A 2.5" exhaust would actually be better suited for a 347 n/a motor and you may even gain some power. It would obvioulsy be best to have a complete 2.5" system since every bend and diameter change affects the airflow and resonance (e.g. back pressure) of the exhaust, but it won't be detrimental. You will need an adapter to fit the 2.5" to the 3" pipe. Summit sells them for cheap and you can likely find them at any decent local exhaust shop.
Why in the world would anyone downgrade to 2.5" when they already have 3.0"
Please.... don't mention your butt meter..... or the value of 'backpressure'.......
Because unless you're making 500hp, or running a turbo, you don't need mor than a good mandrel bent 2.5 system. Stepping up to 3'' when you don't need it will just kill off a crap load of low end torque.
How, where, when, who, and why do you say this? Who told you all of that good stuff?
1. The OP here is not 'stepping up' to anything... he already has the 3" stuff. You are proposing to spend money in order to DOWNGRADE.Because unless you're making 500hp, or running a turbo, you don't need mor than a good mandrel bent 2.5 system. Stepping up to 3'' when you don't need it will just kill off a crap load of low end torque.
You don't sound very confident following that BOLD statement with a question markWell, it's a simple fact?
I have NO problem with you citing a book or 2 in order to make your argument... but be warned... there are a lot of books out there that are actually WORSE than MM&FF or 5.0Mustang.Haven't you guys ever read any books on this crap? I'm not talking magazines either.
I'm not sure you understand how profound that comment isThere's a reason cars are manufactured with the size exhaust that they have. In most cases it's not the optimal size
As mentioned above... is the COMBINATION of parts being properly selected, or are we running a chassis dyno test in which 2.5" exhaust is being swapped for 3.0" exhaust, without re-evaluating any other components in the setup?when it comes to racing and modifying, which is why people step up from 2.25 to 2.5. The only thing you're going to gain with a 3'' exhaust is maybe a little more top end, and that depends on a whole slew of other things like what RPM you can run and how well your h/c/i can breath.
This is like people who think........ backpressure is a good thing for an engineThis is like the people who think running without mufflers makes more
The OP in this case is not 'throwing bigger pipes on'... The pipes are already there.There's more to it than just throwing bigger pipes on and expecting to get gains. If your engine doesn't need it, it's not going to do jack crap for gains and might even hurt you in the long run.
I bet next you're going to tell me that backpressure makes torqueI bet next someone is going to tell me that aftermarket mufflers "make power"?
Why have I always run better with a "free flowing" exhaust setup?....... no magazines or books articles here. Does the intake need to be changed/tuned?..... of course! ... one complements the other, that's what "combining" is all about.Well, it's a simple fact? Haven't you guys ever read any books on this crap? I'm not talking magazines either.
Open headers do make more power, if YOU know how to set it correctly, intake included + tune the exhaust........ yep, tune the exhaust. Restricting the exhaust of an IC engine is detrimental towards performance upgrades...... talk about crutches. If you increase exhaust flow and performance drops, it's the intake side you have to work on in order to maximize its potential, not restrict the exhaust.This is like the people who think running without mufflers makes more power or people who want giant cams in a stock long block, or guys who wanna put an 850 double pumper on a stock 302. There's more to it than just throwing bigger pipes on and expecting to get gains. If your engine doesn't need it, it's not going to do jack crap for gains and might even hurt you in the long run.
I bet next someone is going to tell me that aftermarket mufflers "make power"?
Interesting. A thread with potential, turned negative.
Consult the cam grinder for the exhaust needed.
I didn't care, nor they existed, when I proved that with my little 289 against 350's and a few 396's....... I did it.You guys know the Viper comes with 2.5 inch exhaust? If you think you NEED 3 inch exhaust, show me dyno proof before and after and i'll believe you, otherwise you're talking out your ass. You can pick my posts apart, you're arguing your OPINION vs. mine. If 3'' was so manditory, why don't more people run it? I know guys in single diget cars running 2.5 so i would think if they needed 3'' they would have it wouldn't they?
Mufflers DO NOT make power... as far as I know, they are "static" components in a setup....... they either "allow or hinder"..... so I agree with you..... but why use a setup that could "hinder".And you're retarded if you think mufflers make power. An engine makes X amount of power and then the mufflers take away X amount of power. Getting aftermarket mufflers only reduces the loss.
BINGO!..... you can set for either (closed or open)...... it all depends on the combo..... quite simple, as you have stated yourself. Do you know what an extension "megaphone" does to the exhaust scavenging?....... diameter, length, opening pitch, etc? When you're trying to "tune" a 4 cylinder setup, and a 1" difference is the "win or loose" factor.......And i think by "tune the exhaust" you're trying to tell me about scavenging but you don't know how to word it. Open headers won't make as much power as a properly sized (in length) set of pipes bolted to the end of the headers to enhance scavenging.
Or is it the information to digest? Why would you limit furthermore, an intake flowing biased setup by choking its exhaust? I know of heads selection suggestions based on their exhaust flow when compared to other cylinder head alternatives....... why would this be different?I'm done with this thread...too much stupidity for me.
Bolded comment #1You guys know the Viper comes with 2.5 inch exhaust? If you think you NEED 3 inch exhaust, show me dyno proof before and after and i'll believe you, otherwise you're talking out your ass. You can pick my posts apart, you're arguing your OPINION vs. mine. If 3'' was so manditory, why don't more people run it? I know guys in single diget cars running 2.5 so i would think if they needed 3'' they would have it wouldn't they?
And you're retarded if you think mufflers make power. An engine makes X amount of power and then the mufflers take away X amount of power. Getting aftermarket mufflers only reduces the loss.
And i think by "tune the exhaust" you're trying to tell me about scavenging but you don't know how to word it. Open headers won't make as much power as a properly sized (in length) set of pipes bolted to the end of the headers to enhance scavenging.
I'm done with this thread...too much stupidity for me.
Very nice...I'm done with this thread...too much stupidity for me.
I know of heads selection suggestions based on their exhaust flow when compared to other cylinder head alternatives....... why would this be different?
Ok,You guys know the Viper comes with 2.5 inch exhaust? If you think you NEED 3 inch exhaust, show me dyno proof before and after and i'll believe you,
2008 Viper Baseline = 546 rw hp / 515 rw tq
3 inch Stainless Catback Exhaust System = 561 rw hp
(15 rw hp gain over stock)
3 inch Stainless Full Manifold-back Exhaust System with High Flow Cat = 569 rw hp
(23 rw hp gain over stock)
3 inch Stainless Full Manifold-back Exhaust System with No Cats = 575 rw hp / 546 rw tq
(29 rw hp / 30 rw tq gain over stock)
The power gains are pretty even from 3000 to 6000 rpm on all of the above mods.
Guys,
If the concept that 'The exhaust being TOO LARGE will hurt low end torque' is so well proven, then where is the proof?
Everyone is saying that it is true, but I don't see any proof, and I never have.
I am asking you guys to bring forward proof of a phenomena that has been readily accepted as fact.
If everyone believes it, then there should be proof all over.
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