Straight pipe

DriveHard said:
It can sound good - contrary to the posts so far. The idea is to replace the chambered muffler (stock) with a resonator style muffler. You will keep the deeper tone, but still keep the "rasp" down that is so annoying with V6's.

There is no concern of losing torque by doing this. If you keep your stock exhaust manifolds and cats, then for the most part there is little change in the performance of the exhaust system, even if you remove the muffler completely. You may gain a tiny increase in HP though...but not anything you would be able to notice.
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When you say resonator style muffler, are you referring to what I always call a Glasspacks? You know round and straight through, with holes in the through tube and surrounded with fiberglass insulation type material to absorb sound waves??
 
Stangguy - are you going for sound or for power?

IMHO...

If you replace your current chambered muffler with either a straight pipe or a resonator style, you will see little to no change in torque, and MAYBE a slight increase in peak HP, but certainly a change in sound.

Your car will be no faster than it is today by most measurable standards.

You will not mess up any "tune" as it is controlled by the closed loop control of the O2 sensor and ECU, and you have made very little change to the system.

If you want to increase power you are going to have to go to more drastic measures (headers, turbo, supercharger, etc)
 
Definitely put at least a glasspack on it. A good one won't restrict flow (it's a perforated pipe packed with fiberglass), but it will attenuate high frequencies in the exhaust sound. It will still be louder than stock, but it will sound less obnoxious / much better than a straight pipe and can pass as legal in most places.

I had a '00 Panoz Roadster with that year's Cobra V8. Its stock / OEM exhaust was a pair of Magnaflow glasspacks (no chambered mufflers). It was pretty loud, but not super loud, had an excellent tone, and was street legal. Based on that experience I can recommend Magnaflow.

PS: if the engine is turbocharged you might not need any muffler at all. Turbos absorb some of the exhaust energy & sound.
 
stangguy said:
When you say resonator style muffler, are you referring to what I always call a Glasspacks? You know round and straight through, with holes in the through tube and surrounded with fiberglass insulation type material to absorb sound waves??
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When I hear "glasspacks", I think of the red glass filled mufflers with the flutted pipes...they sounded cool, but they can even increase flow restriction.

I am talking about a muffler with a straight through pipe that uses a smooth perforated core and fiberglass filling. (think motorcycle muffler)
 
resonator style muffler with smooth core...
1613506248144.png
 
You will not cause any engine damage or lose torque with a higher flowing exhaust. Engines(4 stroke) needing backpressure is a myth that needs to die. Engines need exhaust scavenging which is accomplished by a good header or at the exhaust manifold.
 
AZjeff said:
So you take out the muffler and put in a straight pipe and see what's it's like. Not much invested. If it's too loud or sounds like farting frogs then you have a space to put something back. There has to be a Mustang forum where you can talk to guys who have done this on this car rather than opinions of guys who haven't.
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A buddy of mine had a 3.8L Supercharged Mustang (basically started as a SuperCoupe swap and then went further with it). He bought a full cat-back for the car initially and then I believe had a full exhaust system made for it after the work was done. Even bought headers (which are hard to come by). It never sounded "good', but with the full custom exhaust it didn't sound bad. With just the catback on the stock V6 it kinda sounded like a Taurus where the muffler fell off.

I was active in the Mustang scene for a very long time. It was very difficult to make a V6 car sound decent, the best you could hope for was what @DriveHard alluded to, which is to keep some semblance of deep tone, but it would warble, just the nature of the beast.

My wife's truck is loud, my 5.0L was loud, my Lincoln was moderately loud, my Expedition had a pretty good snarl to it, but I've never intentionally made anything with less than 8 cylinders that was licensed for the road loud because I've never liked the sound (that qualifier is because I have a Hindle pipe on my old Suzuki sport quad that is now my son's). It's just one of those things I guess 🤷‍♂️
 
stangguy said:
OK, I understand that some don't like the sound of a 6 without muffler. Personally I think sound is like colors, it is a personal thing. I totally know that it will never sound anywhere NEAR as nice a a v/8. But as I said, I just want SOME sound. I mean, some people think the ricers with the s**t can mufflers sound good. Not me but some people. I just wanted to know if it was going to cause any problems with the car mechanically, not if or not I would like the sound.
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Point taken, It won't change a thing as far as performance or tune. Why not try it to see if the performance changes and sound is to your liking? Just because I think it sounds horrible, it doesn't mean I don't keep trying.... I started up my Blazer today and realized I've tried it on three 4.3's now!
 
