What is... ECU flashing


Photography: Kardesign

It's the latest in fuel-injection tuning, and they've been doing it with cars for years. But what is ECU flashing? And how does it work?

Modifying the fuelling on engines is an essential part of any tuning process. Change an exhaust, or airbox, alter the cam timing (or fit a turbocharger!), and chances are you'll need to alter the fuelling, so your engine gets the right amount of fuel to match the air flowing into the motor throughout the rev range.

On carburettors, that meant physically changing the jets: small brass tubes, with precise holes in them, that fed the fuel into the air flow. But things are easier on fuel injection. If you can alter the length of time that the engine's ECU opens the fuel injectors, you can change the amount of fuel put in at that point.

On bikes, the traditional way to alter this injector duration has been to use an aftermarket fuel injection computer, like the Dynojet Power Commander (PC). These smart little boxes work by intercepting the injector signal from the engine's Electronic Control Unit (ECU), and changing the duration to suit, before passing it onto the injector. Used with a Dynojet dyno and the control software, a tuner can quickly and easily alter the fuelling across the rev range, increasing or decreasing the amounts as needed, at all engine speeds, and across a range of throttle openings.

The results are generally really good – a Power Commander gives great control over the fuelling on a bike engine, and can compensate for a wide range of engine tuning.

But there are limitations, and things you can't change so easily with a PC. That brings us to the other method of fuelling tuning – re-flashing the ECU. This means actually 'editing' the control programme that's on the bike's standard ECU, and uploading it into the memory. It's called 'flashing', because in ye olden days, computers used EPROM (Erasable Programmable Read-Only Memory) chips. These were erased by 'flashing them' - physically exposing them to ultraviolet light, which reset all the internal memory components, allowing a new program to be installed onto the memory.

Nowadays, we don't need UV lamps to reprogram memory chips (we use EEPROMs, or similar types of memory), but we do need some specialised kit. To wit, some method of connecting a computer or laptop to the ECU. That's part of the reason why ECU flashing is much more common on cars than bikes incidentally: cars have, historically, had easier ways to connect to their ECUs than bikes. Most of the big bike manufacturers have used closed, proprietary fuel injection systems, with no way to access the sealed ECUs other than official factory methods, or advanced, high-end hacking techniques.

But now, firms like Woolich Racing have come up with tools that let us access the 'brains' inside the ECU on many modern bikes. And that means we can re-program not just the fuelling parameters, but anything at all that's controlled by the ECU. So on Ride-by-Wire bikes, like Yamaha's R6 and R1, you can alter the rate at which the throttle plates open in relation to the twistgrip. Some bikes have restrictions here, meaning the ECU won't open the throttles fully in certain gears. By reflashing the ECU you can remove these restrictions, as well as top-speed limits, or power restrictions in lower gears. You can dump things like PAIR fresh air injection into the exhaust ports, or the EXUP valve operation. On a bike with secondary throttle valves, like a GSX-R or Hayabusa, you can take control of their opening characteristics. You can alter when the fan comes on, bypass sidestand and clutch switches, as well as fundamental things like rev limits, and even use more radical ignition timing to suit high-octane race fuel. Idle speed adjustment, quickshifter function, even datalogging and immobiliser bypass functions are all available.

So that's the theory behind ECU flashing. But in the real world, it's not quite as simple. One basic downside occurs when you change bikes. It's harder to get your ECU flashing money back – a Power Commander is easily removed, and will sell for good money secondhand. A flashed ECU is pretty much going to have to go with the bike, and you may, or may not get the value back. Even worse, if you want to return the bike to stock, and sell off the performance exhaust, cams, air filter or other tuning bits, then the altered ECU won't work properly with the standard settings. You may even need to pay to get the ECU set back to a standard map…

There are other drawbacks too. Reflashing the bike's stock ECU fuelling map is an enormous amount of work. To do it perfectly, you need to alter up to 25 load settings for all the various throttle openings. A dyno operator generally does three or four dyno runs to get an accurate figure for each fuelling alteration. So that means around 100 dyno runs – a massive amount of time and effort. Even worse, the ECUs take up to three minutes for the altered figure to be uploaded. So you have to add those few minutes onto each alteration. It's a proper drag to do properly.


And there's more. Many ECUs have different fuel maps for each gear. So you need to repeat the process six times… Six hundred dyno runs is an incredible amount of time and effort – and it ties up the dyno and operator the whole time. No-one is able to do that for a couple of hundred quid. Okay, you can cut corners, use a single map for all the gears, have a base map which you use to get close enough. But if you start to do that, then you're undermining the case for using ECU flashing in the first place.

Tuners we've spoken to suggest that the best plan is probably to use a Power Commander or similar kit to alter the fuelling – it's a far quicker and easier solution for almost all scenarios. And if you want to mess about with removing restrictions, exhaust butterfly valves, ride-by-wire settings, clutch switches, and the like, then do that via the ECU reflashing. That way, you get the best of both worlds: easier fuel mapping, plus the extra features available to ECU changes.

Power Commander

So if you fancy some flashy action, your local friendly tuning shop will be able to help, or you can go mail order. Try somewhere like Big CC Racing or TTS for ECU flashing advice and help. Alternatively, Woolich Racing sells the cables and software to let you do your own ECU work, if you're feeling saucy.

Biog: Alan Dowds (Dowdsy)