Flowmaster Mufflers

[ES_97Sport]

Ok. People have been asking about Flowmaster mufflers, so ....

I've been running the following on my '97 (big) Sport since the late '90s. This is the one that people usually complain is 'too loud'.

I've run the 50 Series with the stock CAT and three or four different aftermarket CATs (from different manufacturers and of different design). Changing CATs changes the sound level very little - even when using a straight-through CAT.

I run all my Flowmaster's below with the heat shield in place (hopefully, for obvious reasons). Its supposed to make a difference in sound but since I've never NOT used one, I can't speak for that.

Flowmaster® Part #: 942450
Category Street Mufflers - 50 Series Delta Flow
Description 50 Delta Flow Muffler - 2.25 Center In / 2.25 Center Out - Moderate Sound

They're correct - nice throaty sound on the 3.0L. A tad lower in pitch on the 3.5L but NOT any quieter. Contrary to some, this is not obnoxiously loud. This IS NOT even CLOSE to the 40 Series. I've heard way worse from other manufacturers. A set of aggressive M/Ts will drown out the exhaust. Even my Geolandar M/Ts will after they get a little wear and those are REALLY quiet for M/Ts. If you're looking to actually HEAR the exhaust, then this is the one you want.

Personally I LIKE this one. Not nearly as loud as my 'Bird, but just enough to make the vehicle distinctive. 'Wheeling requires a low sound level so you can hear your spotter(s) easily. I've NEVER had a problem with that and my spotters have never had to talk above a loud conversational tone.

Anyway, I've been redoing the entire exhaust from the manifolds back to the hatch as the last remaining piece outstanding of the 3.5L swap. The original shop hacked the exhaust so bad trying to get it to fit that it wasn't salvageable towards the engine and this exhaust is pushing 15 years old. Its been hacked and chopped to replace flex joints, mufflers, and CATs so many times that it was just a series of welds and leaks all the way to the rear axle.

After this springs rash of Flowmaster questions, I decided to change mufflers to Flowmaster's 'quieter' version. The price wasn't any different from Summit Racing and I needed a muffler anyway. Figured the head to head comparison might be helpful to some.

These are pretty much the exact same dimension muffler with the exception of the thickness and width. The Super 50 Series is an 1" thicker and 1/4" wider. Either will easily fit in the stock location with plenty of room and lots of clearance. The Super 50 is a bit heavier.

Flowmaster® Part #: 52455
Category Street Mufflers - Super 50 Series
Description Super 50 Muffler - 2.25 Center In / 2.25 Center Out - Mild Sound


So, new OEM down pipes, OEM CAT, and OEM intermediate pipe (between the CAT and stock muffler), and new 2.25" pipe and muffler from there all the way to the rear. So, this is exact factory exhaust with the CAT-back 2.25" conversion I usually recommend. The only change is the Super 50 Series muffler install.

AH, a new, not leaking exhaust is SSSSSOOOOOOOO nice! Especially without leaks in front of the O2 sensors!!!

The Super 50 Series is REALLY quiet! Its a little louder than the stock muffler and the tone and pitch is a little different, but not by much. In a side by side with my friends '97 LS 3.0L they're identical. I can't hear mine idle at a stop light with all the windows rolled down. The only time I can really tell I don't have a stock exhaust is if I really put my foot in it from a light and the RPMs start hitting 3K+. On the highway I can't hear the exhaust anymore with the windows down - at any speed. With brand new tires I MIGHT be able to hear it again, but ... we'll see in a couple months. Its 95 here today, so I haven't tried with the windows up. I'll see how it sounds with the windows up on the way home this evening.

Right now, I'd strongly suggest this if you're looking for a stock-ish replacement or a little tone change but have a cranky 'sensitive' wife you plan to keep around.

I suspect I'll eventually miss my original Series 50. I really like that muffler. Good tone with the 3.5L. One unforeseen drawback is that now I don't know when to shift. I drive all my M/Ts by sound - not off the tach, and now I can't hear my engine! Hope my clutch survives this! lol!!

Edward

[dirk]

So really quiet under normal travel, just cruising and Idle? Really quiet with light acceleration but louder under harder acceleration. Less restrictive exhaust flow? Sounds like what I've been looking for. I don't like loud exhausts besides when I want less back flow under harder acceleration.

