Equipped with a Keihin ECU, the turbocharged L15 family of Honda engines (as found in the Civic SI from 2017-2021) behave a bit differently, and are tuned in a different manner than the K20C1 civic Type R and it’s Bosch computer. That being said, many of the fundamental ideas and concepts of how to tune are pretty standard across the board.

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Torque Control

The FC1 generation Civic SI uses a torque-based control strategy. The strategy used is a bit simpler than what is found in many of the other bosch vehicles (Ford/VW/Porsche) and even the other Honda vehicles. It is probably a bit closer to a Subaru in terms of the amount of changes needed to get the desired changes done.

Torque Request

Torque requests start with three tables:

• Throttle Torque Request RPM

• Throttle Torque Request Error 1

• Throttle Torque Request Error 2

Throttle Torque Request RPM

This table is valuable for increasing torque requests at wide open throttle (WOT) as well as dialing in throttle response. Adjusting the table is pretty simple, the x and y axis show throttle position (not accelerator pedal) and RPM, and the z data represents the torque being requested. The higher the value of the request, the more torque will be requested from the engine.

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Throttle Torque Request Error 1 &2

The two error tables are gear-dependent torque reductions for 1st and 2nd gear (table 1&2 respectively). The values in these tables are removed from the main Throttle Torque Request RPM. In order to make the torque request and responsiveness identical across all gears you can zero all of these out. Conversely if you’re finding traction is limited or the car feels overly sensitive at low speed, you can leave most of those per-gear differences in place.

Torque Limit

There are two main limit tables for the torque system.

• Torque Rate Limit

• Torque Limit RPM

Torque Limit RPM

A 2-D table used as a limit for the maximum requested torque for the RPM the car is currently at. Make sure to increase this as you increase your torque requests to avoid hitting the limiter. You can also use this to taper off power at high rpm to give a safety margin for some cars (or slow your teenager down).

Torque Rate Limit

This table sets the rate at which torque is allowed to increase every second. The lower the value the less torque is allowed to be increased at that RPM as you accelerate. When driving and datalogging the factory calibration, you’ll notice that boost response after shifting in a multi-gear pull is slow.  While part of that is the delay of mechanical response from the turbocharger to spool back up after closing the throttle, opening the bypass valve, and dumping boost to shift, another element of control will limit the rate at which torque can be reintroduced.  Looking at the table, a quick glance above 4000rpm you’ll see the torque rate is limited to 113 ft/lb/second stock. This can create a bit of a delay or lazy feeling when doing a multi-gear pull, and isn’t a limitation of mechanical parts on the vehicle. Increasing the values in these tables can increase the rate at which the boost will be increased.

Boost

Like many modern vehicles, the Civic SI of this generation aims to produce an amount of torque to match what the driver is requesting. To achieve that goal the computer looks at ignition timing, air/fuel ratio and boost pressure and sets them all to hit the target. In instances where the computer is targeting less boost than it’s currently producing the throttle body can be used (as wellas the wastegate) in order to reduce the amount of boost pressure to keep MAP on target.

MAP Limits

Once the torque model has calculated a target manifold pressure, there are several boost limits that can trim down the final boost output. These can all be found under the Boost Limits folder. Our maps have been set up to use Boost Command Selection Table Pressure Ratio as the primary boost limit. Making sure to set a healthy table for your boost target at lower pressures will help keep turbo speed and EMAP under control under those conditions

Boost Maximum Selection Table 1-8

These tables are of an identical size and activate at different temperatures (based on IAT2 monitor) as determined by the curve Max Boost IAT2 Selection Axis. Once you’ve determined what temperature applies to each table, modify the boost target as desired for that temperature for optimal performance, or to help turn things down and keep temperatures under control. Stock many of these tables have the limits pushed well out of the way, but as things warm up you will find that they reduce boost pressure with factory settings.

Boost Command

Now that you’ve gotten a torque request which gave you a target boost pressure which has then been limited by the set of limiter tables, the Boost Command table is used to translate that target into a throttle inlet pressure target. When tuning, make sure to extend the x-axis (MAP) and z-data (throttle inlet pressure) as needed to achieve your boost targets. If you don’t extend the values, pressure targets will be limited by the highest values in this table.

