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Tech Tuesday: Rotax Max EVO – 10 Things You Need To Know

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1. Why has the EVO been introduced? 

The MAX range of ROTAX engines has remained largely unchanged for the past fifteen years. This is the first time in the history of karting that a single engine model or type has continued to be successful and grow on the market to become the World leader. After this period of time the technology in production has improved to the point where latest electronics and mechanical design can be introduced without de-stabilising the existing product in use today. In short, the Rotax Max EVO engine is the natural progression of an already successful theme, to enhance and protect the market for the forthcoming years.

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Reubens Barrichello at the wheel of a Rotax Evo

2. What are the changes to performance and power? 

The EVO engine remains fundamentally unchanged internally, the crankshaft has improved tolerances in the area of the main bearing and oil seal journals. This means that all new products from the factory will have an end float on the crank when delivered, the oil seals will also be free running. This should reduce the need for pre-race preparation and therefore significantly reduce the price of the new engine to the end user. There is no difference in performance between the EVO engine and a current race-prepared unit. The Piston skirt has a slightly different taper, this allows quicker running-in and reduced wear in use. Again, this should lengthen piston life and be less costly for the end user. The Con-rod has been altered slightly, the big end has been strengthened and now has two lubricating slots. The external component changes include ignition system and carburettor.

3. What do the dyno charts look like? 

At the time of writing, there are no official Dyno charts available. In simple terms the ease of use shows through there is no specific gain in maximum horsepower. The mis-understood press release from the factory where gains in performance were reported, is as a result of BRP-ROTAX redefining their testing procedure and having improved Dyno technology for more consistent results. If anything, the Dyno charts for the Rotax Max EVO engine offer a smoother power curve which is less affected by changing meteorological conditions.

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EVO DD2’s Lined up for the 2015 RMGC

4. Will the engine be more reliable?

The detail changes inside the engine will all enhance reliability. The BRP-ROTAX warranty scheme is in place in order for the factory to closely monitor any recurring faults in the engine or its ancillaries. The Rotax Max is the most reliable kart engine that the sport has ever known, this is due in no small part to the engines built in component strength and the warranty scheme. The new Piston, Con-rod and refined crankshaft tolerances will all enhance component life and reliability.

5. Will the EVO engine be eligible for MSA competition? 

Yes, but the question is when? The MSA are helping to arrive at the best possible solution for the introduction of the EVO specification. The good news is that there will be a number of offers in place to help the end user financially. There is no reason why the internal components cannot be installed as soon as they become available. The Piston is effectively the same, the crankshaft is the same component as before with improved tolerances. The con-rod is the only question mark as it is clearly not the same as the outgoing component.

The fact that the Rod does not affect performance but does improve reliability should help its introduction. All external accessories will be available complete with new engines throughout 2015 and as a subsidised upgrade kit to be used with existing engines from January 1st 2016.

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Note: New spec engines do not improve driver talent

6. How much will it cost to upgrade? 

The engine unit will not need to be upgraded until it is due for a service, then the new replacement components may be fitted as standard parts. There is no specific price increase for these parts over existing components. Upgrade kits of external parts will depend on which class. MiniMax is expected to stay exactly as it is for the foreseeable future. Junior upgrades will include Carburettor, Ignition, wiring loom and Exhaust. Seniors will include all the junior parts plus the electronic power valve and its associated components. We believe that these will be at a very low introductory price of up to 50% discount.

7. Will servicing costs increase? 

Definitely not. All new component prices will match their predecessors or be subject to introductory offers that could reduce servicing costs. New components are expected to have a significantly longer service life, thereby reducing running costs to the end user.

8. Can I convert my current MAX to a Rotax Max EVO? 

Yes. The engine unit itself will not require upgrading, the new internal components may be fitted as and when the engine is due for service. There will be upgrade kits available to convert existing engine accessories to the new specification. These are expected to be available soon, but will not be in use in the UK for MSA racing until 2016. Click here to ensure you get the right Rotax Max jetting.

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Maintainence is no more difficult on EVO

9. Can I buy individual parts to fit to my MAX?

Yes all components will be available as individual spare parts. It is not yet decided whether the EVO must be used as a complete set of accessories or if it will be acceptable to use some of the upgrade parts and not others. There will be plenty of time to test and decide on this before the official introduction of the accessories for MSA racing in 2016.

