modifications > Ethanol Content Analyzer

Why did you install an Ethanol Content Analyzer (ECA) on your RS?

The Focus RS is not designated as a flex fuel vehicle from the factory. However, there are many benefits of running higher than premium 93 octane unleaded fuel. One of the biggest benefits of running a higher octane fuel is that you can run more spark advance to generate more power. It is also highly recommended to run an aftermarket intercooler to lower the charge air temps so that timing advance is not reduced. We are trying to prevent knock (detonation, pre-ignition) from occurring in the cylinders. The highest ethanol mix that is safe to run in the Focus RS on the stock fuel system is E30 or E40. Anything higher than that will require either a high pressure fuel pump (HPFP) and injector upgrade or a port injection system. A tune is required to take advantage of the higher octane. Race gas is also an option, but blending E85 with 93 octane to get E30 or E40 is much cheaper in the long run.

In steps Tune+ to offer a Fuel It Bluetooth Ethanol Content Analyzer (ECA) kit for the Focus RS. Included in the kit are (2) fuel hoses, ECA, and wiring harness.

Date Completed:



- Tune+ Fuel It Bluetooth Ethanol Content Analyzer (ECA)
- Add-a-Tap fuse to power ECA
- Scrap metal for ECA bracket
- Several zip ties
- Sweet Tea (optional)


- 1/4" drive ratchet, 6" and 12" extensions, various sockets (7mm, 8mm, 10mm)
- Allen wrenches (ECA bracket + Battery Box)
- Needle nose pliers (to pull mini fuse)
- 5/16" fuel line quick-disconnect tool
- Soldering iron or electrical connectors
- Wire stripping pliers
- Drill and bits
- Wire crimper
- Must download Fuel-It App (Apple - Link, Android - Link)
*A friend for moral support is always optional.


1. Install should take about 30-45 mins. I took my time because of taking pictures for this website.
2. Only (1) wiring plug needs to be disconnected/reconnected for this installation (intake temp sensor).
3. Caution - Release fuel pressure before disconnecting fuel lines. See first pic (#00) below.
4. ECA attaches to factory RS battery box. I made a custom bracket for my lightweight Grimmspeed battery setup.
5. Reversible back to stock.

Proven Results:

1. I compared (2) datalogs to check the results of different fuels (93 octane vs E30).
2. Barometric pressure = 14.68 psi (93 octane), 14.65 psi (E30).
3. Ambient Temp = 78-80 F between both datalogs.
4. The results speak for themselves. E30 makes tremendous gains for little cost!