Buying Guide: RSX E-85 / Flex Fuel Conversion
If you've read my comprehensive article about the benefits and considerations of E-85 and you're convinced that it's a good solution for you, here's my guide on a "do it yourself" setup. I've included information so you can scale it from bolt-on horsepower, all the way to the moon, and save money by getting what you need. With no further delay, here we go!
DISCLAIMER
This can only be done if you are running K-Pro 4, or Hondata S300 ECUs. Aftermarket ECU's allow adjustment for different fuels when equipped with a Flex Fuel sensor. I use K-Pro 4 on my RSX.
Also: Prices listed in my previous article do not include tuning and injectors. They do end up being more expensive than DIYing this. There's a price breakdown at the bottom of the article.
Sourcing E-85
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| A Map of E-85 Stations Across the US |
In America, the AFDC has a website you can use to find E-85 pumps near you. Make sure there's one decently close to you, on your commute to work or school, or a little bit out of your area as a last resort. If there's only one slightly out of your area, you can use a portable gas storage / pump solution like this one to stretch out your time between fill ups.
Fuel Pump
E-85 requires 30-50% more flow to make the same amount of horsepower as gasoline. Additionally, the stock fuel pump in the RSX contains rubber seals that may not hold up to higher ethanol content.
RSX Base Fuel Pump: 160 liters per hour @ 40PSI
RSX Type S Fuel Pump: 190 liters per hour @ 40PSI
AEM 50-1200 Fuel Pump: 340 liters per hour @ 40PSI
The AEM fuel pump I use and recommend will support around 600 horsepower on a turbo or supercharged RSX. It also is rated for E-100 and methanol, which means it's more than good enough for E-85. The pump drops right in, but with any RSX fuel pump upgrade you have to make some small mods to the fuel sender unit.
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| AEM Pump Horsepower / Pressure Graph with Different Fuels |
Link:
Buy the AEM 340lph E-85 Rated Fuel Pump hereInjectors
Much like the fuel pump, the injectors also need to be rated to higher flow rates to make the same power, and similarly rated for contact with E-85.
RSX Base / Type S Injectors: 310cc
For a full-bolt-on build (cold air intake, race header, 3" exhaust), I chose 750cc injectors. They are more than enough for 93 octane, but meet and slightly exceed needs for E-85. For forced induction applications, I recommend 1000cc injectors at a minimum. They will support up to 400-500 flywheel horsepower with boost. For anything higher, 2000cc injectors. It should go without saying, but only EV14 platform injectors make sense to use due to their size and performance at various fuel rates.
NO RDX 410CC INJECTORS - 550CC IS THE SMALLEST YOU SHOULD GO
Just to cut your apples for you, here's a simple guide to pick injectors. The data is calculated for running the injectors at 80% Duty Cycle, with 43.5 PSI coming from the fuel pump (stock).
Naturally Aspirated Application:
- Up to 250 Peak Crank HP
- Use 550cc Injectors
- Up to 350 Peak Crank HP
- Use 750cc Injectors
- Up to 350 Peak Crank HP
- Use 1000cc Injectors
- Up to 420 Peak Crank HP
- Use 1200cc Injectors
- Up to 700 Peak Crank HP
- Use 2000cc Injectors
- Up to 390 Peak Crank HP
- Use 1000cc Injectors
- Up to 470 Peak Crank HP
- Use 1200cc Injectors
- Up to 780 Peak Crank HP
- Use 2000cc Injectors
While you can use bigger injectors in your engine at lower horsepower, I would not recommend it. Injectors have certain size nozzles, and therefore, there is an optimal duty cycle to achieve a linear flow. Keeping injectors between 80 - 85% duty rate will make them work really well for daily driving. There are more sizes of injectors available, these were just the ones I did calculations for. The smallest I would personally go is 750cc on a K20A2.
Link:
Fuel Line
The RSX stock hard lines are technically fine, and have been known to flow as much as 600 horsepower; however, I wanted to put my ethanol sensor under the car, so I removed the stock fuel line.
Fuel line for E-85 needs to be the right size for your fuel flow, as well as being resistant to degrading from contact with the fuel. CPE, or Chlorinated Polyethylene, is inappropriate for this job because it is permeable and the E-85 fumes will escape. NBR, or Nitrile Butadiene Rubber is also inappropriate, because E-85 will degrade the inner lines. The correct answer is PTFE, or Polytetrafluoroethylene, also known as "teflon". In addition to the inner line being made from PTFE, I like the ones that have meshed stainless steel jackets to protect the inner line, and braided nylon on top of them to protect the car from the meshed steel from rubbing away at paint or vacuum lines.
As far as sizing goes, -6AN is plenty for most people. It will support up to 600 horsepower. I suggest buying a kit that comes with the line and most of the connectors required all in one box. 10 feet of hose is more than enough to get the job done.
