that, which has been appreciated over the years for being robust, reliable and long lasting – they say there’s an interval of 1000 (one thousand) hours from one overhauling to another for the Micro and Mini classes... – so overall economical, also connected to a certain power that

T Alejandro Jurado for the Micro, Bruno Borlido for the Junior, Louie Pagano for the Max and the multiple champion Alan Rudolph for the DD2, they not only gave us a hand with the pictures but also for the exchange of opinions on drive performance for the karts they used and the general characteristics of their respective classes, which you can find next to our opinion concerning the individual kart tried. So, now it’s time to proceed with the study of these karts: enjoy your reading!

TRIED THEM ALL We tried them all; all the karts used for the Rotax Grand Finals. No, not all those taken to the track for the drivers, more than 300, here aligned on the straight at Portimao, but only the single models that each manufacturer supplied for each class.


track testROTAX MAX RANGE - KARTS


#1 PRAGA SPEEDY no supplementary bars and also camber ands caster adjustment of the spindle. The body is Csai (22-CH-14) homologated and has 28 mm diameter tubes, while axle used is 30 mm. There is however a braking system with automatic clearance recovery.

A TEST ... INDIRECT At this point, perhaps it is better to talk about how we checked actual kart response on the track. However, bear with us, I am sure that you understand, we really thought we wouldn’t have a chance of driving it, obviously it was more for the size factor not age or personal pride. For this reason we move

to the Junior kart in the next pages, after telling you that Alejandro Jurado had the pleasure of racing it and have a lot of fun with it.

Micro for younger drivers

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During the final in Portimao we also saw the Micro class race, but we

could say it was an “added” event: in fact, existing norms that do not allow drivers who are under 13 years of age to compete in international events outside their home country, also apply in this case. But, in any case the class for younger drivers was present for a race reserved for Spanish and Portuguese mini-drivers, a sort of super-mini-final. The same wasn’t set up for the Mini class, always Rotax 125 FR powered, hence we are not taking it in consideration in this

column.

FROM 8 TO 10 YEAR-OLDS WITH ABOUT 7 HORSE POWER The Micro class is reserved for young 8 to 10 year old drivers and it is always powered by a Rotax FR “full displacement” engine, however, it is particular because it reduces power to just 6.8 hp: well, just a quarter compared to a “basic” reference engine. This has been obtained by means of various restrictions and using a specific exhaust system. This way the engine works

so little that it requires a much smaller cooling system, the radiator is half the size of those normally used. Furthermore, it easily goes for one thousand (1000) hours from one overhauling to another: brilliant, isn’t it? The chassis used in Portimao for this class was a Praga Speedy model. In accordance with the philosophy of this specific class (but of all the Rotax series) the kart is rather simple without any sophisticated solutions that are too difficult for the drivers it is aimed for. Therefore, there are not too many solutions concerning set up: there are

FULL DISPLAcEMENTAlso for the younger drivers the Rotax FR maintains 125

cc displacement, but power is reduced thanks to the exhaust,

which is different.

birel ry 30 sodi kart celesta mach 1 a03 haase edox

praga speedy





#2 biREl RY30this choice, max speed is reached as soon as you have gone over the finishing line, in the slower turns you can actually feel how much the engine is working, so drive has to be very accurate and smooth trying to drop revs as little as possible. From this point we think that the class undoubtedly forms and rewards drivers with a millimetric drive. The chassis helps from this point: it is precise on the steering wheel, rather free behind so

that it does not “block” an engine that is already working hard and in the end with a very well balanced braking system between power and adjustment, so as to allow braking, which is firm but does not unbalance the kart before turn entry. Well, also the Mojo D1 tyres are a good combination, compound is quite hard and with the cold track it did take a bit to warm up.

