Daniel,
To optimise your induction system, you should use ram tubes that lengthen
your inlet tract to a point where you are getting a tuned length resonance
in the induction tract. The length from your valve seat to the end of the
ram tube is worked out by the formula L=(TV)/N (full wave resonance)
typically you would run a quarter wave of this length for practicality
L=length Inches" of inlet tract to end of bell mouth from valve seat,
T = number of crankshaft degrees after BDC where valve closing occurs (then
add 180 for effective inlet duration and subtract the number of degrees
before close where you want the pulse to occur at the valve (typically 5 -8
degrees before valve close. 5 degrees for 5000 rpm power and approx 8
degrees for 6500 rpm power).
duration
V = velocity of sound in air 1088 ft/sec (at sea level but close enough)
N = the engine speed at which the benefit is desired (typically 6500 -7000
for a race car or 4000 - 4500 for a good fast streeter.
An additional benefit of ram tubes is that they can also increase the
volume of air in the inlet tract so that any back wave is fully contained
in the ram tube if the length of tube and diameter is large enough. This
can stop the dreaded reversion splash onto the inner guard in race cars
where the back wave blows the fuel air mix outside the carb and the fuel
mist comes out of suspension causing a lean out. The tubes also help[ align
flow into the carb body. Box filters without ram tubes are at best a
primitive device for air filtration at low engine speeds.
Ram tubes are not just a something you bolt on to look pretty. The correct
lengths can actually provide a little 0.5 - 1.5 lb boost ( free
supercharge) at some engine speeds if the "system" is matched up. Good
quality filter socks with a large surface area over tuned length ram tubes
are the best way to go
Sorry about the length.
Cheers
Feral Errol.
----------
From: Daniel Kroehn <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Twin Webbers and Air Filters
Date: Friday, July 14, 2000 5:36
What would be the best air filters to put on twin webbers to extract max
performance? I am currently using the ram tubes(short ones) with four air
socks. A mate of mine is using the proper box filters on his twin webber
set-up which was prescribed by a guy at the performance shop where he buys
his parts from. Is it true that you don't use the ram tubes with the box
type filters? To me that reduces the effect of fuel/air mixing as I've
always thought that the tubes greatly increase the effect of the fuel and
air mixing. This is due to the tubes "tuning" the air flowing into the
carbs. What are the advantages and disagvantages to both?
Daniel Kroehn
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