2 5 inch vs 3 inch flex pipe vs no flex pipe belanger

[frostrocket]

Learning more and more about the Viper every day, and now I'm on to learning more about exhaust systems in general.

Our good friend JonB was kind enough to spend about 30 min with me the other day explaining the different options I had for the belanger cat and cat-back exhaust setup. In the end, I went with a 2.5" system with NO flex pipe. I'll paraphrase from our conversation: "2.5 inch will give you more of a deep muscle car sound and 3.0 inch will be more exotic sounding". Also, "flex pipes are more costly and are more restrictive and generate more heat, generally unnecessary with this setup". All good points, which I agreed with.

No headers for me. Didn't want to deal with the heat issues. Mainly wanted the cooler sills and the HP was a bonus.

No disrespect to Jon, but I am curious to hear about what everyone else's experience has been so far with these systems. The whole backpressure vs freer flowing argument is lost on me, and I'm wondering if folks can comment on if I'm leaving HP on the table by going with the 2.5 inch instead (will be tuned and that's about it). Also, are there any concerns removing the FLEX midpipe re: additional vibration, longevity, stress fractures, etc over the non-flex variant.

Why didn't SRT just forgo the flex altogether?

Thanks!

[Lawineer]

I cant imagine the factory added flexpipes for no reason. Exhausts grow a lot. Lots of thermal stresses there.

IDK, I seriously doubt it costs any measurable amount of HP on anything resembling a stock/bolt on setup.

I went 2.5" just because it was loud enough as it is for a street car. I love the sound of mine.

High flow cats, flex, 2.5", stock mufflers (and everything else)

https://youtu.be/HZo80OAARG0

Kind of funny- I have no idea who took that video. It just made a local Dallas Facebook group and I was like "lol! Someone recorded me!"

[AAA96]

I have stock headers, Belanger 3” mid pipe, no flex, and stock muffler. Sounds awesome, no complaints.

[Old School]

I believe Chrysler added the flex to prevent cracking the exhaust manifolds. As usual, there are trade off with most everything. Chrysler probably had a design goal of the vehicle lasting 200k miles, without the flex the manifolds might only last 20k miles.....

[AAA96]

I believe Chrysler added the flex to prevent cracking the exhaust manifolds. As usual, there are trade off with most everything. Chrysler probably had a design goal of the vehicle lasting 200k miles, without the flex the manifolds might only last 20k miles.....

I’be only driven the car 600 miles since I’ve had it so I’m good. Hahaha

[Steve M]

The flex pipe is there for a reason. The engine on stock motor mounts moves a fair amount, and something has to allow the exhaust to move along with it or you'll end up with cracks somewhere in the system. When Belanger eliminates the flex section, they also eliminate the front exhaust hanger - this allows for some movement, but is it as good as the factory flex section with the front hanger? Not sure.

I'm not buying the flex section lost HP argument unless someone has some really good data saying otherwise. And by data, I'm not talking about feelings or intuition. You'd need to do a true A-B-A back-to-back-to-back dyno test, and ain't nobody got time (or the money) for that.

And yes, while flex sections aren't free, they aren't all that expensive - they are about $40 each by my quick look, but would also require additional welds, so the extra labor also has to be factored in.

One thing I didn't see you mention was the catalytic converter substrate material - ceramic vs. metallic and the cell count will likely both make a difference in the amount of HP freed up as well as how the exhaust sounds. Did they give you an option, or was this another "Lou Belanger" knows best type of deal? This is one of those areas where the buyer needs to be well informed - for many years after the Gen 5 was released, there was no tuning option, but folks still wanted to do headers and/or high flow cats. The only way they could keep the PCM from throwing a check engine light was to put in restrictive cats that actually cleaned the exhaust well enough to keep the PCM happy. If I had to guess, unless you specified otherwise, you might be getting cats that aren't exactly high flow - that's one surefire way to eliminate customer complaints about check engine lights.

While my Gen 4 isn't exactly a Gen 5, the exhaust configurations are nearly identical. For me, I went with a 2.5" metallic substrate cat with no flex section. Reasons:

1. I retained the stock muffler
2. I needed a place to install a pre-cat wideband O2 sensor - a flex section would not have allowed me to do that

So far, I've not cracked anything in my exhaust, and I've had them installed for the past 5 years. I don't put that many miles on my car though.

Also of note - my car threw a catalytic converter efficiency check engine light on the 2nd or 3rd drive. It wasn't a big deal to me since I knew I could tune it out myself, but not everyone is comfortable doing that.

[Lawineer]

I’be only driven the car 600 miles since I’ve had it so I’m good. Hahaha
I’d venture to guess that how hard you drive it is more relevant. Getting it very hot and then cooling it (ie: track sessions) is way worse than a cross country trek

[AAA96]

I’d venture to guess that how hard you drive it is more relevant. Getting it very hot and then cooling it (ie: track sessions) is way worse than a cross country trek

Agreed

[frostrocket]

The flex pipe is there for a reason. The engine on stock motor mounts moves a fair amount, and something has to allow the exhaust to move along with it or you'll end up with cracks somewhere in the system. When Belanger eliminates the flex section, they also eliminate the front exhaust hanger - this allows for some movement, but is it as good as the factory flex section with the front hanger? Not sure.

I'm not buying the flex section lost HP argument unless someone has some really good data saying otherwise. And by data, I'm not talking about feelings or intuition. You'd need to do a true A-B-A back-to-back-to-back dyno test, and ain't nobody got time (or the money) for that.

