[quote:b2d5d327c4]Dlot: Unitek even has a
patented or copyrighted combustion
chamber design. [/quote:b2d5d327c4]
At least in North America, that
would be impractical- you might technically be able to do so for a large legal fee, but to enforce it would be
impractical. Look at all the "replica" wheels for example. General combustion chamber design, let alone
modification, can be virtually impossible to patent even with the resources of a major auto
maker- see taper
quench for a more on-topic example. I'd toss that into the myth
category...
[quote:b2d5d327c4]Doug242ti: Wow, pretty full of ourselves aren't we?
[/quote:b2d5d327c4]
Well Doug, I'm assuming you meant the reference to the catalog, not the what I
thought to be fairly gently worded comment to someone more educated than I, about a possible arithmatic error. To
be fully qualified to criticize you would have had to 1/ buy the catalog at full price 2/ feel it was full of
relevant info, and 3/ feel it has had an impact on the direction of your project, or a close friends project.
To my knowledge that isn't the case for you any more than for me.
[quote:b2d5d327c4]stealth: Mike
uses understatement[/quote:b2d5d327c4]
My thoughts were/are (and the mods can delete if they so choose)
that the tendency was to use a practiced vagueness, overly large words misused, and a studied avoidance of
practical knowledge, even to the point of avoiding any CFM figures completely. It would appear his hope is that
virtually anything can be read into his generalities, and he will be able to pick and choose which he takes
credit for, relying on a 'foreign mystique' to work in his favour. I don't disagree that he has had the
opportunity to work on Volvo engines full time for many years. I more intended to convey
my
personal opinion that neither his remarks on here or his catalog are worthy of the overly generous
compliments they receive.
Full stop. Everyone happy? *seeks in vain for an appropriate emoticon*
My point
is that the avoidance of specifics is well beyond what is required in the trade. Look at the Endyn site, with
many CFM figures, combustion chamber close ups and so on. All of very current high $ projects. For Volvo's you
might watch the Amazon Forum where Janne Lundin regularly advises on engine specifics, and shows rubber castings
of his modified ports. In fact, most marque-specific boards will have someone qualified and who will freely
volunteer aid on porting. I can remember a whole site with dozens of pictures of Ford 429-460 heads, put up by a
fellow in the business of porting them.
[quote:b2d5d327c4] DBS: I implied that ports on a 16v motor flow
more because the port to valve angle is much better so the port can flow more in respect to the
bathtub/heartshape chamber the volvo engine has. [/quote:b2d5d327c4]
It would appear you may have a point
as the best Honda DOHC are getting within about 10-15% as much flow as the much larger valved and chambered
NASCAR heads (370 vs 435), but if it were as simple as you imply, all one would need to do is raise the angle of
entrance of the 8v port, radically so in the case of the exhaust, (combined with some canting of the valves). In
general, 8V Race heads do tend to do that, but there is no meaningful correlation in flow velocity in the sense I
read you as. My point was
only that in a general sense,
flow *per valve* divided
by area is likely to make the 16V head look a lot less efficient than the overall figures might show. It was a
minor point...
[quote:b2d5d327c4] DBS: back up your information with some figures ian.in a N/A motor there
isn't enough energy to get to that air speed. Relative to piston travel at what speed do you think the air speed
should be ?
And should we be listening for the sonic boom when it reaches 728 mph?
[/quote:b2d5d327c4]
Well, back in the quench thread there was a link to a site which had a long porting
theory page. He mentioned exhaust gas speed of 400 ft/sec on an old-tech 2V British motorcycle.
I have a David
Vizard article scanned from Circle Track that suggests about 340ft/sec is a useful rule of thumb for
'restricted' circle track stock car V8's, and another from the same source that suggests a working velocity
range of 330-370 was used in developing a Nascar head. Email me if you want copies of either.
Probably the
strongest proponent of high velocity, and the guy who worked with supersonic ports, is Larry Widmer of
http://www.theoldone.com A guy could spend some time there looking it all over, and learn a lot. He has what I
think is a very good honest way of presenting the total evolution of his concepts. It came as a surprise he
allegedly hasn't always had an equally clean business record. You might also want to post some questions to his
forums. As to your questions- apparently yes there was an sonic boom of some kind.
It was theorized that the
powerful wave created might help exhaust scavenging. I don't believe I have the knowledge even to repeat
statements made by those theorizing on it, as to when in the engine cycle the peak gas velocity will occur.
Earlier than the peak lift of the cam given current cam technology, is what someone said.
I think those
ft/sec specs may be more empirically derived, wherein it has been found that increasing your pressure drop on the
flow bench and reducing the port cross section area get you the most relevant results for taking good flow bench
data and getting good dyno results, implying that in use the
average speeds might be
in that range.
That's actually and excellent practical question.. I've managed to remember the stats, but
you're right, I'm not sure I know their full application/source. If/when I find out you'll be the first to
know... Cool?