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Re: Weber Trumpet Length

PostPosted: Thu Mar 05, 2015 7:52 am
by pauljones
John,

You are off course correct. Without one in front of me to measure i recall about 4mm. Not sure the exact amount.

Sorry.a slight miss judgment on my behalf.

Re: Weber Trumpet Length

PostPosted: Thu Mar 05, 2015 8:08 am
by Andy8421
john.p.clegg wrote:"Mechanical Engineer, happily retired!" but still surrounded by buffoons....

John :wink:

John,

Do you disagree with the analysis?

I have only read one or two books on the subject, but they dumb down the whole analysis and paint a picture of a single negative pressure wave charging down the inlet tract to the fresh air, which in turn gets replaced by a positive wave charging the other way toward the valve.

It is all much more complex than that.

There isn't a single pulse (the engine doesn't just fire once), and the initial wave actually continues to bounce back and forward from valve to inlet trumpet, decaying over time. This then interacts with the next induction wave. Although I may have stuffed up the maths, I recall that to end up with a practical inlet length, you can't use the primary reflection, but have to use a wave that has done the round trip at least a couple of times.

I reached the conclusion that it was far better to consider the system as a resonant cavity, excited by a series of negative pressure pulses, and that aiming for a positive pressure node at the valve throat was the way to go.

I am more than happy to be corrected.

Re: Weber Trumpet Length

PostPosted: Thu Mar 05, 2015 8:13 am
by john.p.clegg
No Andy,you are spot on,it's just people not reading the question and diverting the threads etc.etc

All he wanted to know was where to put the end of his tape measure......

John :wink:

Re: Weber Trumpet Length

PostPosted: Thu Mar 05, 2015 9:04 am
by Galwaylotus
I think I'm sorry I asked the question in the first instance!! :shock: :shock:

Re: Weber Trumpet Length

PostPosted: Thu Mar 05, 2015 6:05 pm
by pauljones
I think John is referring to me. My apologies if it diverted the origonal question.