[ES_97Sport]

Jun 26, 2015 19:08:28 GMT -5 dirk said:

So really quiet under normal travel, just cruising and Idle?

Both. At idle with the front and rear windows down, I can't hear the exhaust. Sounds just like my stock '03 3.5L. So smooth and quiet now I can't even tell if its running.

I THINK I can just barely hear the exhaust through the tire noise on the highway @ cruise (55-75 MPH) sometimes. I'm still not sure I'm not just imagining things. Again, this is with all four windows rolled down.

<edit>
Ok, so I bumped the tire pressure up to 34 to pull a bit more of the side lugs off the pavement and retested on a quiet section of highway. I just wanted to get rid of as much tire and road noise as I could. Anyway, I tested it with the windows rolled up and stereo off. At cruise - so 65-70 MPH - I can't hear the exhaust at all. All I can hear is the engine and drive train - M/T and transfer cases.

If I give it throttle, I can just hear the exhaust over the engine and drive train. You can hear it but it doesn't really get any louder in the cab.

So, its comparable to my stock '97 and '03.
<edit>

I took it up to Estes Park through the mountains this weekend - so, about 120 mile round trip. 30-55 MPH two lane road with a LOT of fairly steep up and down and up and down the entire way. This is usually a good road to test on because the speeds are low and I get very little tire noise and I can really lug the engine. Again, all four windows rolled down. I can tell the exhaust isn't stock, but its still only a little louder than my stock '03.

Really quiet with light acceleration but louder under harder acceleration.

The only time its very obvious its not stock is under throttle from a stop. At that its still considerably quieter than my previous Flowmasters. And you really do have to give it some serious throttle. Just easing off the the stop it doesn't sound much different than stock.

KIM, that this is in my big '97 Sport. The '97-'99 has better sound insulation in the cab and engine bay but mine sits 25" off the ground. I get more reflected under cab/engine noise than a stock Sport. An interesting point - I can HEAR that now. On the the other hand, my two '97s are considerably quieter than my '03 in the cab. So, YMMV.

I did try with the windows rolled up this last week. I don't think its any louder in the cab than my '03 or little stock '97.

My guesstimate is it can't be at most 8-10db difference - and that only under certain conditions.

Less restrictive exhaust flow? Sounds like what I've been looking for. I don't like loud exhausts besides when

Yes. Considerably. The stock '97-'05 muffler is big and heavy and really doesn't flow that well. I've done JUST the muffler and pipe and you can tell the difference between the two.

I can't tell any difference in flow/performance between the two Flowmasters. I don't believe there should be any. The new one is actually bigger internally, but not dramatically so.

Actual performance (and mileage) on my big Sport has gone up but I attribute that to removing the exhaust leaks before the forward O2 sensor. Taking that into account, I think the performance between the two mufflers is the same.

FYI, there are four pieces that make up the stock exhaust that you'll need to work with - the CAT, the pipe over the cross member, the muffler and the pipe from the muffler to the rear of the vehicle. Retain the stock CAT -AND- the little short pipe that goes from the CAT over the cross member. Run 2.25" from that pipe coupling to the Flowmaster and from the Flowmaster to the rear of the vehicle. DO NOT replace the little short pipe. That pipe is less restrictive than anything an exhaust shop is going to bend up and its too short for a change to 2.25" to make any difference. Been there, got the t-shirt. Retaining this will also make service on your vehicle a lot simpler.

I want less back flow under harder acceleration.

Wow. Those are two words I haven't heard in a LONG, LONG time. Back flow is more a side effect of cam profile. i.e. long duration cams. Not really an issue on stock NA cams - especially not the Mitsu 3.0L and 3.5L.

'Back flow' is exhaust being sucked back into the cylinder by the vacuum in the cylinder before the exhaust valve has a chance to close.

I believe what you're really talking about is exhaust not leaving the cylinder because it has no where to go. Definitely not the same thing.

In fact, what we're trying to do by freeing up the flow past the CAT is to create more vacuum in the exhaust system to more efficiently scavenge the exhaust from the cylinder thereby sucking more fuel/air into the cylinder. (increase the volumetric efficiency of the engine) This is actually where the performance gains come from.

In order to have a meaningful amount of back flow with a stock 'suv' cam, you'd have to have a plugged up (defective) exhaust.

If you're coming from a FI environment, forget everything you know about induction and exhaust. FI and NA are totally different.

Edward