OVERKILL said:
A buddy of mine had a 3.8L Supercharged Mustang (basically started as a SuperCoupe swap and then went further with it). He bought a full cat-back for the car initially and then I believe had a full exhaust system made for it after the work was done. Even bought headers (which are hard to come by). It never sounded "good', but with the full custom exhaust it didn't sound bad. With just the catback on the stock V6 it kinda sounded like a Taurus where the muffler fell off.

I was active in the Mustang scene for a very long time. It was very difficult to make a V6 car sound decent, the best you could hope for was what @DriveHard alluded to, which is to keep some semblance of deep tone, but it would warble, just the nature of the beast.

My wife's truck is loud, my 5.0L was loud, my Lincoln was moderately loud, my Expedition had a pretty good snarl to it, but I've never intentionally made anything with less than 8 cylinders that was licensed for the road loud because I've never liked the sound (that qualifier is because I have a Hindle pipe on my old Suzuki sport quad that is now my son's). It's just one of those things I guess 🤷‍♂️
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This is going to sound funny...

I have owned all kinds of motorcycles, trucks, cars, V8's, V6's, V4's V2's, straight sixes...the list goes on and on...

My Fiat 500 is probably the best sounding car I have ever owned. It has nothing but a turbo and a dual exit straight pipe, and it sounds like a rip-snorting beast. I always get several folks at Auto-X events that comment on how bad a55 is sounds...my son loves to ride with me in that one. Funny thing is at cruise on the highway, it is still quiet.

My 6.2L V8 L9H has been the hardest engine in the world to "keep quiet" - it has two mufflers, and two resonators, long tube headers, but still drones on the highway, it is known in the exhaust industry for being hard to keep quiet.

Along the way I have learned it is more about reducing the higher frequency sounds, which can normally be done with careful design or the resonators I suggested.

One thing I have always wanted to try with my truck is a 1/4 wave resonator pipe (side branch) to see if I can eliminate the drone on my truck.
 
cb_13 said:
You will not cause any engine damage or lose torque with a higher flowing exhaust. Engines(4 stroke) needing backpressure is a myth that needs to die. Engines need exhaust scavenging which is accomplished by a good header or at the exhaust manifold.
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Generally true. But you may (or may not!) get a slight performance increase from a higher flowing muffler.

Here's how it worked almost 20 years ago when I last dyno tuned a car... maybe things have changed since then.

EFI has open and closed loop modes. In both modes it's always listening to the intake MAF to dial in the fuel to optimize AF ratio. In closed loop mode (normal driving), it's also listening to the O2 sensors so that is also contributing to the AF ratio. In open loop mode, it stops listening to the O2 sensors and only uses the MAF (and TPS, engine RPM, etc.).

The idea is that closed loop mode is dynamic negative feedback targeting a lean mixture for optimum efficiency. Open loop mode has no negative feedback, but simply uses a configuration (e.g. lookup table) for max power, based on throttle position, airflow, RPM, etc.

So, if you have a higher flowing exhaust that leans the mixture, the engine will detect and compensate for this in closed loop mode (most normal driving) but it won't in open loop mode. When you stomp the pedal to the floor, the engine goes into open loop mode and stops listening to the O2 sensor. Now it will run a bit leaner. And you will probably gain a little HP, because most engines are tuned at the factory to run rich at or near WOT, to improve cooling and resist detonation. Of course you lose that safety margin too.

That '99 Cobra V8 ran AF ratio of 10:1 on the dyno in open loop mode, and that was with the high flow custom intake and magnaflow exhaust that Panoz installed at the factory, so the Mustangs that used that engine ran even richer! After installing FMS shorty headers it ran 12:1 and gained 8-10 RWHP. Not much for a 300+ HP engine, of course. Peak power is typically 13:1, and peak efficiency (target AF in closed loop mode) is around 15:1.
 
