Judging by the amount of "extra" exhaust produced by force induced Contours, I think this new Bosal cat-back system is best suited for it. All mandrel bent pipes, 2.5" before the split, 2.25" after the split, 304 S/S, chrome plated, and straight-through mufflers/resonator. This is exactly the cat-back I was going to have custom made for me, and now it comes in a bolt-on package (not slip fit/crimp).
And, considering the reputation they have for VW, BMW, Honda, etc. I feel even more comfortable getting it. Not to mention we have a rep from the company roaming around these boards (Bandit).
For those of you that just happen to be running stock exhaust with the Vortech, I would jump on the group buy. $500 shipped directly from the manufacturer isn't bad. One has my name on it, for sure.
Of course, this is just my honest opinion.
-Chris
Brullen has the same thing. I think Brullen is better because you can choose different options like resonator/tips/mufflers.
I definitely disagree with you!
It's much too small for forced induction or 3L engines.
2.5" O.D. single piping is just not large enough.
Now this would make a decent setup for any NA 2.5L not going true duals.
Provided of course all the mufflers are straight through??? (couldn't find that info)
I agree with your disagreement. 3" for FI, no less....
I would say 2.5" is large enough for any N/A setup seen here, be it 2.5 or 3.0L. But like you said, I'd prolly go 3" on a forced induction setup.
So, would you say 3.5" for a TC3L?
Originally posted by AirKnight:
So, would you say 3.5" for a TC3L?
No.
Originally posted by Ausgedient:
I would say 2.5" is large enough for any N/A setup seen here, be it 2.5 or 3.0L. But like you said, I'd prolly go 3" on a forced induction setup.
I disagree (again 
)
2.5" piping only has ~75% of the flow diameter of 2" true duals!
Plus being the fact it is one large tube the exhaust velocity is slower then the smaller yet higher volume flowing dual pipes. (being as the exhaust comes in pulses, not total volume)
Jump to 3" piping to slightly surpass (+10%) the flow volume of 2" duals and your velocity suffers further.
Okay that was more of a bash on Y-pipes, but it still proved my point. 
Originally posted by AirKnight:
So, would you say 3.5" for a TC3L?
....Turbo Contour 3 liter?????
Originally posted by Faboo:
Originally posted by AirKnight:
So, would you say 3.5" for a TC3L?
....Turbo Contour 3 liter?????
I think he means Turbo Charged 3 liter
But it's all the same
FWIW, a 2.5L engine at ~14PSI will put out the same amount of exhaust as a 5.0L engine. I was under the impression the Bosal exhaust was 2.5" ID pipes, then split to two 2.25" ID pipes. Plus, they are straight-through design mufflers/resonator.
If a 5.7L engine is fine with a single 3" (Camaro, Firebird, Corvette), why can't a roughly 3.7L engine be fine with a 2.5" ?
You also have to look at the exhaust components in front of the cat. Is the smallest piece equivelant to a 3" ID pipe? Still keep in mind the velocity factor.
Oh, and the stock Y-pipe sucks
Because a 5.7L engine is NOT fine with a single 3" exhaust. The F-bodies are just hosed by poor underbody design (ring a bell
)
Also there are companies that make larger exhausts (3.5" & IIRC even 4") for the F-bodies that show power improvements over the 3" systems.
There are even people that feel 2" duals are too small for a really hot 3L and too small for any S/C SVT's.
2.5" single is only ~75% of 2" duals (like I mentioned) Plus all the other drawbacks of having one larger pipe! (like I mentioned)
If one
was going to still use this "sucky" (as you mentioned
) Y-pipe design and has a moderately modified SVT (~175FWHP) or below then 2.5" O.D. piping would be plenty for them. Not ideal or the best, but definitely would work well.
