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Response Time

Response time is a measurement of the time it takes for a diesel injector to respond to an electrical firing signal by beginning to deliver fuel. It provides an indication of the injector's condition, as response times typically range from 200-350 microseconds for piezo injectors but can be slower at 350-700 microseconds for coil injectors depending on design. Response time is important to measure because deterioration may occur before delivery measurements change, allowing issues to be detected earlier through response time drift. Measurement of response time provides a key part of the diagnostic picture for diesel injectors.

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Ahmed Elkashif
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207 views1 page

Response Time

Response time is a measurement of the time it takes for a diesel injector to respond to an electrical firing signal by beginning to deliver fuel. It provides an indication of the injector's condition, as response times typically range from 200-350 microseconds for piezo injectors but can be slower at 350-700 microseconds for coil injectors depending on design. Response time is important to measure because deterioration may occur before delivery measurements change, allowing issues to be detected earlier through response time drift. Measurement of response time provides a key part of the diagnostic picture for diesel injectors.

Uploaded by

Ahmed Elkashif
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Response time:

What is it and why measure it?


Written by Anthony Lyle, Hartridge Engineer
The concept of Response Time of a diesel injector came about with the introduction of
electronically-controlled injectors used in Common Rail systems. It is a measure of the time
taken for the injector to respond to the electrical firing signal, i.e. the time between the start of
the electrical firing signal and the start of fuel actually being delivered from the nozzle.

I
t is an important performance
characteristic giving an indication of
the condition of the inner workings
of the injector. To give an idea of the
typical values you can expect, there is
a distinct difference between injectors
actuated by a solenoid valve and those
actuated by piezo stack; piezo injectors
have faster response times, typically
200 – 350μs, whereas for coil injectors
the values can range between 350 –
700μs depending on manufacturer,
injector design and vehicle application.
Additionally, later generations of injector
design have produced incremental
improvements.
to occur and will exhibit the same effect picked up sooner by response time
Contamination Build Up and symptoms as on any diesel engine, drift than by delivery measurement. For
Timing issues on engines with this being rough idling or even not example, an injector may deliver within
Common Rail systems are the same as starting, and white smoke. limits but if the response time is high
on engines with traditional mechanical then you will know that the injector may
pump-injector systems, with the Necessity or not? not have much serviceable life left.
exception that Common Rail engines You could say that “if the response
are less likely to see problems of timing time is bad, the delivery will also be bad, Summary
being too advanced (unless there is a so why do we need to measure response In summary, without response time
separate problem with the electronic time?”. In certain circumstances this measurement you will be missing a key
control system). From an “as new” may be true, however there can also be element in the overall diagnostic toolkit
condition, injector response times will situations where if the injector is slow to for an injector. The major Hartridge test
not get faster with use, they will only open then it will also be slow to close; solutions for Common Rail injector,
ever get slower. Causes of gradual this would result in the total delivery AVM2-PC and CRi-PC machines plus the
response time deterioration will be being within limits but yet performance new Sabre CRi Master, include Response
primarily related to build-up of deposits on engine will be compromised. Time measurement so you can be
or lacquering causing sticking of the confident of an all-round diagnostic
injector valve components or needle Even discounting the above situation, picture.
and/or restriction of the flow channels it is a useful additional measure in
within the injector. Problems of timing assessing overall injector condition as
being too retarded are therefore likely deterioration in performance may be

Hartridge. The Hartridge Building. Network 421, Radclive Road, Buckingham MK18 4FD. United Kingdom
Tel: +44 (0)1280 825600 Fax: +44 (0)1280 825601 Email: sales@hartridge.com www.hartridge.com

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