Ignition

Ignition timing is fairly easy to control for these vehicles. There are two main ignition tables Basic Ignition Timing 1 & 2. These tables are set identically from the factory and we recommend doing the same thing when you make changes. There are multiple compensations that get applied to the ignition timing before it gets to a final values, so the values you see in a datalog will typically be a bit lower than in the table. The x-axis (Airflow) can be seen by choosing the airflow monitor for any of the cylinders, while there is a little variance it should give you the necessary information to know where the table is being used.

Temperature-based Timing Compensations

There are two tables for compensation for both air temperature and coolant temperature. One for high and low pressure MAP. Since the knock threshold typically changes with temperature, this allows you to optimize for multiple conditions.

Octane Learning & Knock Retard

The Civic SI uses a simple learning system when it encounters knock. This is a global multiplier to ignition advance that changes when the car knocks (or doesn’t). When reflashing (on the factory values found in the Learned Knock Default Value table) the car will reset to the lowest multiplier value (-349.19) and learn back up as you drive. for peak values you’ll typically see values of low 40’s for low load, and 53 at WOT.

Knock Sensitivity

Controlled by a table for each cylinder, knock sensitivity is decreased (ignores noise) when the value in the table increases. If trying to reduce noise from a built engine setting off the knock system, add a high enough octane fuel that the car won’t knock at all, then increase values of the areas in question until you don’t see any more engine noise.

Fuelling

Airflow

The Civic Si uses a MAF based airflow measurement system (adjusted in the table AFM Scalar. The signal is frequency based and will need to be tweaked whenever you mess with things affecting airflow such as an intake. Using the monitors MAF Airflow and MAF Frequency along with your fuel trim monitors (Short term and Long term) should allow you to modify the curve as needed.

Target Lambda

Wide open throttle fueling is run off of four different lambda tables.

• WOT Lambda Adjustment 1-3

• WOT Lambda Adjustment LBT

To determine where in each table you’re operating you’ll want to use the monitor Airflow Axis AFR this should be a direct translation of what airflow value it is currently using for the x-axis in the WOT Lambda Adjustment tables.

You’ll notice that target lambda values in these tables are on the richer side, going down as rich as 8.7:1 in some of the tables. Based on testing with the stock sensors and external widebands, the afr value in these tables and in the monitor are not accurate to what the vehicle is doing. It’s recommended that you use a wideband and then make percentage changes to your target afr based on what the car is running on the wideband.

WOT Lambda Adjustment LBT Uses ignition retard as an input axis to richen the air fuel target when knock events occur. As knock occurs you may want to add greater enrichment with this table, but make sure you’re staying within the fuel system’s capacity. If the injectors are already maxxed out, trying to increase the fuel won’t do anything.

Fuel Pressure

There are 5 different tables to handle the high pressure fuel pump pressure target. Target HPFP Pressure 1-5. These tables can be modified at higher loads to increase or decrease the pressure target for increased boost/delivery needs.

Closed/Open Loop

After a flash or ECU reset, closed loop fueling and o2 sensor activity reactivate quickly at low-load, part throttle driving. That being said closed loop will not be active at WOT until the car has been driven on the road at varying amounts of load for 10-20 miles. What this means is that as you iterate your calibration on the dyno or even on the road (safely please), a WOT pull after the reflash will result in open loop fueling. This means that once you’re fairly confident in your calibration, you should evaluate it on the road or after some road driving, which should allow you to make sure the car behaves as desired once the car is using closed loop fueling at wide open throttle.

Variable Cam

The FC1 generation L15B7 engine does not offer Honda’s flagship VTEC variable lift system, however it does offer variable cam timing on both the intake and exhaust cams. There are two main tables for each cam, Intake Cam Set Point WOT (as a real shocker) sets the cam set point under wide open throttle conditions. Intake Cam Target sets the camshaft setpoint during the other driving conditions (not WOT).

Links

Map Notes for FC1 / FC3 Civic Si