Exhausting Thoughts

[gto78]

I'm planning to upgrade my exhaust within the next week and have a few ideas. First off, the goal is to have dual exhaust, less restrictive, and not noisy. As a result I should have better mpg without sacrificing a quiet ride.

The main question I have is about the FOUR catalytic converters that ford factory installed on the Expedition. I originally wanted to axe them completely since I don't have emissions testing- and doing that gained me 3+ mpg on my Explorer. The owner of the muffler/performance shop said not to remove the stock converters because it would kill my mpg and lose lots of power..... He also says the stock 4 converters are very high flowing, and doesn't even recommend replacing them with a high flow aftermarket converter.

Sounds like a bunch of horse $hit to me, I think he just doesn't want to do the job.

Now as for the dual exhaust. I'm planning a dual in/dual out 2.5/3.0 muffler with a dual side pipe setup and angle cut tips just like the Lightning. I got a quote from the muffler shop for $350 to do the install with new pipes from the converters back, using a stainless Magnaflow muffler. I'd rather use Gibson because Gibson doesn't use packings inside the muffler that will fall apart like Magnaflow.

Does anyone have suggestions or know what either brand of muffler sounds like? Which is quieter?

If I can get the exhaust as free flowing as possible I think it's possible to gain 2-3 mpg like I did in my Explorer.

 

[Remo]

I'll start by saying I have no experience with custom exhaust, but I'll offer my two cents...

I don't think the shop owner was bs'ing you. I'm sure he'd rather make more money on the job, but would rather have a happy customer. Also, vehicles are designed to run with some backpressure and removing all the cats will take most of it away. Yes, you will gain hp, but you will lose quite a bit of torque that way.

As far as the mufflers go, I've read that the Gibsons sound about the same as stock. The Magnaflows are louder, but nothing like Flowmasters. Personally, I'd go with the Magnaflows. I've never heard anyone complain about them. They are 100% stainless steel so they won't rust out. Plus they come with a lifetime warranty.

I hope that helps some.

 

[Racenut]

On my '02 with the 5.4L I got rid of the factory Y and ran dual 2.5" pipes into a 70 big block series Flowmaster Dual In / Single out and got rid of the rear resonator as well. I also did the rear cat delete, but left the front 2 in place.

I did loose a little bit of Torque, but it more than made up for it in the top end and I did pick up a little on the MPG's as well. I have heard that the Expy's do not like to be completly straight piped because they do get really " doggy " on the low end with out at least a little back pressure.

I really like the 70 series Flowmaster ( it is made for Big Blocks / SUV's ) because it is just barley louder than stock at idle and crusing speeds ( slight rumble but sounds good not anoying ), it does NOT have a lot of " drone ", but when you step on it you will definatly hear it but not in a bad way ( I get compliments on it all the time ). The muffler is 26" over all length so it is about the same size as the factory but flows much better, and is a 3 chamber without any packing ( the 3rd chamber is what takes away the " drone " and annoying sound ). I got the dual 2.5" in and a single 3" out so it eleminates the need for running an X pipe and you can run just one 3" pipe out the back or reduce it back down to 2.5".

 

[joezek]

I like the idea of Flowmaster 70 series dual in/single out. Is it quiet on the highway? I can't seem to find any real information about what the rear catalytic converters really do. I researched through the Ford SHOP manuals and emissions description manuals with no luck.

It seems to be that the forward converters are called a "Light off catalyst" and is as close to the manifold as possible. The exhaust flames basically light the converter to operating temp almost instantly.

The rear converters don't seem to have any real value, it's almost impossible to find a source of information describing why they're there.

I think the best option is the remove the rear converters and run two pipes all the way back into a dual in/single 3" out muffler. Just by removing the rear converters and that fugly horribly flowing factory Y pipe should make a pretty noticeable improvement in both mpg and sound.

 

[Racenut]

I like the idea of Flowmaster 70 series dual in/single out. Is it quiet on the highway? I can't seem to find any real information about what the rear catalytic converters really do. I researched through the Ford SHOP manuals and emissions description manuals with no luck.

It seems to be that the forward converters are called a "Light off catalyst" and is as close to the manifold as possible. The exhaust flames basically light the converter to operating temp almost instantly.

The rear converters don't seem to have any real value, it's almost impossible to find a source of information describing why they're there.

I think the best option is the remove the rear converters and run two pipes all the way back into a dual in/single 3" out muffler. Just by removing the rear converters and that fugly horribly flowing factory Y pipe should make a pretty noticeable improvement in both mpg and sound.

I run 75 -80 mph on the interstate here in southern new mexico with my wife, my daughter that is only 2 1/2, and my son who is only a month old and have never once had them say anything about the noise.

With the radio at a normal listing level you really do not hear it very much, unless you have your foot to the floor ( you can tell it is not stock, but it is not anoying. Once you put your foot to the floor it gets LOUD ).

By removing the rear cats and the Y pipe, I noticed about 2mpg increase ( if you can keep your foot out of it ) over the stock set up and that went up more with the addition of the Edge programer.

Currently I average about 19 mpg interstate driving.

Also by removing the rear cats and the Y you will notice a pretty decent power increase. Small inclines that used to make my Expy shift out of OD do not anymore, and if you do any towing you will really see the difference. By doing this you do loose a little bit of torque, but it definatly makes up for it in the higher rpm horse power.

 

[joezek]

Thanks to the advice and ideas from you guys, I placed my order today for a Spintech "Truck/RV 8000 series" muffler. I got the 2.5" dual in/3" center outlet model. I'm gonna have it installed with rear cats deleted and also gonna have them put a 4" angle cut chrome tip on it. I want the tail pipe to come out on an angle behind the right rear tire.

Since I frequently run Avgas (it's free sometimes...) I'm always worried about the converters getting clogged and hurting performance/mileage. I really want to delete all the cats but don't want too much noise.

Next week everything should be installed and I'll post pictures and results. Maybe a before and after sound clip would help too. I've watched lots of video clips and even though they sound good there's no way to telling a difference in noise level without comparing the same person's video of the stock exhaust.