Junior: a great step forward

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A s we were saying, jumping the Mini class, not present in the

Rotax Grand Finals event, you get to the Junior. This is already a good class as it mounts a normal chassis and is powered by a Rotax FR almost in its “normal” configuration. Then again it is destined for drivers aged between 13 and 16. So, as we well know the driver’s height is basically the same as the height of an adult.

JUST THE EXHAUST MISSING In this configuration, Junior, the Rotax 125 FR engine is the same as that for the “Senior” class except for one visible factor: a pneumatic valve on the exhaust.

There isn’t one on the Junior, where, in fact, you have a specific cylinder that together with a limiter set at 12,500 revs limits maximum power to 20.4 hp. So the cylinder is the only difference, and if you want to go on to the next class there is just one component to change to adapt the engine. As for the chassis, it is a “normal” Birel RY 30 ST that is normally used for direct drive classes like the KF3. So, there are no front brakes but there are the usual foreseen adjustment settings, from cams for adjusting camber and caster accurately, to the front supplementary bar (standard on this body, while the rear one is an optional). As the model initials

suggest, for the chassis 30 mm diameter tubes are used, bent and welded following a traditional design with double curve at the sides of the tank, while the axle is 50 mm in diameter.

FOLLOWING RATIOS Driving this Junior, it is easy to see that everything is adjusted and works according to final ratio. The fact that the rev limiter acts fairly early on together with the unending straight (even if it isn’t so “straight”) of the Kartodromo do Algarve, makes it necessary to use a “long” crown (73 teeth compared to 76 for the Max senior) and on the mixed part of the track you do feel this quite a lot. Even if with

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Driving this Junior, it doesn’t take long to understand that everything is set according to final ratio

LIKE THE BIG GUYS - In the Junior class they use chassis without q limiter. The same level as KF3 that is, with all the adjustments including the “fine one” camper and caster.

sodi kart celesta mach 1 a03 haase edox praga speedy

birel ry 30

my opinionBRUNO BORLIDO - Team Portugal, National Junior Champion and Rotax Champion 2012, born in 1994: Junior Max class“The Junior Max has good traction at low speed, in the mixed part of the track you have to drive accurately or you risk dropping speed. The Birel is well-balanced not too loaded at front or rear. It certanly helps performances for drivers who don’t know the rather difficult track in Portimao.”





A BALANCED MODEL The passing from Junior to Senior class makes you see the fundamental characteristics of the Max class with some immediacy. You see how the Mojo D2 tyres, softer compound (but always on a scale that tends towards hard), gets to the right warm up point quicker. The Sodi chassis is quite neutral in response, tending to be “lighter” at the rear but not too much. Engine yield is homogenous thanks to adequate gearing that manages to deal with slow

turns but also with more power along the starting straight. The valve on the exhaust helps here too because it offers more elasticity in delivery. To conclude, summing up all these characteristics produces a balanced drive that is just as good as any “traditional” kart. Thanks

also to a braking system that – as in many other cases – is

adjusted with a pin so as to get less leverage, requiring more pressure on the left pedal but creating less risk of blocking during braking due to the tyres mounted,

not really too soft.

A Max that’s maximum

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So, we get to the baricentral class of the Rotax Challenge: the Max

“Senior”, sometimes it is so called more to set it apart from the Junior than for anything else. It is this class that contributed to make the usual 100 cc obsolete and looks down at today’s KF despite the different official titles. In fact, in several countries it has become the most important national karting category, in all the races, and not tied to the role of single-make trophy event as it is in Italy.

