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Piping issue

Question : I READ with incredulity your answer to the pipe size query in Auto Care of May 4.

The subject came up last December and the answer then contained the blunder that when the exhaust valve opens, the inlet valve is still open.

I wrote about this on Dec 31 2007 which, contrary to all my previous comments, you chose to ignore. Now, in the recent answer, the same blunder is made.

If the inlet valve would still be open when the exhaust valve opens, there would not have been a compression and power stroke; hence no need for any combustion gases to be exhausted.

The opposite is true - when the inlet valve opens, the exhaust valve is still open!

I think your answer in these cases is wrong and must be confusing to many people.

Answer : I stand corrected. Somehow between thinking out the answer and typing it out, the facts got jumbled. What I was trying to say was that while the exhaust valve is open and the exhaust gases are flowing out, the inlet starts to open before the piston gets to top dead centre and if the exhaust system is designed correctly, the exhaust gases will be extracted out.

However, before too much of the inlet mixture goes out of the exhaust a positive wave will return to stop it, and together with the movement of the piston down- ward the inertia of the mixture coming in will maximise the inlet charge.

If the exhaust system is not designed correctly, the pressure waves will come at the wrong time and instead of improving performance, the performance will drop.


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Piping issue

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