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The mathematics of the 8V vs. 16V problem
Wow .. hehehe ..
I guess this one got everyone busting out pens and pads along with the
calculators :)
I wonder after thi who will pick on Josh's Injector size :P
Adrian C.
Project Scirocco R2.oT - "The Turbocharged 16Valves of Fire Breathing
Fury"
( 2.0L 16V T66 )
-----Original Message-----
From: scirocco-l-bounces@scirocco.org
[mailto:scirocco-l-bounces@scirocco.org] On Behalf Of Adrian
Sent: October 20, 2003 7:12 PM
To: scirocco-l@scirocco.org
Subject: RE: The mathematics of the 8V vs. 16V problem
Well here is my non-biased opinion, engines are engines.
Doesn?t really matter how many valves it has (I seen engines having 1,
2, 3, 4, 5 and even 6 valves for each cylinder!!!), it still performs
the same task: Takes the gas, burns it and turns that thermo-chemical
energy and turns it into mechanical energy. But what really matters is
how much air can flow through it!
As we all know engines are like big air pumps. The more air you can get
into it the more power it will make. So here is the scientific aspect of
it...
Air Capacity (in CFM) = ((CID * RPM) ? 3456) * VE
Where a 2 valves per cylinder engines, use a VE of .8-.85 at torque peak
and .7-.75 at power peak and 4 valves per cylinder engines, use a VE of
.9-.95 at torque peak and .85-.9 at power peak.
To find out Displacement in CID = # Cyls * 0.7854 * bore * bore * stroke
Or you can convert CC to CID -> CID = CC*061037
If you want to get the results in Lbs/min then -> Lbs/min = CFM * 0.069
The pressure ratio is simply the pressure in compared to the pressure
out of the turbocharger. The pressure in is usually atmospheric
pressure, but may be slightly lower if the intake system before the
turbo is restrictive, the inlet pressure could be higher than
atmospheric if there is more than 1 turbocharger in series. In that case
the inlet let pressure will be the outlet pressure of the turbo before
it.
Injector Sizing
lbs/hr = ((BSFC / #Cylinders) * HP / Injector Duty Cycle
Brake Specific Fuel Consumption is normally (lb/HP x hr)
0.42 BSFC - Race Engine
0.47 BSFC - Hi Performance Engine
0.52 BSFC - Stock or with Light Modifications Engine
0.57 BSFC - Supercharged / Turbo Charged Engine
Injector Flow Rate Conversion
CC/Min = LBS/HR * 9.71
LBS/HR = CC/min * 0.103
BTW Most Injector burst pressures are at 125 PSI.
The density of air also varies with its temperature. A cubic foot of
cold air weighs more than a cubic foot of hot air. A round average for
airflow vs. hp is 1.5 to 1.6 cubic feet per minute for each hp
developed.
So as we can see here the more flow the more power the engine will
produce.
Sorry for the Long post but someone got to put an end to this.
Each engine has its advantages and its disadvantages.
If anyone might have any other concerns or questions please email me.
I used this as a Guide to Build my engine that is about to be completed.
I more information regarding engine builds and operation.
Thank you, for reading this and taking your time to understand where im
standing at in this 8V Vs 16V Feud.
Have a Good Night.
Adrian C.
Project Scirocco R2.oT - "The Turbocharged 16Valves of Fire Breathing
Fury"
( 2.0L 16V T66 )
-----Original Message-----
From: scirocco-l-bounces@scirocco.org
[mailto:scirocco-l-bounces@scirocco.org] On Behalf Of C Boyko
Sent: October 19, 2003 6:53 AM
To: scirocco-l@scirocco.org
Subject: The mathematics of the 8Vvs16V problem
This is a preliminary post resulting from my dyno yesterday, and I
though
I'd better post it, since this is such a popular topic for discussion. I
believe this should lay to rest forever the 16V vs 8V discussion...(as
if)
Hypothesis:
That doubling the number of valves doubles the horsepower
Method and all that crap: Toss my two cars on the dyno
Observations:
1987 16V 132.8 hp to the wheels
1979 8V 66.6 hp to the wheels
Analysis and Conclusions:
2^3 = 8 (or 6 in certain circles, when used in probability questions)
2^4 = 16
2^4/2=8, or 16/2=8
132.8/2= damn close to 66.6
Next Experiment:
Toss a 20 V on the dyno....WTF, over 300? Well, now we need a formula I
guess...
Seriously, dyno day was fun as usual, and after all that tuning (with
Klaus
making the day's low, and Josh C's red beast making the high)
Since Klaus was supposed to have 76 at the crank according to the
owner's
manual (and you lose a bit getting that to the ground) , 66.6 (though a
bit
evil sounding) is damn fine for a car with 171000 miles on the engine
(just
nicely broken in). I guess there is even a picture with his needle
buried,
despite the fact that you could go have lunch while he got to redline.
(see,
there is that time component in the hp formula...)
A few surprises, but most dynoed about where they figured they'd be.
I'll post more about the weekend later, but that should get the flames
fanned...
cathy, resident stirrer of the poo
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