NEARLY 30 HORSE POWER “EASY” Ever since the Rotax FR 125 Max was introduced it has only had some

changes in detail that regarded more manufacturing/production requirements more than anything else. The basic project is a good one that derives form a tested motorcycle engine. Among its main characteristics we have direct drive timing with centrifugal clutch, electric start, integrated water pump (radiators are mounted directly onto the engine) and a balancing counter shaft; each element has a reason for being there and don’t give any problem at all, differently to other classes that has got the idea from (imperfect copying) Rotax. Having a pneumatic valve on the exhaust and limiter setting at 14,000 revs allow you to get 28.5 horse power, more than

enough to get good performances without overstressing the engine. In this class they have used, on occasion of the final in Portimao, the Sodikart Celesta chassis. It is a frame made with 28 mm longitudinal members and cross members 30 mm in diameter, with a fourth removable lateral tube (usually present together with a front “balancing bar”). This frame has been made by the French manufacture let’s say, for universal use, that is, to be used with tyres made of various compound and for nearly any situation. The axle is 50 mm and it has a cam adjustment with just 4 positions for camber and caster, set here to get maximum setting.

#3 SoDiKARt CElEStA

Among its most important characteristics we have direct drive centrifugal clutch, electric start...

THE BASEThe Max “Senior” is the barycentric kart of the Rotax

Max challenge maintaining all the characteristics of

simplicity: there is a valve on the exhaust,

but front brakes are not allowed.

birel ry 30mach 1 a03 haase edox praga speedysodi kart celesta

my opinionLOUIE PAGANO - Team UsA Driver, skUsA and PanAmerican Challenge 2012 vice champion, born in 1991, senior Max class.“I was a bit nervous at the start, but after a few laps I gained confidence with this track, which I found fast with one or two critical points. The Max FR125 has character, no hesitation in delivery and works well both in the mixed part and fast part of the track. The Sodi Celesta is perfect for this class; it’s neither too stiff nor too soft. It’s an ideal combination and reacts well both on wet and dry.”





#4-5 MACH1 A03 & HAASE EDoX

DD2 One class for two

To conclude here we are with the class “that couldn’t be more Rotax

than what it is”. DD2. It is for a type of karting that has been practically invented by the Austrian factory, seeing that it has unique characteristics compared to those found within the karting panorama. We don’t refer just to the particular rear bumper that was thought to reduce risk of flying in case of two karts touching wheels, but also to the engine, which to define it as “particular” is really saying something. An engine that due to its technical characteristics was brand new when it was presented and is still one of its kind. And on this occasion, for the final in Portimao has powered two classes, the normal DD2 and the Masters,

distinguished by the age of its participants.

TWO GEARS AND NO CHAINLet’s see what this unusual engine, the Rotax DD2 is like. To start with, there is a gear, but jus two ratios and connected to the centrifugal clutch; moreover the axle goes directly through it and goes as support on the right hand side. This solution has caused one or two problems for chassis suppliers – you must have great manufacturing accuracy to maintain axle alignment – but it avoids all problems connected with having a drive chain. And it is not just that grease dirties everything around. As for gearing, there are two pairs of gears that can be interchanged on the right hand side

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of the engine. As for the rest, there are the same components and the same characteristics as the Max, but power rises to 32.6 hp thanks to there being less need to pull at low revs. In this case though, we have to talk about two chassis: in fact, the DD2 has used the Mach1, while the Masters has used the Haase, both specific for this Rotax class. The Mach1 FIA9 A03 stands out for its characteristic, it is possible to add two supplementary bars at the front (in this case they have mounted the one which is further back), for the rest, design is quite traditional made with 30 mm tubes. The layout is similar also for the Haase model Edox, made exclusively for the DD2 class but with 30 and 32 mm diameter tubes, with front supplementary bar “direct”

WITH PALETTE - Karts with 2 ratio Rotax DD2 engines have gear lever control on the steering wheel, with two “palette” like on racing cars. There is a braking system complete with front discs. On this occasion, we had the opportunity to also testing the DD2 autographed by the three-time Rotax Grand Finals world champion, Ben cooper.

birel ry 30 sodi kart celestapraga speedymach 1 a03 haase edox

my opinionALAN RUDOLPH - Team UsA Captain, multiple National Champion, born in 1970, DD2 Masters“The DD2 is fun to drive because it guarantees good performance and it’s quite easy to race. Both chassis react well to stress from the track and adapt well to the DD2 engine, making the most of its characteristics. Obviously I found it easier with the Haase, as I have been using it throughtout the weekend, therefore we could say I know it inside out. I found the Mach 1 slightly less prompt, maybe due to the seat position and it is not so aggressive on braking.”

we tried the kart raced by the World Champion







#4-5 MACH1 A03 E HAASE EDoX

between the C spindle supports. In both cases axle diameter is 40 mm in diameter (the engine does not allow for other sizes) and the braking system also has pedal controlled front discs.