I'd highly recommend an aftermarket Y-pipe to get the most gains. (which is basically 2" duals Y'd into one 2.5" pipe!)
for all you out there who may think that larger diameter will produce more power- I have an idea- go listen to the tape on headers by Headers by Mike IIRC- this will astound you- he has been makeing custom headerand exhaust comboes since the 60's. He really knows his stuff- and the funny thing is that he is all about flow rates, and velocity- not diameter- so usually a single step smaller will provide more horsepower! I dont remember the exact example he uses on the tape - but he states that when he went from a IIRC 2inch header to a 1 and 7/8 he gained almost a half second on his E/T. This theory of his is amazing and will change how you look at exhausts! A MUSTread!
PS- for what its worth a 427 Cobra loses about 100hp through its exhaust. Yes those Fabulous 2" tube headers into a 4" exhaust coming out the sides(usually with a glasspack or similar) LOSES CLOSE TO 100HP
so with all this talk about doing 3'' exhaust on the street flight setup would be a bad ideah????????
you have to remember, if this guy is working with NA applications, it's a lot different. . .
FI is forcing air in, you don't even really have to change headers out on an FI s/c since the flow is that much the better, so I think this dude's theory may stand on certain NA app's, but as far as tc, the wider the better since it RUNS on exhaust gases velocity exiting in order to turn the turbine to pump the air in. . ., it'll exit faster if it's BIGGER. OF course headers come with most tc app's, but I'm sure DemonSVT or someone else mentioned you really don't need headers with a sc. . .
just my .02, I may be wrong, everybody has their theories, hell we could banter about this for 200+ posts. . .
Originally posted by DemonSVT:
There are even people that feel 2" duals are too small for a really hot 3L and too small for any S/C SVT's.
If I was running almost any FI setup I would be using 3" single or 2.25" duals.
But I still do not see how 2" duals on a N/A setup can even be remotely considered too restrictive! I certainly would not consider 2.5" single the perfect race diameter, but even it is only flowing 78% of 2" duals, it is still not holding the car down by any means.
Originally posted by ssmumich00:
you have to remember, if this guy is working with NA applications, it's a lot different. . .
FI is forcing air in, you don't even really have to change headers out on an FI s/c since the flow is that much the better, so I think this dude's theory may stand on certain NA app's, but as far as tc, the wider the better since it RUNS on exhaust gases velocity exiting in order to turn the turbine to pump the air in. . ., it'll exit faster if it's BIGGER. OF course headers come with most tc app's, but I'm sure DemonSVT or someone else mentioned you really don't need headers with a sc. . .
just my .02, I may be wrong, everybody has their theories, hell we could banter about this for 200+ posts. . .
I mentioned before that you don't need headers with FI. However that isn't entirely true. The cost/performance ratio is not good enough for most people to justify it and there are other factors that make header design with turbos a very complicated process.
The part about what you said bigger = faster, is not really true as well as it may not be the whole story. Think of an analogy where you are washing your car on a concrete driveway. You want to push some dirt off the drive with the hose and put your thumb over the end. The water shoots further now than it did before....What's changed? It has a higher velocity now, but the opening is smaller because your thumb is pressed over it. Well, that is the first rule, smaller diameter hole = higher velocity, and also allows the jet of water to shoot further than it normally would. The next factor is volume. If you hold your thumb over the end you are restricting the flow and reducing the volume. Now you may be shooting out a jet of water real far, but you aren't letting out enough water volume to push the dirt off the driveway now. The result is you are letting off the pressure at the thumb and allowing a little more water to come out and provide enough force to push the dirt the rest of the way off the driveway.
This analogy makes sense to me, but then it is friday night and I am buzzing off of a good French wine! 
