-----Original Message-----
From: George Schiro [mailto:gschiro@lni.net]
Actually, I wouldn't recommend drilling out the birdcage without doing a
proper engineering stress analysis.
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I hear you.
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The Turbo 13B swap is very interesting. I hadn't considered that option.
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I didn't either for a long time. I thought that the car was too heavy for
that engine, because it's not famous for its torque, and it's hard to get
more than ~350-400hp out of that little 1.3 liter engine and still be
streetable. I want 350 at the wheels, which means almost 400 at the crank,
and that's right on the edge of what you can comfortably manage.
But when I did some research into how much weight I could save just by going
to the rotary, it brought the weight of the car down to the point where it
seemed to make sense. And it cuts the weight where it matters most, which
is a big plus.
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My son the mechanic tells me that there are many after market goodies for
the rotary.
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Absolutely. But they all fall into a small number of categories:
1) Turbos
2) Engine Management
To make >300hp, you first port the motor and intake manifold. Porting the
motor has the same effect as a new cam and heads for a piston engine. The
only aftermarket goodie you need for that is a grinder and the patience to
use it. ;) Actually, you buy templates too...
Then you put a turbo or two on there. Single turbo setups give you better
max power, but twin turbos reduce lag if they're properly set up and
managed. You'll also need turbo-related stuff like a pop-off valve,
wastegate, EVC, and turbo timer. Peter Farell Supercars
(http://www.pfsupercars.com/) and Pettit Racing
(http://www.pettitracing.com/) both know an awful lot about this stuff.
Check out those pages if you're even moderately interested in the rotary.
Everybody should read about Pettit's "Banzai" RX-7 with the _mighty_ 20B
rotary (a 3-rotor, 600hp, 2.0 liter version of the same basic 13B design).
Now, you need to give it fuel and spark - Haltech and Electromotive both
make engine management systems that are rotary-friendly. Or you could go
with carburetion and a good old distributor. For <300hp applications, you
can adapt the factory computer from a 2nd gen Turbo (driving oversized
injectors), and it supposedly works OK.
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Can you go over the details of the swap?
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Well, I think you can expect a series of Brickline articles when the car's
done, but in the mean time, I can share some more info.
There's nothing really special about the engine swap, so far at least.
Unlike a typical engine swap, the new motor is much, much smaller than the
original. Seriously, the 13B is a teeny little thing, and the long-block
weighs barely over 200lbs. One guy can pick a short-block up and move it
around by himself in a pinch... I think the outside dimensions would be
something like 20" wide by 20" high by 24" long or so.
So mounting it isn't hard, because you've got so much space in there - it's
just a matter of making some mounts that position the engine as far back as
possible. The springs and shocks, and swaybar obviously have to change to
account for the reduced weight.
All that's left is plumbing the exhaust/turbo and figuring out what else to
put in that big engine compartment so that the 13B doesn't look like a toy
in there! I think I'll opt for a big intercooler and rad, and race-style
ducting to route the air out through some holes in the hood.
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What IRS are you using?
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Corvette - I think it's out of a '76. It's got a 3.73 posi, but that gear
may have to change to a 4.11 or 4.56 to compensate for the turbo's lack of
torque and 8000rpm redline.
The track is widened (from the Bricklin dimension) or narrowed (from the
Vette dimension) to 60", and will remain a trailing-arm type setup. The
center section is rigidly mounted to an aluminum crossmember, which is
isolated from the frame by rubber mounts to reduce NVH. The transverse-leaf
setup has been replaced with coil-overs, but I haven't done anything wacky
like move the disk brakes inboard (although it sure would be trick!)
The springs will have to have a pretty aggressive progressive rate, because
the geometry of the Vette IRS starts getting silly without an awful lot of
travel, and narrowing it from its original dimension aggravates that.
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What front suspension?
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Spindles and brakes will be from a GM mid-sized car or maybe a van. Rack &
pinion steering will be from an RX-7 or maybe Mustang. Everything else will
be from a block of billet aluminum. ;) This is still being designed, but
we're looking at an unequal-length A-arm setup, also with progressive rate
coilovers. I'm considering mounting the coilovers inboard, but this would
be _purely_ for sex appeal - it could actually hurt performance because
there are a few extra joints in there which means more play in the
suspension. But man, would that look trick.
Front track will also be widened to 60", and the geometry will be pretty
conservative because I'm going with 17x11" wheels at all 4 corners. With
315/35-17 tires up front, the geometry will have to be designed to keep
those damn tires from undergoing camber changes. Also, those big tires will
tend to make the car darty, so I'm hoping that can be dialed out a bit with
less aggressive geometry & alignment settings.
I'd like to note publicly that Greg Monfort has been an invaluable help in
planning out these mods, and perhaps more importantly, goading me into
actually going for it! ;) Not that I needed much prodding, but he's been
very good at reinforcing my "if I've done all that, why not do this?"
mentality. ;) If I ever get this pig done, I'll have to make a road trip
to Georgia so he can have a chance to take it around Road Atlanta.
Also, the high-level design and general approach is something I've come up
with as a result of a few hunches, my aesthetic sense, and quite a bit of
research, including _patient_ and friendly advice from Greg and others, but
the actual construction and detailed engineering is being done by the guys
who are building the chassis for me. There should be drawings of everything
available when it's all done, if anybody else wants to do something similar.
But I kind of like the idea of being the only guy in the world with a
Bricklin built to handle. ;)
--
Phil Martin pmartin@surgnav.com
"I'm a Charger, charging through the night,
Like an orange bolt of lightning passing everything in sight"
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