IDEAL FOR PORTIMAO In the study of how to drive these karts on the track in Portimao, the first thing is the engine: this because, compared to the other Rotax classes, having two gears allows you to make the most of engine thrust on this circuit. In fact, in the mixed part the narrower turns are covered in low ratios, so you aren’t “too low in revs”, while along the straight a higher gear is stretched out almost up to the braking point, without letting the engine “block”. What I mean is that the power available is used in full, practically 100 percent. Therefore, most work for hands – don’t forget that gear change is through two “palette” on the steering wheel – it does offer a remarkable counterpart. As for the two different karts, the Mach1 was basically “light” at the rear: on one hand this was useful as it helped

to “round off” the turns , but on the other one often it tended to suddenly “skid” back a bit the in the faster turns. Instead, the Haase was immediately more balanced and neutral in response on the track and then again, as we have said concerning the engine, there is no need to help delivery round slow turns thanks to the first gear. As for the brakes, here too, there is a difference: not too hard for the Mach1, therefore you must “press” hard with your foot; the ones on the Haase are “neat” and more powerful, therefore you have to be more careful, at least at first you have to.

Along the mixed partthe narrow turns are easier thanks to low ratio “no stalling” while along the straight, the extra gear is drawn to the next breaking point without letting the engine reach “limit”

mach 1 a03 haase edox

micro 1550,00 € + VAt

mini 2080,85 € + VAt

Junior 2080,85 € + VAt

max 2184,38 € + VAt

dd2 2846,74 € + VAt

cost rotax Fr 125

rotax FR 125 MAX

A class of its ownLet’s see what the reasons that have decreated the success of the

Rotax Max Challenge are and the diffusion of the FR 125 Max engines

in antithesis to the other more “traditional” classes.

Sooner or later someone will be asking themselves why: every time

that a big engine manufacturer comes in our midst (not one of those who don’t know that there is anything else besides karting, but who has an open visual) hoping to get the same conclusion. That is, to defend the use of these karts the method must be changed. Yahama did

it, suggesting a low cost class mounting very simple engines (a great success in the East), and also Rotax Europe has done it in Europe. With an “aggravating circumstance”, so to speak: that the Austrian manufacturer already had more competitive 100cc. And yet, when they wanted to do “that something extra”, they decided to change the whole approach.

So that’s how the FR 125 Max was born: that is, an engine deriving from something that already existed in the motor cycling field, suitable for direct drive karting, getting a unit that was capable of supplying adequate performances but without compromises regarding reliability and simplicity in use. And all this without having to give up manufacturing skill and







experience: just think how the cooling system has been made efficacious and efficient requiring a radiator that is half the size (or less9 than those you see in the KF classes.

POWER WITHOUT COMPLICATIONS So, let’s take a look at all the “crafty” characteristics concerning Rotax engines, starting with the same displacement. In fact, using the traditional cubic capacity of 125 cc (when among the direct drive, the 100 cc is all the rage) allowed to get more torque and power without so many technical sophisms. The same applies to using a 36mm diameter carburettor from the start, a float type carb and already suitable for that cylinder, made of aluminium treated with nikasil.

