Motorsport Plumbing Systems: Boost Leak Testing
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Boost Leak Testing
03.51
| 00:00 | One of the most common issues faced with forced induction applications in our charged air plumbing is boost leaks. |
| 00:06 | It's likely you've heard this term before, but to put it simply, this is a leak in the charged air plumbing that results in the boost pressure escaping from the system before reaching the engine. |
| 00:17 | This causes a lower pressure than targeted in the intake manifold and therefore less power, while also meaning the turbo has to work harder than it needs to, resulting in a higher intake air temperature for the same manifold pressure and potentially causing the turbo to over speed, risking serious damage to the turbo itself. |
| 00:36 | The symptoms will be a reduction in power which could be anywhere from maybe a few horsepower for a small leak or for big leaks we could see our power cut in half. |
| 00:45 | Alternatively, for a new build where we don't yet know exactly how much power we should be making, the symptom could simply be not reaching our target boost pressure, assuming this is actually achievable. |
| 00:56 | Regardless, for a substantial leak it'll be easy to tell that something is wrong, but we'll still need to confirm it's a boost leak and not another issue before going any further. |
| 01:06 | If a silicon coupler has popped off, which is a typical culprit, it's likely that we'll hear it and since this would usually happen under load, there'll also be a sharp, very noticeable reduction in power. |
| 01:17 | It may be as easy as looking under the bonnet and finding the issue, but some engine bays are much more complicated than others so sometimes it can be difficult to find the offending leak. |
| 01:28 | The most common methods of hunting down our leaks in this situation involve pressurising the system or the use of a smoke testing machine, and there are plenty of kits available to help with this process, all of which are similar and fairly simple to use. |
| 01:43 | But while the idea is simple, there are a few special considerations. |
| 01:47 | Let's have a quick look at how they work. |
| 01:49 | The pressure testing process involves using a plug or cap over the inlet of the turbo that features an air valve. |
| 01:56 | With compressed air connected, we can open the valve and pressurise the system between the inlet and the throttle body. |
| 02:02 | It's often possible to hear a hissing noise and feel the pressurised air escaping at the leak point. |
| 02:08 | To make finding leaks easier, we can also spray soapy water over the outside of connections and look for bubbles. |
| 02:15 | Or alternatively we could perform a smoke test. |
| 02:18 | In this case a smoke machine pumps smoke through the system to make the air coming out of the leaks more visible. |
| 02:25 | Smoke or pressurised testing devices are typically separate items, with smoke testers being much more widely used. |
| 02:32 | However, it's possible although less common to use a pressure tester with an inbuilt smoke machine. |
| 02:38 | If the car uses a dual port blow off valve or a circulation valve, there's another factor we need to consider. |
| 02:44 | Without over complicating this module, in simple terms, these will return a false positive or in other words, show a leak that wouldn't actually be there in a real situation. |
| 02:55 | This is because there won't be positive pressure in the intake manifold that would normally force the blow off valve closed. |
| 03:02 | To get around this we need to disconnect the recirculation plumbing and seal it with a plug, as well as ensure the top of the valve gets the same pressure as the bottom so it can't open. |
| 03:13 | To summarise this module, boost leaks are common in forced induction vehicles leading to a loss in power. |
| 03:19 | We can find these using boost leak testers, which act either by pressurising the system or pumping smoke into the system or both to help us pinpoint the source of the leak. |
| 03:30 | While this process is simple, there are some special considerations when blow off valves are involved. |
| 03:35 | In the end what's important is to understand that boost leak testing is very useful for identifying leaks, but won't actually tell us the root cause. |
| 03:44 | It not really highlights areas that need more investigation. |
