Ford and Dual Turbos

[Frederic Breitwieser]

>yes and 2x 150 = 300
>they are too small

Been following this thread somewhat lightly, but I think I can add some
information, just to confuse you all <grin>.

First, I'm building a 4.1L V6 Buick, twin turbo setup, just so we have a
frame of reference.  The "stock" turbo was from a 1987 Buick Grand
National, which has a 3.8L V6, which I grafted onto a FWD 3.8L engine for
testing.  Haven't tested the 4.1L engine, as its spread out on my garage
floor at this point.

I found that going significantly larger in turbo size (borrowed from a
friend), the turbo lag was pathetic.  Going too small (using a subaru XT
turbo), it spooled up way to fast, and maxed out at about 2700 RPM.  Not
good, considering the rev limit will be set at 5700 RPM.

So, I got a second junkyard Subaru XT turbo, and connected to each side of
the engine.  Then, I found that the two turbos, were a decent setup, maxing
out boost at about 5000 RPM.  It was suggested on this list a while back,
that running twin turbos require a balance tube between the two turbos, to
ensure the pressure between the turbos would be identical, and while I
laughed and said "bullshit", its absolutely true.  I made an aluminum
manifold that took cylinders and isolated them in such a way that every
other cylinder in firing order came from the left turbo, and the ones in
between came off the right turbo.  I figured that would keep things
balanced.  yeah, right.  The left turbo, being in better condition (these
are non-rebuilt junkyard turbos) spun better and brought on 11pounds of
boost, whereas the right turbo, hit 8-9 and pooped out.  The crossover tube
was necessary.

This is as far as I got, as the FWD engine decided to toss a rod through
the wall, but I did hit the 400HP range on a dyno.

I'd highly recommend Corky Bell's "Maximum Boost" as he provides a LOT of
information, math and ideas for single and dual turbo setup.  I'm still
reading through it for the third time.

A friend of mine has a dual-turbo 4.6L modular Ford mustang engine running
two TE-49's with minimal lag... he gets close to 500HP out of the beast
with no effort at all, running the seperate headers into seperate turbos,
which merge their intake output into the cobra intake manifold.


Frederic Breitwieser
Bridgeport, CT 06606

Homebrew Automotive Website:
http://www.xephic.dynip.com/

1993 Supercharged Lincoln Continental
1989 HMMWV
2000 Buick-Powered Mid-Engined Sports Car

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