Parameters that, allow you to have a certain amount

of power from the start and there has been no need to

look for it in other ways; on the contrary, everything else has been

studied to contain problems regarding reliability and life. For example, there has been no need to look for stratospheric revs; on the contrary, a limiter has been used to set revs at 14.000. A pneumatic exhaust valve was already forseen, so there was no problem at all, exp7cept for carbon residues: something that then again is connected to the vast number of kilometres that can be covered only by thinking about “starting” the engine. The aim that has been achieved, to supply an engine which is suitable for beginners and racing has motivated the use of a balancing counter shaft and

electric start, that were already foreseen at the start (of the engine deriving from motorbikes) so devoid of problems. Along this same line of thought we have the radiator mounted directly on the engine, so all the operations of mounting it onto the chassis are simplified. Furthermore, there are other indirect advantages like less sensitivity to carburetion (one problem less), while on the other hand you have to keep the battery on charge always, if you want ignition to work well. Well, already at the start the best ideas for motorcycling have joined up synergistically with the best in the karting field (plus some intelligent new idea) that have justified the world success of this engine. Only in Italy there has been a tepid welcome, but then again, here in Italy traditional

DIFERENT POWER - This graph shows the different power and delivery curves of the different versions of the Rotax 125 engines used for the Max challenge, from the Micro to the DD2. The Max “base” curve has been marked, Right, Mojo tyres used for the Grand Finals: separate those for the Micro class, smaller, the others stand out for the compound used: harder for the Junior class, softer for the DD2, but always basically long lasting.

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Chassis technical formMODEL MICRO JUNIOR MAX DD2 DD2 MASTER

make Praga birel Sodi Kart Mach1 Haase

model Speedy RY 30 St Celesta Fia9 A03 Edox 15

track Front/rear 100 cm / 110 cm 121 cm / 138 cm 121 cm / 139 cm 122 cm / 139.5 cm 122 cm / 139.5 cm

chassis height Front/rear average/average Average /average average/average average/neutral average/neutral

supplementary bars none front Front and lateral 2 front + lateral Front

hubs Front/rear none / 60 mm 90 mm / 110 mm 80 mm / 90 mm Standard 90 mm / 115 mm

camber and caster neutral 2 mm / max neutral / +2° 2 mm / max neutral

toe-in 2 mm open 4 mm open 4 mm 4 mm open 4 mm open

tyres Mojo C2 Mojo D1 Mojo D2 Mojo D3 Mojo D3

tyre pressure 1.20 bar 0.80 bar 0.72 bar 0.65-0.70 bar 0.65-0.70 bar

driVe ratio 13/63 13/73 13/76 37/60 37/60

For everything that has not been mentioned (axle etc.) the chassis have been supplied in standard configuration from factory

Rotax Max 125 enginesCLASS MICRO MINI JUNIOR MAX DD2

age 8-10 year-olds 10-13 year-olds 13-16 year-olds over 15 year-olds over 15 year-olds

max power 6.8hp @ 6500 rpm 13.6 hp @ 8500 rpm 20.4 hp @ 8500 rpm 28.5 hp @ 11500 rpm 32.6 hp @ 11750 rpm

max torque 8 Nm @ 5500 rpm 12 Nm @ 7500 rpm 17 Nm @ 8500 rpm 21 Nm @ 8750 rpm 20 Nm @ 10500 rpm

limiter 11000 revs 12000 revs 12500 revs 14000 revs 13500 revs

weight 11.8 kg 11.8 kg 11.8 kg 12 kg 16.8 kg

driVe Direct drive Direct drive Direct drive Direct drive 2 ratios

exhaust ValVe none none none yes yes

note Smaller radiator, specific exhaust

Flange on induction duct and exhaust

Specific cylinder engine "base" No chain

Common CharaCteristiCs: displacement 124.8 cc; bore x stroke 54.x54.5 mm; liquid cooling with integrated pump; reed induction; Dell’orto ø36 mm carburettor; balancing counter shaft; centrifugal clutch; electric start

manufacturers dominate (also in conditioning the sports authorities), for whom it would be unheard of to them to supply a guarantee on purchasing differently to what happens with Rotax.

