RE: engine decision's...)

["Scott Williams" <scwillia@genuity.com>]

> > Ummm. dude. I think you just described a backfire. LOL!!

Nah, man. A backfire is what happens when that fuel/air charge *ignites*.
Have you ever noticed that this does sometimes happen occur when you uncork
the exhaust or change the cam duration? The likelihood of the fuel/air
charge being expelled into the exhaust and the likelihood of it being packed
back into the combustion chamber is altered at a particular rpm range.

Btw, a major point that I set up but did not complete is that the shockwave
decreases the chances of the fuel/air being expelled into the manifold in
the first place. Perhaps this should be considered the primary   goal of the
tuning. I dunno. I'm at the limits of my technical understanding on that
detail.

> OK, once you get the water to start flowing out of the tank into the
> bucket thru the hose, what maintains the water flowing is the water
> that is in the hose. It draws out more water and will do so until the
> tank is empty. This is how a slight restriction in an exhaust system
> helps draw out more of the exhaust gasses thusly allowing the
> refreshment of air/fuel to flow into the cylinder without having to
> share space with the icky burnt fuel.

Your model is illustrative of the effects of vacuum, perhaps. But I fail to
see where restriction is contributing positively to the evacuation of the
exhaust.

> Ive looked at the shockwave theory and also have imputed its
> use on a few systems. I think its safe to say that the typical
> VW motor doesn't flow enough to make use of the mathematics available
> for decent power gains.

All motors flowing through an exhaust can be tuned. Consider how a 4/2/1
exhaust design affects a VW's (or any motor, really) torque/power deliver
verses a 4/1 header.

> Have you ever cut a small section off the exhaust tip to break the
> shockwave as it exits the exhaust? its reported to make more power as
> well. (less restriction for the wave to penetrate.) Ive never noticed a
> difference.

I've never tried that. However, I have tried varying the length of the
primary and secondary header tubes. That is, the pipes before and after the
first collector in a 4/2/1 exhaust. That makes a very substantial
difference. The flow rates of that "tri-y" (4/2/1) header and the 4/1 header
may be the same, but the tuning makes a big difference. hell, I got that
straight from the Techtonics catalog! ;^)

> > See, I disagree. The size of the primaries are absolute KEY to making
> > great power. Large ass primaries (bigger than the exhaust ports flow)
> > will do more to restrict flow than allow flow. As the exhaust pulse
> > exits, it swirls into a confused vortex of lost power.

Right, in this case, there is a turbulent instead of laminar flow through
the pipes. This restricts the flow. I agree with you. I didn't say that pipe
diameter and flow are not related, I said that they are "not necessarily
linked". Perhaps I should have added "in a linear relationship".

> if the primaries are larger
> than the exhaust port it cant flow more than what can exit the port, no?

Agreed.

> Seriously. it was nothing more than an open exhaust right off
> the header. How could anything of been "hurt". If anything, according to >
your theories, it should of been better since it was much less
> restrictive.

Like I said, when your exhaust disconnected itself and opened up entirely,
the acoustic tuning and the scavenging was upset.

Okay, Meze, unless I am cajoled back into this discussion by way of taunting
or other subtle manipulations, I will defer to Mr. Larry Fry and his
superior engineering understanding. :^)

Hit it, Lar! (ba-doom-pishhh...)
--
Scott F. Williams
NJ Scirocco nut
Golf GTI 16v rallycar
Mazda 323 GTX turbo assault vehicle

Check out our rally team's website!
http://www.usrallyteam.com


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