Calling all v6ers who have gone from 2.5" to 3" exhaust...

[jessica2112]

Well the main reason I went to 3" is the fact I have an SC. Now without that, I would have gone 2.5" I noticed my hp and torque went way up in the RPM range, which is kind of what I didn't want, but that's ok, it's liveable. I usually run in short bursts, so I would have been better off with smaller pipe, but I will have a cam and heads later, and given the sc, headers and ff exaust 3" made sense. I have 3" to the over axle pipe, then 2.75 to the muffler, or whatever stock V8 size is.

[HBHRacing]

a boosted engine is a totaly different beast. You don't have to worry about overcoming the pressure because of the extra pressure in the cyls. So big is not as harmfull on such motors as NA.


You can't compare top fuel or prostcok cars to us. They have A TON of exhaust pressure to get out of the motor as fast as they can. But they still tune for resinence to help scavenge the pulse out of the motor.


To a point Nick has the right idea. He understands part of it. Yes Zero restriction is ideal and yes it is hard to get there. But thats not really important. As long as you free up restrictions where you can (including the restrictions from having pipe too large for your aplication) you will be doing great. There are formulas to predict things like collenctor size, length, pipe diameter size and length ect ect. These are used in the link that I put up as a general "idea" to get you started. http://www.magnaflow.com/07techtips/faq/question10.asp look at the chart. Take your 232 CI motor and your HP rating and see what it says. they will be pretty close .

[phantomzer0]

who gives a **** how fast it makes your car. we are dealing with 6's. there isnt going to be that drastic of a gain no matter what your putting on. 3in sounds the best, and since 98% of people on this board want killer sound, just go with the 3 in.

[mjparme]

Originally posted by toast:
Now obvously you cannot take care of all the restrictions and you do need some for backpressure.

The fact that you say this shows that you haven't done enough research about exhaust systems. YOU DON'T NEED ANY BACKPRESSURE! You want 0 or near 0 backpressure with high exhaust gas velocity.

I actually have a 3" exhaust system on my car mostly because I was ignorant of exhaust system design when I bought it. Although I do think 3" systems sound better. I like the sound of my car better than any other V6 Camaro I have heard (without headers).

If you want good sound go 3", for optimal performance you probably want 2.5 or 2.75.

The Magnaflow link HBHRacing posted explains things quite well.

[toast]

So no backpressure, or as little as possable, yeilds to more power; then why is it when you run a car with open manifolds you lose power throughout the rpm range-this is not fiction but fact. Its all about how the exhaust flows through the pipes and you want the smoothest flow with very little restriction. Since most n/a engines do need some backpressure in order to produce good power throughout the rpm range. It goes back to not having enough air to flow through the system by not enough pipe or too big of a pipe. Yea i know i said it, but it would be silly to have a 4inch pipe on a V6 or even a NON-MODDED V8, but get rid of the restrictions in the intake, add a cam, head work, even stroke the motor, then it justifies running that size exhaust system. Going back to the V6 if all i did was just a 3inch exhaust and nothing eles i would hardly have gained a thing, but since restrictions were removed on both the intake and exhaust side i gained in power. I believe you said this before HRB "that exhaust has to be tuned to the engine itself" and i agree with you totally. I have leaned this from over the past 5years of working with exhaust systems not only on my past 6 cars (in 5years mind you) but on other engines. I am working on another whole other theory that will rock people who say "tru-dual exhaust is better than a single pipe exhaust." That is for another thread discussion all in its self. ;)

[ August 10, 2005, 10:42 PM: Message edited by: toast ]

[toast]

[ August 10, 2005, 11:14 PM: Message edited by: toast ]

[HBHRacing]

toast. Read the links provided. The answers are in there. When you dump exhaust into atmosphere the location in which it dumps will make the difference in where teh power comes in. When you dump it too close to the motor you are take the power and moving it so far up the RPM range that you would need to be shifting at 8 grand to use it. When you move it back farther and farther it will start to drop this range down more to where you can use it. yes, freeing the restrictions is going to make power, but how you free them will depend on where that power shows up.


again. These are all GOOD questions. Open your mind to teh asnwers and don't just assume that one person is right or wrong. Look at the info and you will learn all of these answers. Exhaust tech is NOT simple. It takes a lot of planing and time to get it right. But when you start to understand the princapals and reactions it will open a whole new performance world.


And for Mr "who cars it's only a V6".... Then why are you on a V6 mesage bored that helps people to improve on thier cars and make them faster?


mjparme: Good post. You hit the nail on the head.

