MG Sports Cars

When I built my car I used Borla mufflers on the end of the twin pipes.
The sound is smooth and deep. Unfortunately, the sound turns into a drone on the highway at cruising speed.
Are there any 302 owners that could recommend a great sounding system that doesn't drone?

I have a 331 CI SBF in my Model A Ford, I'm running a Dynomax Super Turbo #17769 in each pipe, just forward of the rear axle with a stepped adapter from 2 1/2-3" (2 1/2" pipe, 3" muffler) with the 2 1/2" extended through the adapter and partially into the muffler for tuned length and anti reversion properties.

You are unlikely to fit those under any MG (they're huge), I've been considering running a pair of the Super Turbo #17676 sideways forward of the rear axle in my CB B, sideways, with some sort of bullet muffler at the end of the pipes as a resonator.

On my B I'm planning on running RV8 style headers and routing the pipes between the rocker and the structural piece to either side of the transmission tunnel.

For what it's worth, the model A has block hugger headers and is fairly quiet, 'till you stand on it. :)

While I can't tell you if my proposed system will drone or not, the one on my Ford does not (not that you could hear it over the wind and road noise at speed, working on that ;) ).

Hi Martyn,
Gonna miss you & Carol at Indy!

This might help:

[www.britishv8.org]

I found an internet suggestion that closed end pipes equal to 1/4 the wavelength of the sound waves at cruising speed will set up a standing wave equal to 1/2 the wave length of the exhaust sound waves (1/4 wavelength up and 1/4 wave length back). These standing waves are 180 degrees out of phase and so will cancel the sound. For best results the closed end pipe should be the same diameter as the exhaust pipe. Anyway, I built a set for my car and there is absolutely no drone. As I recall at 2000 rpm (8 cylinders, dual exhaust) 1/4 wavelength is about 24 inches. With 8 cylinders and a single exhaust it is twice that which is not practical. I have a crossover pipe (H pipe) in my exhaust so each pipe is not perfectly "pure" in its sound, but the system still is effective in cutting drone. It may be worth a try.

On my 86 Mustang GT with a 5.0/302, it is my understanding that the mufflers were different sizes on the two sides to avoid resonance; each muffler having a different characteristic resonant frequency. When I replaced the mufflers, I had an argument with the shop owner about my insistence that the mufflers be different sized. He was insistent that they would not drone. I didn't care what he thought, I wanted different mufflers. The car was quiet and did not drone after muffler replacement.

Paul, what mufflers did you wind up with?

I used a pair of off-the-shelf mufflers from the muffler shop. The car was still capable of doing 120, and still pulling, through those mufflers. The exhaust system has a cross-over, so muffler flow becomes less of an issue in that configuration.

Thank you. :)

IIRC I believe Rob Ficalora's car has one of the best exhausts I've heard if you are looking for a car that is more, shall we say understated? Very nice tone and not in the least offensive.

Jim

I PM'ed Rob, and he not only responded but graciously consented (via email) for me to post the pertinent information here. :)



Per Rob Ficalora:

"My exhaust is very quiet. I have a Ford 302 with the headers Fast Cars Inc. sells (I got them from Steve Carrick back when he Wes doing them, but Fast Cars sells an improved version now). From the bottom of the headers, I use 90° elbows that I modified to be reducing elbows to transition from the header collector (3 1/2" if memory serves) to 2 1/4". I then use a short length of 2 1/4" round to oval transition pipe and run the oval to Spintech Cruiser series mufflers under the seats on both sides (http://www.spintechmufflers.com/mufflers/street-mufflers/cruiser-7000-series-round-oval/cat_31.html). I also have an oval H-pipe before the mufflers. I had to make the connectors to tie in the H-pipe. Just oval pipe the I made fit between the two sides, traced around with a marker and cut to make the opening. Then welded it in and made some cuts to make it removable).
From the Spintechs I use more 2 1/4' oval to just in front of the battery boxes where I use another pair of oval to round transitions (one for each side). I modified the transitions to step down to 2" and I then snake through my IRS with 2". I then have some generic 10"x2" glasses pack round type mufflers that I'm using as resonators.

I drive to work every now and then and without the glass packs it would set off some car alarms. When I added the glass packs, that problem went away.

I'd like it a tad louder and a tad more mellow, but it meets my current need (not annoying my co-workers :) ).

2.25" and 2" may be a tad small - I think 2.5 and 2.25 would be ideal, but generally speaking, smaller pipe is quieter than bigger and the further back you put the mufflers, the quieter too."





He's not in a position to look under the car at the moment, so going from memory this is an excellent description. :)



Edited 1 time(s). Last edit at 07/22/2015 02:43AM by Nexxussian.

Here's a picture...

Nice work under there Rob.
Is that one of those magnetic car lifts? ;-)

Cheers
Fred