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A Flowmaster Series 40 might be about right. It will fit where your current muffler is. Get an exhaust shop to fit new pipes from the cat to the muffler and from the muffler rearward.

Flowmaster 942043 Flowmaster 40 Series Delta Flow Chambered Muffler

This two chamber design incorporates Flowmaster's Delta Flow® technology. The Delta deflectors generate increased scavenging for better performance and reduced interior sound. Milder exterior tone and reduced interior resonance over standard 40 series. Constructed of 16 gauge aluminized steel...
www.holley.com www.holley.com
 
stangguy said:
Just out of curiosity, if it isn't going to cost me low end torque, why shouldn't I try to race anyone. Other than of course it is a low power engine.
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I was just joking about the racing part, feel free. That car is not a rocket and would lose a race to a minivan so I was trying to help you save face when Debra and the kids dust you at the light in the Pacifica while watching Finding Nemo.
 
MRC01 said:
So, if you have a higher flowing exhaust that leans the mixture, the engine will detect and compensate for this in closed loop mode (most normal driving) but it won't in open loop mode. When you stomp the pedal to the floor, the engine goes into open loop mode and stops listening to the O2 sensor. Now it will run a bit leaner. And you will probably gain a little HP, because most engines are tuned at the factory to run rich at or near WOT, to improve cooling and resist detonation. Of course you lose that safety margin too.

That '99 Cobra V8 ran AF ratio of 10:1 on the dyno in open loop mode, and that was with the high flow custom intake and magnaflow exhaust that Panoz installed at the factory, so the Mustangs that used that engine ran even richer! After installing FMS shorty headers it ran 12:1 and gained 8-10 RWHP. Not much for a 300+ HP engine, of course. Peak power is typically 13:1, and peak efficiency (target AF in closed loop mode) is around 15:1.
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That doesn't sound right.

If it goes leaner, it means it is ingesting more air that is NOT being picked up by the MAF.

This is the same reason you can throw a supercharger or turbo on a MAF car and if it is within the fuelling capabilities of the factory injectors, can get away without even putting a tune on it. It's the same reason you can do heads/cam/intake on a MAF car and it will still run well.

The base table says for X CFM and Y RPM at Z coolant temp that timing should be A and injector pulse should be B. If you increase the flow out of the engine you increase the flow into the engine, which shifts that to a different series of cells in the table, which still results in the same amount of fuel relative to the same amount of air, so your A/F stays the same.

If your engine ran 10:1 it was either not metering the incoming air correctly or something else was off. Did this car have a factory MAF and air intake plumbing? Clocking of the MAF within the air stream can have a significant impact on fuelling as it changes the measured airflow.
 
RhondaHonda said:
I was just joking about the racing part, feel free. That car is not a rocket and would lose a race to a minivan so I was trying to help you save face when Debra and the kids dust you at the light in the Pacifica while watching Finding Nemo.
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Yup, or gets dusted by a lady and her kids in a pick-up blaring Nikki Minaj :ROFLMAO:
 
I once bought a 77 chevy impala with the 305 engine, and got dusted at the stoplight by a vw bug. Ran great, but figured there had to be a problem. checked it out and found that the manual advance in the distributor was rusted solid. fixed that and made a big difference.
 
OVERKILL said:
That doesn't sound right.

If it goes leaner, it means it is ingesting more air that is NOT being picked up by the MAF.

This is the same reason you can throw a supercharger or turbo on a MAF car and if it is within the fuelling capabilities of the factory injectors, can get away without even putting a tune on it. It's the same reason you can do heads/cam/intake on a MAF car and it will still run well.

The base table says for X CFM and Y RPM at Z coolant temp that timing should be A and injector pulse should be B. If you increase the flow out of the engine you increase the flow into the engine, which shifts that to a different series of cells in the table, which still results in the same amount of fuel relative to the same amount of air, so your A/F stays the same.

