[Diy_efi] : tuned port manifolds

Eck, Joel Joel.Eck at hp.com
Tue May 14 17:20:24 GMT 2002


well, my best guess would be to examine the header or exhaust manifold =
from something like a turbo supra or, basically, something that came =
from the factory with a turbo inline 6. the use of the turbo, from my =
view, sort of negates the need for the high flow and scavenge effect =
typically associated with headers. additionally, trying to pipe 6 =
primaries into a single collector for the purpose of feeding a single =
turbo could end up being a plumbing nightmare.

personally, I would use the stock manifold (or other OEM manifold, if =
there is a different application that fits and flows better in stock =
form) and port it out to open it up some.

my reasoning is this: the extra flow and scavenge benefits of a tuned, =
equal-length header (which, building the header itself is no easy task) =
will be minimized by the process of driving the turbo. If you use a huge =
turbo to get better flow through the turbine, you'll end up with serious =
turbo lag and a screaming top end. if you use a smallish turbo to =
minimize turbo lag, but you'll run out of steam up top, and, you'll =
introduce more restriction into the exhaust system.

If you look at the headers Clifford performance offers for various =
inline 6 applications, they end up with 3 of the primaries dumping into =
one collector, and the other 3 dumping into a second collector. (They =
may have some applications with single collectors, I don't recall =
offhand.) If you went that route, and then placed the turbo at the end =
of a "Y" pipe that joined the two collectors into a single pipe, that =
would probably place the turbo under the vehicle. IMHO, this wouldn't be =
a good way to go for a single turbo. You also would not want to have one =
of those 2 collectors running the turbo and other one not running it, =
that would place unequal stress on the engine components. Now, if you =
were to use twin turbos...

are you looking for more low-end or more up top? for low-end, I would =
work a slightly ported OEM Manifold with a smallish turbo. for top-end, =
you can go ahead with the header and run a huge turbo, although an OEM =
Manifold should work just as well, if you can port it out quite a bit.

one downside to porting cast-iron exhaust manifolds: if you get the =
casting too thin, it will crack easily. I had laid my hands on a set of =
old "ram's horn" manifolds for a small block chevy one time only to find =
that they were terribly cracked due to someone having gotten carried =
away with the die grinder.

the other thing to note is this: with the cast iron manifolds, there =
shouldn't be any problems with hanging the turbo off of it. with =
headers, you may need to fabricate some sort of mount; the added weight =
of the turbo will likely induce more exhaust leaks. headers are =
notorious for leaking anyway, and if you hang more weight on them, it =
may be even worse.

Anyway, that's my take on it. I'm sure others out there will be =
vehemently opposed to my ideas, thinking that I must certainly be wrong. =
But I think that the time, effort, and money exhausted (pardon the pun) =
on building an L6 (or is it I6?) header could be better spent elsewhere, =
especially when you consider that the extra flow from the header will =
only be restricted about a foot down the pipe anyway.


-----Original Message-----
From: ruppeljw at capital.net [mailto:ruppeljw at capital.net]
Sent: Tuesday, May 14, 2002 11:27 AM
To: Diy_efi at diy-efi.org
Subject: Re: [Diy_efi] : tuned port manifolds


Thank you all for the info,
     I just took a look and my school library has a copy of the Blair =
text=20
available.  I just need to head over and pick it up.  It looks like it =
covers=20
exactly what I am looking for.  I'll report back my success or lack =
thereof. =20

     Does anyone have any concepts for a turbo header for an inline 6 =
engine=20
that has worked well in practice?  I have a good handle on analytically=20
modeling systems, but I still have a very long way to go when it comes =
to=20
making it work in the real world, and primary research is alyways very =
useful.

Thank you,

Jesse Ruppel
ruppeljw at capital.net

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"Visit Capital.NET online at http://www.capital.net"

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