The importance Of Individual Cylinder-Specific ECU Mapping

On virtually every modern motorcycle engine, you have more than one cylinder (with very few exceptions). Even modern entry level motorcycles, such as the Ninja 500, CBR500, etc are small displacement twin cylinder engines. Most "middleweight" bikes these days are twin or triple cylinder engines, and most "liter bikes" or flagship models are V4 or inline-4 cylinder engines. On all of these engine designs, the specific fueling needs from one cylinder to the next are NOT identical. 

Each cylinder has slightly different fueling needs, as the intake air provided to these cylinders AND the exhaust gasses ability to exit the cylinder, are not the same. Slight variations in intake runner designs, or velocity stack heights, that "feed" each cylinder create slight differences in the intake air flow and volume, just as slight variations in the routing of an exhaust header or manifold dictate small changes in exhaust pulse velocity, between cylinders. Internal combustion engine manufacturers have known this for decades, which is why the OEM fuel maps are not identical from one cylinder to the next. The differences in the fuel maps between cylinders is known as "cylinder balancing", and generally the OEMs do a pretty decent job of creating proper cylinder balancing for the stock intake and exhaust components.

When you install an aftermarket intake and/or exhaust system, you are changing the cylinder balancing significantly, and the OEM cylinder balancing is now far from accurate. Most other "tuners" in the motorcycle performance industry either do not properly understand this, or they do understand it and simply choose to not take the significant amount of time necessary to address the unbalanced cylinders appropriately. 

99.99% of all dyno graphs you'll ever see that display an AFR (air:fuel ratio) are collecting the AFR sample at the exhaust manifold/header collector. This is an average sample of all cylinders, and can only be used to make "gross" changes to all cylinders at the same time. There is no way to make cylinder-specific changes when this method of AFR sampling is utilized. For example, on a twin cylinder engine that is sampled at the collector you could see an AFR of 13.5:1, but cylinder #1 could be actually be at 14.5:1 and cylinder #2 could actually be at 12.5:1. These two AFRs would average out at 13.5:1, which is not terribly far off from an appropriate AFR target for many twin cylinder engine applications at WOT, but in reality you have one cylinder operating at a ~15% too lean and one cylinder operating at a ~5% too rich. A tuner only sampling AFR at the collector would not know this, and likely increasing fuel volume at WOT by ~5% at this specific point in the RPM range. This would bring the sampled AFR at the collector down to ~13.0:1, but in reality cylinder #1 would still be ~10% too lean at 14.0:1 and cylinder #2 would be ~10% too rich at 12.0:1. 

The example above is a scenario that we find on almost every modern motorcycle that we offer tuning support for, when aftermarket intake/exhaust components are installed. On some popular models, we've even seen as much as 15% swings in cylinder balancing when velocity stack lengths are changed dramatically (which is a popular solution to increasing intake airflow on many modern motorcycles) in conjunction with a "full exhaust system" that replaces the stock header, midpipe and muffler. The only way to properly develop custom fuel mapping when making these types of modifications is to sample the AFR at each cylinder individually. This can sometimes be done by running a "sniffer" tube back through the exhaust system and into each head pipe, so the only AFR being sampled is only from a single cylinder, but oftentimes modern exhaust routing and collector designs simply make this method impossible. In these situations, the aftermarket exhaust system has to be modified and individual 18mm wideband O2 sensor bungs have to be welded onto each head pipe at specific distances from the exhaust port on the cylinder head. This process is incredibly time consuming, and often costly, which is why (as we stated previously) almost none of the other popular tuners offering ECU flashing services for modern motorcycles develop their fuel mapping in this manner. It is the only "right" way to properly develop fuel mapping and rebalance the cylinders, so it's what we do here at 2 Wheel DynoWorks.

Obviously, this method of tuning R&D allows us to create massively more accurate fuel maps for all of the models that we offer support for. As is common internal combustion engine knowledge, a leaner burn is a hotter burn, and a richer burn is a colder burn. Equalizing the combustion and exhaust gas temperatures through proper individual cylinder fuel mapping is crucial to both maximizing performance AND maximizing engine longevity.

The OEMs also understand that combustion and exhaust gas temperatures are dramatically impacted by ignition timing advance, so they address the ignition timing maps on a cylinder-specific basis as well. On many engine configurations, there are several degree differences in ignition timing advance, at the same throttle position and RPM range, from one cylinder to the next in the stock igntion advance maps. On an inline-4 cylinder engine, for example, the inner two cylinders (#2 and #3) often have significantly less advanced ignition timing than the outer two cylinders (#1 and #4). This is often done by the OEMs for heat management of the inner two cylinders, as #2 and #3 often see higher combustion temperatures than the outer two cylinders simply due to heat transfer through the material of the cylinders and cylinder head. The inner two cylinders are surrounded on both sides by other cylinders that are generating heat, whereas the outer two cylinders are not exposed to as much heat transfer due to their physical positions inside the engine.

Another common example of this that is worth mentioning is on a V-twin or V4 motorcycle engine configuration, where the rear cylinder(s) ignition timing is often less advanced than the front cylinders for similar heat management issues. In many cases, the heat that manufacturers are trying to manage here is the heat felt by the rider between their legs, as the rear cylinder(s) are generally the one right below the rider's seat.

In either of the examples given above, understanding and analyzing ignition timing advance on a cylinder-specific basis is crucial when a tuner is looking to maximize engine performance. Again, most tuners are either unaware of simply how different the timing advance maps are from one cylinder to the next so they simply unify their ignition timing changes between all cylinders (while maintaining the cylinder offset, as is a common option in most modern motorcycle tuning software), or they simply do not want to go through the lengthy process of adjusting ignition timing advance on a cylinder-specific basis while monitoring for engine knock (detonation). Just like building cylinder-specific fuel mapping, the development cylinder-specific ignition timing maps is a VERY time consuming, and often expensive, process. That said, it's the only "right" way to properly maximize engine performance, so it's what we do here at 2 Wheel DynoWorks. 

We have been asked countless times by other tuners how we achieve certain power curves on certain platforms, that they simply can't seem to achieve through their own testing and tuning, and we immediately know that they are not developing their fuel mapping and/or ignition timing maps on a cylinder-specific basis. In fact, in EVERY single case of a customer sending us their ECU that has already been flashed by one of our competitors, and that they're unhappy with (which sadly occurs on a nearly weekly basis), both checkboxes for "unify all cylinders" and "maintain cylinder offset" have ALWAYS been checked in the various tuning softwares that we utilize. Even more shocking is the fact that in all of the conversations we've ever had with other modern motorcycle tuners over the past two decades, we have only ever heard of THREE other tuners developing their fuel AND ignitions maps on a cylinder-specific basis. Of those three others out there, one of them does not offer tuning to retail customers, as he owns one of the most successful Moto America teams in history and only focuses on his racing program, and another only focuses on tuning modern Harley Davidson motorcycles.

If you've ever watched any of our social media videos where we discuss proper fuel mapping R&D, you'll have likely heard us mention that fuel mapping is, by far, the easiest part of this job to get right...and almost nobody else actually develops it properly. Ignition timing mapping is the second easiest thing to develop, and it is even less common to see that properly developed.

Cylinder-specific tuning is incredibly time consuming, but when the goal is to maximize both engine performance AND longevity, individual cylinder-specific tuning is a requirement. This is why we ALWAYS optimize cylinder-specific ignition timing and rebalance cylinder-specific fuel maps for aftermarket intake and exhaust systems for every platform that we offer tuning support for here at 2 Wheel DynoWorks.