Finding out the time duration for which intake valve remains open

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Discussion Overview

The discussion focuses on determining the duration for which the intake valve remains open in a 4-cylinder naturally aspirated diesel engine, specifically using a Tata Indica model as a reference. Participants explore the relationship between engine cycles, camshaft specifications, and valve timing.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant calculates that it takes 0.012 seconds to complete one cycle (4 strokes) and seeks to determine the intake valve open duration.
  • Another participant asserts that knowing the exact camshaft specifications is necessary to determine the valve open duration.
  • A participant suggests that if the time duration for the intake stroke is known, it may be possible to find the valve open duration in seconds.
  • Discussion includes details about cam specifications, noting that they typically provide degrees of duration at specific lift points, which are crucial for understanding valve timing.
  • One participant estimates the intake valve open duration to be about 0.006 seconds, assuming a 180-degree open duration out of 720 degrees for one cycle, while cautioning against oversimplifying the timing of valve openings and closings.
  • Another participant emphasizes the complexity of cam design, noting that maximizing open time while ensuring proper seating is critical, and suggests that measuring this in a running engine is challenging.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of determining the intake valve open duration without specific camshaft data, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight the dependence on camshaft specifications and the complexity of valve timing, indicating that assumptions about timing may not hold without precise data.

monty37
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I set out to find out how many seconds it takes for a 4cylinder naturally aspirated diesel engine to complete 1 cycle(4 strokes):
I considered a tata indica model
max power:53.5PS@5000rpm

therefore 5000 rev per min or 83.3 rev per sec
now it takes 0.012 seconds to complete 4 strokes or 1 cycle and 6x10^-3 seconds for 2 strokes

Now I want to find how much time does the intake valve remain open.
 
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That is impossible to know without knowing the exact camshaft specs.
 
you mean to say the crank angles at which the valves operate ..now if i know the time
duration for the intake stroke can i not find out the valve open duration..in seconds?
 
About 0.006 seconds, assuming 180 open duration out of the 720 degrees needed to complete one cycle (0.024 sec., not 0.012).

It sounds like you're assuming that the intake opens exactly at TDC and closes at BDC; not so. As mentioned, the intake opening and closing points will depend on the design specs of the camshaft.
 
The whole point is racing cam design is to get maximum open time while still getting the valve securely seated in time to prevent blow back when ignition begins. Lots of effort goes into cam design, and as a result, the performance with each cam will be different. Measuring this in a running engine is going to be extremely difficult. You would be much better off to get the cam profile and then work through the kinematics of the valve gear in order to predict the valve open time.
 

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