10. Summing up

1 The EVO engine is not being introduced to step up performance.

2 The EVO internal parts are introduced to improve reliability & component life.

3 The EVO accessories will not be eligible in MSA racing until 2016 to help class stability.

4 EVO engine accessories will not be more expensive
than current components.

Written by George Robinson

 

Like this article? Then read these:

Tech Tuesday – Engine Cleaning

Tech Tuesday – Seat Mounting and Adjustment

Tech Tuesday: Rotax Max Jetting and carb setup

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If you have an EVO, you need to read our Rotax Max EVO article.

There are several different brands of software available like the Jet-Tech Max program that can really help save a lot of time when you go to the track. However the software needs to be calibrated to your engine and carb. That is when you need to have a strategy and become very familiar with the signs that indicate the correct rotax max jetting. These signs can be the plug colour, the dryness and colour of the piston crown and the exhaust header. If the main jet is correct, the plug will be light brown in colour and the piston crown will be dry with a dark brown hue. The engine should also be reaching maximum revs at the end of the longest straight. Using the base settings on a software such as the Jet-Tech Max program will get you close to the correct jet. It then takes several practice sessions to find the correct jet and calibrate the software to the engine.

To choose the correct setting for the needle takes a little effort from the driver who really needs to give good, consise feedback to the mechanic mechanic and needs to be objective and honest about how the engine is performing. It also requires  disicipline not to waste a valuable carb development session just to chase someone else around the track in the heat of battle, try and get yourself some space. As the needle has most influence between 1/4 and 3/4 throttle, the driver needs to focus on how the engine is performing out of the corners. It’s best to keep it simple, pick one corner on the track and get a feeling for how the engine pulls out of that corner. Getting the fastest exit on the best line is not the point of this test, it is to try and optimise the needle setting so the engine pulls strongly and cleanly down the straight.

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Jetting affects the amount of fuel mixing with the air

It is a good idea to start rich by lifting the needle up to its highest position. Because the two stroke engine is not very efficient lower down in the revs due to the design of the pipe, the cylinder can be insufficiently scavenged which means a fresh charge of air and fuel is then mixed with exhaust gases. To help overcome this problem the engines typically run a lot of ignition advance to help get the air/fuel mixture burning a little earlier in this dirty environment. If you lift your needle up so you can richen the mixture and make best use of all that ignition advance you may well feel quite good gains in bottom end torque.

By repeating the procedure of going out and feeling how the engine pulls from 1/4 to 3/4 throttle, and then coming in and changing the needle position, the driver can get a good feel for what setting is best. The driver could also try accelerating from different throttle positions on the straight, say from 1/2 to 3/4 throttle, to help evaluate how each needle position effects the performance. To confirm what works the driver could then focus on his line through a portion of track and use split times to see what setting is quickest.

A short note on needles: the K27 and K98 needles have slightly different profiles. The K98 has a steeper taper which will have the effect of richening the mixture ever so slightly above 1/4 throttle. It would take a good driver to notice but the difference would become apparent on a dyno.

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Clip Positions on the K98 Needle

You may ask why does anyone need jetting software if they can just go out and feel how the kart is performing? After all that is what every karter did before laptops were common at the track. The truth is that setting up a carb correctly can often be very time consuming and sometimes frustrating for everybody, not just the beginners. What jetting software does is act as a time saving instrument that once you have put the hard work into calibrating the software to your engine and carb allows you to go to the track, plug in the figures from a weather station to the computer and be very very close if not dead on the correct jetting immediately.

The beauty of a program like Jet-Tech Max is that it will take into account things like your choice of floats and idle jets and has features that allow you to easily fine tune to a high degree how close the software will be to the actual needs of the engine. One of these features is called Flow Bench which is a quite advanced adjustment that, according to the developers of the software, is best left alone until the driver and mechanic are quite experienced and confident with how well matched the software is to the engine, as it is a very fine adjustment. It is also possible to set the program up so that you have database settings for several different engines and carburettors, even if they are spread among the range of Rotax classes.

