[DeTomaso] Dan Jones Dyno update

Mon Aug 3 18:09:22 EDT 2009

Mike,

Do you have a pic or two of how your muffler mod looks like inside the can to post for us to see?

Tomas

----- Original Message ----- 
From: <MikeLDrew at aol.com>
To: <detomaso at realbig.com>
Sent: Monday, August 03, 2009 11:52 PM
Subject: [DeTomaso] Dan Jones Dyno update

> 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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