My 3" exhaust right now is the crappiest kind ive seen, its welded in every place, its too close to the frame so it ratlles, and the pipes are different sizes everywhere. Therefore I am going to get a hood exhaust system on there.

No one has tried 5 or 6" exhaust? Why is everyone telling me its gonna loose power if no ones tried it?

 

 

Well, I for one don't think he's so crazy; not really realistic about fitting a 6 inch exhaust - but on the right path a least.

I personally feel that anything less than a four inch single exhaust is merely a sheep following the herd. HERE IT WAS SHOWN that a 3 inch exhuast was just about right for a 3.4 liter engine... do you really think that an engine 98 - 147 cubic inches bigger should breath just as well through that same exhuast, or only slightly larger?

3 incher's are avaliable all day long, but just because they are easy to get and install does not mean that they are best suited for the task you want to accomplish. Sure, 30 cars ran 11 seconds with a 3 inch exhaust, but once again - that is not evidence that it was the best part for the job and that they wouldn't be faster with a larger or dual exhaust.

If I was this guy, I'd go with a dual 2.5 or 2.75 inch exhaust and not mess with anything else, not even the 4 incher given he's blown. Unless someone has dyno charts showing a loss in low end torque, don't beleive it - the 3.4 guy gained power EVERYWHERE on the graph by using a v8 "Performance " exhaust.

 

To quote myself:

I never said he shouldn't do it and in fact I believe it would probably sound absolutely wicked. The reason I wouldn't do it is due to an overabundance of pipe surface area acting as a heat sink; slowing down exhaust gases. This, coupled with the inability of his engine to utilize the entire exhaust would simply prove detrimental up until maybe 3000 RPM (and that's just a guess). If his engine cannot move enough air to justify that pipe size, then it's not going to help and will, in fact, more than likely hurt performance. I'm just more interested in performance than show. Not that there's anything wrong with it, but I don't care what someone else thinks of my exhaust tone/volume as long as it performs for me.

pixeldev: You said that there are different sized pipes everywhere. That could very well be the problem. If someone hacked his exhaust and has not matched anything properly, that'd definitely explain his problem. NOTE: If you do go with some incredibly large exhaust, it would help to wrap the entire exhaust to help hold in some heat. When I go dual 2-1/2", I'm gonna wrap it all the way to the muffler.

 

I would think with a 6 inch exhaust you would lean the engine out too much poss. causing exhaust valve scorching

 

Not to mention the rollergizer would get hung on the catchaphram causing the ****** valve to flatulate.

 

thats what everyone tolld me when i drove w/ stright headers... and i personaly think when i got my exhuast that it was a Performance UPGRADE.... i know it sounds dumb.. i dont have any numbers so it could just be all mental.

 

has anyone every actually seen burnt valves? it's nearly IMPOSSIBLE! people run with strait headers all day long at the track with no issues. i doubt very much that running this large of an exhaust will burn valves. maybe if you ran with no exhaust what so ever (open ports) that you'd have a problem. what i still want to know, is where this guy intends on putting this massive exhaust. there is not enough room under the car for you to stick this large of an exhaust under it.

 

dood, you said yourself that you are not an "Engine" guy.. so you really need to listen to the guys on this board..

you are not finding 5"-6" pipe because ITS NOT NEEDED!!!! so.. if its not needed, no one will make it.. why make something that no one will buy??

your engine can only produce "X" amount of exhaust air at a given time.. just because you have a supercharger doesnt mean its producing more exhaust air than a normally asperaited engine. the super charger just compresses air for a denser charge or burn..

anyways, really listen to people on the board.. if you want to be "different" then go ahead.. if you want something that is going to work, sound good, and be a benifit.. then listen these guys. if you dont want to believe us, then try another board, hell try www.LS1tech.com.. go look at the guys with 8 second 1/4 mile times.. NO ONE has a 5" pipe.. cause its not needed..

your sound coming from that thing will be worse than what you have now.. it will be clangy and sound like there is nuts and bolts rattling around in the pipes..

but do what you want.. your car and money.. and dont be mad if you get laughed at.

 

In addition to the performance loss youll experience with a pipe that big.....that will be the worst sounding car on the road. It would be terrible.

 

I've got a few moderate studio quality microphones here...I'm tempted to slap some 6" PVC on an engine just to see what it sounds like. I know...PVC would sound different than stainless or even mild steel and the plastic would melt, but this would be a temporary thing for the afternoon.

Actually, what would be really cool is if I could find a play to make my engine sound like steel drums in some calypso song. hehehe.

 

Okay, now just hold on....