Link:
Fittings
While the kit contains all the connectors you need to get the fuel line routed from the fuel tank to the fuel rail, you need connectors at the fuel rail and fuel tank, as well as where you put in the Flex Fuel sensor. These are what I used, and they fit everything perfectly, don't leak at all, and are quick-disconnect style for maintenance. You'll need 4, so order 2 pairs.
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| 6AN Male to 3/8" SAE Quick Disconnect Push On EFI Fittings |
Link:
Buy -6AN Male to 3/8" EFI Female Fittings
Flex Fuel Sensor and Wire Pigtail
The Flex Fuel sensor tells the ECU how much ethanol is present in the fuel in order to change the amount injected for combustion. The wire pigtail is the connector and group of 3 wires protruding from it that connect to power, sensor ground and signal.
There are 3 variants of Flex Fuel sensors compatible with K-Pro:
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| GM Part #13577394 - Notice the Longer Tube |
- 2011 Buick Regal
- 2012 Chevrolet Captiva Sport
- 2012 Chevrolet Equinox
- 2012 - 2018 Chevrolet Express 3500
- 2012 - 2016 Chevrolet Express 4500
- 2012 - 2018 GMC Savana 3500
- 2012 - 2018 GMC Savana 4500
- 2012 GMC Terrain
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| GM Part #13577379 - Notice the Short Tubes |
- 2012 Buick LaCrosse
- 2013 Buick Verano
- 2012 Buick Regal
- 2012 Cadillac SRX
- 2012 Chevrolet Impala
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| GM Part #13577429 - Notice the Short Tubes and Lack of Mounting Holes |
- 2009 - 2011 Chevrolet HHR
- 2013 - 2016 Buick LaCrosse
- 2013 Buick Regal
- 2013, 2016 Cadillac ATS
- 2013 Cadillac SRX
- 2013 Cadillac XTS
- 2012 - 2017 Chevrolet Caprice
- 2013 - 2015 Chevrolet Captiva Sport
- 2011 - 2017 Chevrolet Equinox
- 2006 - 2020 Chevrolet Impala
- 2014 - 2021 Chevrolet Silverado 1500
- 2021 Chevrolet Silverado 3500 HD
- 2015 - 2020 Chevrolet Suburban
- 2015 - 2020 Chevrolet Tahoe
- 2014 - 2021 GMC Sierra 1500
- 2021 GMC Sierra 2500 HD
- 2021 GMC Sierra 3500 HD
- 2013 - 2017 GMC Terrain
- There's more but documentation is kind of spotty and I can't confirm unless I go to the junkyard. This will at least get you started!
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| GM Part #13352241 |
Link:
Fuel Rail
The stock RSX fuel rail is fine for E-85, so there's really no need to upgrade unless your car is using forced induction. Above 450 horsepower, the stock fuel rail won't flow enough to feed the injectors, and the car will run lean. I wanted to be able to mount a fuel pressure gauge on my fuel rail to diagnose any problems in my fuel system, and eventually switch to a return-style fuel setup. Hybrid Racing often makes some of the best parts for K-series engines, and their fuel rail is no different. If you're staying under 450 horsepower, you can stay with the stock unit and save some money.
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| Hybrid Racing Fuel Rail |
Link:
Fuel Filter / Sock / Strainer
When your car has been sipping on 87 Octane, or maybe 91 or 93 Octane its whole life, it's a really good idea to change your fuel filter. With E-85's corrosive / cleaning properties, if you don't change your fuel filter and you start using it, the junk in the fuel filter can corrode away until it's small enough to get out of the filter and into the engine. It's probably about time you changed your fuel filter anyway. A good test is to blow through from one side of the filter to the other and see if you can even feel it. I could not with 150k miles on the clock, so it's worth the added safety to swap it out. Sometimes you can get away with using the filter that comes with the fuel pump, but it sits weird in the fuel sender assembly which might affect how low you can run the tank before you run out of fuel. Here's a before and after picture.
Link:
ECU Tuning
Price Breakdown:
- $122 Fuel Pump
- $430 750cc Injectors
- $50 6AN PTFE Hose and Connectors
- $34 2x 2 Pairs of 6AN to 3/8" Fittings
- $70 GM ACDelco Flex Fuel Sensor
- Or $3.99 from junkyard locally
- $8 GM Flex Fuel Sensor Wiring Pigtail
- Or included with FF sensor for free from local junkyard
- $0 Stock Fuel Rail
- Or $180 Hybrid Racing Fuel Rail for 450HP+
- $0 Included Filter with Fuel Pump
- Or $26 OEM Fuel Filter Replacement
- $8 Zipties (For Modifying Fuel Pump Cage)
- $300 ECU Tune
