A Surge in EVOs

We see our fair share of Evolutions here at Powertune. This one in particular though, we’ve been looking after for over three years. As with most EVO enthusiasts, plans were always in place for a proper power build in the future. Slowly but steadily armed with a set power goal in mind, we outlined the required parts to achieve this power safely. In general we recommend and prefer to over engineer the package insuring the engine is never running anywhere close to ten tenths.


Over the years the factory EVO 9 has been improved substantially, specs listed below :


Our final piece of the puzzle (for now) has just been put in place with the addition of an Aftermarket Industries surge tank setup. Up until now we have been running temporary Walbro 450 fuel pump inside the OEM housing, for the purposes of making sure the engine build was performing as intended. The single 450 pump was delivering sufficient fuel flow for our requirements at the time, providing fuel for up to 330kw on E85.

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More often than we would like, we see cars roll in through our doors with very poorly installed or thought out fuel system setups. When choosing the correct fuel delivery system there are a few key notes to keep in mind. The first and most obvious is; how much power are you needing to supply fuel with? Another very common mistake we see is the incorrect wire gauge being used. Heating up of the wiring system is catastrophic without the need to explain why. Couple bad wiring with incorrectly placed fuses, or in some cases not fused at all ! And you have yourself a recipe for absolute disaster.


When selecting the correct wire gauge, the most simple of formulas is used. OHM’S law says to find the current (amps) you divide the Voltage in question by the Resistance of the system ( I = V/R). So to apply that to our purpose; we need to find out how many Amps the fuel system will draw. Only then can we select the correct wiring, and fuses required. The Voltage we know is 13.5V. The resistance is something we measure across the fuel pumps individually as it may vary from pump to pump. In this case we measure a total of 0.7ohms across each of the pumps.
So we’re left with 13.5V / 0.7Ω = 19.2A. This means for SAFE function the wiring needs to be rated at 20A. With 20A fuses protecting each of the pump’s circuits, as pictured below in the final install.  


Now that it is time to dial up the power, we were given a green light to upgrade the single fuel pump  setup, to a proper high flow surge tank system in the boot. Keeping in mind that this EVO is a daily street car, the customer requested we source a quieter surge tank setup. With that in mind we opted for the Aftermarket Industries SP800 setup which also allows us to install x2 Walbro 450  pumps. Generally a safe and ample fuel system setup will fetch around the $5,000 mark, but with some planning and foresight we were able to save our customer some dollars here and there.

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Here we see Adam disassembling the Ai surge tank, readying it to fit the two Walbro 450 pumps. Previously we had installed a 450 Walbro pump into the OEM housing. That pump will be getting brought over into the surge tank setup, and an OEM fuel pump will be put in it’s place to supply the surge tank directly. Adam gets to carefully removing the fuel pump housing out of the EVO 9.

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One of the most common errors made when removing almost every OEM fuel pump system is damage being caused to this little factory fuel pump seal pictured below. We need to be incredibly careful when taking off the little rubber grommet. After a prolonged time being exposed to high pressures, 9 times out of 10 they become very brittle and crack or snap. Even though this was not the case here as the pump had been upgraded not long ago. Adam still takes precautionary measures in preserving the grommet while it’s out in the air, by spraying it and soaking it in WD40.

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Once out, the second 450 Walbro is brought over and installed into the surge tank housing. Nothing left to do now but wire up the internal system, seal everything up properly, and install the system into the boot.

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With the surge tank ready to install, and the OEM pump refitted back into its position. Adam gets stuck into the catalogue ordering the Teflon braided lines and fittings we’ll need to supply this motor with a far greater volume of fuel.

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Connecting up the fuel lines neatly and correctly takes some focus and attention to detail. In an attempt to combat total pressure drop across the entire system, Adam will utilize the straightest of runs in laying out the fuel lines. But; more often than not you have to get around tight spaces, and that’s where the intricacy attention to detail really pays off. Capping any sharp areas off with rubber grommet inserts, completely eliminating any rubbing or cutting of the lines under any circumstances.

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With the correct gauge of wire selected Adam follows the EVO’s factory wiring loom neatly to the battery. The 20A fuses are also neatly mounted on to the battery box for ease of service in the future. With everything now being hooked up, and wired up; nothing left to do but get it onto the AWD Dyno for a test and tune.

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Our Mainline AWD Dyno is somewhat a little different from the average. Pictured below is our fuel pressure module. This machine allows us to monitor not just the fuel pressure, but the fuel flow, fuel temperature, and ethanol percentages during any run. All this information is relayed across to the Dynlog software allowing us to log the information across the RPM, Battery Volts, Boost etc. In this test we will be monitoring the fuel pressure and flow between the fuel pump outlet, and the fuel regulator.

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Pictured below is the Dyno sheet from our test and tune. The Blue line is logging the single fuel pump run, and the Red line logs the dual pump setup. The most crucial event we want to outline is the drastic loss in fuel flow that occurs when power is being produced. Take special note at about the 320kw mark (marked with the green box). At this point onward there is less than 1L/min of fuel reaching the fuel regulator, and this is NOT GOOD. A conventional Dyno would not pick this flawed system up as it would only be logging the fuel pressure. Which as you can see, across the short duration of a Dyno run stays constant and does not show any signs of worry. A minimum of 2L/minute of fuel delivery is what Chea would consider a safe operation.

At the same time take a look at the red line. You will notice a considerable dip in fuel delivery, but then a constant supply of 5L/min or more of fuel. This action is triggered because Chea stages the pumps by limiting only the one to be on at low RPMs. Once the second pump kicks into action ample amounts of fuel are delivered.

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Unlike last week’s feature ( see here ) where by our customer was misled into installing parts that were simply not up to the specification required for his project. Only to have to spend further money on top to rectify the issue. To avoid any misinformation we first sit down with the customer and establish the goals for the project. Only once we have all the information can we go about selecting and ordering the correct systems and parts. With this particular vehicle it was a lot easier to plan ahead as we’ve looked after it since it’s purchase. But for all enthusiasts out there planning on modifying their rides just remember to keep that end goal in mind, and save yourself having to do things twice. Do it once, do it right.