Ethanol versus Boost: Power requires balance

As warranties start to expire and aftermarket options become available, more and more Civic Type Rs are starting to look for extra power. In this blog post we'll cover why the 'best' ratio of ethanol to pump gas can vary greatly depending on your setup and how certain aftermarket upgrades help you run more ethanol. But first, a short intro on ethanol.

One of the main things you can tweak to gain power in an engine without changing the engine itself is when the spark plug fires. Known as ignition advance, it is expressed as a number of degrees on the crankshaft relative to top dead center and once a piston reaches that angle the coil pack energizes the spark plug. Advancing it further can potentially result in power gains, but you can also go too far and lose power and/or get engine-damaging knock from the air fuel mixture detonating instead of smoothly burning and causing the pistons to rattle in the cylinders.

An example ignition map

There is a solution to push it further, however! Better gas! Ethanol is significantly more knock resistant than pump gas and as such lets you advance the ignition timing further and gain mo powa, babeh. It's cheap, too, especially compared to race fuel. 

But there's a catch...

Ethanol increases fuel requirements

The most important thing to understand about ethanol in a Type R is that using it means your fuel system has to do more work. The more ethanol that you have in your gas tank, the more overall fuel your ECU has to inject to be able to maintain a proper ratio of air to fuel in your cylinders. We won't get too much into the chemistry here, but this is because ethanol is oxygenated. Pump gas is typically only 3% oxygen whereas E85 is about 30%. More oxygen in the mix means more overall fuel is needed to achieve a perfect reaction with the same amount of intake air charge.

This is a big problem since our fuel system is near the limits from the factory. Exceeding the fuel system's limitations will cause a loss of fuel pressure, misfires, and/or unsafe air fuel ratios, leading to reduced performance and engine damage. How, then, are we using ethanol?

Balancing with boost

Running ethanol with a forced induction engine that has a limited fuel system ends up being a balancing act between boost and ethanol content.

The other way to make power is, of course, boost. By forcing more air into an engine with a turbocharger, you can increase its effective displacement. But just like a larger engine with more displacement or running a highly oxygenated fuel, a turbocharger increases your fuel demand too. This ultimately means running ethanol with a forced induction engine that has a limited fuel system ends up being a balancing act between boost and ethanol content.

You can reduce boost on a Type R in order to increase ethanol content/ignition timing and possibly get a net gain in power overall. However, possibly is the key word here because the extra ignition advance may not outweigh the lost boost very much if at all. Not only is the stock fuel system on the Type R fairly limited, it's also not very consistent from vehicle to vehicle. Roughly 1 out of 5 Type Rs have a fuel system that already struggles to make the most of the stock turbo with pump gas and a custom tune. Whether it's due to manufacturing tolerances or something else we do not know. It is a known problem for all model years and domestic markets, but ultimately not a problem for Honda since it's plenty for the stock tune.

Fuel pump duty versus air charge. It is a near linear relationship and so we can limit boost for any fueling setup very effectively.

Using a flex fuel kit and flex tune, we can automatically adjust the maximum boost and ignition advance on the fly based on the ethanol content and RPM. With a proper tune, you can safely run anything from ethanol free to straight ethanol without having to adjust anything. However, there's a particular range or 'sweet spot' where you will make the most power overall. Too high or too low of a concentration of ethanol ends up in lost power. E20 may work best for one car, E40 for another.

After a few years of tuning Type Rs, we've found the sweet spot for the majority of stock fuel systems seems to be around 20-30% ethanol with peak air charge reduced from 235-245% to about 210-220% (boost PSI isn't a useful metric, read why here). This generally lands around 390-410whp with a custom tune which is definitely a huge boost above 91 octane's average 330-350whp and a decent gain over 93 octane's 370-400whp. But again, this is on an ideal fuel system that not all Type Rs have.

There's a few other ways your tuner can pull out some more capacity from the fuel system, but their safety and potential gains are fairly limited. You can run a leaner air fuel ratio, but this burns hotter and reduces reliability. You can also lower the requested fuel pressure, but this negatively impacts fuel atomization and distribution and will quickly reduce power and can cause unsafe conditions. Using external fuel systems like methanol and port injection not controlled by the ECU is an unsafe mess that can damage your engine very quickly if something fails.

