2014 CBR1000RR Aftermarket Exhaust and Dyno Tuning

I'm the owner of a 2014 CBR1000RR (non SP) and I've recorded my experiences here with installing an aftermarket slip on exhaust and subsequent dyno tuning. Many thanks to Julian for giving me access to his treasure trove of dyno chart data.


The post 2008 CBR1000RR comes with a really neatly faired in exhaust canister embodying Honda's "mass centralization" dictum that mandated a move away from undertail exhausts.

However, like all modern motorcycles, the OEM exhaust is forced to compromise performance with meeting emissions regulations. It has two valves in its construction. One is opened by an ECU controlled servo motor to meet low rpm noise regulations. When this valve opens there is a noticeable change in engine performance. The other spring loaded valve is opened when there is a sufficient pressure differential between two internal chambers. Only when exhaust gas pressure builds up to overcome spring tension does the resistance to gas flow drop. Both of these valves are welded into the canister and cannot be removed.

This exhaust is beautifully constructed in stainless steel. Its complicated three dimensional shape packs its mass tightly near the centre of mass of the motorcycle. And no doubt it's gas flow properties were carefully designed and tuned by the genius engineers at Honda. However, to meet EU regulations it ended up being massive (6kgs) and restrictive to gas flow, resulting in sub-optimal volumetric efficiency.

It has to be said that the stock ECU fueling with the stock OEM exhaust is pretty good and throttle responsiveness is generally excellent. Nevertheless, within its "closed loop" area it will be fuelled to meet emissions regulations and be very lean. 

This closed loop area is where fueling is changed in response to the signal from the oxygen sensing exhaust Lambda sensor, generally attempting to keep the air fuel ratios (AFRs) close to stoichiometric (AFR=14.7) to minimize emissions. Note that the intention of closed loop fuelling is reduced emissions, not enhancing performance. On the Fireblade the closed loop area is 0 to 20% throttle opening and 0 to 5500 rpm. Outside of these conditions (so called "open loop" area) is where your real performance lies and here the ECU does fuel more generously.

(Lambda sensors measure exhaust oxygen partial pressures from which AFRs are indirectly calculated.) 

>>>>>>>>>>>>>> 0 <<<<<<<<<<<<<<

My main reason for removing the stock exhaust and replacing it with a slip on was to reduce resistance to gas flow, and hence improve volumetric efficiency. Weight loss was an added benefit. I did not replace it so that my bike would make more noise. To me noise is a drawback of a pipe that breathes better.

From 2014 onwards the catalytic converter is no longer in the silencer, it has now become a fixed part of the headers. The only way to remove it is to replace the entire exhaust system. Also from 2014, and because of the catalytic converter, the link pipe for a slip on has increased to 60mm, making older slip ons incompatible (the USA bikes are different).

When choosing a slip on for the Fireblade there are a few choices. The link pipe can either be a convoluted "S" shape or it can be short and direct. The silencer can can either be compact and low to preserve what Honda was trying to do with mass centralization, or it can be bigger and protrude further and higher. Silencers that were not specifically designed for the Blade are often like this.

And then there is a choice of materials. Stainless Steel, Carbon Fibre reinforced plastic, or Titanium.

Stainless Steel is heavy and ages disgracefully. Where it gets really hot it discolours, looking like controlled rust. It is also prone to stress cracking.

Carbon fibre reinforced plastic has the virtue of being light. However, plastic is adversely affected by heat and carbon fibres will burn if heated enough. You will not find this material being used on a MotoGP bike exhaust despite its appealing lightness. No OEM exhausts are made of this material either. It doesn't tolerate localised stress points so the can is usually suspended by an unsightly encircling band. CF tipped exhausts are a cosmetic touch only.

Titanium is the perfect exhaust material.

Lighter and stronger than steel, rustless, attractive colour changes on heating, single piece construction possible without external springs and clamps. Material of choice for the hot end of jet engines since they were invented.

