Test Vespa Box exhaust

Boris Goldberg, in collaboration with MMW Racing, commissioned the very informative English online magazine (SLUK for short) carried out a very elaborate exhaust test for the Vespa PX200 Models made. The focus of the test was on the now very popular box exhaust systems. This means exhaust systems that are more or less similar to the original exhaust in optics and sound, but offer a significantly better performance than, for example, the BGM BigBox Touring or Polini Box.

In order to make the results available to all readers, here is an excerpt of the most interesting tests.
In general, two different engines were tested:

  • Original PX200 12PS motor
  • PX200 engine with Malossi 210 Sport cylinder, long stroke racing crankshaft (60mm stroke with extended inlet control angle), serial carburetor SI24


The original PX200 engine is designed as a throttle engine. As a result, it offers a lot of torque with a flat power curve.
Due to the short control angle and small flushing areas, the engine cannot be operated sensibly with a classic racing exhaust. The torque loss in the lower range is so great that it can lead to problems with the gear connection from third to fourth gear. At the switching speed, the engine falls exactly into the range where the racing exhaust has significantly less power than the standard exhaust. Under unfavorable circumstances, the engine then literally starves to death in fourth gear and does not go any faster than in third gear.
In addition to the optical and acoustic inconspicuousness, this is one reason why the box exhaust systems have become so popular. With almost the same performance as a 'real' racing exhaust, these offer a significantly more linear performance curve without any dips. Thus, the engine with a box exhaust is usually much more harmonious and relaxed to drive.

The Polini Box and the Big Box Touring are a prime example of how a good exhaust can help a production engine get going.
When developing their exhaust, Polini has based itself very closely on the Big Box Touring, which was previously on the market.
On the original engine, the BigBox Touring is clearly ahead in terms of torque and pulling power:


The performance curve of the original Piaggio PX200 exhaust is always used as a reference. In addition, a not for sale exotic was stored in the diagram (an exhaust of the special model PX125 T5, which in turn was provided with an exhaust manifold of the PX200).
The Polini Box runs very harmoniously on the series engine. It broadens the usable speed range and increases the available torque and power quite considerably.
Compare the lower yellow curve of the original exhaust with the upper red curve. The engine speed is specified via the left / right axis and starts at 2800 rpm. The motor power is read over the vertical axis, the higher the curve, the higher the motor power at the given speed.
The original exhaust reaches 9,5 HP which is the normal rear wheel performance of a 12 HP Vespa. The 12 HP are measured in the factory on the crankshaft without the losses from the gearbox, tires, etc.
With the Polini Box you get the maximum here 11,5PS achieved, so already 2PS more than the standard exhaust. The absolute torque is identical to the standard exhaust.

Performance data and improvement compared to the original exhaust: 11,5PS / 16,2Nm (+ 2,0PS / + 0,0Nm)


The BGM BigBox Touring runs much more powerfully on the series engine than the Polini. Up to approx. 5700 rpm, i.e. exactly in the speed range for which the original transmission was tuned, the BigBox Touring is well above the already good Polini Box. The slightly earlier end of engine speed at 7000rpm (Polini 7400rpm) is not relevant because the production engine in fourth gear (due to the normal driving resistance) only rotates up to 6000rpm anyway.
The BigBox Touring is therefore still unbeaten on an original engine when it comes to early, high torque with a very good bandwidth.
It gives the original engine, without any other changes, an increase of 2 hp. Compared to the Polini, it also increases the absolute torque by over 1Nm.
You can already feel this quite clearly while driving, because this higher torque extends over the wide speed range of 3000-5500rpm, which is very important for everyday use.

Performance data and improvement compared to the original exhaust: 11,5PS / 17,4Nm (+ 2,0PS / + 1,2Nm)



The modified engine in this test is, despite the changed cylinder and crankshaft, still extremely tour-friendly and rock solid with, albeit very sporty, classic Vespa characteristics. The engine therefore develops at least the same performance as a standard engine from the lower speed range, with significantly better performance in the middle and upper speed range.


