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Sports Exhaust Testing- 50cc and 70cc Sports Mopeds- PART ONE


Moped Sports Exhaust Pipe Testing

The purpose of this blog is to compare how some of the most popular moped sports exhaust pipes perform when fitted to both standard 50cc cylinders and some of the more popular 70cc sports cylinder kits.

A sports pipe and sports 70cc cylinder are by far the most common and simplest scooter tuning upgrades undertaken in order to gain a significant but cost effective performance increase from an otherwise standard 50cc moped.
We posted a blog a year ago (click here) comparing some popular sports exhausts on a standard 50cc Yamaha Aerox, but we also noted that those exhausts which performed well or poorly on standard 50cc moped cylinder may of course perform completely differently when fitted to a 70cc sport.
The object here is to make all the information available so as an informed decision can be made when purchasing an exhaust keeping in mind that the moped may be further tuned or upgraded from a 50cc to 70cc at a later date.

Ok, first the pipes and cylinders used for testing...

click here to enlarge...
scooter exhaust dyno testing

We selected the above exhausts which were chosen because they are all classed as sports exhausts. Sports exhausts are fairly cheap exhausts designed to give a reasonable increase in performance when fitted to a standard or sports 70cc cylinder kit. A sports exhaust will allow a scooter engine to develop more power than a standard exhaust but in order to do this the scooter has to rev higher than it would with a standard exhaust. Consequently a sports exhaust will normally result in your moped making peak power but at say 1000rpms higher than it would with a standard exhaust.
If you wish to tune a scooter more highly than a 'sports' level of tuning, different exhausts and cylinder kits are available which allow your moped to make even more power but again at the cost of much higher revs. The increase of revs when fitting a sports pipe and sports 70 kit (say 10%) is fairly harmless to the engine unless it is old and worn but once you go past the basic 'sports' level of tuning and venture into 'mid-race' and upwards your scooter starts to need more significant work and maintenance... engine wear increases significantly and disproportionately as the revs are pushed ever higher and you will need to consider everything from a stronger crankshaft to handle the additional power to larger carburettor and performance variators etc.
This is the reason 'sports' level tuning is so popular. It offers substantially power increase with little outlay and almost the reliability of a standard moped, without need for a high level of technical knowledge to make it all work properly! Basically fit and forget!

Please note that we have only tested E-marked road-legal exhausts which carry an EU homologation certificate. This E-marking is generally the signature of a reputable branded manufacturer and E-marked exhausts tend to be the highest quality exhausts at sports level since they have undergone expensive standardised EU testing to ensure they meet safety, quality and road worthiness criteria. All homogated exhausts will have an E-mark certification number stamped onto them, although technically if you de-restrict the exhaust this E-mark should be ground off.
True high end race pipes will not be homologated simply because they aren't designed and aren't suitable for use on the road, but be cautious about buying non E-marked sports pipes advertised for standard and sports cylinders, as there is no reason for them not to have been put through the E-marking process unless they are *very* cheap.

The exhausts from left to right are...

Tecnigas Silent Pro Piaggo Exhaust Piaggio/ Gilera Tecnigas "Silent PRO" Exhaust £74.96
Stage6 Pro Rep Exhaust Piaggio Zip Stage6 PRO Replica Exhaust - Piaggio £89.95 (lacquered version)
piaggio yasuni r exhaust Yasuni R Exhaust System - Piaggio/ Gilera £139.95
Yasuni Z Piaggio Moped Exhaust Yasuni Z Exhaust System - Piaggio/ Gilera £116.95
piaggio zip leo vince zx-r exhaust Leo Vince ZX-R Exhaust - Gilera, Piaggio £109.95
Piaggio/ Gilera Leo Vince TT exhaust Leo Vince TT Exhaust- Piaggio/ Gilera £75.95
Giannelli Next Sports Exhaust Piaggio Giannelli Next Exhaust - Piaggio/ Gilera £69.50
Piaggio/ Gilera Endy Exhaust Moped Endy Powerpipe Piaggio/ Gilera Exhaust £71.94 (lacquered)

All of these exhausts fit into the 'sports exhausts' class of scooter exhaust and are all suitable for use with both standard 50cc and sports 70cc cylinder kits.
With prices ranging from £70 to £140 the Yasuni R is right at the top end of the class at £139 but is included because it is a very popular choice on standard and sports tuned mopeds. In fact it is one of the only exhausts conventionally considered as entirely suitable for use with all states of tune without compromise from standard cylinders right up to mid-race level. We will soon see!