The moral of the story is that you must restrict the flow to speed up velocity, but you also need to compromise between velocity and volume. There is a 'sweet spot' for exhaust in either turbo or Forced induction where the diameter and the length of the pipes come together to provide the right combination to yield the best power...AT A SPECIFIC RPM! It doesn't apply to the whole rpm range either. Sometimes big power numbers don't tell the whole story. Just compare the vortech kits with 275HP to the streetflight kit at similar HP measurements, 240-290 depending on state of tune, the average being 265HP. The area under the torque curve is hugely in the turbo kits favor and the car should out-accelerate the average vortech kit significantly. (I say average because some people out there have above average kits!!).
warmonger
If I was running almost any FI setup I would be using 3" single or 2.25" duals.
But I still do not see how 2" duals on a N/A setup can even
so when i put on the street flight kit should i do a single 3'' or could i just have the 3 in the middle and still have it branch off to two pipes in the rear. b/c to be honest i dont want to have just one pipe coming out in the back, i like having dual tips, looks clean.
Another good analogy from a while ago is the straw analogy:
try drinking a coke through a 1/2" straw and a 3" straw. Although the 3" straw has the ability for more volume, most people can't suck hard enough to see the gain. (No jokes guys) This makes sense to me because I've been drinking microbrew.
Anyway, I am vorteching my car and keeping the stock exhaust. If you look at the y-pipe, it is rediculously restrictive compared to any cat-back so I put on a shoshop pipe and am calling it good.
LMAO- you think you know more about exhaust than a man who has been doing it for 40 years?
RIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIGHT!!
Quote:
[it'll exit faster if it's BIGGER./color]
LOL- again- WHATEVER- FASTER is by a restriced area- ever heard of a venturi?? thats the principle that a carburator works on- narrow the area and the speed through which it flows will increase!
Lets just say you werent yourself when you typed that last post ok? someone stole your log in and posted without your approval!
(FYI- FI or N/A doesnt mean a thing - all it ammounts to is more air entering the system- all an internal combution engine is, is an air pump- wether you pressureize the system or not- its just an airpump- so you just need to design the entire system to be as efficient as possible- you CAN have a N/A system with more than 100% efficiency, and FA systems with less. There are even theoretical systems (Idont remember the designation) were exen the exhaust is supercharged to maintain a pressurized enviroment, so in closeing - remember when you dont know - dont argue!)
Originally posted by Horse:
Quote:
[it'll exit faster if it's BIGGER]
LOL- again-
it's the damn COLD, it's frozen my brain cells, and the local brewery isn't helping it thaw out. . .damn the cold. . .i know this much with this much beer in me tonight, cold air=fun driving, I swear I'm pluckin' off 13's in her tonight. . .
Suneil
Horse-
Smaller primary headers are not a new idea or concept. ...and Yes; 2" primaries are HUGE!!! Far too large to be efficient on all save select race engines. (seen any NHRA headers
)
It's "headers" and we are talking about exhaust piping. They are related yes...
Also we are talking about combining exhaust from both cylinders too. That is completely different than headers.
Also if you were actually following the discussion it was all about the higher velocity flow of 2 smaller pipes over 1 larger pipe & also the need to jump up in pipe size because flow volume dictated it.
Don't worry boys...i think an exhaust like this will solve EVERYTHING.....
Don't forget scavenging and backpressure.
Not enough backpressure (exhaust too big) and you lose low end torque because you lose intake charge because of too much scavenging.
Too much (exhaust too small) and you lose top end HP because of the lack of exhaust evacuation from the cylinder. Also get lots of heat.
Think of it as your hi Revving race cars (or even some bikes) vs. RVs respectively.
Camshafts come into play here as well.
Originally posted by Ausgedient:
1. But I still do not see how 2" duals on a N/A setup can even be remotely considered too restrictive!
2. I certainly would not consider 2.5" single the perfect race diameter, but even it is only flowing 78% of 2" duals, it is still not holding the car down by any means.
1. I agree for NA applications. (oh wait I've already stated that many times )
2. It's mingling/merging exhaust gases from both cylinders. This is definitely not the best way to design/route exhaust.
Also like I have previously stated the exhaust come out in pulses. To get enough volume the diameter of a single pipe has to be considerably larger than a pair of pipes. Since the exhaust does come in pulses this larger diameter pipe will slow the exhaust velocity versus the pair of smaller pipes.
