Supercharger Performance and Engine Performance Parts

In part 1 of this engine tuning guide , we explored the difficulties associate with altering the target air to fuel ratio on cars equipped with wide-band oxygen sensors and self learning ECU’s

In part 2 we are going to look at three products that offer different ways to solve this problem. All of these product work on the same premise which is:

1- Intercept the Oxygen sensor current or voltage signal (depending on the sensor type) going to the ECU

2- Monitor a set of control signals that tell the piggyback when and If the car goes into a performance state (such as wide open throttle, or a predetermined boost or rpm level)

3- Once car crosses over into this ‘enrichment region’, alter the oxygen sensor signal such that the On Board ECU thinks that the engine is running leaner than required (for example to enrichen up the mixture by 5%, make the ECU think that the current mixture is 5% leaner than the factory target)

4- Over time , the ECU will compensate either directly (through its own feedback control range which is typically +/-15% duty cycle) or through an external fuel controller or piggyback controller to now regulate fuel delivery at a new target air to fuel ratio that is set by our signal interceptor.

5- Check using an external wide-band oxygen sensor (which is separate from the sensor who’s signal is being altered to fool the ECU) that your actual air to fuel ratio is closer to the ideal required air to fuel ratio based on your boost level, compression ratio, rpm, octane level, and timing advance figures.

6- Check using an OBD scanner that your Short Term Fuel Trims (STFT) are now near 0% which means that the ECU is now happy with what it believes the fuel mixture to be and will not make any adjustments from where you are now…. which is … the perfect tune

The three products on the market (and as far as I know, the ONLY three piggy back controllers that work on this type of problem) are:

• The SplitSecond Enricher
• The URD AFR sensor calibrator
• The AEM F/IC O2 Skew function

The Split Second Enricher:

The split second enricher has the following features:

• Dual Channel Correction which is handy on Boxer 4, V configured engines where every engine bank has its own primary wide-band oxygen sensor.
• External voltage triggered which means you can start altering your oxygen sensor signals based on an external map sensor at a preset pressure level, an external rpm trigger at a certain rpm level, an external MAS sensor once the car goes above a certain flow level or any other combination of external voltages (a nitrous kit arming and activation trigger signal would be a great example).
• In addition to the external trigger option, the enricher has an Internal Pressure Sensor and a voltage adjustment setting that allows you to trigger enrichment based on a preset boost level using all the built in hardware which reduces the cost, installation complexity, and most importantly the probability of failure when having to buy and wire up a second pressure sensor for activation.
• Dual mode operation: Since the enricher is triggered by a certain voltage point (internal or external) the enricher’s functionality is fairly straight forward and basic where you toggle between only two preset air to fuel ratios namely 14.7:1 (stock) and the air to fuel ratio that you set using the adjustment knobs. This works well on lightly modified cars but may not be enough to smooth out boost transitions or part throttle hesitations on certain applications.
• In addition to having two wide-band channels, the enricher has a pair of inputs and outputs to alter the voltage of the downstream narrow-band oxygen sensors positioned after the catalytic converters. These additional adjustment channels can be used to adjust the narrow-band signal to prevent the factory ECU from triggering check engine lights for catalytic converter efficiency (since the ECU can no longer read the correct cat efficiency figures due to the altered primary AFR sensor’s signal under high load).

The URD AFR sensor calibrator

Underdog racing and development URD has been in the business of modifying Toyota engines for a long time coming now. Their original focus was the 1mzfe engine and related supercharger kit upgrades building on the original TRD (Toyota Racing and Development) supercharger package with additional fuel, more boost, and a better tune. Since then URD has branched out into more platforms, with more fueling options, and more tuning controllers including the URD AFR sensor calibrator and they have a very strong following on in the Toyota SUV market.

The URD AFR sensor calibrator has the following features:

• The unit has a built in programmable enrichment table that can either be pre-programmed by URD for common setups and familiar applications, or connected to their software for a custom program that fits the demands of your engine combination.
• Having a programmable enrichment map rather than a dual setting target AFR (like the SplitSec Enricher); the URD Capable of smoothing out transition enrichment and fixing hesitation problems related to part throttle & part boost conditions as well as altering the target AFR at full throttle and full boost.
• The device comes with dual channel capability similar to the AFR calibrator which works on V configured engines with dual sensors… however it does not have the ability to alter the secondary sensor voltages to prevent possible Check engine lights (for catalytic efficiency error codes) and additional narrow-band sensor simulators or oxygen sensor spacers might be needed on the downstream sensor depending on the exact application.

The AEM F/IC O2 Skew

AEM is Advanced Engine Management, and although their primary claim to fame was the advanced design of their intake systems and dry element air filter (which won the famous filter shootout for maximum flow AND maximum filtration of all the tested elements); they have recently diversified the company into offering a full arsenal of performance equipment including standalone engine management systems, water injection kits, gauges and more..

The AEM F/IC is a piggyback fuel and ignition controller with an expanded feature set that is almost as capable as a standalone engine management system and comes with an O2 skew feature that is our focus today

The O2 Skew feature has the following characteristics:

• The O2 skew has a 16 X 21 (iirc) programmable enrichment table that has different enrichment capabilities with respect to engine load and rpm. Engine load can be mapped to a map sensor, or a flow meter alternatively depending on what your engine primary metering sensor is.
• This programmable table allows for extreme fine tuning of the entire throttle and boost range of the fuel map, all the way from Idle up to full throttle and full boost.
• The O2 skew feature can operate both in current and voltage mode (just as the other two products mentioned here) and also has two channels of adjustment for V configured engines with two AFR sensors.
• In addition to these features, the F/IC has the ability to control your fuel injectors and ignition timing directly has an advantage over the previous two devices…
  • On lightly modified cars, using an enricher alone for minor corrections relies on the ECU to fine tune the fuel table which works well for minor corrections, however when the modifications are extensive and the corrections are large, an additional fuel controller is required to deliver the right duty cycle to the injectors to compensate for the OEM tune being so different from the target tune and the AEM F/IC has the built in capability to do this.
  • Lying permanently to your ECU using the enricher will eventually reprogram your long term fuel trims (LTFT) to match what the ECU thinks is going on with your motor. If you reset your engine or ECU these trims will disappear and the car will have to relearn your tune from scratch. Since the AEM FIC zeroes out all your fuel trims and relies on your AEM FIC fuel map to deliver the correct fueling (rather than the trims in your factory ECU) then resetting the ECU has no affect on the stability of your tune, no matter how big the corrections.
  • You can not only prevent your ECU from going into limp mode or cutting power, but you can further maximize your tune to take full advantage of your modifications with the proper fueling and timing.
• Finally, as far as I know, the FIC does not have the ability to alter secondary O2 channels and an external O2 simulator, voltage drop resistor (500 ohms to 1k ohms depending on the sensor current), or oxygen sensor spacer may be required to correct the richer signal being read by the post-cat sensors to prevent the ECU from throwing catalytic efficiency check engine lights.

All three of these devices are capable of making the modification experience a better and more refined experience on ULEV (ultra low emissions vehicles) and vehicles adhering to more stringent emissions requirements using wide-band primary oxygen sensors.

The choice of which device to go with will vary with the severity of the problem you have from minor corrections at WOT from a basic intake & exhaust install to a major retune for a ground up custom turbocharged application that has a completely differently shaped power curve.

Finally, if you are interested in more details on how to maximize the performance of your engine including what air to fuel ratios to target for your specific buildup, how to tune your timing curve to match the volumetric efficiency of your engine, and how to maximize both the response, power and longevity of your setup … be sure to checkout The Tuner Mastermind