Re: If you have your choice...
hello all - good discussion...
is it not true that a positive displacement supercharger effectively "adds"
cubic inches? for instance the stock eaton m-112 on the 03/04 cobra
actually adds (taking into account inefficency losses) approx 80 cubes to
the 281 modular (4.6), effectively making it around 350 ci engine? and a
2.2 kenne-bell twin-screw which equals 134.4 cubic inches, would add 90 or
so (after losses)? and then the 2.4 kenne-bell even more? i had read that
the inefficiencies of a supercharger equate to only about 70% of the total
with regards to the gas mileage argument, and it may or may not be directly
related to the above, my experience is showing that although there is a very
small displacement modular under that blower, it's as thirsty as a big
block. i'm not talking about around town driving when i'm constantly into
the boost from light to light. i mean the best highway mileage i can get out
of this car is about 21-22... real highway 6th gear cruising. i average
only 10-12 city with an overall average of 13.5. those numbers remind me of
60's big block muscle type mileage - pretty bad. i know that this is a
heavy car, and rear end gearing and transmission overdives play a big part
in it. but the idea that you can take a small engine and get the benefits
by staying out of the boost does not seem to be working for me in the real
world. my 96 gt vert (stock with a 3.27 rear) would get around 21/22 city
and 28/30 highway, and that is with only 1 overdrive gear. it was a lighter
car than this 04 cobra, but still, that is a pretty big difference - and gas
aint cheap these days. that being said, trying to get good gas mileage is
NOT why i buy an american v-8...
from what i understand, the chevy ls-1's which are powerful engines, get 30
highway - even in the heavier cambirds. i think they have 3.55 gears with
the t-56 like my car, but are a little lighter? so i can see the logic in
the argument that cubic inches is king and why chevy has stuck with their
simple ohv small block but just kept the displacment large and the
04 comp orange cobra vert
<email@example.com> wrote in message
> Michael Johnson, PE wrote:
> > RichA wrote:
> > > What method of horsepower increase would you choose?
> > > -Supercharger.
> > > -Nitrous
> > > -More cubic inches
> > > -A more refined (upped compression, etc) motor?
> > >
> > > Personally, I think more cubes is the sensible path, owing to
> > > it's simplicity, but then bolting on a supercharger or nox bottle
> > > is perhaps easier.
> > > -Rich
> > A twin screw blower or turbos is the best route, IMO. A twin screw
> > blower on an '03-'04 Cobra gets you a reliable 600 rwhp/rwtq out of
> > 4.6L. Plus when you keep your foot light you get the mileage benefits
> > of a smaller displacement engine. When an engine is properly designed
> > for forced induction it is very rugged and reliable, even under high
> > boost conditions.
> I'm with MJ. Two small turbos, an air-to-air intercooler, and EFI on a
> 302 or 331 -- that's the ultimate. Nitrous is only good till the
> bottle runs out. Anything over 350 ci, you're stuck with terrible gas
> mileage all the time. A turbo small block doesn't need all that much
> cam, and if gas hits $3-4/gal, you just dial back the waste gate. A
> big block destroys handling and braking, and because you can't
> eliminate the low end torque if you want to have anything left up top,
> it's alot harder to hook up. The twin screw is attractive, but it's
> not easy to control the low end torque either.
> 180 Out