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Ethanol & Flex Fuel Tuning: Fuel System Requirements

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Fuel System Requirements

05.41

00:00 - Regardless whether you're planning to tune your engine to run on ethanol fuel full time or you're developing a flex fuel system, there are some aspects you'll need to keep in mind regarding your fuel system and some potential upgrades you may need to make if you're starting with a system designed around gasoline.
00:17 Let's start with the safety aspect of converting to ethanol fuel.
00:22 Any time we're dealing with fuel system components, some caution is recommended as the result of a fuel leak may be catastrophic.
00:29 If your car's fuel system was not designed with ethanol compatibility in mind, it's possible that certain components in your fuel system may not be tolerant of alcohol.
00:40 This typically includes the O-rings that are used to seal the fuel injectors into the fuel rail, as well as the actual fuel lines and even potentially the fuel pump.
00:50 When ethanol fuels first began appearing, this presented quite a large problem, as many factory fuel systems were not tolerant of ethanol.
01:00 In more recent times it's common for even conventional gasoline to contain small amounts of ethanol and the majority of current vehicles being sold have fuel systems that are tolerant of ethanol.
01:12 If you have an older car though, and you're unsure about the fuel system compatibility, you can refer to the owner's manual which will list what fuels the system is safe to use with.
01:23 This information is also often noted inside the fuel filler cap for convenience.
01:29 Many cars will be listed as being compatible with E10, which is a 10% blend of ethanol.
01:35 But also may specifically state they are not compatible with E85 or E100.
01:41 This is usually not a reflection of the compatibility of the fuel system itself however, and simply means that your car is not a flex fuel vehicle.
01:51 The relatively minor fluctuation in fuel requirements as we move from gasoline through to E10 is able to be coped with adequately on most newer factory vehicles via the close loop fuel control strategy however thee higher ethanol concentrations will require flex fuel capability.
02:11 Once you've covered the basic compatibility requirements of your fuel system, you'll also need to give some thought to the size of your fuel system.
02:21 As we've already discussed, due to the characteristics of ethanol, we know we're going to need to provide approximately 40% more fuel volume to mix with the same volume of air, when we switch from gasoline to E85.
02:35 Considering usually the switch from gasoline to E85 has been made in an effort to allow us to run higher boost levels in a turbo charged engine, and hence make more power, our actual fuel system requirements may be even higher when we start considering vastly higher power levels.
02:54 In general the areas we'll need to consider are the injector flow, fuel pump flow, fuel line size, and possibly even the flow capability of the fuel pressure regulator.
03:06 There are ample resources already available on the internet to help you find the right sized injectors for an application when running on gasoline, and we cover these calculations in detail in our EFI Fundamentals course.
03:20 If you're using an online fuel injector calculator you'll often find that the numbers they produce are scaled for gasoline but you can convert the resulting injector size to something that will suit E85 by multiplying the value by a factor of 1.4 For example if you find that you need a set of 1000cc injectors for an application running on gasoline, then you'd need 1400cc injectors to support the same amount of power on E85.
03:51 One of the best references I've come across for choosing both fuel pump and injector size on an ethanol based fuel system, is care of the Injector Dynamics fuel flow calculator that you can find in the link below.
04:03 During their testing to develop this calculator Injector Dynamics found that on average an engine will require 0.35 litres of gasoline per hour, per horsepower.
04:14 While on E85 this increased to 0.5 litres per hour per horsepower.
04:20 This study was assembled from chassis dyno data so the results are horsepower at the wheels not the flywheel.
04:27 If you're building a fuel system from scratch, then it's important to make sure the components you select are rated for ethanol fuel.
04:34 This includes the injectors, fuel lines, and fuel pumps.
04:39 When it comes to the injectors, one precaution to keep in mind is that some aftermarket injectors, are not compatible with the fuel additive MTBE.
04:48 This is often included in commercially available race blends of E85, such as C85 from VP Racing for example.
04:57 As far as fuel lines go, there are now several manufacturers that are offering specific fuel hoses designed for ethanol use, that are guaranteed not to break down.
05:07 And example of this is the barricade product from Speedflow.
05:12 Another common option when it comes to fuel hose that is ethanol safe is Teflon braided hose.
05:18 This offers the added advantage of being 100% impermeable which means that you will not be able to smell fuel if your fuel system is plumbed inside the car.