If your engine ran 10:1 it was either not metering the incoming air correctly or something else was off. Did this car have a factory MAF and air intake plumbing? Clocking of the MAF within the air stream can have a significant impact on fuelling as it changes the measured airflow.
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In general, the car always sets the AF based on the MAF, TPS, RPM, etc. Call these the lookup table or LUT settings that determine the AF setting. In closed loop mode the ECU changes this based on the O2 sensor sensor. In open loop, it doesn't. Now imagine that the LUT settings are on the rich side. In closed loop the exhaust O2 sensor detects this and the ECU dials back fuel to lean it. In open loop, it uses those LUT settings as-is, no adjustment or feedback.

Those mixture settings came straight from the dyno, before and after runs. Installing the FMS headers leaned it just a bit. The car ran at 14.7 to 15:1 in closed loop mode (light throttle, low to mid RPM). When you opened the throttle the AF ratio immediately shifted to the richer setting. The dyno operator said the original 10:1 which is rich, was actually leaner than Mustang Cobras he tested having the same engine.

PS: the notion that more power always requires more air flowing through the intake is only true if efficiency is constant. But efficiency is not constant! Changing the headers can increase combustion efficiency, which can increase power without increasing air volume through the intake.
 
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MRC01 said:
In general, the car always sets the AF based on the MAF, TPS, RPM, etc. Call these the lookup table or LUT settings that determine the AF setting. In closed loop mode the ECU changes this based on the O2 sensor sensor. In open loop, it doesn't. Now imagine that the LUT settings are on the rich side. In closed loop the exhaust O2 sensor detects this and the ECU dials back fuel to lean it. In open loop, it uses those LUT settings as-is, no adjustment or feedback.

Those mixture settings came straight from the dyno, before and after runs. Installing the FMS headers leaned it just a bit. The car ran at 14.7 to 15:1 in closed loop mode (light throttle, low to mid RPM). When you opened the throttle the AF ratio immediately shifted to the richer setting. The dyno operator said the original 10:1 which is rich, was actually leaner than Mustang Cobras he tested having the same engine.
Click to expand...

I'm very familiar with the Ford EEC programming (EEC-IV in particular) which is why I made the remarks I did.

Let me clarify further, we'll use two example scenarios:

1. Stock:
- 4,800RPM
- 100% TPS (WOT, so open loop)
- 485CFM
- 195F coolant temp

Based on the above, the ECM goes to say E19 which is where 4,800RPM at WOT and 485CFM align and injector pulse is 0.5ms. Timing is 26 degrees based on coolant temp.

2. Modified:
- 4,800RPM
- 100% TPS (WOT, open loop)
- 495CFM
- 195F coolant temp

Based on the above, the ECM goes to E20 which is where 4,800RPM at WOT and 495CFM align and injector pulse is 0.51ms. Timing is 26 degrees based on coolant temp.

In scenario #2, because we increased airflow through the engine, more air was registered by the MAF, which in turn resulted in an increase in injector pulse-width to compensate.

So in both cases, the ECM expects roughly the same A/F because it's supplying the appropriate amount of fuel for the metered amount of air.

When in closed-loop it is constantly searching to go lean so that it can go rich (switching) to try and keep A/F a bit above stoic for economy and will enrich as load increases unless throttle application drives it out of closed-loop and feedback adjustment is paused.

However, you can bugger up the actual A/F achieved while in open loop by changing how much air the engine thinks it is ingesting. A cone filter on the end of the MAF for example, eliminating the airbox, can have a significant impact. A CAI with an elbow is another scenario where "clocking" the MAF to get it back to where it should be by using a dyno is employed. The MAF is calibrated based on its stock location within the stock intake air tract plumbing, so any deviation from that can have an impact on what it registers.

10:1 is pig rich and I'd question the accuracy of the equipment if this is being registered by stock engines. Stock for a 5.0L was around 12:1, my H/C/I 302 was 10:1 with 30lb injectors and a boosted app Pro-M MAF and I was leaving about 20HP on the table running that rich. 24's and a Pro-M for a CAI made a big difference.

Boosted engines will of course be richer (like a Termi) to ward off detonation, but for a naturally aspirated mill, OEM target is usually around 12:1.
 
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