Generally if you're going this route you probably don't need any guidance about how to do it. Here are a few aftermarket ECU options and some differences:
| Stock PCM | MegaSquirt | Haltech Sport | Haltech Elite 750 | Haltech Elite 2500 | Holley Terminator X | Holley HP EFI | Holley Dominator | |
|---|---|---|---|---|---|---|---|---|
| Cost of ECM | ~$100 - $300 for tuning tools | ~$600 | $1,187 | $1,200 for ecu alone | $1,950 for ecu alone | $1,200 with harness and 3.5“ lcd | $1,433 | $2,300 |
| Cost of Wiring Harnesses | Uses factory 3800 harness | extra $224 for premium harness | extra $255 for premium harness | Comes with the harness | ~$700 Can buy as a kit | >$700 Harnesses sold individually |
||
| Ease of harness install for 3800 | Plug and Play | Requires custom harness | Plug and Play | Requires custom harness | Requires custom harness | Will need some modification or custom harness | Requires custom harness | Requires custom harness |
| Ease of use | Moderate | Difficult | Easy | Easy | Easy | Easy | Easy | Easy |
| Reviews | Good enough for most people | Difficult to put together, but a lot expandability. Pretty dated now | not great | State of the art. Created in Australia though support can be tricky | Terminator X is a lot like HP EFI but with a few less bells and whistles | Similar to Dominator but with less inputs/outputs | Dominator is basically the state of the art. Holley is very reputable | |
| water-proof? | yes | no | no | yes | yes | no | yes | yes |
| Wideband auto-tuning support | no | no | no? | yes | yes | yes | yes | yes |
| MAP limits for speed density tuning | 1.4 bar | 22 psi for ECM's internal MAP sensor | 5 bar | 5 bar | 7 bar | |||
| drive by wire support | Some PCMs | yes | yes | yes | yes x2 | |||
| Transmission control | yes | yes | yes | yes | only with “Terminator X Max” | no | yes | |
| anti-lag / launch control built in | no | yes | no | yes | yes | yes | yes | |
| CO2 control | no | no | no | yes | yes | yes | yes | |
| Boost by Gear | no | yes | yes | yes | yes | yes | ||
| Flex Fuel sensor support | not with a 3800 PCM | yes | yes | yes | yes | yes | yes | |
| Stages of nitrous control | 0 | 1 | 1 | 6 | 4 | 8 | ||
| fuel injection outputs | 6 | 6 | 1-6 | 1-8 | up to 8 | up to 8 | 12 “peak” + 12 “hold” = 24 injectors | |
| Ignition Outputs | OEM | 6 | 8 | 4 ground Can expand with CAN IO Module | 4 12v or ground PWM Can expand with CAN IO Module | 20 12v PWM 16 ground PWM Can expand with CAN IO Module |
||
| Digital Outputs | none | 28 | 0 | |||||
| Analog inputs | none | 10 | 20 | 4 | 4 | 13 “multi-inputs” + 30 sensor inputs (0-5v) | ||
| injector stages for fueling | 0 | 4 | ||||||
| Internal Data Logging | no | yes | yes | no | yes | yes | ||
| Known Oddities | oh boy, yes | not potted can't use external battery charger with ECU connected | can't use external battery charger with ECU connected | can't use external battery charger with ECU connected |
It's true, aftermarket ECUs are not cheap but they open up a lot of doors and remove a lot of the limitations of tuning the stock PCM. Tuning an aftermarket ECU is much more intuitive and much quicker than flashing tunes to the factory PCM.
If you are planning on getting serious with your build you're going to be piggybacking a lot of modules to give you all of the typical functions you would need while retaining the factory PCM. The costs of all of these begin to add up compared to using an aftermarket PCM that can replace all of these things so there's a good argument for just building the car with an aftermarket ECU right off the bat.
| HPTuners or DHP | $300 - $600 |
| wideband | $ 200 |
| electronic boost controller | $ 300 |
| MAF Scaler (mini AFC) | $ 160 |
| WOT Box (anti-lag & no-lift shift) | $ 220 |
| LS style coil near plug (CNP) conversion module | $ 160 |
Total cost if you added all of these modules would range from $1,640 - $1,340. If you went with just the basics: DHP, wideband, and MAF scaler you would stll be spending $660 and have a pretty archaic way of tuning your car.
An aftermarket ECU can eliminate all of these modules while also being much more user friendly and are much more extensible if you want go with some sort of wild inputs and ouputs in the future.
To use the Holley as an example, switching to the most basic Holley gets you built-in:
- wideband based fuel self-tuning
- boost control
- speed density tuning (Throw away your MAF)
- anti-lag / launch control
- run any coils you want to
- customizeable advanced tables
- customizeable inputs and outputs
- extremely fast reads and writes
- live tuning for things like fueling and timing
- expandable with Holley's CAN bus
- much much more