Rotorsport (Rotorsport Racing & Engine Balancing Ltd) previously known as Rotary Power are rotary engine specialists with over 40 years of rotary rebuild experience serving motorsport and car enthusiasts in New Zealand and many other countries.
Now run by me, Grant Munro, I’m acknowledged for a stong work ethic and the ability to provide you with the best rotary engine rebuild possible.
So much so, word seems to have spread, and we regularly carry out rotary rebuild projects for customers throughout New Zealand as well as Australia, United States, The Middle East, Asia and The UK.
We have a 20B engine arriving direct from Japan in the second half of July 2011.
We will be overhauling and balancing this engine prior to sale, but if you need one for built for a special application, contact us now or call Grant on 021-298 5146 (+64212985146 if outside New Zealand) to discuss your requirements.
A deposit will be required prior to commencing any work.
Explaining how we balance a rotary engine can be difficult as it’s a very skilled procedure and an area where no shortcuts can be made.
Hopefully this post will give you a better appreciation of what’s involved.
Firstly, the rotors are weighed, then the heavier rotor is lightened so both rotor weights are identical (less than 0.1 of a gram difference)
During this process, both rotors are also balanced to remove any rotational imbalance.
Rotor weight matched at 4452.3
Spun on balancer to check and identify any imbalance
Note: Rotor mounted on special spindle, not the eccentric shaft.
Results displayed on computer screen, Balanced To Tolerance!
Secondly, each rotor is reconstructed as a rotor manderal with bob weights attached.
These are matched identically to replicate each rotor so the weight and balance is the same.
Each rotor manderal checked to ensure it is identical in weight and balance to the rotor it is replicating.
Thirdly, the rotor manderals are assembled onto the eccentric shaft along with front and rear counterweights.
This full assembly is then spun and checked for imbalances in the counterweights.
This spin showed there was a 6.51 g imbalance from one counterweight and a 6.5 g imbalance from the other.
Note: this engine had been previously “balanced” using a long outdated method that is prone to error. As shown on the screen, both counterweights were out of tolerance and would have produced significant vibration potentially damaging the engine.
The counterweights had 6.51g and 6.5g removed by drilling.
Finally, after the imbalance is removed (or added as extra weight in some cases), the rotating assembly should be well within tolerance!
On this assembly, the imbalance was corrected to within 0.02 of a gram.
We provide you with a full printout of all data for your information.
Contact Us now or phone Grant on 021-298 5146 for your rotary engine balancing requirements using state of the art equipment from CWT.
Many of our clients like to have their engine customised, especially if it is for a car restoration project.
There are two main things to consider for your 13B rebuild.
What happens inside the engine and, what happens on the outside!
On the inside, we will talk with you about any porting work you may wish to have carried out.
Most popular porting is the ‘bridgeport’ which you can see more about in our 12a rebuild section. This is a high performance modification providing a significant power increase over standard.
Mild porting is also a popular alternative which provides smoother operation at lower rpm and probably better driveability in low speed situations.
The ‘Peripheral Port’ rotary modification produces the highest power and designed specifically for race and rally use. Not recommended for street use because of low rpm roughness, they come into their own once the throttle is opened wide!
Once you have decided to either have the engine ported to some degree or leave it unmodified, we strip the engine down to inspect for wear in any of the components. All parts are cleaned thoroughly before reassembly.
We use genuine Mazda parts for your 13b rebuild, including all gaskets, housings, seals and bearings, although for high performance applications we sometimes use special ‘unbreakable’ apex seals from the US.
We highly recommend our rotary engine balancing service which eliminates any imbalance in the rotor assembly. One of the biggest cause of engine failure in rotary engines is because of poor balance which places excessive stress on the bearings and other components. Not only is significant power lost or consumed by the imbalance, the engine performance can be seriously degraded, so let us balance it for you. It will be the best investment you can make in your engine!
On the outside, we can provide any finish you require. From the standard factory look, to full custom spec, you ask for it and we will achieve the look you want.
Colour matched housings to the vehicle? No problem!
Polished alloy housings? No problem!
All nuts and bolts zinc plated? No problem, your choice of gold or silver finish.
