Pico Automotive has partnered with Garage Wire to answer your PicoScope questions in a new and exclusive GW Views series of question and answer features.
GW readers have the opportunity to get their PicoScope questions answered by Pico Automotive by leaving their questions in the comments below this article or by emailing them to [email protected].
In the third Q&A of the series, Pico Automotive discusses PicoScope exhaust pressure testing.
Question: What’s your go-to test to quickly check the health of an engine?
If you are looking for a quick and easy test to indicate to a customer that his/her vehicle has an engine fault, it is hard to beat an exhaust pressure test using a PicoScope and the WPS500X pressure transducer.
The exhaust is the end result of all the interactions within an engine.
One possibility, is to use exhaust gas concentrations to identify air-fuel mixture or combustion problems, but they provide only a broad indication of an issue.
An exhaust pressure measurement, however, can indicate a fault with a single cylinder; such as a misfire or mechanical problem.
To get such an exhaust pressure measurement, all you have to do is place a probe into the exhaust outlet.
There is no expensive and unnecessary stripping of engine components.
You don’t even need to remove the engine covers.
This measurement relies on the fact that the exhaust pressure rises and falls with every one of the engine’s exhaust strokes.
When the engine speed and load is fixed there should be no difference between them.
If one or more of the peaks is reduced, then the exhaust from one or more cylinders has been reduced.
Possible related faults
- A worn inlet cam, which will limit the inlet valve lift.
- A poorly sealed inlet valve.
- A misfire (combustion anomaly).
- Piston blow-by.
- A head gasket leak (to the coolant).
- A worn exhaust cam, which will limit the exhaust valve lift.
- A burnt-out or poorly sealed exhaust valve can cause waveform issues relating to the affected cylinder’s compression and power strokes.
Any waveform anomaly that occurs once or more per engine cycle provides sufficient evidence to justify further investigation.
As such, the exhaust pressure measurement is a great way to show your customers (and boss) that you can see a problem and that you can justify spending further time investigation a cylinder-related problem.
GW readers are invited to leave their PicoScope questions in the comments below this article or to send them via email to [email protected].