The Mitsubishi Lancer Evolution is a raw nerve. Jumping on the gas is like squeezing lemon juice on that sensitive nerve ending and rubbing it in. Few cars offer the performance out of the box, vast tuning potential, visceral driving experience, and low-dollar entry fee that the Evo brings to the party in 2016.

Used examples of Evo VIIIs and IXs can be had in the $15,000 range, and the thrill of ownership is worth every penny. The Evo IX is unique. It is a one-year model, 2006, and is the only version of the Evo to run a 4G63 outfitted with Mitsubishi’s MIVEC variable valve control. This is the high watermark of the 4G63 and the IX was the last stop for the legendary four-cylinder powerplant.

In our first Project Evo 4G63 article we installed a Wagner Tuning staggered front-mount intercooler, Extreme Turbo Systems (ETS) short-route pipe kit, Turbosmart blow-off valve, and a Dyna Batt mini battery to accommodate the ETS pipes. The new set-up increased airflow to the point that our stock fuel pump lacked the flow to keep pace with our tuning.

We had arrived at the doorstep of glory, flash tuning our Evo IX when Drift-Office tuner Bill Lee noted a lean condition at the top end. The consequence? We could not run the 4G63 past 6,500 RPM. We had just added 21 ponies to the corral but couldn’t drop the hammer and let them loose… frustrating.

At 190 liters per hour, the IX’s fuel pump flows more than the Evo VIII’s but we had maxed the old girl out. To reach the finish line we acquired a high-flow unit, part number 50-1220, from AEM Electronics. It flows 320 liters per hour at 43 PSI and is designed to pump ethanol, methanol, gasoline, or any combination of the three.

AEM 320 LPH Fuel Pump

Fuel pumps all look the same and AEM has a lot of pumps, which begs the question, “What’s the difference?” Lawson Mollica, AEM’s marketing and PR director, says AEM’s line of import-focused pumps were a direct reaction to customer demands. “When we released our 50-1200 E85 high-flow inline fuel pump, we saw a lot of people who wanted to use it having to modify their fuel pump hangers to fit in certain applications because of its length, so designing a drop-in style, short-bodied fuel pump with and without hooks to fit a wider variety of applications was a natural progression.”“The 50-1215 (hooks) and 50-1220 (no hooks) are the result of this,” Mollica explains. “They have a 65 mm body length and 115.5 mm overall length, versus the 81 mm body length and 124 mm overall length of the other inline pumps we manufacture. They deliver the same performance as the longer pumps but in a package that is a direct fit for many Hondas, Mitsubishis, Subarus, Scions, Toyotas and more.”

Fuel Pump Tips

Mollica says never compromise on using a pre filter on the pump! AEM includes a universal pre-filter in its kits but if, for some reason it doesn’t fit right, you need to get one that does. Given that some injectors have orifice holes as small as .010″ if one gets clogged then a large part of that injector isn’t going to flow, which could cause a lean condition.

AEM 50-1220 In-Tank Fuel Pump

  • 320 LPH Flow Rate
  • E85 Compatible
  • Methanol Compatible
  • Drops in Evo VIII/IX
  • Requires OE Filter Sock
He is also quick to point out the importance of validating your voltage at the pump. If you want the advertised flow, then you should have 13.5 volts at the pump with a minimum 10-amp current. The gauge of wire will dictate the wire’s ability to deliver the correct voltage, and as a rule of thumb, assume 12-gauge TXL wire for up to 12 feet of total circuit length, and 10 gauge TXL wire for 20 feet of total circuit length (for both power and ground wires). While many of today’s performance cars provide enough juice to realize the pump’s full potential, it is wise to run the numbers.

AEM 320 LPH Fuel Pump Install

Here are some less-technical tips before turning the wrenches. Don’t start the installation process with a full tank a gas, as it makes for a messy install. And open the gas cap to relieve pressure in the system. The pump swap was performed by Will Hernandez of A&W Automotive. After the aforementioned precautions were completed, Hernandez popped out the rear seat bottom seat cushion and removed the cover plate to gain access to the pump assembly.

Hernandez disconnected the hoses and lines and unbolted the six nuts securing the lock ring to free-up the assembly. The fuel pump module was then lifted out of its nest. Keep it level so you don’t spill fuel inside the car.

Drain the module. It contains the fuel pump and the sending unit that measures fuel level for your fuel gauge. At the bottom of the module, a cap is removed to gain access to the pump itself.

The pump is pulled out, unplugged, and the caps and clips are removed for use on the AEM pump. The exterior of the assembly is not disturbed.

The AEM pump comes with fuel sock that has a center-positioned port. A pre-filter should always be used and in our case a stock Mitsubishi Evo sock is used.

The AEM pump is reinstalled into the module and since it is designed for this application no alteration of hooks and the like are necessary. The new fuel sock, a stock Mitsubishi part, is installed and the cap is replaced to secure the pump.

The pump module is reinstalled into the gas tank and care is taken to ensure the O-ring is properly seated. The fuel lines and wiring harness are reconnected. The module is in place and the locking ring has been installed. Hernandez just screwed in the cover plate and it was off to the dyno.

Flash Tuning On The Dyno

With the pump up and running the Evo was jogged on the Drift-Office dyno to get the 4G63 up to operating temperature. Tuner Bill Lee’s plan was to readjust the target air/fuel map to compensate for the additional fuel going to the engine so the proper air/fuel ratio can be maintained throughout the powerband.

Unfortunately, with the car running richer and higher ambient temperature, the engine did not perform as well as the first session. In the month since the original tune the weather in Auburn, Washington warmed up significantly.

“We all heard of the saying ‘leaner is meaner’ and it is true, but it is not without consequences,” says Lee. “A continuous lean condition can cause premature engine failure due to high exhaust temperature and harmful detonation. My job as a tuner is to strike a balance between extracting the most power and keeping everything intact. In this case, I had to deal with the higher ambient temperature. It was almost 20 degrees hotter than the first session, and as temperatures rise the air becomes less dense and there is less oxygen and less power potential. So keeping the engine at the same boost adjustment (manual boost controller) or duty cycle (electronic boost solenoid) level it will generate less power. In order to extract more power we had to turn up the wick and increase the boost to make up the difference.”

So we were in fact, reclaiming the power gains realized in the first session.

The dyno charts tells a rather anti-climactic story as peak power went virtually unchanged. The peak numbers check in a 330 and change on both runs. But looking at the middle plot that displays air/fuel ratio we can see how the engine was running lean at 12.05:1, and heading higher, during our last session. Compare that line with post-pump pull that shows a steady, and safe, 11.83:1 ratio and the success of the dyno session is clear.

The AEM fuel pump gave us the flow capacity to make this possible and also push forward and tune the 4G63 in the remainder of its rev range. Tuning is not always about the peak; the driveability of a given car can be enhanced well below peak power. Further, as in our case, a tune is only complete when it spans the entire powerband. We had no problem laying off the boost but the potential for destruction was always looming.

The Evo is surrounded by Subarus in the Puget Sound/Seattle area, and the ratio must be 10 or 12 to 1… and these guys like to rev on the Mitsu. We have run the needle to redline a few times and marvel at how well the engine runs with 107,000 miles on the clock. We have done well; in fact the local STIs don’t even bother us anymore.

We plan to address footwork in our next Project 4G63 installment. The Mitsubishi’s stock rotors have been turned to their max and we are experiencing a pulsating pedal which signifies warpage, so fresh discs are in the cards. We are running lowering coils so an upgrade to a set of coilovers are also in play. From there we will be looking into bars, bushings, and wheels. Stay tuned…