[DeTomaso] Dan Jones Dyno update

MikeLDrew at aol.com MikeLDrew at aol.com
Mon Aug 3 20:17:27 EDT 2009


In a message dated 8/3/09 16 31 45, daniel.c.jones2 at gmail.com writes:


> Given the short length of the intermediate pipe, it may not be the
> restriction you think it is.  I can probably answer this question with
> an engineering text book by calculating the head loss for smooth wall
> pipe of various diameters versus length. 
> 
>>>Ow.   My head hurts already.   I think it would be a lot easier to just 
chuck some pipes on the dyno. :>)


>  Still, it would be worth
> testing.  I was considering testing an intermediate size of 2.5" though,
> not 2.25".  That puts the cross-sectional area at 4.9 square inches, a
> meaningful increase that can still be easily routed past the Pantera
> halfshafts.  The collector exit is 2.25" diameter and does not appear
> to greatly choke the flow since the 3" exhaust with GTS headers is
> within 5 HP of the 3" collector long tube headers with the same Magnaflow
> mufflers.
> 
>>>The point of the exercise though is to validate the effective of the GTS 
mufflers.   We've already determined that the system creates a power loss; 
what we want to know is *why* it creates a power loss.   Is it due to flaws 
in the design of the muffler, or is the power loss inherent to the 2.25 inch 
pipe?

If the mufflers themselves are the source of the restriction, then people 
may be inclined to chop the mufflers off their tailpipes and weld different 
mufflers on.   If, however, the tailpipes themselves are the source of the 
restriction, then that won't be effective.   That's why I think it's important 
to test for only one variable at a time--different muffler styles on a 2.25 
inch pipe.

I think it's fairly obvious that by going to a larger-diameter pipe, you're 
going to get performance gains.   What's not obvious is the degree to which 
the current power losses with GTS systems can be attributed to the muffler 
itself, versus the 2.25 inch pipe.   Methinks a straight section of 2.25 
inch pipe grafted to your Magneflow mufflers with a 2.25 to 3 inch reducer 
should be very illuminating.
> 
> >Agreed.  Dave mentioned he has a guy that does good exhaust work at
> a reasonable price.  I've considered dropping off my Pantera to have
> the exhaust fabricated but the car currently has iron 4V heads and
> Hall headers and I'll be running high port heads with matching headers
> so anything I have fabricated now won't match the later set up.  Simpler
> would be to a couple of diameters of straight pipes that could later be
> bent to fit the Pantera.
> 
>>>To what degree do you think the few, gentle bends in the pipe play a 
role? For the sake of simplicity, I would think that straight pipe would be 
sufficient for our needs, no?
> 
> >Magnaflow makes a single inlet, dual outlet muffler with 3" inlet
> and dual 2.5" outlets (inlet area = 7.1 square inches, exit area
> 9.8 square inches, 2.25" dual outlets would be sufficient at 8
> square inches).  Another option would be dual round Magnaflow mufflers
> Y'd together like the big bore mufflers.
> 
>>>Probably much more functional than the stock-style systems for sure.   
But what about aesthetics?   That plays a large role too, for many of 
us...and for that, the GTS system is king! :>)

Mike



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