Help with exhaust

[Early93Viper]

When I first got my Viper I cut out the cats and muffler and put Thrush glass packs on it. Mainly because I was cheap and wanted to cool down the sidesills. My thought was that it would be a temporary fix until I found something better. To my surprise it didn't sound any worse at all, MUCH cooler sidesills and when I dynoed at 421 RWHP and 491 RWTQ I really thought I had a winner. No reason to change

Until I bought this Corsa race exhaust system from the Viper Christmas auction. I really stole it when I picked it up for $100. It's the same race exhaust that the Comp Coupe uses. (So I am told)

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I believe it is this:
http://partsrack.blastmart.com/customer/product.php?productid=1487&cat=103&page=2

With a few parts missing.

My first question:
Now this exhaust is 3 inches (stock is 2 1/2). And in theory it should flow better.....Right? I should see a slight HP gain? Right?

My Second question:
The muffler is also as big around as my old muffler and cats so I am a bit afraid I might have hotter sidesills. (The thrush glass packs are a lot smaller and I don't have a heat problem with them.) Should I be worried about sidesill heat with this setup?


Any help would be appreciated.

 

[bluesrt]

When I first got my Viper I cut out the cats and muffler and put Thrush glass packs on it. Mainly because I was cheap and wanted to cool down the sidesills. My thought was that it would be a temporary fix until I found something better. To my surprise it didn't sound any worse at all, MUCH cooler sidesills and when I dynoed at 421 RWHP and 491 RWTQ I really thought I had a winner. No reason to change

Until I bought this Corsa race exhaust system from the Viper Christmas auction. I really stole it when I picked it up for $100. It's the same race exhaust that the Comp Coupe uses. (So I am told)

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

I believe it is this:
http://partsrack.blastmart.com/customer/product.php?productid=1487&cat=103&page=2

With a few parts missing.

My first question:
Now this exhaust is 3 inches (stock is 2 1/2). And in theory it should flow better.....Right? I should see a slight HP gain? Right?

My Second question:
The muffler is also as big around as my old muffler and cats so I am a bit afraid I might have hotter sidesills. (The thrush glass packs are a lot smaller and I don't have a heat problem with them.) Should I be worried about sidesill heat with this setup?


Any help would be appreciated.

i think the 3 inch stuff will rob ur low end torqe,but give u super top hp if its stock,just my exsperience on a zr-1.dont know about a viper.

 

[vipzilla]

i went with the roe side exhuast i lost boost from my supercharger due to back pressure being reduced but i gained hp top end and a great sounding exhust yes i did keep high flow cats on the set up

 

[dave6666]

Question 1... Larger diameter exhaust pipe reaches a point where hp can be lost. Most street and even racing engines rely on some amount of back pressure as balanced with the cam profile. I'll stop on that concept there as I'm really not an expert on that subject, other than I'm very aware of it's existence.

So on to your hp gain concerns. There are plenty of claims, reports, etc. on the benefits of cat-back exhaust exhaust systems. Which in what may be the most basic of their use is a 2-1/2" factory system up to the cats, and then the better flowing 3" system exiting the car. Once again, there is enough information on that type of installation to safely speculate that yes, you will see a small power increase. 5, 10, maybe even 15 hp.

Your biggest gain on that will be from the noise. Yeah, the proverbial butt dyno. Louder is more powerful right?

Question 2... The only way I can imagine that a larger diameter muffler could increase sill temps is by restricting air movement in the sills. Cats increase heat because there is an exothermic (generates heat) reaction going on inside of them. Mufflers on the other hand are going to be passive. They might actually remove a little heat due to their increased surface area over just straight pipe, but you must also factor in the insulation value of the sound dampening material. Bottom line is, as long as there is at least some amount of air space for air movement around everything in the sills, you should be fine with any size muffler. Petite or honkers.

Final comment, from the master of sill ventilation here, have you added vents to the front of your sills in the wheel well area?

 

[Early93Viper]

Question 1... Larger diameter exhaust pipe reaches a point where hp can be lost. Most street and even racing engines rely on some amount of back pressure as balanced with the cam profile. I'll stop on that concept there as I'm really not an expert on that subject, other than I'm very aware of it's existence.

