MotoGP Case Study: 250R air box and more
Introduction
During the 2005 season the most evident gap consisted in the power output of the engine and this is why in 2006 most of the job has been focused on it.
In these articles we will illustrate part of the work done by CRP Technology in the development of the engine exploiting the rapid prototyping technology and the Windform materials.
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Fig.1 – R250GP. On the right the R250GP that has attended the ’05 World Championship.
On the left the frame(chassis) prototype made of Windform and used for the first assembling tests in January 2005. |
Airbox 2005 performance’s analysis
The 2005 250cc engine set up is a 90° 2 cylinders, with reed valve and two 40mm carburettors. (Fig. 2)
Two air intakes on the side of the cowling bring fresh air to the two separated air boxes.
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Fig. 2 – . It is possible to see the 90° configuration of the engine. |
During the 2005 season, several tests have been made to study the
configuration of the two separated air boxes but, due to the overall
dimensions it hasn’t been possible to have 2 air boxes of the same dimensions. This would have brought to a similar functionality of the two cylinders.
The performance achieved at the CRP dyno is illustrated below (fig. 3)
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| Fig. 3 – CRP Technology’s dyno. Torque and power curves obtained for the 2005 R250GP.
Looking at the curves you can see quite a regular output of power. In
particular a worsening of the power and torque curve is noticed due to
the research of higher power in a lower range of use. |
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| Fig. 4 – CRP Technology’s dyno. A comparison between two 2005
configurations. Working on the electronics you can reach higher power
but in a smaller range of use. |
2006 development
From the analysis of the tests done on the dyno and from the behaviour of the engine in the different conditions, static, dynamic and combined (accelerative with progressive load) there has been a certain difficulty of fuel supply. These problems were different from cylinder to cylinder.
In particular the lower cylinder’s carburettor is very critical because the venturi is very close to the side of the air box.
The carburettor has therefore been rotated respecting the limits of the fuel level. Realizing a new structural (it means it supports the carburettor) induction insulator in Windform XT it has been possible to improve the functionality of the cylinder nr. 2 (Fig. 5)
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| Fig. 5 – Particular of the R250GP carburettor. On the left the CAD image of the
air box and lower carburettor, on the right the completely assembled
system. The air box has been realized in Windform and used for the test. |
A one-piece air box in Windform has been realized in order to exploit in the better way the space inside the frame with the front air intake under the lower triple clamp (fig. 6)
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Fig. 6 – . In light and dark green the elements
of the new air box. Beneath the triple clamp there is the air intake.
To be noticed how all the space has been exploited. |
This has permitted to reach a similar behaviour of the two cylinders, therefore making the set up of the engine easier. The engine has immediately improved and the setting of the two carburettors was similar.
Below the curves obtained with the Windform XT insulator and the new airbox. (fig. 7)
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| Fig. 7 – CRP’s dyno. The curves with the new configuration. |
Results
Comparing the two results it has been noticed that with an increase in volume, a better geometry of the air box and a better positioning of the lower carburettor, a higher power and torque curve has been achieved, which allows the rider to exploit the engine already from low rpms. (Fig. 8)
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| Fig. 8 – CRP’s dyno. In green the 2005 configuration, in red the result achieved with the described modifications. |
Increase:
Rpm Power (%) Torque
9750 +9,2 +10
11000 +3,7 +3,7
12000 +5 +4,5
12500 +9,5 +10
Thanks to the mechanical wear resistance of CRP’s SLS material, it has been possible to realize the air box and over all the insulator directly in Windform shortening a lot the development and realization timing.Diverse kind of insulators have been made and have been directly tested on the dyno until the best geometry was found. Holding the files, the “story” of the component can be preserved.
Cooling and front fender
Using an air box that exploits the whole space inside the frame, a big increase of power has been achieved. This increase is ruined by the engine’s temperature that reaches in a while 65-75°C with peaks of 75-80°C in the worse climatic conditions. These temperatures penalize the efficiency of the engine frustrating the job done on the air box. This problem was present also during the 2005 season.Exploiting the potentialities of the rapid prototyping, a front fender, whose function was also of an air conveyor, was created. (fig 9)
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Fig. 9 – R250GP front fender.
CAD image of the front fender with air intakes. It’s possible to see the air flux pushed to the radiator. |
The idea is to bring fresh air to those “hidden” parts of the radiator to increase the engine’s cooling. (Fig. 10)
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Fig. 10 – R250GP front fender.
The front fender realized in Windform XT, painted and assembled directly on the bike.The geometry is quite complex and the production of that piece would have been very difficult (in time and money) with the traditional technology.Exploiting the SLS technology and the Windform XT material it has been possible in a short time to realize the fender and test it on the track.Only the use of this fender lowers the temperature of 2°C and doesn’t have any side effect for assembling and dynamics. |
2006 fairing – Work in progress
In order to improve the cooling and the aerodynamics we are also working on the aerodynamics, trying to improve the penetration and the hot air extraction (fig. 11).
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Fig. 11 – R250GP fairings. In white the 2005 fairing and in purple the 2006 fairing. To be noticed how the air’s front entry has increased in order to exploit the whole radiator.Under the triple clamp has become bigger to facilitate the air’s entry.As soon as possible we will test on the track this solution to verify its real efficacy |
Rear fender
In order to optimize the air flux in the rear part of the bike, thus avoiding turbulences, we realized in Windform XT a rear fender with two lateral fins to protect the swingarm.
Tests have demonstrated the importance of this part in helping the extraction of the hot air flux from the front.
It has inside a duct for the rear braking oil pipe. (fig. 12)
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| Fig. 12 – R250GP rear fender. Realized in Windform XT and then painted and used on track. To be noticed, on the right of the figure the passage for the rear brake hose. |
Also in this case it has been possible to realize complex and very particular shapes in a short time.
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