Does anyone have a dyno chart showing that 5 or 6 inch exhausts kill power? I mean, really, do you? If not than all you're saying is baseless. Purely baseless. BONE STOCK l98's pick up 15+ HP with 4 inch exhausts over the 3 inch units. STOCK.... STOCK! Not some high rev'ing small block. 4500 RPM L98's - 15+ HP with 4 inchers OVER 3 inchers! Nobody has tested a 5 inch unit yet, so don't be the same guys that said 4 inch units would kill power and burn valves, because they were wrong too.

Too the original author - that size exhaust probably won't be seen due to fitment and cost issue's. If you need that much flow, go with a true dual 2.5 - 3 inches per side.

 

I do believe there's a decent possibility that a 5" could allow for more power but only at higher RPMs and at a power deficit in lower RPMs. In any case, if I can gain 15 HP @ 4500 RPM, but lose 10+ at 1500, then it isn't worth it for me except on a drag only vehicle.

I think the torque loss could almost be accounted for in a manual transmission, but you'd feel the lag in an auto.

 

If your gonna go w/ a loud sound.. and no backpreussre, then why dont you just run striaght pipes? i think the sound wont be that much different, than it just being directed towards the back.

 

Everyone needs to stop and pick up a fluid mechanics book and do some reading. You don't have to bunjee jump with a string to know that it won't work. Some simple analysis will increase common sense.

An engine is nothing more than an AIR pump. The more air you get in the more air you need to exhaust. Just because a 6" pipe is bigger doesn't mean the exhaust that the motor produces will "flow more". You want to move the exhuast out of the pipe as fast as you can. Sizing an exahust relative to power output will ensure you will not lose certian concepts behind sizing a system. Going too big will reduce flow because you are not utilizing its potential volume. The exhaust will expand to a maximum volume less than than what a large pipe has. This will in turn kill the velocity of the flow and most likely will cool it down more than you want. You will create nothing more than a large plenum that is filled with inactive and cooled exhaust. You take any advantage that a properly sized system offers and you throw it in the trash. The pumping loses of the motor could actually increase (data would have to be collected to validate this though) due to the large gaps in the exhaust pulses that would most likely occur. The more air you can get your motor to pump the less losses you will see in a system that big. You would need an insane amount of power to make a 6" exhaust perform the way an exhuast system should.

The reason why you see L98, LT1 and LS1 cars gain so much power with an exhaust epgrade is because of the restrictive nature of the stock exhaust systems. It is wasted displacement for the most part. So even if you see gains with a 4" system it doesn't mean that was your best choice. It only means that the system you chose was better than stock. The stock exhausts on these cars constipate the motor so bad that going too big still yield power gains.

 

I think that's what it comes down to: Stock sucks and just about anything else will perform better. I am all for empirical evidence, but until someone gets the same engine on a dyno on the same day and tests all the different exhaust sizes, all we have to go on is theory and theory tells us that a 5"-6" exhaust would kill low end torque -- best case scenario.

 

Car company's just don't guess at what size exhaust to put on cars. They size it to meet certain desing criteria. Math takes away the geuss work. There are certian things you don't need to test to see if they won't work. Period. Go on the net or get a text book and do the math yourself. Find out how much potential flow a 6" pipe has and then determin how much flow your engine exhausts at peak power. An engine is an air pump and as as long as you know how much power it is making you know how much air it is flowing. If the two aren't close to each other than you have a mismatched combo. If you go too big you are wasting the usefull energry of the exhaust gasses and system.

 

having a s/c produceing 14.5 psi of boost would produce roughly twice the amount of exhaust as a na motor.

if a motor is compressing air to fill the cylinders, then it is putting more air in, and more fuel.

dont comment unless you have something helpful to say. please dont post misinformation like this.....

 

Shifty, I respect what you've done on this board for the most part, and you're an Ohio'an, so I will just say one thing and leave this thread...

Exhaust companies will build what sells and is the easiest to package and ship, not what is best for the car or application. But what a great line they have you repeating when they want to sell you a product that they have spend "X" hours testing on a dyno. Point in case : how many companies are selling 4 inch exhausts, DESPITE the fact that is DOES NOT kill low end power, but rather has shown to improve torque EVERYWHERE?

How many companies make long tube headers for our cars? 4, 5 maybe? How about true dual kits?

Too the author: "One test is worth a thousand expert opinions." From this thread (click me!) this post was taken:
Notice his peak numbers were HUGE jumps over a 3 inch system, and they occured AT LOWER rpm's!!! So much for big exhausts killing power. Air is not water!! Air does not have the weight and mass of fluid, therefore it will not slow down as quickly due to it's own weight! Yet, borla - flowmaster - hooker.... no 4 inch kits? Exhaust companies don't spend time doing whats best for you, they do what's most likely to flow off the shelf! (read, fly off the shelf) Theory can be shoved up the self righteous *** of whomever tries to get you to buy into the norm by shoving it down your throat, because "TESTS" are best.

