Well Bradley has twin _super_chargers, there are pics of it on the
jag-lovers site, and at various times he has posted the process he has
gone through and what he has done, try the archives. He did it on an
HE, which is contrary to conventional wisdom, BTW.
In his case I would have gone Pre-HE. The concept that I believe his engine
builder (which I used to follow, but have since changed from after reading
some dyno charts), is that the HE has the better combustion chamber/swirl,
which is better for forced induction. Will allow more boost, etc. This is
true! Problem: HE heads don’t flow very well. However, Bradley still managed
to make 488 rwhp (so figure 550-575 flywheel hp) from a 6.0L V12, in a VERY
streetable form, and I might add the car is damn fast (I rode in it).
Another list member, Ted, is just beginning his twin turbo odyssey. I
will be “watching” him closely. I have heard of others, but only rumor.
Oh so that’s YOU who’s been stalking me! Sheesh why don’t you just come up and
say hi? I’ll hand you a wrench! You can help!
Bradley must be (or perhaps more accurately, was) loaded, but Ted
doesn’t seem to be. Hanging a couple of T3s on a preHE shouldn’t be a
big deal. T3s are a few hundred bucks, nothing compared to the cost of
building an entire car, and isn’t that why you asked about dimensions in
the first place? The rest is just plumbing. Admittedly the fuelling
would not be stock and it could be a big ticket item, but it might be
accomplished by megasquirt or variant.
Last figure I heard on Bradley’s car was probably about twice what I have to
pay for college (for those who don’t know, that’s a whole lot of $$$). I am
not loaded, I’m a college student (also known as “broke” or “the opposite of
loaded”).
As for turbos, do the math and you can figure out what’s adequate turbo wise.
A lot of it depends on how much boost you’re going to run. I know what I’m
doing and have figured out a stock application turbo that I can use. Do the
math and you can figure out the same. It’s not nearly as simple as just
picking out two turbos and bolting them up, at least not if you want optimal
results. You would be surprised just how undersized most factory turbos are
for a V12, even in pairs, even on “high performance” cars. Fueling is also
not as simple as just a MegaSquirt. The factory fuel lines can’t flow enough
fuel, the factory fuel injectors (at least on an HE) can’t flow much more
fuel than a stock V12 with minor upgrades (i.e. where mine is currently), not
to mention the fact that trying to use the stock fuel rail for much more
horsepower is like trying to breathe through a straw while doing a heavy
cardiovascular workout.
As the saying goes, “Speed costs money, how fast can you afford to go?” There
are ways around this to a certain extent (as I’m finding out), but make no
mistake, unless you have a whole lot of spare parts sitting in your garage
(that happen to be perfect), it’s going to cost some money to do this. I’ve
done enough calculations that I have a good idea of what I need to
successfully pull this off and at this point I’ve spec’d out every major part
I’m going to need. It’s a lot of parts, not to mention all the fabrication I
need to do, and other expenses I have along the way. You have to also assume
that you’re going to discover problems with your car along the way that
you’re then going to have to fix.
Oh, don’t forget the cooling system. Anyone who thinks their V12 runs warm
now, add twin-turbos! 
http://caffrey.dk/megasquirt/
* *MegaSquirt - Electronic Fuel Injection Computer by Bowling & Grippo * *
and spark (megajolt or something)
MegaSquirt, MegaSpark, MegaJolt, MegaJoltLight, MegaSquirtnSpark, MegaEDIS,
MegaSquirtnEDIS. There’s lots of them out there!
Hmmmmmmm I have spent way to much time collecting information I am not
likely to use… It almost sounds like I know what I am talking about.
What a great parrot I am. Sigh, sob, sniff…
Hey, collecting information is all that I’ve done up until now. Now I’m
beginning to use some of it. Doing something like this is a LOT of work. It
makes you appreciate how much work the people who make turbo/supercharger
kits for stock cars have to put into it to make it work, be reliable, and run
using otherwise stock equipment. Do I ever have respect for them.
Also, for those who are interested, this weekend I’m going to start some of
the groundwork for the project. And that’s not even going to be working on
the engine, that’s work I need to do on the car to make it prepared to accept
the engine, among other things. Maybe next weekend I can get started on some
of the fabrication… maybe. Don’t worry, I will take pictures along the way
and try to keep pretty detailed documentation of everything I do so if I
succeed it will be easy for others to follow in my footsteps (relatively
speaking), and if I fail then people will know where I went wrong.
-Ted
'82 Jaguar XJ-S – 5.3L V12
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