Motorsport Plumbing Systems: System Overview
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System Overview
05.30
| 00:00 | As you're most likely already aware, not all cars use hydraulic power steering, as many manufacturers have switched to electric systems in the recent years for better or worse. |
| 00:10 | This is true for motorsport too, the difference being that many race cars have manual steering racks that forgo any assistance and therefore require no plumbing. |
| 00:20 | That doesn't mean a hydraulic power steering system is irrelevant though, as plenty of modified road and race cars still utilise one, so on the coming modules, we'll be focusing on the plumbing of a traditional power steering system that uses hydraulics to provide assistance. |
| 00:37 | To clarify, the principles this system works on is using a pump, generally run off the engine's rotation, or an electric motor to pressurise hydraulic steering fluid, which is then used in a power steering rack or box that provides assistance to the driver as they turn the wheel and move the rack. |
| 00:56 | Other than the pump and rack or box, the system will also feature a reservoir to hold excess fluid and potentially a cooler for more demanding applications. |
| 01:06 | This cooler is a heat exchanger, similar to the radiator or oil cooler, where the fluid is passed through it while the fresh air stream the vehicle moves through transfers heat away from the system. |
| 01:18 | Sometimes with the help of electric fans. |
| 01:20 | The power steering fluid itself is oil based, be it synthetic or mineral and is often the same or very similar to ATF or automatic transmission fluid. |
| 01:31 | The fluid provides working assistance via hydraulic pressure but also helps to lubricate the internal parts of the system. |
| 01:37 | Let's dive a little deeper into the function of the system to get a clearer picture of the plumbing involved as that's our main focus. |
| 01:45 | So, as we just touched on, the pump pressurises the fluid and provides flow through the plumbing to a rotary control valve on the steering rack. |
| 01:53 | The steering column acts directly on the control valve and depending on the way the driver turns, pressurised fluid will be directed out one of two ports. |
| 02:03 | These ports are plumbed to the steering rack, one on each side of the hydraulic piston. |
| 02:08 | The pressurised fluid will flow into one side of the piston, helping to force it in the direction of movement which is primarily achieved by the rack and pinion gear arrangement at the end of the steering column. |
| 02:20 | The more force the driver applies to the steering wheel, the more fluid the valve allows to the pistons. |
| 02:26 | Therefore, the pressurised fluid provides assistance, lowering the force requirement from the driver to move the steering rack. |
| 02:33 | On the other side of the hydraulic piston, the fluid is forced out of the rack, back through the plumbing to the control valve. There is also another plumbing line from the control valve to the power steering pump via the reservoir. |
| 02:46 | The cooler if present will be between the rack and the reservoir. |
| 02:50 | Before we go further, it should be noted that some power steering racks have internal plumbing between the control valve and the hydraulic piston section of the rack. |
| 03:00 | In these cases, the only external plumbing we need to consider is that between the pump, control valve, reservoir and cooler. |
| 03:09 | Steering boxes, although with a different mechanical arrangement, work much the same in terms of the use of the hydraulic fluid. |
| 03:16 | By using a control valve to direct the fluid to each side of a hydraulic piston, steering force assistance is achieved. |
| 03:24 | Steering boxes tend to not be used in performance applications other than off road and older classic vehicles due to the extra weight and reduced efficiency. |
| 03:34 | Regardless, the fluid flow between the valve and the pistons is typically through internal plumbing and the same considerations to the external plumbing can be applied. |
| 03:43 | Before moving on, it's important to understand the difference in function between the flow of the fluid and the pressure of the fluid. |
| 03:51 | The pressure, as we've discussed, is required to help the driver overcome the steering load. |
| 03:56 | So, the amount of pressure will determine how hard or easy it is to steer the vehicle, all other things being equal. |
| 04:04 | The pump will self regulate the pressure output. |
| 04:07 | What this means is that the pump will only supply the pressure it's required to by the control valve, which is the amount of pressure needed to achieve the desired assistance based on a certain steering torque input. |
| 04:20 | The system will have an operating pressure it's designed around, for example, 1000 psi. |
| 04:26 | But the maximum pressure the pump can achieve will be around 200 psi more than this and naturally there needs to be enough flow to maintain the pressure requirements. |
| 04:37 | Common modifications for motorsport use, such as wider grippier tyres and aero downforce will require more force to turn the tyres and therefore more pressure from the pump to maintain the same driver input. |
| 04:50 | The flow rate will determine the sensitivity of the valve as well as the steering feel and performance. |
| 04:57 | However, this is naturally also impacted by the design of the valve as well as the suspension and tyre dynamics. |
| 05:04 | The key takeaways to understand from this module is that the power steering systems use external plumbing that conveys the working fluid from the pump to the control valve of the steering rack and in some cases between the control valve and each side of the hydraulic piston on the rack, as well as back to the steering pump via a reservoir and a cooler if one is being used. |
