[urq] Re: 10 vT EM? K24 is good for 278 HP

[QSHIPQ at aol.com]

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Javad:
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In a message dated 4/29/02 10:03:25 AM Central Daylight Time, JShadzi writes:

>Well, I have not been talking absolute power, I think that's been clear, my
point is >that power output of a 10v vs 20v engine wrt turbo is relative, say
the 20v head >flows about 25% more cfm than a 10v (in that ballpart IME), how
much harder will >a K24 have to be pushed to create the same power output,
its relative, especially >when you bring in factors such as turbo efficiency
and how they relate to IC size, >and other flow related issues such as intake
and exh. manifold design - the 20v is >in better shape wrt to all the above.


Maybe.  If you do the accepted math, to get the smaller WX (2.1L) to flow the
same CFM as the larger 3B (2.3L) with a 10% gain in VE, the math shows that
boost equivelency to be 15%.  IOW, you need 2.3psi more boost pressure in the
WX to have the same CFM flowing thru the motor.  It's that simple.  You put a
better IC on the WX (increase the density ratio), you can get that
differential even less.

>I'm talking practical application, even with EFI, a K24 will need to be
pushed very >hard to produce the cfm needed to make 280hp, of course it only
gets better with >head work, cam, etc.

Your limitation is the cold side on the k24, not the hot side.  Be careful
about quickly swapping turbos.  The WX especially, needs a turbo that can
spin up with a low exhaust velocity.  Again, a bigger cold side on the k24
can put you over the 300 mark in either engine, without losing low end grunt.
 If you look at the RS2 hot side, it's not much bigger than the k24 hot side,
and it's capable of 400hp.

>I know first hand how much power a 10v can make, I spent about 2 years
tinkering >with 2 TransAm cars, those motors were easily making 5-600hp, but
they were no >were near the motors that we get, relatively speaking.

They also hung some impressive IC's off the front of them, I remember seeing
them at Monterey Javad.  It's pretty well documented too, that without the
displacement (read small motor), these cars tended to be very peaky with the
mongo turbos on them.  I say pick a HP level, then get a turbo that gets you
there with the best hot side design to the displacement of the motor.  Big
turbos need more displacement.  Glen is probably shorting himself with the
2.4L conversion, but again, the issue is the CIS at 280hp, NOT the
turbcharger unit.  If the given is that you are maxing the fuel system, why
not accept a better low end?  IF the given is the EFI (non MAF type), then
your options open some.  But, displacement still rules the roost for all
around driveable power.  IF that's a given (in most cases here it is) go for
torque (read better turbo output at a lower rpm)

>My advice to anyone looking for 280hp is a 10v, stay away from maxing out a >
K24, and use a bigger turbo which will be much more efficent at those kind of
air >flow levels.

My advice is drive different setups.  There is no question in my mind Javad,
that for 2.1L and 7.0CR, the k24 turbo outperforms the k26 hands down (btdt).
 280HP?  I don't see that happening on the stock WX fuel system.  The
restriction however is that fuel flap, air routing and air density not the
VE.  For a non cross flow design, the 10vt does very well for itself.

The EFI audis all use MAF (stock or tweeked motronic), that too is a
limitation in terms of HP levels, NOT the turbo.  The S car boys have
demonstrated and documented clearly that the HP level of the 20vt is 420
tops, then the MAF becomes the restriction, NOT the turbocharger, and that
level can be had with the bone stock RS2 turbo setup.

HTH

Scott Justusson
83 urq mit k24
84 RS2URQ
'87 type 44tqw mit RS2 turbo