The Polini Box works very well on the Malossi Sport cylinder and offers a considerable plus compared to the original exhaust (+ 5,4PS). Up to 4200rpm it is a little below the level of the original exhaust, but then takes in more air from 6000rpm and offers a good peak performance.

Performance data and improvement compared to the original exhaust: 21,2PS / 23,7Nm (+ 5,4PS / + 3,4Nm)

The BGM BigBox Touring works perfectly on the Malossi Sport cylinder and offers a very high torque from idle. At 5000 rpm it is a whole horsepower stronger than the Polini Box and already reaches its performance peak at 6000 rpm. So the name says it all and every touring rider with the BigBox Touring is on the safe side when it comes to perfect drivability and thrust from the low revs. Compared to the standard exhaust, + 3,5Nm are extracted from the engine, all at a significantly lower speed level. If you are in a hurry, you can benefit from the wide speed range of the BBT, which still lets the engine turn easily up to over 7500 rpm with a lot of power on the rear wheel. That is already over 125km / h with a standard gearbox, with such a motor pulling a longer gear ratio without any problems. Fast motorway stretches are therefore not only not a problem despite the early onset of torque, they are also a lot of fun!

Performance data and improvement compared to the original exhaust: 19,9PS / 23,8Nm (+ 4,1PS / + 3,5Nm)

Friends of the classic two-stroke characteristic will love the BGM BigBox Sport. If you want the resonance kick *, go a long way and at the same time expect a high level of performance, this is the place for you. On the Malossi Sport cylinder it is still a little underchallenged, but this is ideal for those who want to expand their engine concept. The Malossi Sport cylinder is ideally suited for this, as it offers the identical overcurrent layout as the much more powerful MHR brother.
The latter works best on a diaphragm-controlled inlet (or a heavily revised rotary valve inlet) with a large carburetor. Therefore, the MHR was not used as a basis in this test. However, increasing the control angle and enlarging the exhaust window quickly bring the Malossi Sport cylinder into very high performance regions. With the BBS, as the BigBox Sport is also called in short, engine outputs of well over 25 HP are then easily possible.
But even on an engine with a fairly conventional design, as used in this test, the BBS has the winner's crown in terms of top performance. The nice thing about it is that, despite the highest performance peak in the test field, it runs almost as powerfully as a standard exhaust up to approx. 5000 rpm. This is rather unusual for exhaust systems with high peak performance. From 5000 rpm, however, there is no stopping and the exhaust begins to fully charge. It then maintains the high peak power over a wide speed range. Perfect for chugging through the city inconspicuously and taking out the performance hammer in between times. As I said, the BigBox Sport works with more powerful engines and does not stop at a performance of over 30PS / 30NM (see here also the Performance diagrams in the online shop). In summary, one can say that the BBS is the proverbial wolf in sheep's clothing.

(* you can feel the turbo-like use of the exhaust)

Performance data and improvement compared to the original exhaust: 22,0PS / 23,7Nm (+ 6,2PS / + 3,4Nm)

Buy BGM BigBox here
Buy the POLINI Box here
bgm big box sport

bgm BigBox Sport just new and already sold out -

We were amazed: within a very short time it was the new Vespa racing exhaust (BGM1010SP) already sold out. With the positive feedback and the tests that were carried out by various parties, it was actually clear that we are very happy about the great success of this exhaust system - Thank you!

The BGM BigBox Sport - the wolf in sheep's clothing
Performance like a racing exhaust - optics and acoustics like a series exhaust

Update: now also for PX200 and Rally 200 available again!

Now available again!

Order BigBox Sport here

bgm bigbox sport vespa exhaust bigbox-sport-vespa-exhaust_3

The BGM BigBox Sport is a thoroughbred racing exhaust, in the unsuspicious design of an original exhaust. It positions itself as a clear alternative to eye-catching and mostly loud and large resonance exhaust systems. The high level of motivation clearly sets it apart from other boxing systems. Designed for performance-oriented drivers who appreciate the benefits of an inconspicuous vehicle.