2.5" is the best choice for single piping on a NA car (oh wait I've said that before too )
Forced induction raises the bar.
2" minimum for duals with 2.25" being the ideal setup for the few top dogs.
3" is the ideal single pipe diameter for the turbo. The biggest drawback I see with the turbo kit's exhaust is that it uses a 2.5" downpipe from the turbo to the cat-back position. From what I've been told is that 3" piping just would not fit. 
Don't forget scavenging and backpressure.
Not enough backpressure (exhaust too big) and you lose low end torque because you lose intake charge because of too much scavenging.
Too much (exhaust too small) and you lose top end HP because of the lack of exhaust evacuation from the cylinder. Also get lots of heat.
Think of it as your hi Revving race cars (or even some bikes) vs. RVs respectively.
Camshafts come into play here as well.
Sorry about the double post - DSL is acting funny.
Originally posted by SalKhan:
Don't forget scavenging and backpressure.
Needing backpressure is a myth.
What you are saying is 100% true, but just use exhaust velocity in place of back pressure.
Ideally you want Zero back pressure. You tune your exhaust velocity and scavaging by pipe diameter in relation to exhaust volume. Anything in the exhaust system is a factor as well (mufflers, cats, X-pipe, etc)
isn't there a formula that will allow us to scientifically find the correct size of exaust based on the scfm coming in to the throttlebody?
Funny we are talking about this, I was fabricating the exhaust down-pipe today and trying to figure out the right size and direction to route it.
No way would 3" fit the flange they use for the T28. Hell, 3" won't even fit the exhaust flange for my T3/T4. 2.5" ID is the perfect size to weld up to the exahust flange used on my T3/T4. It may offer some benefits to go 3" from the downpipe but it just wont fit; no way to crush it down to fit either. Probably a graduated increase from 2.5" to 3" near the entrance to the main cat would work. The only disadvantage of using 2.5" is the length that we have to go using the stock exhaust path. Too long = more time that the exhaust is under drag before venting to atmosphere. I think if the pipe length were shorter, 2.5" id would be fine.
I am going to stick with my 2.5" for now until I can afford to upgrade to 3" stainless.
warmonger
Y-pipe is less efficient because you are combining the two exhaust streams which has to cause at least some disruption of flow. Going the other way, single to dual pipe wouldn't really be inefficient unless the combined pipe cross sections are smaller, or if the split is not conducive to flow like two 90 degree bends.
warmonger
Don't really need to worry much about scanvenging. All that is taken care of before the turbo, after the turbo you'll want no restrictions at all.
Originally posted by AirKnight:
Don't really need to worry much about scanvenging. All that is taken care of before the turbo, after the turbo you'll want no restrictions at all.
Correct. For the handful of turbo'd cars. Everyone else has to worry about it though.
That was my big point in the beginning.
Originally posted by Ausgedient:
I see what was mixed up. I was trying to state that 2" duals were the optimal and ideal choice in that post.
I later went back and stated if one was forced/stuck/choosing of their own free will to stay with a Y-pipe setup that 2.5" exhaust is the best size for NA applications.
So I do agree with you. (again?) 
i have a suggestion since you want no restrictions after the turbo,,, how about no exhaust pipe.
If you like loudness and exhaust fume inside the cabin, go ahead.
Originally posted by AirKnight:
If you like loudness and exhaust fume inside the cabin, go ahead.
lol I do not think "loudness" would fully describe it...
Originally posted by Kremithefrog:
i have a suggestion since you want no restrictions after the turbo,,, how about no exhaust pipe.
Once again....refer to my previous post..... no restriction exhaust 
Originally posted by AirKnight:
If you like loudness and exhaust fume inside the cabin, go ahead.
nothing wrong with loudness, and just roll down your windows.