One other feature of the software that adds value is the sheer amount of supporting information included in the package, such as a wide range of chassis setup guides from the manufacturers, as well as driving tips, carb preparation guides written by the developers of the software and official Dellorto and Rotax guides to the engine and carburettor. If you can absorb all that valuable information and put it in to practice then you are well on the way to be a winner!

Jetting
Alternatively, You can also use this chart to help with your jetting

 

Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Karting Tools App

Tech Tuesday – 5 Toolbox Tools


Rotax Driving tips

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The art of driving a Max powered kart is always made to look easy by those who are really good at it. Much like any sport, the people at the top appear to apply the minimum of effort to achieve what looks to be impossible.

There is usually one common thread that helps to unravel the secret. They all, whatever their chosen sport, spend a lot of time doing it! It really is a case of practice makes perfect. Most top drivers will seldom admit to doing many perfect laps, every lap is a compromise in some way. Starting from the beginning therefore it is important that your Kart is in good condition and assuming that your initial level of knowledge is slight, it has to be a good idea to have your chassis professionally set up to ensure that it is all true and safe. A slightly bent chassis or misaligned steering can make any Kart really hard to drive but the less experienced will often assume that all is well and drive around an inherent problem. There is no need to make life unnecessarily difficult. Now that we know all the wheels are pointing in the right direction and that the brakes and steering are safe, the time has come to get out on track and start enjoying your Karting.

If you are really new to the sport, most clubs will have an onsite ARKS (Association of Racing Kart Schools) examiner. This guy maybe very busy, but his role is to make sure that as many newcomers as possible pass their test and start racing as a regular club member. This does not mean to say that the ARKS test is a walk in the park, but it does apply a set of guidelines which the driver needs to achieve before being allowed out in a race. The ARKS examiner is a person worth meeting, he will be sure to give good basic advice and help introduce you to others that have first-hand knowledge of your local circuit. If you are new to the sport or the circuit it is a good idea to get to the track early, get yourself ready and go for a track walk. Make sure with the officials that the track is open for you to walk round and if possible ask someone with local knowledge to show you the lines, braking points etc. Once you’ve been to the circuit, a walk round loses its value very quickly, you’ll subconsciously remember the circuit and will be on the pace after a couple of warm up laps.

1When you go out onto the circuit keep some space around you and don’t get too close to others that may involve you in their accident. There is not much point in spoiling a potential new friendship by crashing into them. As you drive onto the track remember that the tyres will take at least a lap before they have any predictable grip. Please do not leave the grid with a flamboyant full throttle wheel-spin only to disappear into the bushes at the first corner. This happens at every club meeting every weekend of the year, just don’t let it be you! Having warmed yourself, your engine and your tyres, now is the time to start applying a bit more throttle and start enjoying Karting for what it is, probably the best form of motor sport in the world! Concentrate on being smooth with all the controls, squeeze the accelerator down and brake firmly but smoothly without locking the wheels. If the Kart is correctly set up it should slow in a straight line without snatching to one side or the other.

The best early advise is try to get your braking done in a straight line and only accelerate when the kart is well turned in to the corner. It could be said that acceleration should only begin past the apex, but in Karting, even at an early learning stage this is really too late. The whole idea of a Kart is that the chassis is the suspension and the live rear axle has to rely on the driver making best use of the extraordinary handling capabilities of a kart. The transition between braking and acceleration is a real balancing act and probably the most important element that defines a fast driver from an ordinary one. At first my advice is to take it easy and explore your own limitations. It is very likely that you will soon find that you are catching some others up as well as learning from those that overtake you. Wrap up warm, it’s still good fun in the winter!

Rotax Carburettor Explained

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The pressure at “1” is higher than at “2” because the fl uid speed at “1” is lower than at “2”
Source: Public domain from Wikipedia (http://en>wikipedia.or g/wiki/File: Venturifi xed2.PNG)

I thought it would be a good idea to talk about how float bowl carbs like the Dellorto actually work. I know there are more than a few people out there who know that the carb mixes the fuel and air to be burned by the engine but not much beyond that.

