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78 Posts Member #: 9073 Advanced Member Edinburgh |
14th Oct, 2010 at 01:10:55pm
On 13th Oct, 2010 Paul S said:
The other interesting fact is that if the exhaust flow goes to a restriction like a turbo, then the reflected pulse will be positive. So do we want that pulse anywhere near valve overlap???? I'm not sure how this applies to mechanics but in electrical engineering you only have to worry about transmission lines (ie signals being reflected back at the end of lines) when the length of the track is >~ 6* the signal edge length. With an exhaust system the analogy probably holds. The initial pressure wave is caused by the exhaust valve opening and has a certain 'length'. If this flows to the end of an exhaust pipe it can be reflected back as you have read. However if it comes across an obstruction in a short pipe it will reflect and hit the exhaust valve after a very short period so the fresh exhaust gas will overcome the reflection. The short length of the pipe to the turbo will tend to 'smear' out any pulse effect and there will be a fairly uniform pressure in the pipe. Probably. Nial. |
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 8604 Posts Member #: 573 Formerly Axel Podland |
14th Oct, 2010 at 01:45:50pm
On 14th Oct, 2010 Nial said:
However if it comes across an obstruction in a short pipe it will reflect and hit the exhaust valve after a very short period so the fresh exhaust gas will overcome the reflection. The short length of the pipe to the turbo will tend to 'smear' out any pulse effect and there will be a fairly uniform pressure in the pipe. I think that you are correct. This page shows graphically the difference in pressure pulses in the exhaust of a NA engine and a turbo engine. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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 1137 Posts Member #: 1450 Post Whore Near Paris - France |
15th Oct, 2010 at 04:04:11pm
My point rather than issue is VE is not about geometry ie filling a cylinder with its volume less obstruction of the inlet path.
Rusty by nature
On 23rd Jun, 2008 paul wiginton said:
They said "That sounds rough mate." I said "Cheers it cost me a fortune to make it sound like that!" |
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 9502 Posts Member #: 1023 Post Whore Doncaster, South Yorkshire |
15th Oct, 2010 at 06:22:48pm
i dont really have much to add but ive had this for a while
Yes i moved to the darkside |
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8604 Posts Member #: 573 Formerly Axel Podland |
15th Oct, 2010 at 07:14:54pm
Thanks for that Brett.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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9502 Posts Member #: 1023 Post Whore Doncaster, South Yorkshire |
15th Oct, 2010 at 08:56:32pm
well if it was of some help i have over 40 of them, all different subjects (ford related)
Edited by Brett on 15th Oct, 2010. Yes i moved to the darkside |
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