And yes, while flex sections aren't free, they aren't all that expensive - they are about $40 each by my quick look, but would also require additional welds, so the extra labor also has to be factored in.

One thing I didn't see you mention was the catalytic converter substrate material - ceramic vs. metallic and the cell count will likely both make a difference in the amount of HP freed up as well as how the exhaust sounds. Did they give you an option, or was this another "Lou Belanger" knows best type of deal? This is one of those areas where the buyer needs to be well informed - for many years after the Gen 5 was released, there was no tuning option, but folks still wanted to do headers and/or high flow cats. The only way they could keep the PCM from throwing a check engine light was to put in restrictive cats that actually cleaned the exhaust well enough to keep the PCM happy. If I had to guess, unless you specified otherwise, you might be getting cats that aren't exactly high flow - that's one surefire way to eliminate customer complaints about check engine lights.

While my Gen 4 isn't exactly a Gen 5, the exhaust configurations are nearly identical. For me, I went with a 2.5" metallic substrate cat with no flex section. Reasons:

1. I retained the stock muffler
2. I needed a place to install a pre-cat wideband O2 sensor - a flex section would not have allowed me to do that

So far, I've not cracked anything in my exhaust, and I've had them installed for the past 5 years. I don't put that many miles on my car though.

Also of note - my car threw a catalytic converter efficiency check engine light on the 2nd or 3rd drive. It wasn't a big deal to me since I knew I could tune it out myself, but not everyone is comfortable doing that.

I didn't specify the substrate, mainly because I didn't know it was an option. But I'm not sure I'm in a position to make a decision one way or the other on the material types anyway. Jon knows I'm going with a tune, so I'd have a hard time believing we chose based on whether it'd throw a CEL or not.

My primary goal was to eliminate the sill heat so I wouldn't have to worry about heat damage on the PPF or paint. Which is why I went with the exhaust + added the heat resistant coating. My secondary goal is ensuring I get a setup that is going to last. I don't want to deal with stress damage on components that are going to be hard to find in 10 yrs.

Since I don't have a lot of knowledge on the subject, I have to rely on the wisdom of respected community members and go from there. My gut reaction was to get the flex pipe despite the extra cost because it's closer to how the stock system was. But again, I'm not an expert, so I went with the educated recommendation.

Thanks much for the detailed info Steve!

[AAA96]

I didn't specify the substrate, mainly because I didn't know it was an option. But I'm not sure I'm in a position to make a decision one way or the other on the material types anyway. Jon knows I'm going with a tune, so I'd have a hard time believing we chose based on whether it'd throw a CEL or not.

My primary goal was to eliminate the sill heat so I wouldn't have to worry about heat damage on the PPF or paint. Which is why I went with the exhaust + added the heat resistant coating. My secondary goal is ensuring I get a setup that is going to last. I don't want to deal with stress damage on components that are going to be hard to find in 10 yrs.

Since I don't have a lot of knowledge on the subject, I have to rely on the wisdom of respected community members and go from there. My gut reaction was to get the flex pipe despite the extra cost because it's closer to how the stock system was. But again, I'm not an expert, so I went with the educated recommendation.

Thanks much for the detailed info Steve!

If the manifold cracks, just get headers hahaha

[Pappy]

With regard to the flex coupling, the issue is that the side exhaust is displaced 33" from the crank centerline (driver's side - 31" on the passenger side as the motor is moved to the right), and any torsional twisting of the motor on its mounts results in a greatly amplified attempted movement of the exhaust in the side pods. Vehicles with the exhaust closer to the crank centerline don't have as much of a problem. I vote to keep/install the flex couplings to ease the strain on the exhaust system. As an aside, I had to add a flex coupling to my track Ford Focus with header because the torsional twisting of the sideways-mounted motor was trying to compress/stretch the exhaust pipe with accel/decal. The short coupling in the photo would be enough for the Viper.

48660

[Jack B]

I believe the fulcrum point is the offset to the motor mount, not the CL of the Crank?

As far as cracking, the G1'Balenger's are virtually identical to the G5 and some of those have been installed for twenty years without cracking

[Pappy]

I believe the fulcrum point is the offset to the motor mount, not the CL of the Crank?

You are probably right. It may even be the right side motor mount under acceleration when the motor torques to the right. In any case, if there is enough freedom of movement for the side pipes and enough room to absorb that movement inside the pods, it shouldn't be a problem. AZ VPR cracked at least one side pipe (titanium) but he also broke motor mounts - I'm not sure one had anything to do with the other. I guess any concern might be based on how hard you are using the car.

[Jack B]

It must not move very much, there is not much clearance as the pipe enters the sill. On the other hand I had one of the first sets of G5 Belanger's and I had to get a newer/dimensionally changed turnout pipe because the first few sets had an interference issue at the turnout. Under torque you could feel the exhaust hit the frame.

Steve may want to comment, but. I believe the G5 was one of the first Vipers to have the energy absorbing engine mounts and transmission mounts, under some conditions this allows more engine movement.

As far as a titanium pipe cracking, that is one hard metal to perfectly form. weld and stress relieve.

[Old School]

The short coupling in the photo would be enough for the Viper.

48660

I agree, because of the location of the flex joint on a Viper. It is close to the engine, which allows it to absorb large movement of the exhaust in the sill with small amounts of flex at the joint. If the flex joint was close to the sill, this would not be true.