oxidizr

iTrader: (4)

Ummm ... I am an exhaust engineer ... and I will assure you nothign i wrote came from a book. It was very much so off the top of my head.

Note the sponsor tag under the name ... I am the Engineering Director @ MagnaFlow Performance Exhaust.

How are you doing?

00SS4780

iTrader: (3)

So you are saying a good Y-merge like the flowmaster and a 3.5 dump before the axle would be all I need? Thanks...

oxidizr

iTrader: (4)

Indeed, if you have the horspower to necessitate the flow, a dual 3" into a 3.5" is a moderatley big power exhaust system.

00SS4780

iTrader: (3)

Well I put 420rwhp down with a flowmaster merge necked down to a 3 I-pipe with a cutout before the axle and hooker muffler outback. I spray 100 shot also and I am goin to switch it to a 150 shot soon. I have a sphon chassis mounted tq arm now but wanted duals but they want fit wiht that arm too well. So I am thinking about staying with the Y but dumping it. So thats why I was just interested in the difference in the 2 systems and if it was worth changing my tq arm for it or not? Thanks.

oxidizr

iTrader: (4)

In my sig you will see a dyno for my truck.
Running through 1 7/8" Longtubes 2.5" collector with open cutouts at the collectors - 449/515
Running through 1 7/8" Longtubes 2.5" collector, dual 2.5" cat-less y-pipe, a 3" I pipe with a cutout open before the muffler - 440/514.
Runningn through 1 7/8" longtubes 2.5" colector, dual 2.5" cat-less y-pipe, a 3" I pipe through a 30" 5x8 Magnaflow muffler (street legal-noise consideration) - 435/510

Had i chosen to Longtube with a 3" collector Im sure a 3" y-pipe would have made for a smaller difference and not cost the 9 hp the dual 2.5" Y did.

Full-Force

iTrader: (11)

i am an exhaust engineer also, i build systems all the time

so now why dont you tell me that a good y pipe and a magnflow catback will make same power than my duals

i hope you dont because someone who has posted in this thread has a dyno proven 15hp loss through the catback apposed to a cutout after the y

oxidizr

iTrader: (4)

Building systems does NOT make you an engineer, it makes you a muffler shop tech ... what is your background?

I never claimed a good Y pipe + magnafllow cat-back would make the same power...
ugggg READ my post COMPLETELY.

...the loss was from a dual 2.5" Y not dual 3" ... stop reading what you want to and read the whole thing. I used a 30 inch long muffler to meet noise compliance SAE J1169 regulations. (If you truely understand SAE standard you will know that compliance means 95 dba measuread 20" 45* off the TIP of your exhaust outlet as measured @ 3/4 your peak RPM.) I can guarantee you a traditional true dual will not meet this standard with the mods you have on your car.

Open header or through the 2.5" Y pipe with 3" I (NOT 3" Y with 3.5" as we are talking about) netted a mere 9 HP and 1 lb-ft loss. the los was not observed from a 3" Y with 3.5" outlet.

The reason I never went to a large diameter Y was purely for the fact the truck made ~300 rwhp off the bottle (75-80% of the driving time) and ~450 rwhp on the bottle.

blkZ28spt

Most of us don't have to worry about dealing bullcrap like noise compliance.

I might be missing something here, but why is it that you need to meet a noise standard and not emissions?

ShevrolayZ28

iTrader: (4)

Maybe because he designs catbacks, and catbacks have nothing to do with polution emissions.

blkZ28spt

Umm, did you read all the posts?

He is talking about systems with longtubes, Y-pipes and cat-backs. Unless those longtubes have built in cats, at the factory location, and were never mentioned (not to mention AIR/EGR hookups) it has everything to do with emissions.

ShevrolayZ28

iTrader: (4)

Well, the thread starter asked about sound, so the rest of us are discussing sound, not emissions.

No offense intended, I thought perhaps you might not have read the thread.

blkZ28spt

The discussion has turned to power, and has been discussing that for some time.

oxidizr said that his longtubes, y-pipe and cat-back setup would pass a certain noise compliance. That made me wonder what the situation is that would call for noise compliance but not emission compliance.

oxidizr

iTrader: (4)

OFF TOPIC ...

I used the illustration with my truck to show HOW LITTLE even a 2.5" y pipe has over an OPEN header. I never contended a street-legal cat-back would outperform a illegal true dual.

I listed the last values to show even further how little a noise complaiant exhaust has over a vehicle with NO exhaust. I'm sorry but, but when you already have 430-450 rwhp ... traction will dictate your ability to "win" a traffic light race NOT 15 rwhp.

The reason i made the point regarding street noise compliant is this:

How many time have you been pulled over because a law officer SAW your non-legal cats or absence of any?
I am willing to be to bet that a noise violation issue led them to look at you a little more carefully, maybe even led them to pull you over or more over led them to believe you had a "modified" exhaust system.