The cylinder kits used are...
Motoforce 50cc Cylinder Kit- Piaggio Motoforce 50cc Standard Piaggio Cylinder Kit £40.95
A quick note on budget cylinder kits. We've recently been seeing a significant number of mopeds which have come into the workshop with complaints that the scooter simply isn't making the power it should be, especially after fitting a performance exhaust. In many cases we're finding this is subsequent to where someone has fitted a budget/ no-brand cylinder kit. When you take the cylinder off the porting is simply incorrect or very poorly positioned compared to the genuine original cylinder.
Replace the kit with a decent branded cylinder kit and everything is fine.
These cylinder kits are normally Chinese made and normally have no brand or no brand you have heard of. They cost the importer maybe as little as £10 each when bought in bulk and should be avoided like the plague! Some of the no brand 70cc cylinder kits we've seen made less power than the standard Piaggio 50cc cylinder.
The Motoforce kit is great example of a budget cylinder kit which works, but as a rough guide if you're on a budget and looking for a cheap cylinder kit or other internal engine parts e.g. crankshaft take a look through the major German online scooter/ moped shops, and select a brand they are selling or buy from them direct if you prefer and you will nearly always be safe.
Polini 70cc Sport Cylinder Kit- Piaggio Polini Sport 70cc Cylinder Kit £94.11
Malossi 70cc Sport Cylinder Kit- Piaggio Malossi Sport 70cc Cylinder Kit £102.95
Stage6 Sport Pro MKII 70cc Sport Cylinder Kit- Piaggio Stage6 Sport Pro MKII 70cc Cylinder Kit £105.31
Motoforce Mid-Race 70cc Cylinder Kit- Piaggio Motoforce Mid-Race 70cc Cylinder Kit £102.75

The Polini Sport and Malossi Sport 70cc kits are very similar and generally represent a typical 'definition' of a sports 70cc kit. They make a decent increase in power over standard 50cc but the power drops off quickly if the scooter starts to over-rev meaning that effectively they self-limit themselves and are a very safe and reliable upgrade although they are considered slightly 'tame' compared to kits like the Stage6 sport kits. They also effectively make their peak power at approximately the same rpm as a standard cylinder which significantly contributes to reliability
The Stage6 Sport Pro MKII makes noticeably more power than the Polini and Malossi Sport kits at the same lowish rpm but more interestingly they are known for being able to keep on making power into much higher revs if pushed. For this reason they normally respond well to more highly tuned pipes which are also designed to run at their best at higher rpm and are also favoured by tuners looking for high top speed.

To demonstrate this here is a power graph of these cylinder kits from an old blog we once did.

(click to enlarge)
stage6 moped tuning

Normally you would tune the variator/ transmission on a moped so as it holds the revs perfectly at peak power. So in the graph above we could set the transmission to engage at say 9200rpms for any of the fitted cylinders as this is roughly where all the cylinders make good peak power. This means that when you mash the throttle the revs go straight to 9,200rpms and stay there as the speed of the moped increases. Eventually the moped reaches a speed where the belt has moved all the way up to the edge of the variator and it isn't possible for the transmission to hold the revs constant any more. From here on upwards the only way for the speed of the moped to further increase is for the revs to increase also in direct proportion (effectively the gearing stops 'varying' and becomes fixed like a car or regular geared motorbike.)
This means that once the variator has reached this point, in order to gain a further 15% in speed the revs must also increase by 15% bringing us up to say 10,500rpm. If we look at the graphs again we can see that the Polini and Malossi kits have already dropped right off in power at these revs (at a speed where the power would be needed most). The Stage6 ones however are still going strong making good power (albeit at the risk of the engine running at higher rpm), this is what Stage6 kits are renowned for!
It's worth noting that Piaggio CDI's normally restrict to 10,000rpm meaning that if you left it restricted you could use the Stage6 on a standard crank without risking over-revving yet still make a substantial performance and top speed increase over the Polini/ Malossi sport kits.

Lastly we've included a mid-race 70cc kit from Motoforce. This will probably be too highly tuned for nearly all of the our sports exhausts and the reason for including it is just to demonstrate how each of the exhausts performances when you start to push them to the limit and to see if they have any potential at a higher level of tune. We don't expect the MF mid-race kit to perform near it's full potential as really it should be matched with a higher revving dedicated mid-race exhaust together with other factors such as larger carb etc. before it will start to work really well.
Additionally we wanted to see how the Yasuni R performed when pushed to the limit as it has a reputation for being very capable with everything from standard to mid-race tuning level.