Performance diagram bgm BigBox Sport:

LML150 5 channel engine (membrane inlet) with cylinder Quattrini M1X (unprocessed) and 1,5mm head gasket (stroke compensation), carburetor SI24

Performance diagram (BGM1010SP)

Powerful engine concept required

Like any good racing exhaust, the Sport Box requires a powerful engine concept in order to develop its full performance. In the environment of cylinders like the Quattrini M1X and Co., it offers impressive results. It also supports engine outputs above 25PS without any problems and pushes ahead with full torque. Despite its high peak performance, the Sport Box gets in early and also enables comfortable driving.

Due to its consistent design for a high gas throughput, the BigBox Sport is not intended for use with near-series engines or tame tuning cylinders. It needs a clear and powerful outlet impulse to fill the large volume and the thick elbow of the Sport Box with life.


  • Original optics
  • Quiet
  • Top performance like a resonance exhaust
  • No performance hole
  • Broad speed range
  • More top speed
  • Very unobtrusive
  • Also fits rally / sprint without modifications
  • Solid construction with clamp on the cylinder
  • Handcrafted in Europe


  • Not for vehicles with 8 inch tires (ground clearance too low)
  • Not for near-series engines

The elbow is attached to the cylinder using a clamp. Compared to loose fastening with an O-ring seal, this results in the best stability and prevents damage to the outlet flange. A long spacer should be used on the rear shock absorber for optimal ground clearance.

Conclusion: pure understatement. Performance like a racing exhaust, optics and sound similar to an original exhaust.

Order BigBox Sport here

Polini 221cc cylinder

Update: Malossi MHR 221ccm cylinder for Vespa PX 200 available Malossi MHR 221ccm cylinder

As with the new one Malossi Sport and MHR cylinders , we also dedicate ourselves to the details of the Polini 221cc cylinder for 60mm stroke crankshafts. We had already measured timing & co for the Polini 221 cylinder for the Vespa here: Polini 221ccm 60mm long stroke.


The one included in the cylinder kit cylinder head is also with the current Polini 210cc used. Polini regulates the adjustment of the compaction simply by changing the pinch edge.

So let's grab the head and give it a suitable one Long thread spark plug and simply apply grease as a seal for our plexiglass instrument.

Cylinder head Polini221

With the Plexiglas plate in place, we fill the cylinder head with the burette in order to determine the exact cylinder head volume.

Cylinder head Polini221_2

The meniscus remains in our burette at 25ml. The volume of the combustion chamber in the cylinder head is therefore 25ccm.

To get the entire combustion chamber volume (Vc), we still need the volume of the domed piston crown. With a defined piston backing, in our case 6mm, we first calculate the volume of this “cylinder”.

piston head polini221
6,85 x 6,85 x 0,785 x 0,6 = 22,1ccm so is the volume.

Also sealed with grease and filled with lamp oil in a playful delicate rose, the burette reveals a value of 14,6ccm. So 22,1 - 14,6 = 7,5ccm for the Volume of the piston crown.

3_bottom polini221

The last ingredient is missing Volume of the pinch edge. Measured directly on the living object, i.e. directly on the engine, this is 2,2mm, which in turn has a volume of 8,1ccm requirements.

Combustion chamber volume

So we come to a total combustion chamber volume of:

Cylinder head 25ccm + pinch edge 8,1ccm - piston bottom 7,5ccm
= 25,6ccm

compression ratio

Does this result in a compression ratio? from
Cylinder displacement 221ccm + combustion chamber volume 25,6ccm / combustion chamber volume 25,6ccm
= 246,6ccm / 25,6ccm
? = 9,63

Polini 221ccm cylinder put to the test

Here is another example of the Polini 221 based on a customer engine.

So Polini 221cc, Polini crankshaft 60mm stroke, Dellorto PHBH 28, Polini intake manifold for rotary valve and ours bgm BigBox. With the original cylinder base seal, control angles of 120 ° / 170 ° result. For more information, see the diagram below.


For a motor that is only plugged together, i.e. has not undergone any machining of the channel surfaces, 26Nm is a reasonable amount of torque. Especially when power and torque are available that early.

