Polini has redeveloped the proven Polini banana and given it a new look. What the new banana or, according to the new Polini nomenclature, the "original" exhaust can do; I took a look for you.
From a purely visual point of view, the new original banana differs significantly from the design of the older vintages. The body has become thicker in terms of material and shaped differently. The plug connection on the manifold looks much more binding and the position for hanging the exhaust spring moves to a more accessible area.
Polini offers the exhaust systems for the PK and V50/PV engine cases. So far, the bananas for the PK models have always been provided with a clear flattening in the area of the manifold. The new original from Polini only shows a different course of the manifold, without flattening.
Another significant improvement is the bracket that connects the muffler and engine case. Once the base plate of the bracket is mounted on the engine housing, the muffler can be easily mounted and dismounted using two M8 screws.
In the previous model of the banana, this principle was already used in racing, for example in class 5 of the ESC, to enable faster tire changes, but individual initiative was required when creating the bracket.
In general, Polini seems to have taken some experience from the racing circuit with him on the new banana. The new Polini banana is also directly suitable for the tire dimension 3.50-10, which is used almost exclusively in the racing series. The usual tires of the Smallframes with 3.00-10 therefore of course still fits.
I put the new original banana on my K5 for you and did a few tests.
The assembly went well. No bending, pressing or worse interventions are necessary to position the exhaust properly on the scooter.
The slotted holes in the bracket provide significant leeway for adjusting the system to prevent contact with the tire and brake drum.
Polini oddly states that the length of the shock absorber should be determined before installing the exhaust system.
The tested minimum size of the shock absorbers, i.e. when the shock absorber is compressed to the stop, should prevent the exhaust system from coming into contact with the frame.
Owners of the bgm Pro rear shock absorbers can feel safe here. The dampers have the required minimum size and in the case of the Sport series, the height of the damper can even be adjusted further.
But now to the result on the test bench.
I would like to say in advance that every engine behaves differently and the differences can be more or less noticeable depending on the processing. It has been shown that the difference is clearer with less powerful or unprocessed engines than with concepts that are a little more sophisticated.
Here the new Polini Banana takes place on a motor that
Class 5 ESC rules.
The carburetor in this case is a PHBL 24, intake manifold Polini membrane, cylinder Polini 133 Racing cast iron. Crankshaft Mazzucchelli Racing.
The motor housing is machined for the diaphragm inlet and the transfer channels in the motor housing are adapted to the cylinder. The cylinder and the intake manifold remain unmachined.
In racing trim, my 508 tends to be in the 15hp range, depending on how I feel on the day. Therefore, the first run is first of all to see whether the engine is still in the best of health.
As expected, the 508 delivers 14.9 hp at 7300 rpm after warming up.
So everything is healthy and the new Polini original exhaust is fitted for comparison.
Even on the test bench, the significantly higher starting torque is noticeable when warming up. Polini did a good job here. What feels different on the dyno is also reflected in the graph.
At a slightly lower speed of 6660 rpm, the new 2022 banana with 15.5 hp increases by 0.6 hp compared to the older design. The maximum torque, increased by 0.9Nm, is already at 5200rpm.
In a direct comparison of the two curves, the character of the new 22 banana can be seen. Earlier - more.
Up to approx. 7200 rpm, the 22 banana has the edge in comparison. Exactly the area in which an engine with this power is most often moved on the road. From about 7300 rpm the older banana looks a little better and shows a little more desire for higher speeds.
The configuration of the carburetor was not changed between the two runs. My assumption here would be that with a subtly smaller main jet and needle/mixing tube combination, the 22 banana can still gain a bit in the higher rpm range.
But I'll leave that to your play instinct to find out.
My personal opinion:
Polini has done a good job developing a very nice everyday rideable exhaust with some good improvements. The easier to reach position of the spring, the more solid plug connection and the easily adjustable bracket are positive. I see the usability on larger tires as a further plus. In terms of noise, the new banana is a bit duller than the previous model.
In the video you can get more impressions of the new Polini Banana