The Dellorto Rotax carburettor works on the basic principle that air passing through a venturi (a narrowing section like the inside of a cone) causes a vacuum. The air being drawn in by the engine is sucked through the venturi in the carb, which is located where the slide is. As the slide opens, the vacuum increases. Imagine putting a drinking straw in a glass of orange juice and sucking on it. The vacuum in your mouth is drawing the juice out of the glass. The carb is designed to make use of this principle so that the amount of fuel coming from the float bowl can be accurately metered so that the engine runs with the correct amount of fuel for a given throttle position.

The fuel is sucked from the float bowl (glass) through 3 different circuits (straws) and comes out in the venturi (mouth). These circuits are known as the idle circuit, the progression circuit and the main circuit. As their names suggest these circuits control the amount of fuel at different positions of the throttle.

The idle circuit allows the engine to idle. A small amount of air is drawn into it through one of the small holes located up stream of the slide in the bell mouth of the carb. This air is mixed in the idle circuit with fuel being drawn up from the float bowl through the idle jet and idle jet emulsion tube, which unlike the main jet cannot be changed for different ones. The emulsified fuel mixture is then sucked through the furthest tiny hole from the slide.

As the slide opens, the responsibility for feeding the engine with the correct air/fuel mixture is taken over by the progression circuit. As with the idle circuit some air is drawn in from the small hole in the bell mouth and the fuel is drawn through the idle jet but this time the emulsified air/fuel mixture emerges from the small hole that is just behind the bigger hole where the needle goes in the main circuit.

At this point the slide is only open about one quarter. As it continues to open all the way to full throttle the main circuit takes over the metering of the fuel. The volume of fuel passing through the main circuit is controlled by the main jet and by the tapered needle. The needle is necessary to control the volume of fuel at part throttle opening because otherwise there would be too much fuel coming up from the float bowl if it was just left to the main jet to control it.

According to the rules, the size of main jet and the position of the tapered needle are all you can adjust. A general rule of thumb is that bigger jet sizes are used when the air temperature is cold and the air is dense. Smaller jet sizes are used when the air is warmer and less dense. Humidity plays a part in jetting too and generally one can jet down if humidity is high and jet up if humidity is low.

The tapered needle is used to fine tune the jetting in the low mid to high rpm range once you are happy with your main jet. Its always worth taking the needle from its lowest (lean) position to its highest (rich) position while on the same jet just to see how the engine responds.

It is rarely worth taking into account what jet the other drivers are running in their carbs because the fact is that there are too many other variables affecting how jetting influences engine performance, including the drivers driving style and their weight. Driving style would include how the driver controls the throttle. As fuel metering transitions from the idle to the progression to the main circuits it is best to try and get a feel for what the best rate is to open the throttle at to give the carb the best chance of work. This takes practice as does finding what jetting works for you. Having a strategy when jetting at the circuit is the best way to get to know your carb and its characteristics.

Know your Tyres

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Inconsistency between batches of tyres causes much consternation and muttering with the most recent victim being Michael Simpson at the Larkhall Super One. “We were going alright until we put the race tyres on,” said Andy Cox as he and Michael consoled themselves with a Scottish breakfast. He isn’t the only one it’s happened to and it’s by no means limited to the Rotax classes and Vega tyres, as European KF3 Champion Alex Albon oon Dunlops thought he was at a big disadvantage in his heats. Carlo Forni demonstrates the handling effects of different compound tyres with the same carcass on page 82.

So I asked Jason Parrott, team manager of Max team Tim Parrott Motorsport, whether the situation is really as bad as all that.

“The junior tyres, the SL8s, are OK, they don’t change much, although some people do complain. The SL6s (Senior) are the worst problem, the balance of the tyres changes dramatically, there’s a big slide then a big understeer. The kart won’t stop, and at the middle of the corner the kart drifts. Once we tested four sets at PF with Tom Armour, and there was half a second between the best and worst set.”

“At Larkhall for the Super One the tyres were mostly OK, then at PF for Kartmasters the following weekend we did some testing on the tyres from Larkhall and then the new tyres were only as quick as the 120-lap old ones! It shouldn’t be possible and there is definitely something not right. With all three drivers saying the same thing there must be something going on.”

Jason believes there needs to be some sort of code on the Vegas as there is on Bridgestones so people know what they are getting.

