Vespa Big box exhaust shootout | FEATURE
Vespa (and Lambretta for that matter) box type exhausts are more popular than they’ve ever been and arguably provide comparable results to an expansion type exhaust, without the downsides.
- Fitting without the need to cut any panel work
- Changing a wheel without taking the exhaust off
- being able to keep a spare wheel on a Vespa
- Plus the chances of a long wobbly exhaust snapping are fairly high
We set our German friend, Boris Goldberg the task of trying not only the current crop of Vespa box exhausts but also some of the ones that are still in prototype form. He tested 13 exhausts on two different scooters, a standard and a tuned PXTX. Tomorrow we’ll have a competition to win an exhaust from SIP and Scooter Center Cologne.
Here’s how Boris got on…
Just a few years ago, it was common sense that in order to work well, a two-stroke exhaust had to be shaped like a proper expansion-pipe. Sticky once wrote that it’s a principle of nature that things that work best look good, too. He explicitly referred to female breasts and expansion pipes.
It’s difficult to say what the box exhaust would resemble if you wanted to continue the analogy, but it definitely is a fact that the development of box exhausts nowadays is a thriving factor of Vespa-tuning and the big race-type boxes perform just as well as a good expansion pipe.
Advantages of a box style exhaust
If you’ve ever had to dismantle a sizzling hot left-hand pipe on the hard shoulder of a motorway to reach a flat rear tyre, fitting a box exhaust instead will come as a revelation.
The number of box exhausts on the market is growing constantly, their performance is improving all the time so today you will be able to find a good box for almost any application, from café racing to dragging a sidecar. At the same time this means that finding the right exhaust for your needs is more difficult than ever. Which is why we thought it’s about time to do a box exhaust test with a slightly broader view.
One thing that hasn’t changed with the re-invention of box exhausts is that every two-stroke exhaust is a bit of a compromise – there is not one single exhaust that works best with any sort of setting. There are boxes that are built to complement a standard or touring engine with rather low exhaust timing – but these will not allow a highly tuned engine to breathe properly.
At the same time, a box designed to complement a high revving Malossi kit will not be able to reach its potential on a standard P200 barrel with its low port timings.
The test scooters
For that reason we chose not only to try and test a good variety of box exhausts, but also to test them on two different scooters – my own completely standard TX200 (a Spanish Motovespa with a P200 engine in a T5 chassis) and a PX 200 that has been fitted with a Malossi 210 Sport kit and a 60mm gas-flowed crank.
In retrospect, in order to complement the variety of boxes tested, we could have made good use of an even higher tuned engine like a Malossi MHR, but even with the Malossi Sport, the results are quite significant.
The tests were again carried out on MMWs dyno in Bavaria. Altogether we had 13 different exhausts on the dyno on two scoots, which meant we spent the best part of a full day swapping exhausts – what better use can you make of a sunny Saturday? At this stage, many thanks go out to Rainer and Kriegy who helped operating the dyno and bolting exhausts on and off. And a big thank-you of course to Harald at MMWs who provided the dyno and much help with interpreting the results.
For each exhaust you’ll see two graphs, the top one is with the standard 200, the bottom one is with the Malossi 210 engine.
Standard PX 200 exhaust
This was used for general reference. It might look a bit tatty as it had been kicking around for a while, but actually, it has not seen much use. The standard exhaust provides a super-flat curve – resembling the tractor-like pulling power of the P200, but it loses almost 2 hp against the next best exhausts even on the standard engine.
With the Malossi kitted engine, the difference is expectedly even bigger, with the standard exhaust being 3.5 hp behind its nearest contender, the SIP Road 2.0.
Standard Exhaust was provided by Tom.
T5 Standard exhaust with PX manifold
T5 with P200 downpipe
Note that this is not a Sito Plus, but a genuine 1942-stamped Piaggio exhaust with a P200 downpipe welded into it. In the early days of box exhaust development, this used to be a common conversion. The exhaust belongs to myself and I simply wanted to know whether it can still hold up against the new breed. As it turned out it was quite useful (with a very similar curve compared to the well-known SIP Road 2.0).
We opted to use it as a reference for all the other exhausts, together with the standard exhaust, as differences in power delivery are a bit easier to compare if the graphs are not too far away from each other.
