smaller exaust pipe for mpg

[mwebb]

so to maximize exhaust scavenging at partial load / cruise

it looks like the primary tube volume should be about equal to the volume of 1 cylinder's displacement or a little more .
and the primary pipe diameter should be the size that allows the flow to be around 240 fps

( as per the formula s posted already )

AT the rpm that optimum efficiency is sought at

but this does not take into account the reduced VE that will be there at partial load ....
is this resolved in the value of "X" you said to ask about ?

and what about the collector ?

[Old Tele man]

...as long as the Mach Index number (Z) does not exceed Z = 0.6, then volumetric efficiency (VE) is OK. But, as soon as Z > 0.6, VE declines rapidly:

Z < 0.5, VE increases
Z = 0.55, VE flattens
Z > 0.6, VE falls off (like a rock!).

...GOOGLE: "inlet-value Mach Index number" for details on relationship of VE to Z, and Z to valve (pipe) diameter and piston velocity (bore, stroke and engine RPM).

[mwebb]

thanks for the info provided so far .
now i have a lot of reading and studying to do ....

but .....
i believe
i have the ability to measure relative VE and it is going to be very much less than 100% at partial load .

my SWAG is
using calibrated pressure transducer threaded into a spark plug thread
and a scope NOT a gauge .

i can measure actual running compression PEAK compression pressure at WOT snap OR
cranking the starter , plugs out , throttle at WOT .

if i assign that a value of 100% ( actual value will be a little less than 100% )

then measure actual running compression at 2500 to 3k rpm

since i know or can determine ,
cylinder volume and compression ratio .

i should be able to calculate
the difference from WOT and Partial load
running compression measured peak pressure
and assign that value as
a multiplier
to determine ACTUAL flow at a the RPM
(which i measure the partial load running compression pressure at)
would then
be
the sought after approximate PRIMARY tube volume value as well ?

for optimum exhaust scavenging AT a chosen by myself partial load

does that make sense ?

[Old Tele man]

...if you're interested in extensive "number-crunching" and details. try checking out Larry Meaux's very reasonablly priced software, PipeMax ver. 3.6xp2 (he has a newer ver. 4.0 coming out soon)

...and, here's a good website about Mach Index: http://hemrickperformance.com/valve.aspx

[moonmonkey]

my brain hurts,, so i guess i should bark up another fe tree,, if i am deciptering all the engineer speak corectly, im sure it's good info,, if only i could understand it.lol.

[Christ]

Originally Posted by moonmonkey

my brain hurts,, so i guess i should bark up another fe tree,, if i am deciptering all the engineer speak corectly, im sure it's good info,, if only i could understand it.lol.

LOL. It's nice to have a background or at least study in another field that you can apply to the math. Looking at something from more than one perspective, in other words.

[Old Tele man]

...it's all about "analogues & duals," ie, similar 'things' in different disciplines (fluidics, electronics, statics & dynamics, acoustics, chemistry, mathematics, etc.):

* RESISTANCE: electrical, acoustic, rectilineal, mechanical
* INDUCTANCE: inertance, mass, moment-of-inertia
* CAPACITANCE: electrical, acoustic, compliance, rotational
* VELOCITY:
* DISPLACEMENT:
* AREA:
* VOLUME:
* POWER:
* PRESSURE:
* TEMPERATURE:

...for instance, FFT is a mathematical technique used in electronics, vibration and shock, acoustic and optics analyses!

...once you've "suffered" through learning a technique or methodology, it can usually then be (rather) easily applied/transferred to multiple "other" disciplines...especially between electronics and mechanics!

...here's a good example published by Dr. Holbert, Arizona State University (ASU).

[90crxHF]

Originally Posted by tjts1

LOL
Despite popular belief, everything that kills performance doesn't automatically improves fuel economy.

Improving efficiency does work both ways, but only to a point to where BSFC starts to take a dive...