Inconsistent tyres aren’t a new issue though. Alex Zanardi was an early test driver for Vega and in his autobiography he recounts a batch that were particularly good. This was a batch that [Mr Vega’s] severed finger had fallen in to! So in my house a decent set of tyres are referred to as having a juicy bit of finger in them. Who knows what might have fallen in to the bad batches! Although I would imagine that the processes are a big more controlled now…

However, tyres and compound mixing is chemistry and a lot of work goes into making sure things don’t interact with each other when they shouldn’t. The make up of race tyres is a closely guarded secret but in general tyres are made from:

  • Natural rubber, or polyisoprene is the basic elastomer used in tyre making
  • Styrene-butadiene co-polymer is a synthetic rubber which is often substituted in part for natural rubber based on the comparative raw materials cost
  • Polybutadiene is used in combination with other rubbers because of its low heat-buildup properties
  • Halobutyl rubber is used for the tubeless inner liner compounds, because of its low air permeability. The halogen atoms provide a bond with the carcass compounds which are mainly natural rubber. Bromobutyl is superior to chlorobutyl, but is more expensive
  • Carbon Black forms a high percentage of the rubber compound. This gives reinforcement and abrasion resistance
  • Silica is used together with carbon black in high performance tyres, as a low heat build up reinforcement
  • Sulphur crosslinks the rubber molecules in the vulcanization process
  • Vulcanizing Accelerators are complex organic compounds that speed up the vulcanization
  • Activators assist the vulcanization. The main one is zinc oxide
  • Antioxidants and antiozonants prevent sidewall cracking due to the action of sunlight and ozone

Tyres are changed from a gloopy mess to something that stays in shape by vulcanization where sulphur or other curatives are added. These additives modify the polymer by forming crosslinks (bridges) between individual polymer chains. So as you can see there are several stages where the manufacturing can go slightly wrong and the resulting tyres won’t work as expected.

However, a lot of the investment into pharmaceuticals goes into making a consistent formula, and medicine is 1) life or death, and 2) often very expensive. It might be that the tyre manufacturers have found the best balance they can between price on the one hand and consistency and quality on the other. However, if a company can offer an improved product we need to go with that.

Next year of course, the Max classes will all change to the Mojo tyres. They would have been changed for this year, but PCA-free tyres are being encouraged for all applications by the EU, and the 2011 Mojos will be PCA-free so the ABkC and MSA decided to avoid having two changes in two years.

In Jason’s experience in Euromax, these seem to be a lot more consistent so hopefully Max racers will have better experiences once the Mojo tyres are phased in. In testing by the ABkC, performance has been found to be similar.

“The tyres are so important that if they aren’t right, changing the chassis, the axle and all of that makes absolutely no difference. It does give people an excuse though!” was Jason’s final point.

Ken’s Komments – The Final Chapter

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Ken’s Komments this month, and for the final time, come from the 2014 Rotax World Finals in Valencia, Spain 

No sooner had Race Director Nigel Edwards arrived in Spain, he was on a plane back to London. He had been summoned to 10 Downing Street to a ‘Celebration of British Motorsport’ reception hosted by Prime Minister David Cameron.

There were 288 drivers from 57 countries at the World Finals, not counting the Micro Max youngsters. I always refer to this event as karting’s annual world family gathering. It is unique.

Great Britain had the 2nd biggest team with 15 drivers, only USA with 21 had more. But neither nation shone brightly. David Wooder was the lone British hero. He led the Junior Final before finishing as runner-up.

Of course, Sean Babington, Ben Cooper, Martin Pierce and Tiffany Chi

Sean Babington talks

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Onboard with Sean Babington at PFi Rotax EuromaxRacing in the two-gear DD2 class, Sean at last had everything go right for him at the Lucas Guerrero circuit near Valencia in Spain. Every driver at the event qualified by finishing in the top few places of a national or international Rotax series. At this event, drivers use karts and engines drawn in a raffle which in theory should ensure parity, but drivers this good will always find the tiniest differences in equipment.

“It’s a lucky draw but in practice we found out we had some good equipment,” Sean said. “In qualifying we were really confident, did two laps and went fastest, then backed off before another lap that gave me pole. “In the heats Ben Cooper was pushing but I was able 
to get away a