RE: Re[4]: [ihc] SSII clone racer for sale

["Jim Grammer" <jgrammer@xxxxxxxxxx>]

>-----Original Message-----
>From: ken.dunnington [mailto:ken.dunnington@domain.elided]
>Sent: Wednesday, November 24, 2004 8:49 AM
>To: Jim Grammer
>Cc: ihc-digest@domain.elided
>Subject: Re[4]: [ihc] SSII clone racer for sale

>Jim Grammer wrote:

>JG> I have recently been exposed to this setup in a roundabout way(Pontiac
>JG> 4.9l).

>Messing with a 301 Trans Am eh?

Nah, just looking at the web pics. Didn't even know there was such a thing
'til yesterday ;)

>JG>So far I've not been sufficiently Google-talented to obtain any a/r or
trim data for the GM
>JG> compressors.

>I'm no help whatsoever here.  I looked around the web a few years back
>for turbo data.  Got all the usual stuff(Garrett t3 t4 variants) and
>not much else.

There's a hint in that the Poncho guys think the OEM unit is restrictive and
think a good upgrade is a T-04 with a .82 turbine a/r(no mention of
compressor trim). I'm suspicious that the stock turbo is a .60 a/r turbine
with a 'super 60' trim compressor. Their experiences could be very
instructive for us.

>JG> They are T-03's, but I strongly suspect the compressor housing
>JG> a/r is larger than desired for a 196. On the relatively low-rev'ing 304
in a
>JG> pre-'69 full size(lot's o' hood clearance!) tho'...... 8P Heck, I've
got a
>JG> 266 in '66 Travelette that *really* wants to be a 392, but *doesn't*
want to
>JG> be as thirsty as a 392 most of the time :)

>I've got a 304 that I would like to see live up to such aspirations.

I mis-typed, should have said I think the turbine housing a/r is larger than
desired for a 196. As a reference point, the stock turbine a/r for the
Nissan SD33T(SII Diesel, 199CI)is .60. That setup spools slowly and doesn't
hit max boost 'til late in the RPM game, relatively speaking. Guys in the
know are swapping turbine housings with a .48 a/r and getting *much* quicker
spool with better mid range performance.

Punching some #'s in the Ray Hall site's compressor map calculator, the 304
sits on the line between a couple choices for a single turbo. It pretty well
maxes out a T-03 with the super 60 trim, with tapering efficiency on the
high end(I'm guessing above 3500RPM. OTOH, a T-04 with a '54' trim
compressor looks to put the 2500-4000RPM range totally in the sweet spot of
the map, and might be a good choice for extended highway towing(Mandera?
;) ). I would prolly lean toward the smaller unit. Open question are a/r's
for compressor and turbine. I'm gonna guess that a .60 a/r turbine would be
a good place to start, maybe a .48 a/r compressor? This setup is gonna be
restrictive at high RPM, maybe to the point of self-regulating boost(as
described in the MacInnes book).

*If* you could direct mount the turbo to the manifold, flipping the exhaust
manifolds(or using tractor/stationary manifolds) would allow greatly
simplified routing. Straight up and over to the turbine inlet. BUT....on an
SV-8, the dang t-stat housing is right in the way! :( Unless, of course, you
turn the whole mess sideways :)

Alternatively, there's the twin turbo option. Something like a T-25 or a
T-03 '40' trim might be the hot tip there.

BTW, I'm running #'s a 4000RPM max, boost @ 8# and all-in by 2500RPM,
looking for boost to start @ 1500RPM, 70% VE and compressor efficency.

Jim