Custom Tune Information - Triumph Water-Cooled Models

What is ‘Engine Tuning’?

The purpose of tuning is to improve the efficiency of a motorbike’s running. This may be any of (or a combination of) the following:

• Power
• Torque
• Fuel efficiency
• Rideability

All tuning involves a trade-off between these factors. A more powerful tune will sacrifice fuel efficiency, and may also impact on rideability depending on how the customer would like their bike to perform. For example a high peak power tune may sacrifice torque at the lower end, making a bike less rideable in the city, or maximising fuel efficiency will lose power as the mixture is leaner than that of optimal power ratio.

 

Does my bike have to be tuned if I’ve modified something?

For most simple modifications the answer is no, but making changes to things such as valving or modifying the heads (porting or compression changes) will almost certainly require a retune.

It is important to differentiate between what must be done, and what can be done.

Tuning is only required if the changes to the setup can cause damage to the engine or risk to the rider. Tuning can be done to improve or release the performance gained by a modification, or to make a bike more responsive or pleasant to ride.

 

Information related to Triumph water-cooled engines:

Removing the catalytic convertor and fitting an X-pipe:

The mixture becomes marginally leaner, but given that these bikes run rich under throttle there is no danger to the engine. Rumours abound that these bikes run lean, but that is absolutely untrue. At cruise and idle they run at the emissions requirement of 14.7:1 (Stoich), and on over-run they virtually close the injectors off to prevent any unburnt fuel being emitted. Under acceleration they can go above 12:1 A/F ratio (rich), and never reach a level considered even moderately lean.

Removing the catalytic convertor and fitting straight pipes:

The performance is similar to an X-pipe, but the stock cams and tuning were designed with the exhausts blending. The two cylinders have different fuelling because they are affected by each other as the exhaust scavenges air from the opposite cylinder, so straight headers don’t give any benefit over an X-pipe.

Fitting an after-market muffler:

On old carby bikes this always required rejetting, as the primitive setup meant the engine would draw in too much air relative to fuel, resulting in lean cruising, which is not good.  Modern bikes have O2 sensors, so regardless of your modifications they will always run at 14.7:1.

Fitting a free-flowing air-filter such as K&N or DNA:

These make no difference to the fuelling on Triumphs. On old carby bikes it was important to replace the paper filters with mesh based ones because tuning modifications would cause fuel to splash back up onto the air-filter, dissolving it, causing small particles to be sucked into the carbs and engine, and removing the component that prevents dust and grit entering the cylinders.

Modern paper filters are extremely effective, and while free-flowing race filters are required with extensive head modifications, on the Triumph WC engines they have almost no effect.

Fitting pod air-filters:

Now this is a complex one. The Triumph’s don’t have enough space to fit a large pod filter, and smaller pods have significantly less surface area compared to the OEM filter. The mid-size K&N filters we often see advertised have a more reasonable intake area, but have the disadvantage that they are close to the injectors in the throttle bodies. A bike air-box is designed to act as a reservoir or buffer to capture the air and let it flow smoothly down the throttle tubes. Removing this can result in turbulent air in the throttle bodies, negatively impacting on the injector spray distribution and hence power.

Fitting an ‘n’ tooth front or rear sprocket:

This is just gearing, and has no impact on power. If you change from a 16 to 17 tooth front sprocket, your bike will go 17/16 times faster at any given rpm, and torque will be reduced to 16/17 of what it was at any given speed. Gearing has no effect on power.

Fitting a Booster-Plug:

Read the first item in this list. These bikes already run rich, and a Booster Plug contains a $0.20 component that falsifies data to your ECU, claiming the air is colder than it really is. Cold air is more dense, so the ECU adds fuel to allow for that density. Your bike runs even richer, so on a water cooled Triumph engine you will lose power.

If you prefer the slightly ‘muddy’ feel you get from an over-rich engine and the associated reduced 'twitchiness' then this is one reason you might want to fit this device, but when we tune a bike this is the first thing we would remove for an instant 2-3% power gain.

What does 14.7:1 mean?

This refers to the ratio of fuel (petrol/gas) to air that is injected into the cylinder. A ratio of 14.7 air to each 1 unit of fuel is the optimal value for fuel burn efficiency. It will burn every part of the fuel, and is referred to as Stoichiometric or ‘Stoich’.

This is not the most powerful ratio though. Maximum power from regular petrol is at 13:1, but will result in some unburnt fuel being ejected from the exhaust, and is the reason modern emission systems require a stoich ratio be used in all modern ECUs.

What does peak power mean?

Power is calculated by multiplying revs by torque. The peak power reading is the maximum value calculated across the rev-range.  It is useful as a gauge or comparison between engines, but peak power on a motorbike is rarely used unless you are on a race-track. Most people spend 95% of their time riding between 2000-5500rpm, so peak power at 6200rpm is not very useful.

What people notice most is torque. Twins have far more torque than four cylinder bikes, and that’s what helps you accelerate from stationary or medium speeds. For this reason you will notice immediately when your bike has more torque in the mid-range, but peak power may only be noticeable on a dyno chart.