[toast]

I wish i could illistrate for you what i am talking about. I tryed to explain it the best i could. It all comes down to have the exhaust gases exiting in the best manner that no only produces a good sound but also leaves you with an improvment horsepower and torque throughout the rpm range and not just at the peak.

[ellik]

Originally posted by HBHRacing:
There are formulas to predict things like collenctor size, length, pipe diameter size and length ect ect. These are used in the link that I put up as a general "idea" to get you started. http://www.magnaflow.com/07techtips/faq/question10.asp look at the chart. Take your 232 CI motor and your HP rating and see what it says. they will be pretty close .

based on this link that you provided, I would say that their chart shows our cars stock are in the top range for the 2-1/4" to 2-1/2" mufflers (good for 200-250CID and 100-200HP). So I read it to say that their 2.5" system is made for a stock v6. nitrous, cam or any bolt-ons that are going to net you more horsepower and your out of their range for their 2.5" exhaust. If you extrapolate the chart, you probably want to start looking in the 2.75" range. There you are pretty much looking at v8 take-offs.

Now, many people do select their exhausts with sound as a big factor. How many sound clip threads to you see posted all over the place where people are trying to chose. So with these considerations (1. hope to add a few HP netting bolt ons pushing you out of this nifty little charts range and 2. sound) 3" becomes an option for many people. Maybe its not a perfect solution for maximum performance by the theory driven individuals, but it makes sense to some.

[HBHRacing]

I honestly could care less about the sound aspect. If someone doesn't race thier car and only wants sound then fine. It really has nothing to do with my point of all of this.

I would "guess" that the point where a 2.5 inch would become a restriction would be "around" 250 RWHP. In which case the take off would work well in addition to a high flow or no cat and a much better muffler. At the point when your pushing 300 HP at the wheels it's time to think about 3 inch

Toat, I understand what you are saying. But it's not correct. If you want performance forget about sound. if you want sound forget about performance. The BEST performance you will find is getting an exhaust system that is restriction free and that allows you to not run too large of pipe. To do this (like I have been saying) for stock to modded 3.8's would be a QUALITY 2.5 inch cat back).

[Chris Camaro]

when i put my pacesetters on, with my 3 inch catback, high flow cat, and no power adder, i want more back pressure cus i gotta work that clutch when tryin to launch, a ton more flow and its great and all. but at least my system is ready for that s/c now =)

[HBHRacing]

no man. you DON"T WANT MORE BACKPRESSURE. your fighting the TQ loss of the 3 inch system. if you slaped a 2.5 inch system on you would notice how better it felt down low getting going. But since you are going the SC route, stay with 3 inch. Just make sure that the muffler is quality and restriction free.

[Chris Camaro]

o believe me i know, i love my car, but i need a power adder, cus on the freeway i can put it in 5th cus it will bog bad unless im doin 90

[ellik]

Originally posted by HBHRacing:
I would "guess" that the point where a 2.5 inch would become a restriction would be "around" 250 RWHP.

so you're 'guessing', just like the rest of us. lets look at your chart provided by magnaflow again. acording to them, a 250CID engine producing 150-250HP should have a 2 1/2" - 3" exhaust. so a 250CID engine with 220ish RWHP should be running a 3" exhaust. thats a cammed 3.8L not to mention anyone that runs nitrous.

I agree with the fact that anyone who is going to stop at intake/exhaust should go the 2.5" route... or even your project with Jeremiah where you are making the most out of suspension and gears. Otherwise, if you plan on going further in the future weather it be heads/cam, nitrous or other power adder, a 3" exhaust is where you will want to be as it will support anything you throw at it without having to rip it out and buy another system. The only thing in question is exactly where that break-point is where you will want to upgrade. Throwing a mild cam into the mix I am 'guessing' is going to put you right onto that edge of where you will need to upgrade to at least 2 3/4"

[toast]

Originally posted by HBHRacing:


Toat, I understand what you are saying. But it's not correct. If you want performance forget about sound. if you want sound forget about performance. The BEST performance you will find is getting an exhaust system that is restriction free and that allows you to not run too large of pipe. To do this (like I have been saying) for stock to modded 3.8's would be a QUALITY 2.5 inch cat back).

Yea, i hear ya but most people (including myself) want the best of both worlds. For me it comes down to having the best sound with a notable power increase. It may not be the most usable power increase, but i rather have my car produce an awesome sound even if it means a scrifice of a few ponys. Plus those few ponys can always be made up in other mods. [img]tongue.gif[/img] ;) I have leaned with any performace car you are never satified, you always want more. :D