STANDARDISATION FOR YOUNGSTERS The same philosophy was followed when the Max class decided to put up another class for the younger drivers. To reach the height of simplification, for example, they have decided to maintain the same cubic capacity 125 cc, lowering power every

time with other systems and artifices. So to pass from 28.5 hp for the original Max to 20.4 for the Junior version they have just used a cylinder without a valve on the exhaust and a limiter lowered to 12,500 revs. The rest is the same, therefore a driver who goes on to the next class because of age limit doesn’t have to buy a new engine, but simplex change the cylinder: a different cost, right? To get even less for the Mini: flanges have been added on the induction and exhaust of the Junior cylinder so as to reduce horse

power to 13.6 (and to 12,000 revs). A little more work has been needed to lower to 6.8 horse power for the Micro class for the younger drivers: in this case they have had to change the muffler and the radiator. Well, apart from the DD2 class (higher cost and slightly more difficulties offer however, higher performance, but maintaining the same general concepts), with the same engine and few changes it is possible to do all the Rotax Max Challenge classes, or it is possible to

adapt performance to the vehicle that your son uses for racing (or you yourself use) on the track also not in races, and you practice. You get all this at a purchasing cost which is already controlled; in Italy 2,643 euros (VAT included) for the Max standard. To this you add the rental formula, if we are hesitant or want to try driving before buying: for a single race, you can get a normal Rotax Max for just over 300 euro, to mount onto your chassis, or even a complete kart for under 500 euro. If to all this we add the fact that there is hardly any cost for overhauling (either because there is little to overhaul or the interval for overhauling are very long) and, for those who race, rules say that engines must be sealed as a guarantee of uniformity and legality, well, we don’t know what else there is to ask for.







maxi-test in numbers The comparison between the three Rotax engines, Junior, Max

and DD2 using data analysis is very efficacious; you can see the manufacturing philosophy used to make them: an engine for everyone. As you know the three engines all have balsamically the same technical components, and also displacement.

Despite the DD2 having a two gear gearbox, it is evident how in the early part of acceleration this engine is similar to the Max. The same can be said for the Junior, in the early phase it offers the same accelerating capacity and

then it is container by the technical component present for limiting performance (different cylinder and no valve on the exhaust).

However, let’s see the track in detail so that we can see the differences better.In the pictures the DD2 results are in red, blue for the Max and green for the Junior. The preliminary study starting from the engine rev graph, picture 1. Don’t forget that the limiter sets a barrier for the three engines;

14,000 rpm for the Max, 13,500 rpm for the DD2 and 12,500

rpm for the Junior. Despite ratios used during the test

prevent the use of the limiter; the main differences between the three engines are evident along the straight near turn 12. It’s at this point that the Max register the highest number of revs, over 13,500 rpm for 118 Km/h, touching the values of the limiter also due to the friction generated round turn 12, which goes to the right along the straight.

For this reason, also the DD2 and

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Graph #1

Comparision on performance of the three Rotax engines used during the Vroom test in Portimao: the Junior, the Max and the DD2

ROTAX MAX RANGE IN NUMBERS BY UNIRACER







Graph #3

the Junior stay just below the value set by the limiter, generating different understandable maximum max speed values, lower for the engine made for younger drivers (112 Km/h), increasing for the DD2 (127 Km/h).

However, the latter only reaches maximum rpm value at the breaking point at turn 3 (13,300 rpm), and this because the driver decides to maintain the first of the two gears. Instead, the points where gear change has occurred are very clear (lower gear > yellow circle; higher gear > red), in the graph we see them in red, going down in acceleration phase and as upward peaks in gearing. Having just two gears it is evident how

the DD2 tackles most turns in first gear, while the second is used for faster turns 4, 5, 7, 11b and 12.

Going on to the Junior, instead in downward peaks in the graph, green corresponds to the blocking phase of the wheels; it is clearer in picture 2 (yellow circles), before turns 6, 9 and 11a.

