[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]
Numbers - a good read
Re: Deflating the 5ktq Mod Thread before Dan does
Anyone who needs to get more clear on the "claims" made or the conclusions
drawn, or who just has a turbo car, should get Corky Bell's book Maximum
Boost - see excellent review by DeWitt Harrison (archives). Of all the
material I've collected on turbocharger theory over the years, this has the
KISS (Keep It Simple Stupid) approval seal on it, and is the most popular
"lender" in my library. None of the claims or the conclusions are rocket
science exercises, they are accepted basic theorems to internal combustion
engines and turbo charger theory. He does a nice job of plotting a lot of
them for you mathmatically "impaired" too.
Given where I see this whole "bigger and bigger" thread going, I might
pre-empt the whole issue by saying this: If what I posted created a stir,
then I advocate this list needs more baseline education on turbochargers.
This stuff is soooo basic, and long-standing, and accepted theory and
practice. Yet all of a sudden it's controversial? What's with that? Cuz I
wrote it with an attempt at humor (admittedly maybe lost on some), and with a
lot of questions? Or cuz it only took one number? Get the book folks.
I would love to expound on questions that might come up in any "homework"
discussion of Corky's book. Denying math and physics wouldn't be my first
choice, and some benign claimed numbers can be VERY revealing. I claim
always to have questions, and a properly functioning calculator. And ready
to stand corrected on my accused ignorance to my bumbling homework.
So, Randall, ease up some, I might too, you are taking this personally.
Eric, some more of your numbers might help yourself improve what you have,
your absolute right not to give them, Ross didn't either. My claimed
ignorance is with 26psi, which defined IS 2.79 PR, a motor size is given at
134ci (Bentley) and that gives a 513CFM flow. That is physics, and has a
BMEP associated with it (which I could calculate, never had to do one that
high before). Not sure I understand what I have done wrong, other than take
a number and play with a calculator and a couple of knowns, accepting the
unknowns, throwing it in an exercise, and creating more questions. Here's
what I used for calculations (via claims and Audi info):
* 26psi in 2nd thru 5th
* 2.5 bar PT
* 16+psi in 1st gear
* .5 PD accross modded IC
* Audi --> RS2 gets 310hp @ 460CFM
* 1325 EGT
* Audi --> MC motor = 134ci
The homework would be
A) How does a 134ci motor flow 513CFM in 10v trim? Can it?
B) Why such a large PR? I thought Density Ratio was more the goal?
Someone give me a hint where I've gone wrong here in my math. Anyone? Take
this exercise, lay it next to my post with all the math in it. What haven't
I done right? Randall? Eric? Dave, Dave et. al.? No slams, just math.
Flow, PR, and heat are the problems as I math them thru the MC motor, mods
aside. Forget the lack of boost control over 2.5 on a 2.5PR computer,
that's another exercise alltogether.
I'm a tenaciously ignorant SOB (self proclaimed), and happy to put to the
list my homework as presented. My apologies to those offended or ruffled,
just looking for ... Truth, claims, calibrations and objective go faster
mods" (insert salute)
Scott Justusson, RS2 wannabe