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Unit 4, 32-34 Peter Brock Drive, Eastern Creek NSW 2766, Australia

Most in Sydney will recognise IFSU with it’s distinctly aggressive widebody by Pete at Bodyform. Now fitted with a freshly built 2.2l SR20 motor by F&E Autoworks it was time to extract as much safe power as possible. With it’s current configuration of a single Walbro 450 fuel pump we cannot expect figures beyond 350kw without entering into VERY unsafe territory. Keeping that in mind lets have a closer look at how we can extract safe power, and more importantly recognising when we’re simply pushing too far!

Spec List :
Built SR20 Nitto 2.2L with upgraded Pins and Rod bolts
ARP main/head Studs
Tomei 1.3mm Metal Head Gasket
BC Valve Springs
BC Stage-3 Cams
BC Adjustable Cam Gears
6Boost Manifold
Garrett gtx3076 with .61 Rear Housing
Tial 44mm External Gate
BPP Top Feed Fuel Rail Kit
Bosch 2000cc Injectors
Walbro 450 Fuel Pump
RB25 Gearbox Conversion
Haltech Pro Plugin ECU

Our main purpose of this article is to give a realistic idea of what power can be achieved with the single fuel pump setup. Too often we come across damaged engines because they were excessively leaned out during tuning, a direct correlation to not understanding the limits of the fuel system.

We begin every Dyno tune by first checking and confirming the ignition timing, making sure that the displayed timing on the engine side matches the displayed timing on the ECU side. This ensures that the tuning procedure is correctly synchronized, and adjusting 2 degrees ignition timing on the ECU side will actually result in the correct 2 degrees being adjusted engine side. In effect if you’re timing is incorrectly offset between ECU and the motor, you have no way of knowing if your adjustments ECU side will be correctly passed on to the engine. It is needless to say that with incorrect synchronizing of the ignition timing you will no doubt be damaging the motor.

Target AFR Log

Once the ignition timing has been physically confirmed, we move on the the actual ECU tuning. We begin by adjusting the Air/Fuel Ratio to safe functioning levels. From years of experience with tuning all things SR20, we know that a safe level of Air to Fuel ratio under high load is between 11 and 12 (as pictured in the above target AFR log). By increasing the boost you directly need to increase the amount of fuel being delivered to the engine. To keep the Air Fuel Ratio in the safe region between 11 and 12 you need to be able to provide the engine with adequate fuel flow. This is where the limits of the single fuel pump come in to play. When a car is being Dyno tuned, the power run itself only lasts approximately 10 seconds. This is a very short time, and in the real world the driver would hold the power down for a much longer period of time. It is only during a longer run that you will notice if your fuel system is at, or beyond it’s safe operating limit. But by the time you have noticed an overworked fuel pump, the chances are you have already caused catastrophic damage, and melted your pistons from an excessively lean Air/Fuel Ratio. It is absolutely imperative that the limits of the chosen fuel pump are understood, and tuning kept within the safe operating limits.

After a correct AFR has been set, we move on to tuning the Ignition Timing. We will revisit the Air/Fuel Ratio once again for a fine tune adjustment once we have set the Ignition Timing. One of the easiest ways to explain how Ignition Timing affects the engine is by using the simple push bike as the analogy, as pictured in the above illustration.
Imagine yourself peddling along. When you’re pedaling, ideally you will push down on the pedal at the point where the torque of your push will propel you forward the most. If you push on the pedal too early it will lift you out of your seat (a too advanced ignition timing), and if you push too late you will not generate enough torque to propel you forwards (a too retarded ignition timing). Now imagine that those very pedals are the connecting rods, and the pistons are your feet. If the timing is too retarded, the downward stroke of your engine will not produce torque and will feel like it is bogging down. This does not cause any damage to the engine, but the tune is obviously not correct. On the other hand If your timing is too advanced, the ignition point of the fuel will be occurring when the piston’s position is too high up in the cylinder, and will cause your top-end to physically be lifted upwards. Just as it caused you to lift out of your seat on the push bike. Unlike the overly retarded timing, an over advanced timing WILL cause significant engine damage. The pressure caused inside the cylinder will literally force the engine’s top-end upwards, so just imagine the potential damage from such forces. Once we have set the Ignition Timing we will once again go over the AFR settings. Now that the ignition timing is set in it’s final configuration we can fine tune the Air Fuel ratio, which will now just be a matter of a few micro adjustments.

In this particular Dyno run we did not hook up the Fuel Flow & Pressure module of our Mainline Dyno to log the fuel flow. From years of experience, and tuning hundreds of SR20’s fitted with this exact same single Walbro 450 fuel pump has given us an intimate understanding of the tuning limits. As a safe precaution we like to keep a minimum of 2L/min of fuel flowing from the exit of the fuel regulator. This amount of fuel flow ensures that the engine will NOT run lean when under high power for extended periods of time. It directly relates to the point mentioned above regarding the AFR. If we cannot provide 2 litres per minute of fuel delivery then we know that the fuel pump is operating beyond its capabilities, and MOST importantly we know that the AFR will lean out and cause catastrophic engine damage.

The final tune resulted in a safe, and very healthy 335.3kw at the wheels. The future for IFSU is looking great! To go forward and squeeze power beyond the 350kw mark out of this built 2.2L SR20 we will have to upgrade the fuel system to a twin pump surge tank setup. This will allow for ample amounts of fuel delivery. Upgraded cooling will also be required.

We hope this article has shed some light on the tuning process, but more importantly established a realistic outlook on what is to be expected out of a single fuel pump setup. We have focused heavily on the fuel flow side of things in this particular article as it is an area where we see many mistakes being made.  Gaining 350+kw on a single fuel pump just is not safe, and do not let anyone tell you otherwise. Keep an eye out on our next tuning article, where we’ll be focusing on the tuning of Ignition Timing in much greater detail.