[s-cars] FMIC Alternatives - ROT thoughts

[mlp qwest]

~-----Original Message-----
~From: s-car-list On Behalf Of steve powers

~Cap'n Hap:
~
~> .... Given a strong enough turbo I don't think it would be too much of an
~> issue.

and Steve jumped on with
~
~this is the avenue I'll be looking at. with my K26/27 and the correct W/G
~spring, boost isn't a problem. Yes Virgina, I found my 5 psi.

~Steve
~

Just two questions Virginia:

A.  To get the additional +5psi needed on the front end to make up for the,
& I realize its purely a guess, IC pressure loss, what do you guess you have
to add on the ass (maybe Anna Nicole Smith would be more appropriate) end?
+15 to 20 psi in the exhaust manifold?

There's no intercooler working back there as far as I know, so the question
is (or maybe it isn't) what's that do for your EGTs, and the rest of the
head's flow dynamics?  Corkey Bell waxes eloquently that this (IC's in
series) shouldn't be done, OTOH I understand this is exactly what Volvo and
the newer Audi TT (I think) are doing.  If you are going to go that route, I
think you will want to get a real close look at the Volvo & TT systems, or
better yet find someone who understands why the double pressure drop isn't
significant.  Since no one, as far as I know anyway, has any pressure drop
data for our existing IC's, maybe Corkey's admonition against running ICs in
series is only an imaginary boogie man.

B.  Have you worked out what +5psi might be in term of additional charge air
°F or C?  How efficient will your 2nd IC be?  Will it remove, say an
additional 90° F out of the intake charge?  Ignoring for the moment where
the additional +5 psi might put your compressor wheel in its efficiency
map - my guess is that could affect your discharge temperatures a lot - I
think the standard formula is T2 = T1(P2/P1)(n-1)/n.  For air I'm given to
understand "n" in the above is @ 1.4 since apparently it isn't an "ideal
gas" which would be 1.  For those in favor the "ROT" method of
engineering**, I picked +90° F based on a conversation overheard at a local
bar in Steamboat, where I think it was Pizzo who said, "Yea, for each
additional psi I get on a date, my temperature goes up roughly 18°.... at
least at sea level it does."  I guess you have to picture Pizzo in a bar in
Steamboat saying this to a Routt County Sherriff's deputy to find it funny,
but I digress....   Hey, Pizzo maybe you can get the new Aggie guy to chime
in?

FWIW, on the FMIC conversation, I find Trevor's comments on the costs &
difficulties of doing an FMIC pretty accurate & compelling, and as the
inimitable, but lamentably long departed from this list, Rod Haney might
have said, bar stool racing by the FMIC critics interesting.  Yeah, sure
once its been done, and someone has shown the way, it looks pretty easy.
Well, if you think it is, I'm all for you getting of the bar stools and have
at fabricating your own.

What's the point of developing a perfect $2,000 intercooler if everyone who
wants one thinks they can copy it for $500; or feels they're getting ripped
off if they're charged $2k?  I put a car up on blocks for @ 8 weeks to
confirm a FMIC could be done WITHOUT the need for a special, shortened
custom radiator and AC condenser that the 1st generation FMIC's (Me, Hap,
Rod Haney and one other car) required.  Maybe everyone already knew that
didn't have to be done.  For those in on this thread looking for short cuts,
have at it.  Hap's paid his dues, Trevor's "BTDT" and paid his dues,  ....
I'm really interested in this "If I just go with a big enough blower, it
(any conceivable pressure loss) just won't be an issue" line of research.
:-)

Is, and if there is, what are the limits on the pressure balance that exists
between the exhaust side and intake pressure?  What starts to fail or break
first if you exceed these?   Hey, some of Cliff Claven's ROT thoughts on the
balance are o.K. too.

Mike "feeling like Norm at the bar" Pederson


** "ROT"- Rough Rule of Thumb or engineering for those with math dyslexia