PDA

View Full Version : Reverse cone megaphone design


richban
20th October 2009, 20:45
Ok so does anyone have a formula for calculating a revers cone for a 4 valve.

The first edition of Four Stroke Performance Tuning has it I think, but can't find one.

If you do know, you may not want to tell coz its seams to be one of those things that a dad might pass on to a son on his death bed and make the son swear a blood oath to never tell another living soul.
slofox
20th October 2009, 20:47
I have a book that may give you an answer. I will look it out tomorrow and let you know if it is of any use...
richban
20th October 2009, 20:50
I have a book that may give you an answer. I will look it out tomorrow and let you know if it is of any use...


Cheers Thanks
Buddha#81
20th October 2009, 22:33
PM Yow Ling....he has the specs for FXR mufflers
richban
21st October 2009, 07:13
PM Yow Ling....he has the specs for FXR mufflers

Cheers will do. Is anyone running a reverse cone mega with any success?

I love you signature it is ture. Hard to loose weight but chasing horses power is like going back to school. I wish i paid more attention in my maths class.
Buddha#81
21st October 2009, 07:18
Cheers will do. Is anyone running a reverse cone mega with any success?

I love you signature it is ture. Hard to loose weight but chasing horses power is like going back to school. I wish i paid more attention in my maths class.

His are reverse cone.
marsheng
21st October 2009, 07:18
Unless you have serious valve overlap, a megaphone will not make any difference. The valve overlap needs to be at least 40+ degrees.
richban
21st October 2009, 07:34
Unless you have serious valve overlap, a megaphone will not make any difference. The valve overlap needs to be at least 40+ degrees.

Yep. This engine has serious everything the exhaust is the last piece of the puzzel.
marsheng
22nd October 2009, 07:11
I'll do your calcs. What is your exhaust opening angle before BDC and where do you want the maximum power ? Probably between 10000 and 11500 RPM?
richban
22nd October 2009, 17:17
I'll do your calcs. What is your exhaust opening angle before BDC and where do you want the maximum power ? Probably between 10000 and 11500 RPM?

41 BBDC and 11000 to 12000 It revs hard up to the limiter but need to get it on the dyno to see what is happening. Will be doing that when I have finished dicking with the exhaust.

Also looking at a pressure bomb design Primary 29mm ID (standard header) cut at 550mm then into a 300cc volume and then muffler short.

Keen on the reverse cone as it looks like it is a more tunable.


Cheers