Roadster Sidepipe Sound Testing

[Blue Classic]

Quiet pipes are the real deal. I had damaged my Sidepipes and bought a new set FFR Stainless Steel Sidepipes. After a spirited season of driving throughout New England my wife asked if there was something I could do to quiet the car down so she could enjoy it more. So, the search was on for an exhaust system that would give that classic deep muscle car sound without vibrating the neighbor’s windows or setting off car alarms while driving through parking lots or having my neighbors stop me to complain about the noise!

I did the research, reviewed articles, called several different manufacturers and narrowed my choice down to Boig Motorsports Quiet Pipes and FlowMaster Slimline mufflers “designed for the Cobra.”
With the help of great friends I was able to conduct an analytical sound level test on my vehicle with three different sets of sidepipes. We conducted all test under identical conditions to verify results.
Each sidepipe muffler assembly was new, installed with new gaskets and aligned with the hangers fitted.

I’m running a Ford Racing 351-W, bored to 392-C.I. @ 430-H.P. With a Holley Ultra 750 – CFM Double Pumper Carburetor, non-catalytic 4 into 4 Headers and Factory Five Stainless Steel Sidepipes.

Sidepipes tested:
1. FFR Stainless Steel Sidepipes. (Used as the standard reference.)
2. FlowMaster Slimline Sidepipes fitted to FFR flanges, pipes and turnouts.
3. Boig Motorsports Quiet pipes.

Test Conditions:
Engine full hot operational temperature, outside in an open area.

TEST FFR FlowMaster Boig Motorsports
RPMs Stainless Steel Slimline Quiet Pipes
Idle 750-800RPM 104dB. 105dB. 90dB
1,500RPM. 106dB. 106dB. 92dB
2,000RPM. 107dB. 107dB. 98dB
3,000RPM. 111dB. 114dB. 104dB

RESULTS
1. The FFR Polished Stainless Steel Sidepipes look great on the car. They created a clean sound that rolls like thunder, but they leave your ears ringing after driving a long distance on the highway and having a conversation is difficult. As they age, they get louder.
2. The FlowMaster Slimline Sidepipes when started spun heads as they barked loud and raspy. As we increased RPM’s FlowMaster Pipes got progressively louder making conversation difficult at a 45 MPH cruise and impossible at highway speeds.
3. Boig Motorsports Sidepipes is the clear winner. These Sidepipes generate a muted, classic deep pulsating muscle car sound that lets you know there is something special under the hood with no loss in performance. The Quiet Pipes allow for a conversation at wide open throttle and you can continue that conversation at highway speed. The precision welding, the fit and alignment of the Boig Motorsport Sidepipes made installation easy as well as putting a beautiful finishing touch to my build!

My son and I drove the Roadster to Florida, 1,350 miles, most that at 75MPH+. It was easy to carry on a conversations at any speed. Today the Boig Motorsports Sidepipes look and sound as good today as the day they were installed.

[Avalanche325]

There was some dyno testing on the other forum. Quiet pipes cost a 347 71hp (365 down to 294). That would tend to get worse as HP goes up as any exhaust system is pretty much a "can handle up to" type of system.

They do what they are supposed to and I have only read good things about the quality. I have thought about them myself. But no "loss in performance" is very unlikely. Maybe you just don't notice it on the street.

[dncharo]

Has anyone compared the Boig quiet pipes to the Gas N pipes? These are the ones I’m considering at this point. Thanks!
David

[steno]

That’s interesting... everyone seems to love the slimline pipes. There’s a comparison done by Bobl that shows horsepower and sound levels and the slimlines came out on top!

[Blue Classic]

Steno, there are two different lengths of FlowMaster SlimLine mufflers a 24”, which is for the Cobra and a 30” for the Corvette. FlowMaster recommended the 24” as this best fit the car. This is the one I tested and there is no way it could be considered quiet. It cost $400 for the mufflers + the assembly cost to fit them to the FFR flange pipes and turn out.
Before buying the Flowmaster check what length those recommending them bought and if they are running catalytic converters as this makes a world of difference in noise level.