And then there is the actual dynamic design of the silencer and link pipe. Some aftermarket slip on exhausts are little more than a standard silencer can mated with a suitable link pipe to attach it to the headers. Others have been made specifically for the Fireblade on a flow bench and improved performance is confirmed with dyno testing.

The slip on I chose was this 1.3kgs of titanium made specifically for the 2014 Fireblade by Akrapovič.

It is obviously extremely light (saves nearly 5kgs) and is a single piece construction. No external springs or encircling clamps. It respects Honda's mass centralization dictum.

I was warned that this exhaust would damage my bike's midrange because the link pipe was too short and that it should have an "S" bend link pipe.

Akrapovič have validated the design of this pipe on the dynamometer and publish the following graph:

Akrapovič is more likely to know and understand the performance of this pipe than the critics I was hearing, so I ignored the "need" to have a long, S shaped piece of plumbing under my bike reminiscent of what you find under the bathroom basin.

After fitting a less flow restrictive exhaust to your Fireblade you will hopefully have improved its volumetric efficiency. Fitting a less flow restrictive aftermarket air filter will add to this effect, so I also installed a BMC air filter.

However, unless the bike's fuelling is now altered to match this improved air flow through the engine, the air fuel ratios are going to be hopelessly lean and this will attenuate any likely performance improvement.

Unless you intend changing your bike's fuelling, you are not maximising the benefits that improved gas flow can bring. Personally, I wouldn't go to the expense of fitting an aftermarket exhaust without also improving the fuelling. If your goal was simply to make more noise then none of this is necessary.

After fitting my new Akrapovič slip on there was no doubt that the bike was a lot rougher. There was some performance improvement but it was slight. The very impressive stock fueling with the stock exhaust had gone. I missed the smoothness.

Honda's ECUs cannot be flash programmed so the fueling map in the ECU cannot be changed and is the one designed years ago in Japan, optimised for your stock exhaust and reaching the compromises required to meet stringent emissions regulations.

So the next step was the installation of a Power Commander (PC) fuelling module. This device merely plugs into your bike's wiring between the ECU and the primary fuel injectors. No wire cutting is necessary and no permanent changes are made to your bike's wiring loom. If you later wish to remove it, it simply unplugs and the ECU is again solely in charge of fueling.

The Power Commander reads the fuel injector signal from the ECU and modifies this according to its own map, before then controlling the duty cycle of the primary injectors. (Injectors are digital devices and are either on or off. The percentage of time that they are on is called the duty cycle.)

Unlike the ECU, the Power Commander is user programmable, simply requiring a laptop and a USB cable. Pre-existing fuel maps can be loaded onto it or custom maps can be created using the Dynojet software and dynomometer.

Pre-existing fuel maps, supposedly optimised for a particular aftermarket exhaust, can be downloaded or shared from other Fireblade owners. These maps cannot hope to be right for the unique charactetistics each bike has.

The best possible fuel map for any particular bike is one that has been custom created by a tuner skilled in the operation of a brake dynamometer. This is a tedious process that requires creating a new setting at every different throttle position (2, 5, 10, 20, 40, 60, 80, 100%), for every rev range in 250rpm increments, in every gear. These values are either a plus or minus number, adding or removing fuel from what the ECU would have provided. A "zero map" is thus stock fuelling.

(The bike did over 100kms and used about 10l of fuel on the dyno)

Here is a sample fuel map, for a single gear:

(Generated on Excel from data downloaded from the Power Commander's custom map.)

So I took my bike to Julian who owns Superbike Solutions and the only person I know who has done his 10'000hrs on a brake dynomometer. His ability to optimise motorcycle fuelling and extract extra power is legendary.

However, before he can start he has do do two things (that I know of). The first is to inactivate the native lambda sensor, replacing it with a resistor that produces a flat reading. Otherwise the signal from the Lambda sensor will prevent the PC from taking over control of the AFRs. The second is to inactivate the whole Pulsed Secondary Air Injection system (PAIR). This system bleeds air from the air filter box into the exhaust ports in the cyclinder head, ECU controlled by a rapidly switching solenoid valve. The intention of this system is to introduce extra oxygen into the exhaust gases to ensure complete oxidation of carbon, nitrogen, sulphur, and unburnt hydrocarbon; providing the extra oxygen for the catalytic converter to achieve these goals. Quite obviously, extra oxygen added to the exhaust gasses is going to screw with the tuner's measurements of AFRs. 

