[DeTomaso] Ansa Baffles II

[pantdino at aol.com]

It seems logical to me that the rpm at which backpressure limits 
horsepower would be determined by the effective size of the orifice and 
the amount of air you're trying to flow thru it.  The latter would be 
determined largely by the displacement of the engine and other factors 
that determine how much air the engine flows.  So a supercharged engine 
may be impacted earlier in its rev range, as it is going to move more 
air molecules at a given rpm.

Does everyone know that the resistance of air flow thru a circular 
opening is inversely related to the of the fourth power of the radius?  
In other words, if you make a hole half as big, the resistance 
increases to 16 times what it was, not twice as much.

Therefore the resistance of the system will be determined largely by 
the smallest point in the system, so if you have huge header and tail 
pipes leading to tiny exit resonators, the latter will basically 
determine the resistance of the system.

So it is possible that the system could be foiled by the resonator tips.

Jim (not an engineer but I've had Physics) Oddie



-----Original Message-----
From: F. & D. Terry <gt5s at bcpl.net>
To: scott black <timepiecepr2 at yahoo.com>
Cc: detomaso at realbig.com
Sent: Sun, 7 May 2006 19:11:21 -0400
Subject: Re: [DeTomaso] Ansa Baffles II

  Scott,

  I probably require more flow area than a non supercharged engine. The 
way I see it, the exhaust system must be of a size capable of passing 
the expanded gasses the engine makes. These gasses are a function of 
the air and fuel that is introduced into the engine. Since a 
supercharger introduces more air, I would think more exhaust gasses are 
produced.

  It's interesting to note, however, that with my first B&M supercharged 
engine there was a noticeable drop in power when I switched from Hall 
big bores to GTS ANSA mufflers. The drop in power seemed to be in the 
same rpm range as those who have written to this list with naturally 
aspirated engines.

  With my present Eaton supercharged engine, I started with ANSA 
mufflers on the chassis dyno but everything went south at about 4500 
rpm. A friend pointed out the trouble to be the ANSA mufflers. I made a 
set of 2-1/2" pipes with free flowing mufflers and the problem went 
away.

  Yes, I probably have different circumstances but it is interesting the 
rpm range where power falls off is very close to non supercharged 
engines.

  Gutted ANSA mufflers will make more power than stock but I feel to get 
maximum power a free flowing muffler is the best way to do it. 
Unfortunately they increase the noise level too.

 Fred T.

 scott black wrote:
 > Fred,
  > > > As you have a motor with forced induction, do you have different 
requirements than a normally aspirated motor? I am just curious if you 
have a great neeed/less need for free flowing exhaust since it seems 
that turbo and supercharged motors are genterally quieter. > > How does 
forced induction change things? Does it matter?
 > > Curious in Texas,
 > > Scott Black
 > > > "F. & D. Terry" <gt5s at bcpl.net> wrote:
 > Will,
  > > I posted something earlier about gutted ANSA mufflers and that > 
even though the baffles are removed a restriction still remains. > It 
has to do with a the protruding square edge of the inlet to the > two 
resonators that is very restrictive.
  > > As far as the resonators go, I don't feel they are as restrictive 
 > as you may think. Consider the sum of cross sectional area of the > 
two resonators compared to the cross sectional area of the exhaust > 
pipe. I no longer have a set to measure but suspect there is ample > 
area in the resonators.
  > > I fabricated a set of 2-1/2" exhaust pipes with a cross sectional 
 > area equal to two Pace Setter resonators with a 7/8" bore. I > intend 
to make the switch from my present pair of resonators at > 2-1/4" each. 
Unless I miss my guess, I shouldn't loose any power.
 > > Fred T.
 > > Will Demelo wrote:
  > >>Can someone tell me how to remove the baffles in the ansa muffler 
tips? I've gutted the interiors, but it's still restricting the flow 
considerably.
 >>Will D.
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