Briefly, the Unichip is a separate programmable ECU which interfaces to the existing ECU and is used to optimise the fuel, ignition advance/retard and boost pressure across the entire RPM range and at all throttle positions. 

It does not alter cold start, knock sensors, temperature compensation, air conditioning or auto trans control etc. 

Unichip will drive a number of other items such as water spray and auxiliary injectors, delete speed limiter etc. 

The construction of the Unichip is circuitry mounted inside an extruded aluminium casing and then resin filled. This ensures the highest reliability and resistance to vibration and heat. 

Primary use for Unichip is to optimise the EFI strategy for the exact requirements of the that particular engine with whatever modifications made to it. Basically the optimum power and torque across the throttle range and at any point in the RPM range with the best possible throttle response and driveability along with the best fuel economy under cruise conditions. 

Self Learn 

1: The factory ECU is an intelligent self learning unit. Once the UniChip is tuned to the car, how does the Unichip cope with the learning characteristics of the factory ECU? 

Modern ECUs employ a number of different mechanisms to optimize engine performance, emissions and engine durability. 

Closed Loop - An O2 sensor is used to monitor the air/fuel ratio and is used primarily under cruise conditions at light throttle opening (generally below 25% throttle opening) to achieve air/fuel ratios within a predetermined window of values. Ideally lambda 1 (14.7:1 Air Fuel Ratio). The standard ECU trims injector duty cycle (amount of fuel) only and does not trim ignition advance in closed loop. 

The Unichip promotes closed loop operation by running an optimum ignition map at part throttle in an effort to make it easier for the ECU to achieve lambda 1. This learning facility is necessary and enhances fuel economy and is mandatory for ADR/emission compliance. 

One needs to understand that the standard O2 sensor is a narrow band sensor which reads mixtures from around 14:1 to 15.5:1. Outside this range, the O2 sensor does not operate and adjust the air fuel ratio. 

Once the ECU is out of closed loop, it reverts to predetermined fuel and ignition tables. There is no or little learning facility in this mode. It is very easy for you to bring the ECU out of closed loop. A light stab on the throttle will bring the mixtures outside those able to be monitored by the O2 sensor. 

If the knock sensor system activates (detonation) the ECU will reduce boost and ignition timing for the sake of engine durability). This takes some time to come back. The Unichip does not affect this function. We see it as an important safe guard for long-term engine durability. This function is also often confused as "self learn". 

Let's take a step back and look at it in general terms and ask a fundamental question. 

How does an ECU know if the engine is producing more power?

It is logical to assume that when a high boost signal is seen by the standard ECU, it will deduce that the engine is making high power. With an interceptor style ECU, the standard ECU will never see high boost (i.e. instead of say 5 Volts, it only sees 4 Volts). The ECU is satisfied and will not attempt to adjust boost or affect other functions.

The standard ECU may see normal boost (when it is actually high) however the signal from the air mass meter may be very high. It is logical that the standard ECU may think that it is producing high power. Again with an interceptor ECU, the ECU may never see that high signal, so the ECU is again satisfied and will not attempt to affect other functions. 

There is no facility for the standard ECU to say that at a particular RPM point and at a certain throttle position, it should see a certain air flow value. Otherwise the ECU would not cope with altitude changes etc. 

In a nutshell, the standard ECU does not try to pull values back to predetermined levels. It tries to keep mixtures within limits at cruise and the ignition timing off the knock sensor circuit. Both good things to do.

In closed loop the ECU makes adjustments to air fuel ratios and not ignition timing. We generally do not alter air fuel ratios in closed loop. The only instance where we do alter closed loop fuel with Unichip is when say aggressive camshafts are used which push the air fuel ratios outside the O2 sensor's narrow band. The Unichip is used to bring the air fuel ratios back within range so that closed loop will again operate correctly. The reason we do this is so that at cruise, the optimum air fuel ratios are achieved - good economy and throttle response. 