I had previously inactivated the air inlet duct flap valves.

As Julian points out, the only way you are going to get more power is to burn more fuel. Having created better gas flow through the engine with aftermarket air filter and exhaust, you have the opportunity to burn more fuel, but only if you decrease the AFRs to an optimum for power production.

To satisfy stringent EU and other emissions regulations, the closed loop area of operation aims for an AFR close to stoichiometric (14.7). From the tuner's point of view this is far too lean for maximum power production. This occurs at AFRs in the 13.0 to 13.6 range. Exactly what AFR produces the most power at any given point on the fuel map is part of the dark art of dyno tuning.

My bike first went onto the dyno in February. Note that AFRs cannot be measured with the stock exhaust.

A good six months later it went back on the dyno with the Akrapovič exhaust fitted, but not yet dyno tuned. And then finally after dyno tuning. Blue is stock, Red is after fitting the Akrapovič and Green is after dyno tuning.

Note that this graph is generated in fifth gear at 100% throttle opening.

At first glance those increments appear small. But it would be entirely wrong to just look at the peak figure and decide that this exercise was largely futile. Also pay careful attention to the AFRs, depicted in the third line. Note how incredibly lean the Akrapovič made the AFRs especially between 4k and 8k rpm. This is exactly the intention of fitting the pipe. There is now the opportunity to add more fuel for more power. The Green AFR line is the result of Julian's tuned fuelling.

This particular graph is just one gear at 100% throttle opening. It doesn't tell you anything about how responsive the bike is to smaller throttle openings in lower gears, or how responsive the throttle is in general. Indeed, the difference when actually riding the bike is very obvious. After the dyno tuning it is far more responsive, smooth, and it accelerates a lot harder. The next graph attempts to illustrate this.

This is an acceleration graph. It is really important to note that the units on the horizontal axis here are seconds and not revs (it looks just like revs). This graph illustrates how many horsepower are available to you seconds after pinning the throttle. Note that after just two seconds the bike now has about 15Newton metres of torque extra. After five seconds you have 13Nm and 21 horsepower more than before the tuning. Not surprisingly, this is very readily felt when riding the bike, and noticed by my friend on his S1000RR.


The next graph is a comparison of my plain 2014 with my pal's 2014 SP. (See here.)

His SP has an Arrow titanium can and a stainless steel "S" link pipe.

The SP was on the dyno in March and mine in August but these two engines have an essentially identical torque and power generation. There is perhaps a slight advantage to my bike, so the predictions I was getting that my minimalist pipe was going to rob it of midrange are demonstrably false.

The next graph is a comparison of my bike and the undisputed 2015 Superbike horsepower king, the new S1000RR. This 2015 S1000RR was admittedly stock. 

Note the truly massive advantage my bike has at 4k and 8k rpm. Up until 11.5k rpm my bike is making significantly more power everywhere. After 11.5k rpm the S1000RR takes over, and enjoys a higher rpm redline as well, enabling him to hang onto the gear for longer than I can. You choose what you would like from your road bike. In fairness I have to point out that the S1000RR responds well to Julian's tuning as well. 

(The S1000RR has variable length, servo driven velocity stacks which are responsible for some of the glitches in the torque curve, especially the one near the top.)

The next graph is a comparison of my pal's SP (as above) and his 2013 ZX10R,  both fully tuned.

Here note that up to 11k rpm the Fireblade holds an advantage but after that the ZX10 makes greater peak power and would use this to advantage on a racetrack. Again, choose what you would prefer from a roadbike.

Thanks to Julian's meticulous tuning, my bike is more responsive, feels smoother, accelerates harder and feels much more like the precision instrument it should be. Highly recommended. There's a lot behind the new sticker on my lower fairing:

Keep it safe!