So on to your hp gain concerns. There are plenty of claims, reports, etc. on the benefits of cat-back exhaust exhaust systems. Which in what may be the most basic of their use is a 2-1/2" factory system up to the cats, and then the better flowing 3" system exiting the car. Once again, there is enough information on that type of installation to safely speculate that yes, you will see a small power increase. 5, 10, maybe even 15 hp.

Your biggest gain on that will be from the noise. Yeah, the proverbial butt dyno. Louder is more powerful right?

Question 2... The only way I can imagine that a larger diameter muffler could increase sill temps is by restricting air movement in the sills. Cats increase heat because there is an exothermic (generates heat) reaction going on inside of them. Mufflers on the other hand are going to be passive. They might actually remove a little heat due to their increased surface area over just straight pipe, but you must also factor in the insulation value of the sound dampening material. Bottom line is, as long as there is at least some amount of air space for air movement around everything in the sills, you should be fine with any size muffler. Petite or honkers.

Final comment, from the master of sill ventilation here, have you added vents to the front of your sills in the wheel well area?

My sidesills barely get warm with my current setup.

Do you really thing 3 inch exhaust with corsa muffler will free flow that much more 2.5 inch? And if it does I will probably lose some torqe down low and gain some HP up high. Will it be worth the trade?

The best case scenario I can't see gaining more than 5 RWHP, Better sound (That would be nice) and I can't see how it couldn't make my sidesills at least a little hotter.

And of course that's the best case.

I'm going back on forth on this mainly because I would like better sound. Wouldn't mind a bit of a HP increase either. I just don't want to put it on and then lose power or make my sidesill unbearably hot. Then have to take it off again and try to sell it used.

 

[Dom426h]

From the snakeoyle cataloge:

Which Do i Want: 2 1/4"ID or 3"ID CAT-Back System?

The ansswer to that question is a matter of financial commitment. Are you willing to spend the extra money for 3" ID headers, or do you just want to purchase a cat-back system?

Its been proven on the dyno and on the track: a 3"ID CAT-back system behind the factory 2 1/4 ID CAT & Header creates a loss of torque and loss of horsepower. Why? Try pouring fluid through a funnel backwards. Although the flow loss is less dramatic in your exhaust system, the same physics apply. The backward-stepped piping inhibits proper exhaust flow within the system, and loss of exhaust flow velocity.

Moral: A 3"ID system only has advantages when it has a 3"ID header and CAT supply.


I remember back from a hydaulics class calculating headlosses for sudden expansion & contraction in pipes that would likely verify. Anyone have any dyno comparisons regarding this?

 

[dave6666]

From the snakeoyle cataloge:

Which Do i Want: 2 1/4"ID or 3"ID CAT-Back System?

The ansswer to that question is a matter of financial commitment. Are you willing to spend the extra money for 3" ID headers, or do you just want to purchase a cat-back system?

Its been proven on the dyno and on the track: a 3"ID CAT-back system behind the factory 2 1/4 ID CAT & Header creates a loss of torque and loss of horsepower. Why? Try pouring fluid through a funnel backwards. Although the flow loss is less dramatic in your exhaust system, the same physics apply. The backward-stepped piping inhibits proper exhaust flow within the system, and loss of exhaust flow velocity.

Moral: A 3"ID system only has advantages when it has a 3"ID header and CAT supply.


I remember back from a hydaulics class calculating headlosses for sudden expansion & contraction in pipes that would likely verify. Anyone have any dyno comparisons regarding this?

Very good information. Somewhat along what I was saying - more detail though - with however a net result of a loss of power. I will not argue that, as my comment was based simply on info that can be found in postings here. I know, mainly un-verified, but repeated at frequency.

Could these be some factors in what I will therefore call a discrepancy?

-> Is Gen1 2-1/4" while Gen2 is 2-1/2"? I seem to recall from my side exhaust conversion that the outlet of the factory cats were 2-1/2". The car already car a 3" cat-back system so I have no idea what size the factory pipe is. Point is, if that is the case, then that may be too big of a jump in size.

-> Does the shorter length of the Gen1 side pipe versus the Gen2 rear exhaust make a difference? Greater length equals greater back pressure, so maybe on later generation cars the system is better balanced to the related components of the car like the cam profile etc.

Just some thoughts, as I am only knowledgeable of the principles of these matters, but if the Snake Oyl info is true, then it seems that there are a lot of people out there that have wasted their $$$ on cat-backs for an otherwise stock vehicle.