Replacing the ECU of your Motorcycle

A couple of months ago we replaced the ECU on a Kawasaki ZX10R. We didn't need to of course, but when has 'need' ever played a part in the things we change on our motorcycles? A few years ago, replacing a motorcycle's ECU would have been a very extreme thing to do – certainly something left to the motorcycle mechanical experts. For the rest of us a Power Commander and gear position indicator, or at a push a new dashboard following a crash, were the extent of our electronic subterfuge. But that's beginning to change.

As we begin to see smart motorcycles being released in showrooms more frequently, our ability to meddle with the motorcycle we own diminishes. In the past, buying a motorcycle, fitting an exhaust pipe and Power Commander was part of the owning process. It made the motorcycle feel unique to us. But try anything more than replacing the end-can on a motorcycle built in the last two years and the amount of flashing lights it triggers on your dashboard is likely to leave you with permanent retinal scarring. Trying to fool the ECU with any form of after-market device therefore is virtual suicide.

That's why we find ourselves in the odd position of considering fitting whole ECU – and why there's a trickle of increasingly smart and cheap after-market ECUs being fitted to motorcycles. So, because they're out there – and to help you avoid having your hat nailed on due to not knowing any better, we thought we'd have a peep at some of the ins and outs of replacing your motorcycle's ECU.

In its most basic form on a carburetted motorcycle (hard to find any now-a-day) a modern ECU will do two things; control the ignition timing and provide the dashboard with the information it needs to display. But on most road-going motorcycles we can add operating things like exhaust valves, cooling fans and variable length inlet tracts to the mix too. It all sounds pretty daunting at first glance – but because the ECU is already wired to everything by the standard loom, controlling these functions is frequently no more hard than telling an ECU when you want something to happen, rather than how.
Perhaps the best example of how this can be done will be in World Superbike Racing. Getting a grid of 20 motorcycles running aftermarket ECUs well enough to race suggests the problem isn't insurmountable. In fact the toughest thing for that World Superbike Racing teams will be ensuring the ECU is capable of physically interfacing to all the original features of the motorcycle. As a quick aside this means being able to drive fly-by wire systems and have enough spare connections to operate all the flaps and valves required.

So, if you do ever find yourself considering changing the ECU on your motorcycle (and you'd be surprised how easy it is to come up with reasons to do so), it's important to do the same thing. Luckily, most manufacturers supply ECUs to fit individual motorcycles, even if they're actual the same unit. The fact they've said it will work with X suggests someone else has already looked at what you need and decided if this model fits the bill. But that's the easy bit.

Fitting a new ECU is either very easy or very hard, with little in-between. At the easy end of the scale we find kit ECUs like we fitted to the Kawasaki ZX10R. These units are made by the same people who made the motorcycle in the first place (although they're not really meant to find their way onto our road motorcycles of course), which means they generally use the same connectors as the original ECU and can control all the standard functions of the motorcycle, but without flashing a million warning lights at you when things change.

At the opposite end are true after-market replacement ECUs. These generally won't plug straight into a motorcycle's existing loom, and even if the connectors are the same size and shape (which does happen), you should never just plug them in. The reason being that although the plugs are the same shape, the wires going into the connectors almost certainly won't be in the same order and next thing you know you've frazzled the ECU and the motorcycle still won't run.

And that's the main reason why fitting is easy or hard. You either have to change nothing or get a complete or partial wiring loom made – and once you've had a bespoke bit of loom made (which can cost up to 90,000 THB) you've still got to remove the old loom and fit the new one.

Why would you want to fit a new ECU? As we said at the beginning meddling with your motorcycle us a way of making it your own. At a basic level this might be something as simple as fitting an end-can for a fruitier sound, but what about the fueling? If goes too far out of sync the ECU will need remapping to make the motorcycle feel good, and as ECUs get smarter it gets harder to fool them into doing things without them noticing. This is only going to get worse in the next five years.

So the first reason someone might consider fitting a new ECU is to get around the restrictions imposed by the OEM one. But in doing so you're also getting rid of the good bits. All the time and effort spent by team of engineers getting the motorcycle to run properly in different weather conditions will be lost. As will any traction or anti-wheelie settings the motorcycle may have had. So you're going to have to reconfigure all that yourself (or someone else to if you can't pinch the setting from somewhere). While this is interesting to do, it can be costly, which is perhaps the most compelling reason not to change.

Buying a motorcycle that's already been configured to use an aftermarket ECU is one solution, but is fraught with danger. There are many cases of people buying things (often ex-race motorcycles) that should have worked well on paper, but which then turned out to be too complicated for them to get working at all. And, of course, proving that's the case is difficult. A simple rule of thumb in that instance is not to bite off more than you can chew and go for the simplest option. If you're looking to buy a motorcycle which used to have a full-time World Superbike level technician looking after it, will you be able to do what's needed to keep it running day to day? Make sure the motorcycle is at least supplied with a base map too.

So it looks like a simple choice at the moment. Either do nothing to your new clever motorcycle because it'll get upset and sulk, or pay over-blown prices and stick to manufacturer approved products that will have been engineered to work but don't make for an individualistic motorcycle.

There is light at the end of the tunnel. In the same way that Power Commanders didn't exist before there was need there are certainly people out there now working on smarter ways to hoodwink clever ECUs. Although that will almost certainly be more of a warranty breaker than before, and chances are the ECU will collect evidence to use against you too, it does mean the whole after-market industry might survive. As it is, anything we can do as riders now to increase our understanding of how these systems work is going to seen us right in the future. After all, you need to know what the rules are before you can bend them effectively.
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