CatBack/ Exhaust size.

[TheStupidFock]

How about you two just find a dyno of a stock V6 Camaro with a 2.5" exhaust, and one with a 3" exhaust. Wouldn't that be easier to argue over instead of using theory?

I'm sure other people would like to see both dynos too.

Oh, and on a side note, who makes a 2.75" exhaust?

[HBHRacing]

thats the thing. I am using theory, and he is just argueing that I am wrong and not backing it up with anything other then."my care gained HP with 3 inch" which is not what I am saying. Sure you will probably gain HP but it will shift the low end up the the rpm range and not let you use any. and TQ is important.

So far I have found one (1) person that runs 4 inch exhaust. but he is no where even CLOSE to stock. he has an ARE 422ci that puts down 525rwhp all motor, and he also has a 300 direct shot of spray..

I perposed the question to other people and they all say the same thing as I do. Even the V8 guyes. here is one quote. "I have 1 3/4" headers into a 3" catback and that's overkill for my engine. I could probably run just as well (if not maybe better) with 2 1/4" true duals, or a 2.5" catback." I have many many others like it.


I emplore this guy to prove me wrong with anything I have said. he will not be abble to. I know that it's hard to accept change. but I make it a point in my long history of being on websites like these to not give bad info. If I am unsure of the answer I will word it in such a way. But I am sure on this one. I would never intentonaly point someone in the wrong direction.

Like I said, HP is not everything. Sure it looks good on a dyno but making best use of the TQ and hp is what gets you down the track faster.

I am sorry that this post took this direction but when people feel there long lived belifes are being challenged it happens. The next thing that I will do is copy and pate the origonal quetion and send it to one of teh smartest people I konw and see how exactly he would word it.

But, to the post starter. I could really use a list of any mods that you have to I can tell him to figure them into his wording.

[mjparme]

I am sorry that this post took this direction but when people feel there long lived belifes are being challenged it happens.

Yeah, I am not sure where all the hostility and the ad hominems came from.

You stated your opinion on a 3" exhaust and then people started calling you stupid and such instead of debating the facts.

Anyway, there have been several posts in the past (it has been a very hot topic on this board for a long time as you can tell) based off of dyno results that suggests that a 3" exhaust doesn't decrease HP or torque. However, it does shift the ower band up slightly (I think it was 300-500 rpm's). Even if it moves up slightly, when you go down the track the percentage of time you spend at an RPM below the powerband is VERY small compared to the time you spend at an RPM in the powerband.

[HBHRacing]

Thank you. I do not know where the hostility came from either. I'm not saying that 3 inch is bad. but it should be used as part or a larger plan. Since we know that it will shift the powerband you can help to make it less noticable by adding more air to the motor. Another thing to consider is somethig like gears to get back into that power band sooner. The topic starter himself said that he had heard that 3 might be too much but no one called him names. Apearenlty I was just the easy target in this battle.


Since no one seemed to want to answer. I will just tell you. at idle on a healty system you shold see no more then about 1 PSI of back pressure and at 2500 should not exceed about 1.5. I like how he acused me of thinking back pressure would good without him even knowing anyhing about back pressure..

[1DangerousV6]

how about the borla rear section for the looks...and a cut out for the power?...unless you're after the sound too...then in my opinion...3" borla cat back with hollowed or high flow cat ;)

[KBeezy]

Here, let me quote myself a few times and you can try to tell me I am just being hostile and not giving you any data:

"With exhaust you have 2 options. Go narrow and get low end grunt.. Or go big and have top end power. If you want speed, you want a lot of power up top -- if you have it all down low you'll have a good hole shot but once you start to really rev you aren't going to have ****."

Hmmm. I think I just said what the guy a couple posts above said. IF you want SPEED you want a lot of power up top. If you want pulling power and lots of torque to climb a mountain you want gobs and gobs of low end torque.


"And in fact, there was a 3.4 guy who dyno'd after he got his 3.4 kit and he picked up I think 8rwtq and 6rwhp over stock."

Do a search and you'll find the guy I am talking about. All I remember is the topic of the thread is called 2.5" vs 3" or something like that.