Maintaining the same colours for the respective vehicles (Junior > green graph, Max > red graph, DD2 > blue graph), in picture 2 you can clearly see the action of the two gears for the DD2, enabling it to gain a lot in the two fast pars of

Graph #2

Graph #1 - RpmPerformance of the three engines seen on the engine rev graph where Rpm value corresponds at the ordinate and Time value is on the abscise: blue for the Rotax Max, red for the DD2 and green for the Junior. The use of gears in the DD2 is evident (gearing up in red, gearing down in yellow).

Graph #2 – Speed and RpmTop, speed canal and engine rev canal at the bottom: the blue graph is the Rotax Max and the red one is the DD2, the Junior is red.Near turn 12, just before the straight you can see how, despite the value of revs for the Rotax Max being higher, the DD2 reaches a higher speed of about 10 Km/h. Junior blocks are evidenced in yellow.

the track (from turn 11a throughout the straight), justifying the advantage of over half a second (0”620 sec.) obtained by the DD2 driven by Alan Rudolph during the Vroom Test (best time 1’00”120) over Louie Pagano, driving the Max. Instead, to Pagano’s advantage we have performance speed round turns 1, 6, 8, 9, 11a, where the driver is at ease, so much so that he makes up for his kart’s inferiority, while round turn 2 and 3 the overlaying of the two speed graphs show

how similar the two drivers and vehicles are, most speed peaks are overlaid as proof of this (turns 2, 3, 4, 6, 7, 8, 9, 10 and 11a).In picture 3 we have longitudinal acceleration for the three karts to show the difference in power between the Junior and the Max, and the effect of the second gear in the DD2 compared to the Max. From the

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top, in the picture we see the graphs showing engine revs, speed and bottom longitudinal acceleration, along a part of the track which is in acceleration, that is, from turn 3 breaking to turn 6.

Remember green is for the Junior, blue for the Max and red for the DD2. Let’s see the analysis where you can see an evident difference in the longitudinal acceleration graph. In A acceleration is greater for the Junior only because at the braking point before turn 3 the kart has slowed down more so it managed to pick up more speed round the turn and reach acceleration point earlier, an action that makes you exclude it from the performance evaluation.It’s zone B that really gives us the idea of a slower performance for the Junior, as longitudinal is evidently less compared to the other two karts, which are very similar.

Always in zone B, we can say that the Max and the DD2 are basically the same as long as the latter remains in first gear. Instead in C, you can see the effect of gear change for the DD2, just geared up into second, while the Max starts to

circuit in Portimao as seen through the GPS canal, turn number shown.

Graph #3 – Lateral and Longitudinal Acceleration Comparing the two acceleration canals (longitudinal at the top, lateral at the bottom). Similitude in performance between the DD2 (in red) and the Max (in blue) is evident at the turn (lateral acceleration is different at turns 1, 6, 9, 12) also considering the different tyres, while as expected the main differences are on the longitudinal acceleration canal, that feels the greater power of the DD2 more and of the action of the gearbox, especially on the braking phases (turns 1, 2, 9, 11b) and at the average-fast turns in rapid succession (turns 4, 5, 7, 10, 12).

Graph #4 - Rpm, Speed, Longitudinal AccelerationDetail of Rpm canal (top), Speed (centre) and Longitudinal Acceleration (bottom) in a tract of full acceleration.

Graph #4

drop.

Looking at C and D it seems that the performance of the Junior is better than that of the Max, but it is not so because the longitudinal acceleration canal gives us information on the varying speed, so looking contemporarily at the speed and acceleration of the green, we see that the Junior goes on accelerating only

because it is the kart that drops speed later than the others.

From this study we see that all these engines made by Rotax are good, and making the most of a single initial project they are capable of guaranteeing different performances depending on the drivers’ targets.


Documents

ROTAX KART LINEUP TEST