I have seen comments on Gas’n Go Sidepipes that they are a little quieter than FFR’s Stainless but not much. Search the Fourm for Post.

I find little to no power loss from the Quiet Pipes. This is my 55 years behind the wheel in the automotive industry and a seat of the pants comparison from FFR’s Stainless Steel to the Quiet Pipes but what little loss there might be “the great sound and quieter operation makes them worth every penny.”

[KDubU]

Those seem like a decent option/upgrade. I have the Gas-N’s and can have a convo at certain speeds but this is a roadster with wind noise as well as engine noise. Having a convo at 70mph no matter the pipes is going to be challenging with the wind, other traffic, etc.

[Pineapplehead]

Thank you for posting this!

[2bking]

I think something is not right about your results. Other testing has shown the Slimlines to have a lower db than the FFR ones at all RPMs. I replaced my FFR stainless mufflers with the Slimline 30" ones and the difference was amazing. I don't have cats. I can carry on a conversation in the car just about at all speeds and seat of the pants says there is no reduction in HP. There is a thread on the other forum where testing was done on the dyno using several noise reduction methods and the 30" Slimlines were the top choice. I have done several set for other owners and they have similar pleasing results. Perhaps the 24" ones don't work very well.

[steno]

I have to admit I have the slimline 30” on my roadster. This will be my third season with them. My neighbors are really glad I have them. The FFR pipes with over 50k miles on them were getting a bit rough.

[MisterAdam]

i too just replaced my FFRs with 30" slimlines. like night and day!!! they still bark but are not harsh. i used to have to wear earplugs due to the high dbs but now i wear them more for wind buffeting and road noise.

[Driver_WT]

I have the 30" Slimline mufflers and I love them. They are definitely not as loud as the FFR pipes and you can easily carry on a conversation with them. I think most on the other forum that have used the Slimlines have used the 30" and not the 24" mufflers.

[weendoggy]

Wow! That's still loud. I run 30" Lobak spiral wound innerd's (no packing) and blow a 96db under full load at Laguna Seca (track known for db noise). They are raspy at idle and when cruising they are hardly (in our world) noticeable. I've been using these for 10 years. Nice thing is, they don't burn out.

[Avalanche325]

From all of the history around here and the other forum, with some guys doing real testing with a dyno and dB meters, here is the way I understand it.

These are the main stream combos:
If you want the quietest possible, Boig Quiet Pipes are the way to go. The do cost some HP.
Gas-n-pipes - technically are not quieter than FFR pipes. But they SOUND quieter and deeper as they knock the harshness out. They are also darned pretty.
Flowmasters - most guys are using 30 inch. You can get the outlet right at the line where the hip meets the body, which looks good. The are quieter, they don't rob HP, they run much cooler than FFR pipes. Dyno tests showed that they picked up a few HP. They are a DIY project though. TIG welding and some work on the hangers required. Heavier than FFR pipes.
FFR pipes - loud and get louder as the packing blows out.
FFR stainless - louder than the steel pipes.

Personal experience. I have a 500hp 347 with a nasty cam and 4 into 4s. That means LOUD. I have been to DSCC rallies and my car was much louder than any of the 30ish Cobras there. I had to wear earplugs 100% of the time. Even if I was working on the car with it idling for 15 minutes, it would make my ears ring. You could not have a conversation even at 25mph. With Flowmasters, I can cruise around town without ear plugs, or work on the car. You can have a conversation at around town speeds. I still wear plugs if I am going on the highway or anything more than 15 minutes. It is still louder than most. I would consider Quiet Pipes if I didn't autocross.

[totem]

There is a need for a Slimeline 24 vs 30in side by side comparison.

When I replaced my FFR SS with Slimline 24in, the difference in sound level was not noticeable nor measurable (Android app). They are less harsh however.

However, people with 30in seem to notice a difference.



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