How we tested

We have taken a lot of care to be impartial in the testing process so the graphs are as factually representative as possible so as they can be interpreted independently regardless of our comments on them.
This sort of comparison testing is much more technique sensitive than it would seem, meaning that the accuracy and validity of the results are highly dependent on the technique and experience of the tester.
All the graphs below were made using a Piaggio Zip AC 50cc 2-stroke (approx 4000 miles), completely standard except for the kits and pipes fitted for testing purposes. Basic tests such as pressurised crankcase testing were done to ensure the engine was in good working order.
In order to achieve the full power graph range the CDI was replaced with a de-restricted one (standard CDI normally limits to 10,000rpm). Additionally the transmission system was replaced with a custom built fixed drive toothed belt system we use for testing and development. This is vital for impartial testing as it shows as close as you can get to a genuine basic engine power curve (short of actually removing the engine and fitting the crank PTO directly to an engine dyno). It simply isn't possible to test in any impartial or meaningful way without doing this (even the efficiency of the variator is significantly dependant on what position of change out it is in).
Another problem in impartial testing is that when moped carbs are set up they only ever really need to run within a very limited rev range due to the variator transmission. This means that whilst it's pretty easy to set up a carb to run within this range, if you try to generate a real power curve the fuel mixture can be significantly out when the engine is running at over or under-revs which can throw the power curves out significantly. Consequently it's necessary to painstakingly fine tune the carb across a far broader rev range than it would ever normally be running on each individual combination of cylinder and exhaust.
8 exhausts x 5 cylinder kits = 40 combinations which must all be each carefully setup, this is a lot of work!!!
It's also important that all dyno runs are done under identical conditions. Although dyno's have sophisticated correction software to compensate for changes in temperature and other atmospheric conditions for absolute accuracy all testing is still best done under identical humidity/ temperature/ air pressure etc.
A difference of 10 degrees can make a real world difference of up to a 1hp power difference to a sports tuned scooter simply because of the lower content of oxygen in the same volume of expanded hotter air. It should be noted that although the results will not be identical if carried out on for example a Yamaha scooter with the same pipes instead of the Piaggio used in the testing, testing results are nearly always representative across scooter manufacturers so the although the figures may not be identical the comparisons and graph shapes will be representative across the board.
There will of course also be variations in individual mopeds depending on engine condition etc. but the results are always fundamentally representative for comparison purposes

And so to the graphs...

50cc Standard Cylinder Kit

click here to enlarge...
50cc standard moped exhaust dyno graph

The graph above is just a standard Piaggio Zip AC 2-stroke with different pipes fitted and jetting optimised for each pipe across the power range shown.
The peak powers are important in comparing exhausts but not overly where you are comparing exhausts which have reasonably similar peak powers as there are other important factors to be considered.

There is no standard exhaust on the graph but for the sake of comparison a standard exhaust would normally peak around 3.5 - 4.0hp.
We can see Endy is unable to outperform even the Tecnigas on a standard cylinder which is disappointing as the Tecnigas 'Silent Pro' is basically marketed as a discrete standard look exhaust (similar noise level to standard exhaust) with modest performance gains whilst the Endy should really be a full sports pipe and ought to be able to keep up with the similarly priced Leo Vince TT.
Although both the Endy and Tecnigas pipes have wide power bands the graphs of both of them are almost full encompassed within the graphs of say the cheaper Giannelli 'Next' pipe which is also cheaper. This means that on a 50cc standard there is no rpm at which either of these pipes can offer any advantage over the cheaper Giannelli (although obviously the Tecnigas has it's standard, quiet appearance to consider)
In fact the Gianelli has quite a wide power band meaning it would be very easy to setup. The reason is that in the above graph the variator could be setup (perhaps in error by the moped owner) to hold the revs anywhere from 7500rpm up to say 9500rpm and it will still make over 5hp anywhere in this range. This will allow for a decent performance increase even where perhaps the variator is worn or the engine is worn or otherwise not set up properly. Although it makes less peak power than some of the other pipes there is no other pipe here which makes >5hp at 7500rpm.
Pipes like this are favoured by scooter shops because they know they can simply fit it for the customer and it will work without the risk of more careful transmission setup or potential comebacks if transmission starts to wear slightly where on a peakier more narrow power band pipe the scooter transmission may more easily drop out of the powerband. Also the transmission can be set to engage at less than 8000rpm (basically the same as standard without necessarily any need for roller change). This means much less engine wear than some of the other pipes which run at higher rpms....
click here to continue reading the rest of this blog!