to "lighten" the muffler

[Winnie]

Hi out there,
i have a technical Question an i hope i will find the right words for it...

I have a old muffler, which has seen some better times. So i decides to make some test, how to get a better sound out of it.

But before i do this, it is essential for me to know, if a 911-Motor lost some engine power or torque, when there is more less backpressure from the exhaust stream???

Does anybody know this?

Best regards
Winnie

[pwd72s]

Hi Winnie...if you have an MFI car, some of us (Chuck Miller & I both) have experienced "flat spots" in the power curve with mufflers modified for "sport". We're both of the opinion that it's hard to beat a stock muffler for power delivered. Of course, if it sounds louder, it has to be faster, right?

[69Sman]

So FAR...nothing SPORT about ANY sport mufflers I've ever used...

[Chuck Miller]

As said before...
I've tried it twice, for enough money to make me order a-double-of-what-ever-you're-drink'n

It seems to work fine for a carbureted car in either street or race tune...

But for the MFI cars in street tune...
I have found you lose bottom end and transition to gain a little top end... To overcome the lag in low end and transition, I've found you have to diddle the pump enough to lose smooth idle...

It seems that all the MFI cars that have been successful with sport mufflers have been in race tune where smooth idle and fuel consumption were not an issue... (BTW- I just ran a full tank of gas at a VERY spirited pace, not on the track but spirited all the same, and I got 10.3 MPH...
(so what the hell am I talk'n about )

Having a pretty good 'seat-of-the-pants' dyno, I've realized that some of these REALLY fast and LOUD MFI cars have turned out to be kind-a fast and REALLY LOUD cars

The funny thing is, if someone came up with 'the Magic Sport Muffler' or the 'Magic Tune' to run a sport muffler w/MFI on the street, I'd probably have my wallet out again....

Now,
A lot of people don't realize that the REALLY LOUD and COOL sound on MFI cars from their induction... (while your in the car it's MUCH louder then any exhaust) ... in fact, a lot of factory literature refer to the MFI air cleaner as a silencer or muffler.
... just drive your car around the block without it!

I know the ITG system is close... but... I want something that I can just remove my stocker and put on (without allteration) that would give me back some of THAT sound and not take anything away from the performance.... I would have my wallet open AGAIN...

Hey Milt, now THAT'S a cottage industry idea you could work on...

[Zeke]

I would love to be able to do mufflers. If I could buy the two halves stamped, I would experiment with the innards until getting the factory back pressure AND the better sound. I

[cosley]

I installed an Abarth muffler on my '73 S coupe w/mfi. I noticed more power (not alot) throughout the rev range. I mentioned this to a friend who also has one on his '72 E. He also noticed the power increase. It has a nice rumble, and is about 25% louder than stock.
I also built 3 sport mufflers, all a little different. One for the street, slightly louder than the Abarth. The second one was for track/street. The third one for the RSR race car. On the third one I cut 2' out of the length and got it down to 11 lbs. vs 26 for a stock muffler.
I started experimenting around with muffler baffles to reduce the noise of the louder sport mufflers. It seems to me by varying the baffle size and packing you could dial in some back pressure.
At some point I will put the street sport muffler back on the '73 and compare it to the Abarth.
'73 S coupe
'73 targa w3.2
'74 RSR clone w2.8 twinplug
'68 v.w. crewcab w2.4 & 5 speed

[pwd72s]

A lengthy thread over on Pelican...but keep reading. I found the comment on "non factory sport mufflers" interesting...besides, the subject car is quite a hot rod! Here's the link:

http://forums.pelicanparts.com/showt...ight=twin+plug