BGM Big Box Touring
BGM Big Box Touring
The BGM Big Box Touring has been around for a while now and again proved its capability as a good allrounder. The body of the exhaust is significantly larger than the original (hence the name) and the additional volume obviously shows its advantages. On the standard engine, it makes a nice even curve and peaks earlier and higher than my T5 box. Interestingly, the Big Box Touring, the Polini box and the new SIP Road 3.0 prototype all made exactly the same peak power on the standard engine. With the BGM peaking a bit earlier than the others – plus it gave the second-best torque figures of the day on that engine, only a little less than the LTH box.
Its touring characteristics are also predominant on the Malossi engine, but here the BGM obviously cannot make as much use of the potential of the kit, so that it falls behind the newer boxes in terms of power output – however, it still has the highest torque figure of the three.
The Big Box Touring is a prime contender for lower tuned engines and heavy motorway work that does its name proud. Available from SCK for 139,- €”
BGM Big Box Sport
BGM Big box Sport
Again the name says where we’re heading. Scooter Center Cologne clearly state that the Big Box Sport has been developed for high potential engines and is not suitable for standard bikes. Its massive downpipe also causes ground-clearance issues so that use on scooters with 8-inch wheels is not recommended. The graphs clearly prove the recommendations to be correct – even if power output on the standard engine is ok, torque is significantly lower than even that of the standard exhaust – this would be an engine struggling uphill or into a headwind.
This situation completely changes when fitted to the Malossi kit – torque is suddenly up with the best contenders and with 22hp the BGM Big Box Sport is the overall winner of the day in terms of peak power – apparently it suits the Malossi Sport and other kits with the same state of tune very well. Available from SCK for 199,- €”
The LTH box (or TSR Vortex in the UK) is unique in that the characteristics of its P200 version are significantly different compared to the rest of the bunch due to its extra-length downpipe.
It gives the best torque figures on both engines and, as a friend of mine put it “makes you feel as if you could ride up vertical walls with it”.”
As always, this comes at a cost, as overrev capabilities are low and power tails off early. This exhaust is asking for taller gearing, or you will end up with a bike that’s at least not faster than standard. Combined with the right gearing this will be an ideal exhaust for touring or other heavy-duty applications – one of the guys present on the day wanted to buy it on the spot for his sidecar combination. Contrary to most other exhausts, the LTH box comes with a flange equipped with a Viton O-ring plus springs to hold it up.
Available from LTH for 139,- €. (Note that the LTH box for 125/150cc is a significantly different design and characteristics cannot be compared to the 200cc box).
Malossi Power Classic
Malossi Power Classic
The Malossi Power Classic box is one of the latest entrants to the market and shows that Malossi is always good for a surprise. Contrary to most other opponents its downpipe is not made from individual cones, but from two pressed and welded up halves, just like the good old Italian tuning pipes from the 80s. Together with the standard-sized body, this makes the Malossi look rather unimpressive. It’s just when you notice that the diameter of the outlet pipe is significantly larger than standard (20mm), that you start to realise that some thought has gone into this box.
This was confirmed when we had it on the dyno. On the standard P200, it beats my T5 exhaust by half a HP and also peaks a bit earlier, even if torque is lower.
On the Malossi Sport 210, however, it becomes clear that this is the sort of application that Malossi has been looking at..
It is nearly up with the performance of the big sports boxes, even if it cannot quite match the best of them. Really impressive when considering the small dimensions of the box.”
This makes the Malossi a good alternative e.g. for someone who can’t use a BGM BB Sport for reasons of ground clearance. One major downside of the Malossi though, it is really noisy – think of a 2000 miles old Sito Plus – you get the picture. Available for 149,- € from SIP or other Malossi retailers.
Polini Original Box
Polini Original Box
The Polini box was the first take of a major Italian tuning brand at the new generation of box exhausts. I can remember forum discussions that were slagging it off before having even seen, let alone tested it. It has been around now for a while, negative opinions have been silenced as the Polini has proven its worth as a well-working allrounder. A judgement we can fully confirm after our dyno runs.
The Polini box is significantly larger than standard, however, the additional dimensions are mainly in width rather than in height, thus avoiding major ground clearance issues. It has a quality feel to it and a nice deep and unobtrusive tone. As already mentioned, it makes exactly the same peak power as the BGM Big Box Touring on the standard bike, but at slightly higher rpm and with a little less torque.
On the Malossi, however, it beats the BGM in power and is up to the same torque figures. What’s especially nice is that it does it with a super-smooth power curve, which shows that the Polini is an especially good option for mildly tuned road engines.”
Together with its comparatively low price this makes the Polini box excellent value for money. Available for about 130,- € from Scooter Center Cologne and other Polini stockists.
