We've had these pipes in for over a year now since they came out.
They've been sitting in the showroom gettin dusty next to the even dustier moped handguards (which Ricky promised us would be a sure seller), so we thought it was about time we ran one up to see what it would do.
To be honest we've never really tried very hard to sell them.

"What's that ?"
"It's the new Leo Vince GP"
"Is it any good?"
"Er...Dunno"
"Have you got any ZX's?"
"Yeah I'll go and get one"

A brief explanation of powerpipes

2 stroke engines are all about the exhaust.

On a regular 4 stroke engine air/ fuel mixture is drawn through the carb into the combustion chamber (cylinder) due to the suction created as the piston goes down.
But if we could cram more mixture into the cylinder than it would normally draw in naturally it makes sense the engine would produce more power.
On a 4 stroke engine we can do this with a turbo charger. A turbine spinning at up to 2,000 times per second stuffs more mixture into the cylinder under pressure than it would otherwise draw in naturally which increases the amount of mixture in the chamber (and effectively increases the compression ratio)
On a 2 stroke engine a perfomance expansion pipe exhaust does something very similar only without any moving parts. When the mixture is ignited on a 2-stroke the piston is forced down... on it's way down, the exhaust port is first uncovered allowing the exhaust gases to escape into the exhaust pipe and then the inlet port is uncovered allow fresh mixture to be drawn into the combustion chamber, but these 2 events overlap. This means that some of this fresh mixture is sucked not just into the cylinder but right through it and leaks into the exhaust pipe.
A well designed expansion powerpipe allows us to make use of this 'waste' to our advantage.
As the fat part of the exhaust reconverges (the back cone) a pressure wave is reflected back through the pipe forcing this fresh mixture back into the cylinder.. This effectively pressurises the cylinder with fuel mixture in a similar way to our turbo. The disadvantage is that a pipe can only work best at a specific rpm because of the timing involved and it takes some considerable skill to fabricate an exhaust which doesn't work well only over a very small rev range.

The pipe...

The pipe itself is very nice looking and probably the only moped exhaust designed to look like a MotoGP aftermarket exhaust. It's E-marked and road legal provided you don't remove the restrictor :)
In usual Leo Vince form it comes with a set of lighter rollers and clutch springs. The body sections themselves are immaculately tig welded stainless steel.
In fact this is its major selling point, stainless steel is expensive but it doesn't rust or corrode anything like a regular powerpipe will. There are virtually no other stainless steel powerpipes in production. With a regular exhaust all you can do is cover it with something to prevent corrosion but whether it's covered with lacquer or chrome plating sooner or later the covering corrodes due to the conditions it operates under leaving a very tatty looking exhaust often within just a few months. The Leo Vince GP should far outlast them.

All sounds good so far, but the most immediately apparent problem with the Leo Vince GP is that in common with standard moped exhausts there simply isn't enough room in it to contain both a full wave expansion powerpipe and a silencer, so compromise must have been made in its design which has to show up in its performance somewhere.

For our testing we used the same Aerox (otherwise standard) as we did for our exhausts comparison article STAGE 6 Pro Replica... to give us some valid comparisons.

(click to expand)



Results...

Amazingly this pipe was able match the peak power of the best of the other pipes. Let me put that another way, on a standard Aerox this pipe makes as much peak power (7.4hp) as virtually any other pipe on the market !
This means that if setup properly this pipe will perform as well as anything on the market up unto the speed at which the variator can no longer hold the revs constant (approx 35mph).
However as previously discussed we knew this pipe would have to have a performance compromise and this is where it is. As soon as the bike reaches this road speed the only way the bike can go any faster is by the engine revs increasing. If we look at the graph again we see that the power drops off very quickly after 9000rpm. In fact from 9,000 to 10,000rpms it has dropped 4hp from over 7hp to just over 3hp which is going to seriously limit the top speed compared for example to it's Leo Vince ZX big brother and because of this it will even be significantly outperformed by the Leo Vince TT which at £74.95 isn't far off half of its price.

Conclusion... who would buy this exhaust?

The best performing exhausts for an otherwise standard Aerox like a Leo Vince ZX or Stage6 Pro Replica will make maybe 50mph. The Leo Vince GP exhaust will perform identically to these exhausts up to approx 35mph at which point it will start to be significantly outperformed and will not be able to match the same top speed (although the top speed will still be better than standard). Also if you are later looking to upgrade to perhaps 70cc or make further tuning mods this may not be the best exhaust to pick because of its reluctance to rev. These are its only real downfalls.
It should however considerably outlast other exhausts because of its stainless steel construction (especially lacquered pipes) and it should be noted that it would probably work quite well with a gearup kit as that way the revs can be kept lower for longer and the high peak power at lower revs can be utilised to get back the missing top speed. Gear kits don't always work well with standard cylinder bikes but this should work well provided the rider isn't too heavy !

So where were we...
oh yes,
"Have you got any ZX's?"
"Yeah I'll go and get one"