Small gains, big difference
A 5% gain in power married to a 4.5kg reduction in mass add up to a big difference
It’s a common problem. All new motorcycles these days are festooned with heavy, and often unsightly, exhaust systems that feature ever-growing catalytic converters. Installed by manufacturers as they battle to meet ever more stringent emission regulations, they’re a necessary, and power-sapping, evil.
And so the hunt commenced for a new system for the Ninja 650. After considering the usual suspects – the Akrapovic system from Kawasaki costs a meaty £1029.95, while a Yoshimura stainless Alpha system is cheaper at £752 – I finally settled on an Arrow system, at just £655.
The new Arrow system does away with the catalytic converter, and in losing the Euro4 restrictions the engine is able to breathe more freely. The manifold pipes are stainless steel and the silencer finished in carbon fibre and Nicrom (an alloy with stainless steel). Helpfully, it puts the Ninja on a diet – losing a hefty 4.447kg over the stock system (8.02kg stock, compared to the Arrow’s 3.573kg).
I had the system fitted at Chris Walker’s Kawasaki dealership in Grantham while the bike was having its second service. I’d chosen CWK as the place to go, because they also have a dyno, allowing me to measure any gains and changes.
The results proved to be interesting, too. Kawasaki claim 67bhp at the crank for the 650 and the dyno revealed 60.38bhp at the back wheel. With an average loss of around 10% between the crank and rear wheel – pretty much what I expected.
‘The Ninja feels more responsive throughout the rev range’
With the Arrow system fitted, we got a measured 63.48bhp at the wheel, meaning an increase of 3.1bhp, which doesn’t sound impressive, but that’s a 5% power gain – and you can feel it. There were gains across the whole rev range that averaged between 2-3bhp, and there’s more to come by creating a bespoke fuel map – as it’s running a little lean on the Arrow system.
So a fuel module went on the shopping list, but there isn’t one available for the 650 right now. That means that the only route open to me at the moment is getting the ECU re-flashed to adjust the original fuel map.
The extra gains, though small, are noticeable. The Ninja feels that little bit more responsive throughout the rev range, and even the 4.5kg loss is tangible, making the bike feel a little more nimble now it doesn’t have to lug the extra weight around. It’s been an all-round boost for the nifty Ninja.