[DeTomaso] Dan Jones Dyno update

[MikeLDrew at aol.com]

Hi guys,

I think Dan meant to post this to the forum, but apparently he only sent it 
to me, so I'm reposting it here.   Dan wrote:

=====

 Thursday after work, we did some additional Pantera exhaust testing.

Test 1.
354 HP @ 5550 RPM (372 HP corrected)
350 Ft-Lbs @ 4900 RPM (368 ft-lbs corrected)

Torker, HVH carb spacer, 950HP carb, 38 degrees total timing, Euro GTS
"tri-y" headers (actually 4-into-1 with a tri-y collector, 2" OD primaries,
2.25" collector) and Euro-GTS mufflers (small lunchbox size muffler with
dual resonators (per side).  Reasonable numbers to about 5500 rpm where
power falls off.

Test 2.
366 HP @ 5600 RPM (384 HP corrected)
359 Ft-Lbs @ 4850 RPM (377 ft-lbs corrected)

Same as Test 1 with Mike Drew's modified GTS mufflers.  The GTS muffler
baffles were removed and replaced by a Y-pipe.  The pipe was perforated
and muffler body packed with steel wool.  Mufflers sounded better
(slightly more whistle tot the tone) and peak power was up 12 HP and
peak torque was up 9 ft-lbs.  Torque was up around 10 ft-lbs over a
fairly wide RPM range so this was a meaningful modification but still
leaves a lot of power on the table.  Interestingly, the Euro GTS headers
plus modified mufflers makes around the same power as our previous test
with OEM cast iron 4V manifolds without mufflers.

Test 3.
387 HP @ 5500 RPM (406 HP corrected)
379 Ft-Lbs @ 4800 RPM (398 ft-lbs corrected)

Same as Test 1 but with 3" inlet/outlet Magnaflow mufflers clamped to the
Pantera Euro GTS headers via a 3" diameter by 12" long pipe.  Good solid
power gain over baseline and modified exhaust system.

4. Prior Test

392 HP @ 5600 RPM (412 HP corrected)
384 lbs/ft @ 4750 RPM (403 ft-lbs corrected)

Same as Test 3 but with 1 3/4" primary diamter 4V Hooker Competition 
Headers
(Mustang/Cougar chassis).  Torquer intake and HVH spacer, Magna flow 
mufflers,
3" x 12" intermediate pipe.

5. Prior Test
366 HP @ ? RPM
351 Ft-Lbs @ ?RPM

OEM cast iron 4V exhaust manifolds without mufflers (only a short length
of 3" pipe bolted attached to the manifold).

Looking at Mike's modified Euro GTS mufflers, it's not immediately obvious
where the restriction is.  One possibility is the resonator tips may be
choking the flow.  The ID of the tail pipes is approximately 1.56" for a
cross-sectional area of 1.9 square inches times 2 for a total of 3.8 square
inches.  The ID of the intermediate pipe is 2.25" which is a 
cross-sectional
area of 3.98 square inches.  The total outlet area is slightly smaller than
inlet area.  A slightly larger outlet than the inlet is desirable but the
difference isn't that great.  If someone has an old set of GTS mufflers
(rusty or banged up is fine) to donate, we can do more modifications
(e.g. saw off the resonators) and testing.

As soon as my hand finishes healing, I'll pull my my Hall big bore
mufflers (dual glass packs per side) from my white Pantera and test
them.  These have slightly larger outlet area (1.66" diameter per
glass pack) but have smaller header collector outlet area.

We're also considering having a couple of sizes of intermediate pipes
made to see 2 1/2" is adequate or 3" is required for the 3" inlet/outlet
Magnaflows.  Dave noted that both he and Kaase made best (average) power
with 3" outlet collectors on their 600 HP Engine Masters Clevelands so
it's possible 2 1/2" is sufficient for this engine.  2.5" is much easier
to route through the Cleveland suspension than 3".

Thanks to Mike Drew for sending his modified Euro GTS mufflers
and Paul Timko for sending his unmodified Euro GTS exhaust (headers
and mufflers) and a set of Hall headers (to mate up to my Hall Big
Bore exhaust).  We also still need to trial fit Larry's 180 degree
headers to see if they will clear the dyno and test the exhaust port
stuffers.  I may also pull the swap headers from my '66 Mustang.
Those headers have a very sharp bend at the port exit which can't do
anything good for flow.

Dan Jones

=====

A thought here--although I am disappointed that my modifications didn't 
result in a greater HP gain, I think that there's a bit of apples-to-oranges 
comparison going on here.  Dan compared stock GTS exhausts, my modified 
exhausts, and his home-brew system.   But that system uses 3-inch pipe instead of 
the 2.25 inch pipe found on the GTS systems.   Dan correctly calculates that 
the 2.25 inch pipe has an area of some 3.9 inches, but doesn't mention that 
the 3-inch pipe has an area in excess of 7 inches, which is a huge 
difference.

The meaningful test would be to put the Magnaflow muffler on a 2.25 inch 
pipe and see what happens.   If the power remains more or less the same as the 
GTS mufflers then we know the constriction is caused by the pipe diameter 
and not the mufflers.   If, on the other hand, there is a big power gain, 
then the mufflers themselves are the culprit.

I think it would be easier to cobble together a system with 2.25 inch pipes 
and the Magnaflow mufflers rather than finding and destroying a GTS system 
in order to test the theory.   Dan, whaddayasay?

I think there is a tendancy to dismiss the ANSA mufflers as being big 
power-eaters, but until we get an apples-to-apples comparison, we won't know if 
that's a valid criticism or not.   It may well be that I have achieved the 
optimum performance available within the constraints of the 2.25 inch tailpipe 
setup.   I know there are some people who have successfully had custom 
3-inch systems made, but that was an expensive and non-trivial undertaking, 
probably well outside the scope of most owners.

I look forward to ongoing tests--and I look forward to getting my mufflers 
back so I can drive my Pantera again. :>)

Mike


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