Closed loop equals perfect air fuel ratios for cruise conditions. I'm not sure why anyone would want to run anything but the optimum air/fuel ratio at cruise - which is exactly what the ECU controls in closed loop. As I mentioned above, we tune engines to have optimum ignition timing when in closed loop to gain more torque, the best throttle response and optimum fuel economy.

Once programmed the Unichip does not need attention or reprogramming unless some other modifications are made which change the EFI strategy requirements - such as poor quality fuel or a fuel pump begins to fail (low fuel rail pressure).

The Unichip is used to adjust fuel, ignition advance/retard and boost pressure - not just fuel. On highly modified engines, items such as auxiliary injectors, water spray or injection, etc. can be controlled and accurately mapped. There is also a good deal of Boolean logic which can be programmed within the Unichip to make intelligent decisions for control of other devices. 

The 3 primary parameters for engine performance are fuel, ignition advance/retard and boost pressure. The optimum values for these change markedly depending on the throttle position, engine RPM, temperature etc. etc. 

Take boost pressure as an example, the optimum boost pressure at 3,500 rpm is different to that at 5,000 rpm. Rather than running a single boost pressure throughout the RPM range, the Unichip is used to set the boost pressure at each point in the RPM range. This means that aggressive boost pressures can be programmed where it is safe to do so (typically in the mid RPM range) and to pull boost pressure down at higher RPM. Of course, as the boost pressure is varied, the air fuel ratios and ignition advance must be corrected - A single ECU should perform this task. 

By running the optimum safe boost pressure, fuel and ignition at each point in the RPM range, the engine will produce the maximum safe power and torque without having to sacrifice engine durability or performance. In other words, you do not have to run modest boost pressure across the RPM range to keep things safe up high.

See 4 above. The Unichip controls the parameters independently. The Unichip tuner is presented with 3D ignition and fuel maps along with a boost vector. The ignition and fuel maps contain 17 RPM points times 12 throttle position load sites - 204 separate adjustments for air fuel ratios, 204 separate adjustments for ignition advance/retard and 8 separate boost values throughout the RPM range.

The Unichip *must* be installed and tuned in real time by a trained Unichip EFI specialist.

The Unichip will remove speed cut (180 kph on the STI for example) and fuel cut under high boost situations. The Unichip rev limit module is currently undergoing testing and should be available early 2001.

In normal operation this is not an issue. You would have to do something very radical to have this happen. 
 

• Apart from the extra power the part throttle response was amazing.

• Just a quick note to let you know that the REX is great, what a rush. It's like a completely different car, my friends and I can't believe the transformation you've done.

• I can feel the extra power at 1/2 throttle. And it feels goooooooooood :))

• Apart from the extra power the part throttle response was amazing. I have had this in the car for six months with 4 track days and can tell you the myth about the factory ECU learned and "tune out" the UniChip adjustments are just that "myth". The car still drive like it was when i first had the UniChip Installed.

• I have just had a Unichip installed last week and let me say that the improvement over what the car previously was immense.  The car drives exceptionally well and the power and torque gains are amazing to say the least.  The power is much smoother and feels more like a large (read: VERY) capacity engine, than a 2 litre turbo.  155kw at the wheels and 4500 Newtons of tractive effort out of a little car is ballistic in my view.  I just wrote to say thank you for installing, fitting and tuning a truly excellent piece of automotive equipment, and for transforming my car from something very quick to something out of control!!!

• I must thank you for all your help you have given me over the last 3 months. I am glad I ended up getting the unichip instead of the XXX plug and play MY99/00 EMS.  My unichip provides everything necessary for my car.

My car now gets to 100Km/hr 0.8 seconds quicker with the unichip and a little more boost, bringing it down to 4.6 seconds..With an AUTO !!

Read all about the WRX E-Group's comprehensive ECU Shootout by David Regenspurger.

Click here to see which vehicles will benefit from Unichip.

Please Note: The Unichip is available from APS in Australia and New Zealand only. For other regions, please contact Dastek.