Wouldn't it be nice to advance your ignition timing and also retain most if not all the boost your turbo is capable of with straight direct injection as Honda intended and no unsafe trickery?

Upgrading the DI fuel system

Components only need to be upgraded incrementally to support increasing levels of power. Over-upgrading is a waste of money as it is just unused capacity.

In the first couple of years of the FK8 Type R tuning scene, fueling was always the number one roadblock. The aftermarket for direct injection fuel system components is almost nonexistent, not just for the FK8 but for all DI platforms. Our only options at the time were port or methanol injection. However, today we now have a few options to choose from.

For most setups, there's four things you may or may not have to worry about upgrading, with those that generally become an obstacle first being ranked highest. Upgrading them in any other order will usually be a waste. There is one exception - very high ethanol contents (E60+) may cause premature failure of the stock in-tank fuel pump. We don't have too much data on this, but just a heads up. You may want to consider upgrading it ahead of time, but since the mode of death is usually like flipping a light switch you can just upgrade it once it craps out and your car refuses to start, too.. if you're about that life.

  1. High pressure fuel pump (~420whp+)
  2. Injectors (~450-500whp+)
  3. High pressure fuel line (~500whp+)
  4. Low pressure in-tank fuel pump (~500-550whp+)

The key thing here is that each of the four components only need to be upgraded incrementally to support increasing levels of power. Over-upgrading is a waste of money as it is just unused capacity.

There are currently two major providers of upgrades for the Type R: Hondata and Xtreme-DI (XDI). Hondata provides a full kit with all four components, whereas XDI provides pumps and injectors sold individually. There are also a plethora of flex fuel kits available and a couple of other small vendors for 1400cc injectors.

High pressure fuel pump

There are three main considerations for the high pressure fuel pump. The main one, of course, is how much the pump can flow at a given pressure. There's also a max rated pressure the pump can provide. Higher pressures are good because the injectors can deliver more fuel in less time. Finally, the pump is driven by the camshaft so it limits how high you can safely rev the engine without damaging the pump.

  • Stock
    • Max RPM: 7200
    • Max rated pressure: 200 bar
  • Hondata Fuel System
    • Max RPM: 7600
    • Max rated pressure: 200 bar
    • Flow increase: 24% over stock
    • Price: $2850 as part of kit (buy here)
  • Xtreme-DI EVO
    • Max RPM: 8000
    • Max rated pressure: 250 bar
    • Flow increase: 36% over stock (12% more than Hondata)
    • Price: $1600 (buy here)
  • There is also an unannounced pump from XDI with even more capacity but it only will be supported on Motec ECUs.


The injectors are why our engines are so damn loud. Clicking open and closed rapidly under 200+ bars of pressure to deliver precise amounts of fuel at exact times, the injectors are the ones really controlling the show. Our stock injectors are pretty decent, but eventually you'll get to around 45-50% duty where they have to be open so long per injection cycle that the fuel doesn't have enough time to completely inject before the spark occurs. The only two options are increasing the fuel rail pressure (thus why XDI's pump is a great option) or getting larger injectors.

  • Stock
    • Max flow: ~1050cc
  • Hondata Fuel System
    • Max flow: ~1330cc
    • Price: $2850 as part of kit (buy here)
  • Xtreme-DI 1350cc
    • Max flow: ~1350cc
    • Price: $999 (buy here) save $250 with pump bundle
  • Xtreme-DI 2000cc
    • Max flow: ~2000cc
    • Price: $1599 (buy here) save $200 with pump bundle

High pressure fuel line

The stock high pressure fuel line has a fairly restrictive outlet that may become a problem once you start going past 500whp. At the moment, the only off the shelf fuel line upgrade available is from Hondata's kit. However, modifying the stock fuel line is easy and only requires a 5/64th drill bit and some patience. Xtreme-DI is working on a fuel line upgrade that will hopefully be released in 2022.

Low pressure fuel pump

Luckily for us, low pressure fuel pumps are much more generic items that can be used across many platforms and has a lot of aftermarket support. There are several options available, most of which you will be hard pressed to max out with even 600whp setups.

  • Hondata Fuel System
  • DeatschWerks DW300C
  • AEM 340lph
  • Hellcat OEM pump
  • and more..