So you ask why i even mentioned noise compliance vs emissions? THAT is why.

blkZ28spt

The illustration used an illegal, catless exhaust, did it not?

What makes a y-pipe setup legal and duals illegal?

A car with duals has "no exhaust"? I beg to differ. Open headers may be no exhaust, duals are definately an exhaust. If you insist it exit out the rear to be considered as existing, you can take 2.5" or even 3" duals out the back with adequate ground clearance.

Police officers can't see whether or not you have cats. You telling me that if I drove by you, you could SEE that I didn't have cats?



I have been running longtubes to true duals for two and a half years. I have been pulled over probably about a half dozen times in the Camaro during that time. I received one ticket that was complete bullcrap, which was not even a moving violation. I received one warning for "defective exhaust" because it was too loud. If it wasn't for the fact that this occured at 1:30 AM on a college campus I wouldn't have even recieved that warning. There are people with y-pipe setups every bit as loud as my car, and people with duals which are quieter.

BTW: I even passed emissions with my exhaust set up as is.

oxidizr

iTrader: (4)

You will have to look at local state laws of which some prohibit altered exit locations.

PLEASE READ the entire thread if you want to comment ...

I listed three dyno results:

1. My truck open header ... NO EXHAUST
2. My truck with 2.5" cat-less y pipe and 3" I with cutout before muffler open
3. My truck with 2.5" cat-less y pipe and 3" I with cutout before muffler closed through a noise compliant muffler.

This is where i derived my NO exhasut vs compliant cat-back info!!!! #1 vs #3

Can you read english???? do you understadn what a retorical question is?
this is what i wrote:
"How many times have you been pulled over because a law officer SAW your non-legal cats or absence of any?
I am willing to be to bet that a noise violation issue led them to look at you a little more carefully, maybe even led them to pull you over or more over led them to believe you had a "modified" exhaust system."

My point is that NO ONE can see ... so sound is what catches a would be cops attention. You don't jsut get emissions violation tickets unless they are acompanied by illegal speed contest or some sort of noise abatement issue.

And I have never been pulled over in the past 3 years ... hmmm 6 vs 0... now there is something.

True ... then intention of this discussion was to address power and size of tubign which led into system layout Y vs Dual. I only introduced the noise issue becasue it happenss to be the only three dynos i have to illustrate the differences in layout and the ramifications it has on power.

I'm not debating noise ... BACK on topic ... a 4" I pipe is over kill for 400 rwhp and a properly designed Y pipe system can produce as much power as a true dual.

blkZ28spt

Nobody cares that my exhaust exits under the car. Even the emissions testing facility employees couldn't have cared less.





No, they did not look more carefully. Besides that, you could make a Y-pipe setup as loud as my car and you could make duals a lot quieter than mine is.





What's your point....? You think if I had a Y-pipe system on my car I wouldn't get pulled over for doing a 0-60 mph run on a deserted country road as a Sheriff drove by the adjoining main road?

Do you think you could drive through a college town at 1:30 am on a saturday night, multiple times, without getting pulled over?



Sure seems like you are.


Yes, 4" I pipe is extreme overkill.

I'm still not sold on the second part of that statement, though.

oxidizr

iTrader: (4)

I don't carea bout the legality of your exhaust system you simply asked a question to which i answered. ex: Michigan State vehicle code - section 707/707c Muffler in good working order and in constant operation & Tail pipe and resonator if orginally equipped.... goes onto elaborate about decible levels.

You are beyond capacity to understand .... YOU brought up noise .. i was only talking about noise in MY applciation not between Y and true dual ...

Again I would enthrall you to read the ENTIRE thread...

I design compliant exhaust systems and am very versed on vehicle codes and their requirements (this one took me a whopping 2 secs to google)

If you agree that 4" is too big that is half my point .... the other half is that configuration has little to do with that and it has more to do with proper sizing and use of equipment ... it is a matter of total caulated flow.

00TAProject

So I hope this helps out a lil, in August I put together a TD system on my car. Now I have a clearance problem(You get what you pay for, $75 installed). But that will be be fixed as soon as I can raise the bullets up a lil more, they hang kinda low right now.

I dont have the problem of fumes in my car, or creeping into my car.....
They are loud, but that is what I WANTED.....they dump just before the axle and I have my turn downs pointed at a 45 degree angle inward towards each other to reduce any drone that may occour....so far I dont think I have had that problem.

I dont have problems with the police for excessive noise, matter of fact I drive through town poast the PD all the time just to see if they do say anything(2nd gear @35 mph)

One last thing, I love the way it sounds, people look hard and I get compliments all the time. I cannot wait until I can get my cam in....MS3 is cam of choice.....

Have fun Gents...I truely enjoy threads like these.....:USA:

blkZ28spt

The cam will make as big of a difference vs the stock cam as the exhaust did vs stock.

SouthFL.02.SS

Hello loud and fumes!