Adam, just because you can buy a turbo for a SBC for $900 you shouldn't
assume you can get the same for another engine. What J-L says about
turbos is true for conventional turbos, but there is a bag of tricks to
help. They don't come cheep. most come under the category of variable
incident, ether vain or multiple inlet. Another approach would be
undersized turbos from a bike, maybe 2. I would expect to have make at
least 2 of every thing in different forms to come close to right, or you
could pay someone with great experience to do it for you (there is no
substitute for cubic dollars). Take a look at www.sdseif.com in the
tech and FAQ sections, good ideas and good advice.
For off road use I think you would be better advised to look into
mechanical or chemical supercharging. A small Vortec or Paxton
supercharger with bypass and electro clutch could give you just abut the
best of both worlds (normal and forced induction). Torque would be only
a down shift away and no waiting for the turbine, compressor and
connecting shaft to spool up another 75000 rmp. Turbo lag is a real PITA
on a race track, I can only imagine what it must be like to deal with in
mud. Nitrous oxide has a well deserved reputation for destroying engines
, but can be used safely. It would be like turbo lag it you hit the
engine with too much too fast, but new hardware and software is making
dealing with it eraser and safer.
Notice the software above? To get smooth torque curve with any kind of
super charging expect to use programmable engine management.
My own prejudges have led me in a very different direction. I want more
torque but not enough so new drive line is needed. I want to keep thing
light as possible. I won't accept a brake specific fuel consumption over
.5 Lb\HP/Hr. at full power and above .4 at light throttle. That last
one rules out most older engine designs do to poor combustion chamber
design. The second heads me towards aluminum at least in the head and
the first caps my displacement at about 3L. I found an interesting donor
in my warranty parts bins at work. Its specs are 2.3L, long stroke,
short rod, variable valve timing, 4 valves per cylinder, with good
compact and clean combustion camber, under 250 lb. Its original use is
rather different than my 88 so some modification would be needed. I have
modeled it with a finite amplitude wave stimulator. I started with cam
specs from a IIA 2.25 and got 174 lb ft at 1700 rpm , 189 at 3000 and 190
at 4500. Not too bad for a first try. As you can see form the flat
torque curve the power curve is a straight ascending line to 5000 where
it flattens out to 6000. I figure with numbers like that from 2.3L I
don't need the hassle of forced induction.
As for modern engines and there electronics. Use after market engine
management and the job isn't too hateful. Do your homework on them to
get one the most closely matches you engine and the job is that much
eraser.
What ever you do keep us posted ( at least me). What doesn't work for
you is just as useful to me as what does.
chris hall
This archive was generated by hypermail 2b30 : Wed Jun 13 2001 - 01:45:06 EDT