At 4000 rpm, 20Nm are already available, which is at least twice the value that an original PX200 reaches as a maximum.

Depending on the gearbox setting and application preferences, one can confidently longer primary can be used to achieve a solid cruising speed at low speeds on the motorway. The low-vibration running of the Polini crankshaft then contributes to the rest of the comfortable journey ...

120km / h cruising speed

With this motor and a longer reduction ratio should permanent 120km / h to be possible. Here ** as an example, once with the original gearbox and once with our bgm Superstrong clutch and DRT pinion extended by one tooth on the original primary of the PX200 with 65 teeth.

PX200 24_65

Since there are still 7000PS at 20rpm, it is possible to crack the often cited 120Km / h mark.

** The gear calculator "GearCalc" was kindly made available to us by GSF member Motorhead. Thanks very much!

Cylinder -POLINI 221 cc aluminum, 60mm stroke- Vespa PX200, Rally200

Article no. P1400084

Vespa exhaust Exhaust bgm PRO MB Big Box Prototype

Vespa exhaust bgm PRO

NEW: Vespa sports exhaust BigBox Sport

Today we proudly present you the first pictures and the first results of the test bench runs of our new one bgm PRO exhaust systems for the Vespa.

The Vespa Big Box exhaust was developed in close cooperation with MB in England and is also the result of over 20 years Scooter Center Experience.

Advantages of the exhaust:

  • More efficient:
    • powerful like a resonance exhaust
    • significantly easier to turn than SIP Road
    • very wide speed range
    • no performance hole like a reso exhaust
  • Looks like the original
  • Quieter than racing exhaust
  • 200 mm outlet socket with Viton® Oring -> no more cracked exhaust ports on 200 mm aluminum cylinders
  • massive, thick-walled material
  • so far without approval
  • with serial number

Purpose of use:
Due to its original look and its low volume, the exhaust is particularly suitable for original tuning or touring setup.
Due to its power delivery, it can be used universally on original as well as heavily tuned engines at home.

First pictures:
Here are the images of the prototype. The exhaust will be available for the following models:
- Vespa PX 200 / Vespa Rally 200
- Vespa PX 125 / Vespa PX150 / Vespa SPRINT etc.

We expect the exhaust from the beginning / middle of summer and are really looking forward to it. The test drives were great.

Test run performance diagrams:
The exhaust systems were made on the professional Scooter Center Ammerschläger P4 test bench tested with laboratory software:
Result: Significantly more power! eg:

  1. + 2PS more on PX200 compared to the original exhaust with significantly improved revving = top speed
  2. + 3PS more on Malossi 210 compared to comparable road exhaust systems
  3. + 5PS more on Malossi 166 (60mm shaft, exhaust made, 28mm carburettor on rotary valve) opposite Vespa Road exhaust

In XNUMX, when Test roller the following candidates were available:

The test runs were all done with the engine warm. The tests were carried out against the existing exhaust systems on the vehicles and against the SIP Road exhaust.
Almost all scooters were then tested for several kilometers on the road in order to really feel the change. That was the very subjective so-called Popometer test ;-)

The conclusion
Awesome part - this is how a Vespa exhaust has to be!
Both for the "laboratory test" with performance diagram and for subjective testing on the road:
The new bgm PRO exhaust puts you in a good mood. The engine turns out much more freely, the Vespa becomes much more flexible and faster and without the consumption or volume increasing noticeably.

Vespa BigBox Vespa exhaust

Development of a new Vespa exhaust system - the Vespa BigBox from Scooter Center

After we and Mark have brought the Lambretta BIG BOX so far that we can only wait for the manufacturer and, at most, issue reminders, we sent a few sets of PX exhaust shells to Doncaster.

Mark has all of his ideas regarding PX BIG BOX implemented directly after the Eurolambretta. On Monday morning the PX 200 BIG BOX was finally here in the store. A few minutes later the test bench computer started and the games could begin.

Vespa exhaust big box test

It was tested on:

Buy Vespa BigBox here


Vespa exhaust performance charts

Here is a small selection of diagrams. Uwe did a lot more runs that we will post over the next few days.