SIP Road 2.0
SIP Road 2.0
The SIP Road has been around for years now and it was the exhaust that made the new generation of box exhausts available to a mass market at a really competitive price. Interestingly its power curve on both engines is extremely similar to my T5 exhaust, also providing very good torque figures especially on the standard engine.
Compared to newer offerings like the Polini it becomes obvious that development has progressed and that the SIP Road 2.0 cannot quite match these boxes any more, especially on tuned engines where it falls behind nearly 2hp to its newer competitors. Which is exactly why SIP is currently working on the 3.0 version.”
As far as our information goes, the Road 2.0 will stay in production due to its capabilities as an allrounder on standard and mildly tuned engines. Available from SIP for 129,- €.
SIP Road 3.0 (prototype)
SIP Road 3.0 Protoype
SIP let us have a pre-series prototype of their forthcoming Road 3.0 (available September) that is going to complement the Road 2.0 as just mentioned. SIP informed us that their main aim was to develop an exhaust with good all-round capabilities for road-tuned engines and with the same dimensions as standard so that ground clearance would not be compromised, but with the same performance as the competition’s boxes.
It’s probably fair to say this mission has been accomplished as the SIP Road 3.0 is the third box that is exactly up to par with the BGM Touring and the Polini on the standard engine in terms of peak power, although torque is a bit lower here. On the Malossi engine, the SIP Road 3.0 again is up to par with the Polini and about 1hp higher than the BGM Touring. Also, the shape of the curve is almost the same as the Polini’s, just about 200rpm higher.
The prototype is already identical to the production version in terms of dimensions, so the SIP 3.0 promises to be a very versatile tool for fast road engines once it hits the shops. Price is expected to be between 125,- and 150,- €.”
SIP Road XL
SIP Road XL
The SIP Road XL was SIPs first take at a performance box – originally developed for the classic Malossi kit. The curves of the Road XL are a good example for an exhaust that doesn’t suit the rest of the engine setup. It definitely is the exhaust least suitable for the standard bike, as it reaches peak performance at the highest rpm and gives the lowest torque figures of all competitors.
On the Malossi Sport engine, things, unfortunately, do not look much better, peak power is at about the same level of the Polini or SIP Road 3.0 proto, but at immensely higher rpm and torque is only a little higher than that of the standard exhaust.
This exhaust needs a high-revving engine really, some people apparently use it successfully on T5 engines (I use one to good effect on a Malossi 172 kitted T5, Iggy).”
It might have been interesting to see what it does on a Malossi MHR kit, but as things are, the SIP Road XL cannot be recommended for either of the engines we had on the dyno that day. Available for 179,- € from SIP.
General notes: Jetting
MMWs dyno has a rather heavy roller and from experience they were confident a road-setting would work fine (rather than having to down-jet the scooter as you need to do when using a lightweight roller). This turned out nearly fine – we only had to go back very slightly on my standard PX and Franz’ Malossi kit ran happily with the setting he’d been using on the road. We made sure with each exhaust that it was running healthily and revving freely. What we didn’t do, however (and for obvious reasons) was play around further with the jetting to find the individual optimum for each exhaust – so bear in mind that some minor gains might be possible by further adjustment.
SIP Viper Box
The Viper Box has been developed by German exhaust gurus Nordspeed Racing and will shortly be produced and distributed by SIP. This exhaust has been developed for highly-tuned engines like the Malossi MHR, but compared to the SIP Road XL, it coped quite well even with a less-than-ideal environment.
For reasons of completeness we also tested it on the standard engine, where it provided results similar to the BGM Big Box Sport. Again things looked rather different on the Malossi Sport engine where the Viper came to life – peak power is only a fraction behind the BBS (0.3hp) but the peak is earlier and there is slightly more torque in exchange.
This will be a powerful good working setup. Also in terms of fittings, the Viper is designed to cater for the high-end section of the market and will come with a Viton O-ring flange plus plug-holes for EGT and Lambda probes as standard.”
This, of course, has its price – the Viper box is expected to cost between 210, and 230, €. Available September from SIP.
The Resi-Box is a project by German scooterist Jürgen (German Scooter Forum nickname AIC-PX) that has been featured from beginning to the present state in the German Scooter Forum.
It’s a true performance box even if it is cramped into a standard-PX exhaust and features a proper absorption muffler built into it.
Again it has been developed on a Malossi MHR engine and is also in the same league as the other big performance boxes. It is the only one we couldn’t test on the standard bike (not that this would have made much sense anyway) as the flange was so tight we couldn’t get it on.
