Turbo header design

[andy quaas]

I just saw an atricle in car craft (i think) where they did a header
test.  On naturally aspirated engines, the tri-y design header created
more HP and torque across the operating range (on a very mild 350
SBC).  I switched from hooker generic headers to doug thorley tri-Y
and the performance boost was noticable.  The first thing i noticed
was the weird exhaust note!  I didnt change pipes or mufflers when i
switched, but the exhaust sounds completely different!

Just some experience nfo.

Andy


---Clarence Wood <clarencewood at centuryinter.net> wrote:
>
>   The tri-Y approach sounds more like the article that I read.  In
the article, there were collectors for each bank.  Damn!  I can't find
the article!  It is here, under a pile of other treasures, somewhere. 
Anyway, they talked about matching the cylinders on each bank to
scavenge, put in short baffles that led into a cone shaped collector
that narrowed into the exhaust pipe.  
>   Now, I hate to share my ignorance with you all, but I have ran
into a problem understanding what is probably the most basic operation
of a V8 engine.  Here is what I did to determine what cylinders should
be matched:
> 
>                 Firing order         
>           1  8  4  3  6  5  7  2
> Stroke
>   1.      P  C  I  E  P  C  I  E      
(P=power,C=comp,I=intake,E=exht)
>   2.      E  P  C  I  E  P  C  I
>   3.      I  E  P  C  I  E  P  C
>   4.      C  I  E  P  C  I  E  P
> 
>   Why is cylinder #6 at a power stroke while cylinder #1 is also at
a power stroke?  I am trying to find out where each of the cylinders
are, in their four stroke cycle, when cylinder #1 is at its Power
stroke.  What am I doing wrong??  Where is cylinder #6, in its stroke
cycle, when cylinder #1 is on the power stroke?
> 
> At 07:56 AM 1/7/99 -0500, you wrote:
> >A reasonably close approximation to true 180 deg. headers can be
made with
> >the old tri-Y approach.  As Aaron wrote, true 180 would require
merging 1-6,
> >8-5, 4-7, 3-2 which is difficult to make.  Merging 1-5, 3-7, 4-6, 2-8
> >enables cylinder pairs to share an exhaust pipe without interfering
and is
> >relatively easy to build.  This is common in high output European and
> >Japanese V-8 engines.  Ferrari, on the other hand, uses a flat
crank to make
> >a true 180 header easy.  Formula 1 and CART V-8 engines also use flat
> >cranks.
> >
> >Flat crank V-8's vibrate like 2 4cyl engines.  A 90 degree crank
V-8 has
> >complete primary and secondary balance with only weights on the
crank.
> >
> >Gary Derian <gderian at cybergate.net>
> >
> >-----Original Message-----
> >From: Aaron Willis <darkmonahue at awwwsome.com>
> >To: diy_efi at efi332.eng.ohio-state.edu
<diy_efi at efi332.eng.ohio-state.edu>
> >Date: Wednesday, January 06, 1999 6:29 PM
> >Subject: Re: Turbo header design
> >
> >
> >>
> >>Clarence,
> >>  This is easily done with an inline four having a 1-3-4-2 firing
order,
> >>as you just pair cyl's 1-4 and 2-3 together.  Commonly done in NA
> >>headers and OEM manifolds too.  However, true 180 degree headers
on a V8
> >>typically take up a lot of space.
> >>   The only firing order i am familiar with is for a GM engine,
which is
> >>1-8-4-3-6-5-7-2.  Picture the cyliders as two rows (which they are):
> >>
> >>     1     2        you can see that #1's 180 degree partner is
#6, #8's
> >>     3     4        is #5, #4's is #7 and #3's is #2.
> >>     5     6
> >>     7     8        Obviously these are all on opposite banks, so
the
> >>pipes need to travel around the engine some distance to collect in
a 180
> >>degree fashion. I really don't know much about whether the benifits
> >>would outweigh the extra bulk and length of the exhaust system,
but I
> >>suspect not.
> >>   HOWEVER it must be said that this arrangement does offer a killer
> >>sound in NA form!  A gentleman in town has a '53 (?) Studebaker
with a
> >>406 Chevy in it, using standard NASCAR 180-degree headers
collected into
> >>a single exhaust, and it will raise the hair on the back of your
neck.
> >>Almost sounds like an exotic foreign supercar (or a flat-crank V8,
come
> >>to think of it)
> >>
> >>HTH
> >>
> >>Aaron
> >>
> >>ICQ # 27386985
> >
> >
> 

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