I understand that every bike is unique, so I shouldn’t buy tunes off the internet:

This is a very important consideration. Modern bikes are engineered to extremely tight tolerances, their heads are ground by CNC machines, valves are manufactured identically, and the ECUs control precision injectors.  As a result of this we find that 95% of each model of bike is almost identical in performance. We have charts showing identical bikes with identical power curves, which give identical improvements when the same new map is loaded.

But there are exceptions. Perhaps a bike was assembled on a Friday afternoon, and the assembler didn’t set the cam timing perfectly, or perhaps the X-pipe someone fitted has slightly less cross-flow than another. Fortunately these tolerances have little effect on the fuelling, so it would be extremely unusual to find a bike that had a mixture we would consider ‘concerning’.

The most common reason for a bike giving a low power reading on our dyno is because the engine is ‘tight’. This is usually because a bike has been carefully run-in, and has never been revved hard (‘thrashed’). This results in much tighter bearing tolerances, so when the bike is run on the dyno the engine gets hotter than usual, the bearings get tighter, and subsequent runs show less power. This is not a concern and will disappear over time as the bearings wear in more.

No matter what happens we always recommend that before any modification you get your bike run on a dyno. This checks for existing issues, and gives you a baseline to gauge your modification against. After all, not all modifications improve performance!

After applying your modification, run your bike again on the same dyno!

Why does it matter which dyno I use for each run?

In a perfect world every dyno would give identical readings for the same bike. In reality they don’t, and this can be for a multitude of reasons. For example:

Each dyno has a different rolling-mass in its roller. Although calibrated, this will give different results.

Different manufacturers have their own smoothing algorithms, so some ‘peak’ power readings can simply be chain slap from a badly adjusted bike chain causing spikes.

Some dynos report in different units. SAE/BHP, DIN, etc. and some even report a calculated crank by ‘adjusting’ for transmission losses.

Environment affects the result because a dyno uses air temperature and pressure to adjust for differences in altitude and air-density to try and standardise. I have seen dyno operators move a temp sensor next to the bike engine to falsely indicate improved performance on post-tune runs, which is why it’s useful to see the environmental values on each run.

This is particularly tricky in places like Australia where it’s not unusual to get 36 deg one day and 20deg early evening. We prefer to do our run in cool air, but it’s not always an option.

Is it true that the throttle closes early on my bike?

Yes, most of the triumph tunes reduce the throttle to 85% just before the red-line. We’ve removed this reduction, but unless you have modified cams you will probably not notice the difference. By the time the engine reaches the rev-limiter it is already losing torque, so there is no benefit in riding in that rev region.

Can I extend the rev-limiter?

Yes, it can be increased from 7300 to 7800rpm. It appears Triumph set it lower because torque is already dropping at 6800rpm, so they added protection by moving the limit down 500rpm.  If you fit the race cam it is useful to increase this limit, but with the stock cam there is little or no gain.

What is ‘Sport’ mode?

The modes on a fly-by-wire bike are a simple mapping of throttle position to desired percentage power, referred to as an ‘ETV’ map. All modes open the butterfly valve to 100% at full throttle, but sports mode opens it more at 35% throttle, and rain mode less. Hence why the mode makes zero difference to power, but sports mode makes the bike feel faster because it’s opening the throttle more with less input on your part.

Care must be taken when working on ETV maps, as the ECU can exceed it’s expected parameters if the map is naively programmed, causing surging and strange behaviour on overrun.

Why does my bike pop on overrun? Does this mean it’s running dangerously lean?

It is running lean by design. All modern engines do this to prevent dumping unburnt fuel. Removing the cat and replacing the mufflers on a bike will cause this effect. The cat is extremely hot, so unburnt fuel usually ignites there, avoiding popping, and any popping is absorbed by the factory mufflers.

When you remove the cat a small amount of unburnt fuel with air ignites in the exhaust on overrun, and unbaffled mufflers will allow all that popping to be heard, sometimes very loudly. We minimise this by adding fuel on overrun to richen the mixture up, which allows it to burn evenly and significantly reduces popping.

How we tune

Each of our tunes has been designed by running the required model of bike on our dyno. We have an eddy current brake that allows us to load the engine to any speed and test every throttle position, so instead of a 25%,50%,75%,100% approach to tuning, we test continuously across every throttle value at each rpm range.

Our initial aim is to get the A/F ratio (which we read real-time through two wide-band sensors) to be as close to 13:1 as possible at all throttle positions. This guarantees us the optimal power from the fuelling.

Next we address the timing, and we investigate the power changes caused by advancing the ignition in different ranges. This has no effect on fuelling, but can give significant power improvements.  Excessive timing advance will give pinging or ‘knocking’, and Triumphs do not have a knock sensor. It is important that we note which fuel octane is used for this tuning, as we would not suggest advanced timing in locations where premium fuel is not readily available.