This article provides a comparison of the pros and cons of the various ECU options available to someone with a 1999 or 2000 model year Impreza.
| Feature | Product | ||
|---|---|---|---|
| Original 'Unisia JECS' ECU | Possum Link ECU | DasTek Unichip | |
| Appearance | |
|
|
| ECU Type | Complete ECU | Complete ECU | PiggyBack ECU |
| Fitting | Plug and play. Change in 3 minutes. | Plug and play. Change in 3 minutes | Requires cutting of loom wiring. |
| Appearance | ECU fits car as standard. No signs of modification. | Replacement PCB - board differs in appearance, though fits in the original casing. | Additional cigarette packet sized unit |
| Reprogrammable | Yes, by Subaru or EcuTek dealer. | Yes. With Link handset or laptop software by dealer or owner. | Yes. By Unichip Dealer Only. |
| Compatibility with Subaru Diagnostic Tools | Full compatibility and accuracy | Not Compatible | Compatible, though diagnostic tools will read inaccurate values from the ECU, since the piggyback module modifies the I/O signals of the ECU. |
| Reports diagnostic trouble codes when engine parameters go out of safe limits | Yes | No | Yes |
| Mapping effort required to get good idle, cold start & aircon function | None - ECU does this as standard. Only modify what is required. | Provided with a default map that will start and run the car. | None - Piggyback only modifies what is required, leaving what is already ok intact. |
| Air Flow Metering Method | Mass Air Flow | Density-RPM principle using MAP sensor | Mass Air Flow |
| Closed Loop Lambda Control | Yes | Yes | Yes |
| Closed Loop Knock Correction | Yes | Yes | Yes |
| Charcoal Cannister Purge Control (Emissions) | Yes | Yes | Yes |
| Air-con aware Idle Control | Yes | Yes (including cooling fan) | Yes |
| Fuel and Ignition Map Resolution (RPM x Load) | 16x16 (256 zones) | 10x20 (200 zones) | 17x12 (204 zones) |
| Load Scaling Maps | Yes | Choice of two default maps held within ECU | No |
| RPM Scaling Maps | Yes - RPM Intervals may be individually specified | No - Fixed 500 RPM intervals | No - Fixed 500 RPM intervals |
| Boost Control | Yes. Closed loop control by duty cycle, boost pressure and atmospheric compensation maps. | Yes. Closed loop by algorithm. | Optional Extra, available as an additional module. |
| Boost Map Resolution | 8x8 (64 zones), 2 maps | 16x1 (16 zones) for target boost values. | |
| Wastegate Map Resolution | 8x8 (64 zones), 2 maps plus configurable turbo dynamics control | N/A | |
| Rev Limit Adjustment | Yes | Yes | No |
| Soft (Smooth) Rev Limiting | Yes | Yes | Yes |
| Speed Limit Adjustment | Yes | Yes | No |
This comparison is quite technical in nature.
If terms are used with which you are not familiar, please check the tuning section of the site for further information and explanation.
If you still need more info, please mail us on 
, and we'll do our best to make things clearer.
This aim of this article is intended to be an objective and fair comparison of products.
If you feel there are any omissions or errors in the above comparison, please email us on
for correction of this article.
Thanks to Bob Rawle of BR Developments (one of the largest Link distributors and tuners in the world) for additional information and confirmation on the current Link ECU specification.
If any data on this page is incorrect, please email us and we will promptly correct it.