Call Grant on 021-298 5146 to discuss your 13b rebuild or contact us.
Need a rotary engine for your project? We have a selection of cores and complete 13b engines for sale.
13b bridgeport with Weber IDA48 carburetor and manifold.
Each time we balance an engine, we provide a printout of the rotor imbalance at various speeds from 1000 rpm to 10,000 rpm.
The printout also shows the final balance figures after we correct any imbalance.
This is done after we make sure both rotors are identical weights, in this case 4611.6.
For this assembly, the initial imbalance was 745.44 inch/lbs at 10,000 rpm.
After correction this was reduced to 0.43 inch/lbs at 10,000 rpm.
The imbalance of 745.44 inch/lbs is quite common because the rotors are never finely balanced by the factory.
However, with high performance engines in particular, it places significant load on the engine and bearings, causing greater fuel consumption and decreasing power output.
This engine will now operate more freely, have less vibration and produce more power than the same engine in an unbalanced state.
Contact us or call Grant on 021 -298 5146 to discuss having your rotary engine balanced.
With this 12a engine, it has been set up as a ‘Bridgeport’ with modified inlet and exhaust ports.
As you can see, we want your engine to look as great as it runs, so all misc items zinc electroplated, this makes them not only look brand new, but protects them from surface rust and corrosion.
All external steel engine surfaces have been painted (to the colour of your choice).
We can now provide a full engine balance carried out on the latest fully computerised CWT engine balancer, with custom rotor mandrels and bob weights that are individually made for each model of rotor from X-treme Rotaries in Australia.
A computer printout is given with the assembly with before and after balancing plus individual rotor weights. This is extremely important if a rotor is damaged in an engine as we can balance up another rotor to suit your assembly without the need of rebalancing the complete assembly again.
Don’t forget that we can build your rotary engine to any specification you require as well as supply genuine Mazda or aftermarket parts at competitive prices.
So deal with the experts for your rotary engine balancing, you won’t regret it!
Rotorsport Racing (Previously Rotary Power) are rotary engine specialists. We take pride in providing you with a top quality rotary rebuild service. Whether it’s an early 10a or an ultra powerful 20b, the care and attention we provide is the same.
With a history that dates back to the first rotary powered Mazdas to arrive in New Zealand, our experience has been demonstrated by producing many of the winning rotary engines in various competitions throughout New Zealand for almost 40 years.
We have been the ‘power’ behind rally and race champions both in New Zealand and overseas.
Before making a rushed or hasty decision about your next rotary rebuild thay you may regret, please call us to discuss your requirements. Phone Grant on 021 298 5146.
Listening to your requirements is important to us so we can provide a top quality rebuild.
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We can now provide a full engine balance carried out on the latest fully computerised CWT engine balancer, with custom rotor mandrels and bob weights that are individually made for each
model of rotor from Extreme Rotaries in Australia.
A computer printout is given with the assembly with before and after balancing plus individual rotor weights. This is extremely important if a rotor is damaged in an engine as we can balance up another rotor to suit your assembly without the need of rebalancing the complete assembly again.
Don’t forget that we can build your rotary engine to any specification you require as well as supply genuine Mazda or aftermarket parts at competitive prices.
So deal with the experts for your next rotary rebuild, you won’t regret it!
We also carry out repairs and overhauls on motorcross bikes and engines, so not just limited to rotaries!
Phone Grant today on 021 298 5146. (Outside New Zealand? 0064 21 298 5146)
Rotor housing after stripdown. Chrome is closely inspected for pitting, flaking or wear before housing is fully cleaned and polished.
With your 12a rebuild, you can leave the intake port standard, but if you choose to increase the power output, the easiest way to do this is to increase the intake port size. This allows more air/fuel mixture to be drawn into the combustion chamber.
The largest port modification possible using the existing intake ports, is called the Bridgeport. This provides a ‘bridge’ over the existing intake port.
Rotary engine specialists like Rotorsport Racing have this work carried out with ‘state of the art’ machinery which makes a precision cut in the plates.
After this has been completed, we further enlarge the ports to match our custom template.
Bridgeport template, showing extra port enlargening required.