Dude, read my actual posts and you'd see I actually know what the hell I'm talking about. Get the book out of your face for once. [img]smile.gif[/img]

[HBHRacing]

if you would let go of your hostility and maybe do some searching of my posts you will see that I know what I am talking about. I am not one to learn from books. I learn from 3 things.

others online
first hand on my car
and the 5 years I have as a mechanic

The thing that gets me is that your getting hostile even tho we are both saying the same thing, just in different ways. You made asumptions into my thoughts that are not yours to make.

your friend with the syno. did you compare the curve to stock VS with exhaust? you will see what I mean.

There are people who put on large exhaust and have no other means to control it and actualy lose perforance in the 1/4 mile. Without thinking about the other systems of teh car that can happen.

Same thing happend with my car with the loudmouth. I put it on and felt dissapointed that it didn't have the grunt that it used to. Once I installed a CAI it felt better. but still didn't do much down low. But the top end was stronger. With the TQ shifting I was having trouble bogging off the line. Now with teh gears I no longer have that issue.

It's just a part of a puzzle, fill in all the peices and you have something tht works. Keep a few out and it will not look the same.

[1DangerousV6]

[img]graemlins/popcorn.gif[/img]

[DescendingAngelz]

Everyone go out today and pick up a book on Fluid Mechanics, You'll find it in the engineering section of the bookstore. Fluid covers air and liquid btw, It'll teach you everything you need to know about Air displacement, Pipe Sizings, Flow etc. Great read, And it'll give you a whole new twist on what you believe is right about exhaust and intake. [img]graemlins/slap.gif[/img]

[1DangerousV6]

^^^...shh..someones fighting and its not me haha .......... [img]graemlins/popcorn.gif[/img]

[KBeezy]

Dude, Im not hostile, this is how I discuss stuff. You saying that a 3" on a V6 is "too much" is wrong. You don't know how much gasses our cars put out and if you do -- please, tell me.. How much exhaust does a V6 f-body put out? Do you know? Maybe one of your books does.

Sure, on the CURVE you move it from the bottom end, but as the RPMs rise the curve gets better and better. In fact, on one dyno I saw of a 3.4 V6 with a 3" exhaust (non f-body, but was still an SFI 60* GM V6) it picked up 4 peak HP but had spots where it had 8-10rwhp over the STOCK curve. Like I said, you can have your books and experience as a mechanic. V6 F-Body guys have been going thru SO many different options and I doubt that you have even done half of them. I've played around with so many of them that I know for a FACT that a 3" exhaust on a V6 F-Body isn't harming your performance at all. In fact, its improving it. My car used to be a dog at above 60, but when I got my 3" put on it pulled to 60 and pulled about 1.5 times harder than it used to...


So please, since you say a V6 car cant fill a 3" pipe.. Tell me, how much does a 3.8 (or 3.4) put out emissions wise. I'd like to know.

[HBHRacing]

I never said that a V6 can't fill a 3 inch pipe. you really do not pay attention to what I do say. It just makes a difference of WHEN the motor can fill the pipe while also considering volicity...

[KBeezy]

Acually. You did.

"3 is too big. you run into a problem with trying to fill more exhaust volme then your motor can push out."

[HBHRacing]

fine. don;t listen to me. listen to what I am saying from someone else

http://www.magnaflow.com/07techtips/faq/question10.htm


now go argue with magnaflow.

[KBeezy]

As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4 to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque.

Well let me see here. My stock exhaust goes from 2 1/2" Y-Pipe with 2 1/2" pipe to converter to 2 1/4" pipe out the back. Bottleneck much?

Why? Ask GM. Sound? Emissions? Who knows.

Like I said, quit debating this. We have proven before that 3" isn't as bad as people make it out to be. That chart is a good BASE way of looking at it, but every car and motor is different. I want to see someone with a turbocharged 4 cylinder follow that chart, it'll get em NOWHERE if they're running a 2 1/4" exhaust as an upgrade. Know why? In most situations like that, 2 1/4" is STOCK.. [img]graemlins/slap.gif[/img]