You can't escape the loudness when you have the exhaust exit right in front of you. I know because I tried this when I first finished my 3L. It gave me headache every time I drove it. I ended up putting the restrictive stock cat back on to quiet it down so I can drive the thing.
Turbo'd cars are actually quite a bit quieter than their N/A counterparts. Open heads on a Turbo'd application wouldn't be half as nasty as the N/A application.
What about true dual exhaust with an H-Pipe? This negates the issue of a sloppy two-to-one-to-two transition yet the banks are equalized via the H-Pipe. Anyone running this set up? Is an X-Pipe more efficient than an H-Pipe?
Questions and more questions.
shouldn't it sound the same? You're just changing the block. .. unless you were talking about driving without any sort of muffling exhaust device at all (like no no exhaust plumbing?)? I'm confused, I figured a 3L would sound the same as a 2.5L given the same exhaust setup. . .maybe I misread. . .
Originally posted by Rev. Po-Jay:
Is an X-Pipe more efficient than an H-Pipe?
Look at the angles and answer your own question.
Originally posted by ssmumich00:
shouldn't it sound the same? You're just changing the block. .. unless you were talking about driving without any sort of muffling exhaust device at all (like no no exhaust plumbing?)? I'm confused, I figured a 3L would sound the same as a 2.5L given the same exhaust setup. . .maybe I misread. . .
3L is a bit louder. More volumn for combustion I guess. When I said I ran open exhaust, I meant what I said, nothing after the Y-pipe. EXTREMELY annoying, and it smelt really bad too.
Originally posted by Rev. Po-Jay:
What about true dual exhaust with an H-Pipe? This negates the issue of a sloppy two-to-one-to-two transition yet the banks are equalized via the H-Pipe. Anyone running this set up? Is an X-Pipe more efficient than an H-Pipe?
Cannot run true dual with the turbo. It's a single turbo with single exhaust outlet from the turbo. You can't run two pipes.
unless you make a twin turbo setup.
Don't know how you're going to make two snails to fit under the hood...
Not realistic at all, and definitely not worth the trouble!
Originally posted by Ausgedient:
Originally posted by Rev. Po-Jay:
Is an X-Pipe more efficient than an H-Pipe?
Look at the angles and answer your own question.
They function on slightly different principles. The X-Pipe forces exhaust gasses to mix, the H-Pipe equalizes bank pressure.
Back to the question...
Originally posted by Kremithefrog:
unless you make a twin turbo setup.
Now you are diggin' where there's taters!
I didn't think of the up-pipe problem. I guess you are right.
Originally posted by Rev. Po-Jay:
They function on slightly different principles. The X-Pipe forces exhaust gasses to mix, the H-Pipe equalizes bank pressure.
Back to the question...
Yes, my answer was poorly written. Either way, the X pipe is more efficient, and that is probably why racing teams runs that over a H pipe.
one thing about the bosal is its 2.25 after the split. isn't the brullen 2.5 from front to end? i thought thats why people like the brullen, especially for 3L.
No, Brullen is the same way. 2.5" up til Y-split, then 2.25" afterwards.
Originally posted by hmouta:
one thing about the bosal is its 2.25 after the split. isn't the brullen 2.5 from front to end? i thought thats why people like the brullen, especially for 3L.
Would not matter anyway.
An exhaust is only as efficient as it's smallest point. Lowered by the number to times the pipe diameter changes (for instance - crush bends, Y's, any non-straight through muffler, etc)
Therefore 2.5" single pipe flows as such no matter what piping is used afterwards. Now velocity afterwards is affected by pipe diameter chosen.
2.5" piping (4.90) could drop to dual 2" piping (6.28) and not lose any flow volume. Matter of fact it would retain more velocity after the rear y split and may produce better power numbers versus larger piping!
i checked pf.com and stand corrected. i should've checked it b4 posting.
Does Bosal have online ordering? I found the part on their site but didn't see any pricing.
BP