Road Tuning: Setting base fuel pressure
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Setting base fuel pressure
02.49
| 00:00 | Next up, we're going to look at setting the base fuel pressure. |
| 00:03 | As I already mentioned, this has a big impact on the injector performance and flow, as well as the injector data we need to enter into the ECU. |
| 00:12 | If you're dealing with a factory car like we are here then there's nothing to do, since the fuel pressure isn't adjustable. |
| 00:18 | A conventional fuel system with a return line uses a fuel pressure regulator, which is tasked with maintaining a constant pressure difference across the injector. |
| 00:28 | What this means in plain English is that as manifold pressure drops, fuel pressure is decreased. |
| 00:34 | And as manifold pressure increases, so does fuel pressure. |
| 00:38 | The aim of the regulator is to keep the difference between the fuel pressure and the manifold pressure the same, and this means that the flow from the injector will also be constant for a given pulse width. |
| 00:50 | If you don't have the luxury of adjusting the fuel pressure, then it's handy to at least know what it is. |
| 00:57 | You can find this by measuring it, or from factory data. |
| 01:01 | If you do have an adjustable regulator, we'll now look at how to set it. |
| 01:06 | Most adjustable fuel pressure regulators have a simple locking nut and an adjustable screw that can be wound in to increase fuel pressure and out to decrease it. |
| 01:16 | There is also a vacuum port that is referenced to the intake manifold so the regulator can do its job. |
| 01:23 | Usually the regulator will also have a pressure port that can be used to connect to a fuel pressure gauge. |
| 01:30 | Adjusting the fuel pressure needs to be done with the engine running to make sure the fuel pump is receiving full charging voltage. |
| 01:37 | One of the most common mistakes people make is to set the fuel pressure without removing the vacuum hose. |
| 01:43 | When we're setting base fuel pressure, we want to set the pressure difference we want across the injector, and while we're doing this, we need the regulator to be referenced to atmospheric pressure. |
| 01:54 | Once we have removed the vacuum tube, we can adjust the regulator by winding the screw in or out to achieve our target fuel pressure. |
| 02:02 | There's no hard rule on what fuel pressure you must run, and it will depend on your injectors and the size of the fuel system, as well as how much power you want to support. |
| 02:13 | As a guide, most conventional fuel systems with a regulator, run at around 3 bar or 43.5 psi base pressure, while most returnless systems run at around 4 bar or 58 psi. |
| 02:27 | Once the fuel pressure is set, make sure to lock up the adjuster and replace the vacuum hose. |
| 02:34 | So by the end of this module, you should be able to correctly set your base ignition timing, check for timing drift, and also set your base fuel pressure. |
| 02:43 | We're now ready for our initial start up. |