On the Malossi Sport it gave similar results to the Viper, but the higher peak-rpm and lower torque figures indicate it would definitely have been happier on an MHR engine.
However – bear in mind we’re comparing the home-made Resi-Box with the top-of-the-range products available on the market here – so these results are more than impressive and show how much thought and effort has gone into it.”
Jürgen has already built some more of these boxes on individual enquiry, so if you fancy one, you can get in touch with him through the forum.
A general find is that it is apparently easier to find power by increasing the volume of the exhaust. Some boxes go in that direction, like genuine T5, the BGM boxes, the SIP Road XL and (to an extent) the Polini. This, however, comes at a cost, as ground clearance becomes an issue. Especially if you are going to fit it to a classic Vespa, you might think twice whether a large volume box is really the right one to use.
RZ Mark 2
RZ Mark II
The RZ was provided by LTH as we not only wanted to compare all the boxes to the standard exhaust but also wanted to see how they fare when compared to a traditional expansion pipe. The RZ is a typical lefthand pipe similar to the JL exhausts and known to work well on a variety of engines. This was particularly interesting as it shows how far the development of box exhausts has actually progressed.
The RZ is actually the winner in terms of peak power on the standard-engine – but only by a narrow margin of 0.3hp. Torque, however, is rather low and – most importantly – power comes in late and tails off earlier – the typical peaky behaviour of an expansion pipe.
The RZ works well on the Malossi engine, with some similarities to the big performance boxes, so that is rather a question of whether you prefer the look and sound of a left hand pipe over its boxy companions. Available in July for € 215,- from LTH.”
There is actually some variation in flange dimensions, both with exhausts and barrels. As usual, the outlet stub of the standard barrel was slightly larger in diameter than the Malossi. This can lead to a rather floppy fit on the Malossi with some exhausts that feature the traditional clamp fitting, so that with some exhausts the good old Coke-can gasket was required to get it tight.
The LTH box, Viper box and the Resi-box have flanges equipped with a Viton O-ring plus additional springs to hold the exhaust. These have the edge on alloy barrels as there is no danger of damaging the stubs, also they are generally a bit tighter, to the extent that we could not fit the Resi-box on the standard cylinder.
Outlet pipe diameter
Outlet pipe diameter is a topic that is frequently overlooked. A small dimension outlet pipe certainly has an advantage when it comes to keeping the noise down, which is nice of course. While there is some discussion whether the size of the outlet pipe actually has positive or negative effects on power and the rev-range, it is common sense that the outlet pipe dimension should increase with the tune of the engine in order to enable it to breathe properly and avoid the build-up of heat.
As a rule of thumb, most expansion pipes aim at a diameter of 25 to 28 mm, whereas the majority of the boxes only have between 16 and 18mm, with the Viper Box, the Resi-Box (both 23mm) and the Malossi (20mm) being the only ones to feature larger diameters. This will not be an issue when using the exhaust for in-town riding or on country roads, however, when riding at high speeds with a lot of throttle for a longer distance, e.g. on a fast motorway trip, you might soon struggle with a pinking engine. This is something we couldn’t test on the dyno – but it is something to watch depending on what you’re going to use the exhaust for.
Exhaust results standard PX200
|Exhaust||Power / hp||RPM||Torque / NM||RPM|
|T5 Original / 200 Downpipe||11.2||5662||16.98||4166|
|BGM Big Box Touring||11.5||4870||17.42||4394|
|BGM Big Box Sport||12.2||5862||15.23||5320|
|Sip Road 2.0||11.1||4881||16.42||4468|
|Sip Road XL||12.1||5982||15.06||4564|
|Sip Road 3.0 Proto||11.5||5249||15.86||4931|
|Sip Viper Box||12.1||5723||15.34||5379|
Exhaust results PX 210 Malossi Sport, Si 24, 60mm crank
|Exhaust||Power / hp||RPM||Torque/NM||RPM|
|T5 Original / 200 Downpipe||19.5||6622||21.90||5013|
|BGM Big Box Touring||19.9||6284||23.79||5560|
|BGM Big Box Sport||22.0||6701||23.74||6351|
|Sip Road 2.0||19.3||6851||22.04||5179|
|Sip Road XL||21.0||7576||20.93||5271|
|Sip Road 3.0 Proto||21.1||6669||23.19||6029|
|Sip Viper Box||21.7||6502||24.08||6143|
New products always in development…