Daniel1312@aol.com wrote:
>
> I have heard of some rubbish in my time but this is incredible - absolute
> rubbish.
>
> In a message dated 15/11/00 04:20:16 GMT Standard Time, sfooshee@home.com
> writes:
>
> << The generalization
> is that you want a more restrictive exhaust and a smaller carb/intake for
> higher
> velocity at low engine speeds. >>
Okay, so besides your subtle disagreement, what's the answer? I
qualified it as
a wide sweeping and incomplete generalization because I didn't feel like typing
that much.
In my experience, engines with smaller and/or longer intake tracts have
made
better low end torque versus high speed power. Mazda's Le Mans winning prototype
used a variable intake (copied, I believe, by Ferrari's F1 program) in which the
intake would shorten as engine rpm increased. This allowed the longer (and more
restrictive) runners to increase the velocity of the intake charge at lower
engine speeds while still allowing the short runners required for higher rpm
power. Mazda has also used this with the '89-'91 normally aspirated car's
variable dynamic intake effect system, and Porsche's variable intake is very
similar. If the intake charge is stagnant (too big an intake for a given engine
speed) then the fuel doesn't mix well and doesn't burn well.
I don't pretend to understand all the physics of engine design, but my
short
experience has shown me many people make their cars slower by simply opening up
the exhaust. I know that 2-stroke engines are desperately dependent on
backpressure for torque, and rotaries are very similar to this. My old SAAB was
in dire straits when the manifold flange rusted off, it wouldn't discuss power
until 3500 rpm or so.
Assuming that the questioner is limited to modifications below
fabricating some
means of variable cam timing, most any change which will increase low end torque
will sacrifice top end power.
Even if I'm wrong, why call it _incredible_ rubbish with no evidence or
opinion
of your own? If I'm wrong, correct me, but don't be an ass.
--
~
-Xavier Onasis.
'87 RX-7 TII: Live fast.
'90 GS-500E: Die young.
MCMLXIX Sprite: And leave an exquisite corpse.
If God dropped acid, would he see people?
~
|