Flex fuel kit

While this technically isn't required to run ethanol, it makes it much easier and safer to use pump E85 and is more, dare we say it, flexible. You don’t have to worry about mixing an exact amount and if you’re traveling and can’t find ethanol you don’t need to reflash to a pump gas tune. There are quite a few flex fuel kits on the market, but they all do basically the same thing. There is no performance benefit for choosing one over the other, although some may have nifty things bundled with it like a physical gauge. It is essentially a sensor placed in between the low pressure and high pressure fuel pumps that measures ethanol content and reports it to the stock ECU by replacing the secondary coolant temperature sensor. We recommend the fan-favorite PRL Flex Fuel Kit. 

Example setups

There's a multitude of different configurations possible for different purposes, but we'll cover a few common scenarios here. Keep in mind that every car is different and everyone lives in different climates, so this should be taken as a general guideline. Your tuner may have a better idea of what's necessary, especially after they start tuning your particular car. All of this assumes you have at least a high flow or catless downpipe.

  • Stock turbo + pump gas
    • Unlikely to benefit from any fueling upgrades except for a very minor increase in midrange/peak torque.
  • Stock turbo + ethanol
    • Stock fuel system: Can give anywhere from a moderate to nonexistant increase in power over pump gas due to variability as explained earlier. 390-410whp max on E20-30.
    • XDI EVO pump: Majority of benefits will be seen with just a pump, reaching 420-450whp with E40-50.
    • XDI 1350cc injectors: Unlikely to be necessary in most setups, but marginal benefits have been observed at E40-50.
  • Upgraded turbo + pump gas
    • Stock fuel system: In most cases, the gains will be minimal and not worth the very high price of an upgraded turbocharger.
    • XDI EVO pump: Majority of benefits will be seen with just a pump, reaching 440-470whp.
    • XDI 1350cc injectors: You can potentially gain an additional chunk of power depending on the setup. All depends how much air your turbo can force in. For example, stock exhaust + front pipe tends to not reach 500whp even with injectors.
  • Upgraded turbo + ethanol
    • Stock fuel system: A total and complete waste of money. Upgrades are mandatory at this point.
    • Hondata Fuel System: While you can make gains on this setup with just a pump, you will be leaving a ton of power on the table without upgrading the rest as well. Hondata provides a nice all-in-one kit that gets the job done for most.
    • OR XDI EVO + 1350cc injectors + drilled line + LPFP: Xtreme DI's pump and injector provide more capacity for significantly less money. If you don't mind having to source a low pressure fuel pump and drill your own fuel line, this is the route to go. You can also optionally upgrade a Hondata fuel system in the future with an XDI pump. In the near future XDI will be offering a full kit as well.
    • E30-50 recommended.
  • Running straight E85
    • Generally speaking, this will result in a loss of power on most setups compared to the sweet spot. We simply don't have a pump available that can handle full boost and straight ethanol. While a fully upgraded fuel system won’t see a significant loss, especially on a stock turbo, you might find it’s not worth it to run straight E85 unless you really want to not mix at the gas station and don't mind losing some power to do it. Technically even the stock pump can do straight E85, but at the cost of having very little boost.


Hopefully you've learned a bit more about a commonly brought up topic on how to make more power with the Civic Type R. There's a good variety of parts now to upgrade our direct injection fueling and people don't need to buy a super expensive one-size-fits-all kit to see moderate gains in the 400-500whp region. A pump and ethanol will give you the most cost effective gains, especially on a stock block.

Ultimately, the perfect ratio of ethanol is something your tuner will have to find and instruct you on as it can vary quite a bit from car to car, tune to tune. But now you should have an understanding of why that is.

If you don't want to upgrade your direct injection fuel system, the best thing you can do is run unoxygenated race fuel... but at $9 or more per gallon, that's something best suited to track and dragstrip events. Otherwise, in the long run fuel upgrades will make more financial sense.

Above all else, the most important thing you can do to make the most of your setup is a custom tune that is thoroughly tested to ensure no fuel component is being pushed past its limits nor leaving power on the table. We've tuned hundreds of Type Rs with every fueling configuration imaginable and can make spending your hard earned money worth it.