 

I agree. There is no way they make an exhaust perfectly tailored for everyones cars. A 3" will suffice and perform well on engines making all sorts of power. It is a general system that fits many applications. We all know that. I was refering to stock set-ups being set-up with countless testing.

Air is a fluid by the way. It may have less mass than water but as long as it is not compressed its flow characteristcs are basically the same when compaired to a liquid. You can't use that argument here.

An L98 makes far more power than a stock 305 so I doubt you would see the same results with a 4" system on an LO3 and or LG4. That test only shows what is good for one engine type.

 

I went back and did more reading in that post that was linked about the power gains of a 4" over a previously installed 3" and I think we need to take a few things into consideration. If the dyno results were to be taken as such a muffler of similar desing should have been used on each test. The flowmaster muffler that he uses isn't the best flowing unit on the market. Had he put a different muffler on that 3" system I am sure he would have seen some quantifiable gain. In addtion he also did a few more things to his car and I quote

"with all this it made 260.2whp and 352wtq, with the muflex it made 271whp and 378wtq. these hp increases are not from one part alone, because somethings were done at the same time and then dynoed with 3 or 4 of the items installed."

Some of his gains could be attributed to the other mods he performed. Some of those gains could also be from the better muffler. It doesn't isolate the larger pipe size as the sole power increaser. Just something to consider.

 

as far as i know chevrolet actually did make a very small bigblock. it was about 360 cubic inches, and it was used in high torque low horsepower apps like the really large gasoline u-haul trucks. why anyone would scavenge, supercharge, and install in anything besides a tar-pit would be anyone's guess.......ah...just found a link.....check the specs on this sweet ride..

http://trucksales.uhaul.com/gmc_c6000.asp

 

You're stupid.

I ran mid 11's on a 3" exhaust. Also keep in mind that the exhaust at the rear of the car doesn't have to be as big as the exhaust at the front of the car. The gases cool as they move further away from the headers ... which means you can run smaller pipes with no ill effects. I had dual 3" pipes going into a single 3" pipe. Plenty of LT1 guys run this combo too. Easily good for mid 11's. Your 355 probably only runs 12's which means you don't even need that. 5" or 6" pipe. You're funny. n00b.

Tim

 

I would like to see the dyno charts of the before and after the Mufflex system was installed. I'm going to install a 3.50" mufflex system on my car and maybe I will do a before and after dyno run. I installed a 58mm throttle body and the car had to be retuned. Might be the same with the Mufflex system. I know I'm up to 231 grams/sec on the Data Master. Thats up a couple of notches over the 52MM throttle body. Allen

 

i was the person who installed the mufflex. shifty you are not correctly reading what i posted. i said the power increases were not from one part meaning the other modifications i did, not the mufflex. i was clear in that i said the power gain with the mufflex alone was 11whp and about 26wtq. that was with the only modification change being the mufflex.

unfourtunatly i didnt have a working printer on the post-mufflex dyno, and the records were lost when that dyno was sold.

 

Dude! If you want 6" exhaust then do it..dont let anyone talk you out of anything you want to try...It will decrease your performance...It will be very loud...it will be hard to do...But if its what you want then man go for it and if at that time YOU decide its not right for you then hey, you tried it, it didnt work but you had the ***** to try it anyway...and everyone thats bashing you can kiss your @ss and mine too for that matter...good luck and hope it works out for you

 

Just a side note. But i know several semi trucks that run a 6" exaust. Granted every semi i have ever seen is turbo charged. and perhaps the dual stack ones can run smaller dia exaust than single.

 

I just graduated high school so forgive me for playing nice.

"Twice as much air (compared to NA) so you need four times the amount of area in exhaust."

My recommendation is go for it then, after you realize that you were a fool and dyno tested it then buy some decent headers and complete 3", 3 1/2", 4" exhaust. Maybe you shouldn't even do round piping, go square.
Hell just lead some tubing to the chasis and then box and seal it against the unibody to the rear then put some huge semi truck tips on it.

This also means you need your induction to be atleast 6" too.

Actually the exhaust companies just want your money, they have lied. You don't ANY need exhaust. Just port the crap out of the exhaust ports and you are good to go

 

Oh you need the exaust. not so much for the engine although some sort of header is needed really, but for the fact you try running around with no exaust and you will spend more money paying tickets than you would just putting in a nice 3.5" or 4" exaust.

 

Thanks for the clear up. I thought you meant that your power gains were attributed to all the various stuff you added after your initial dyno run. How did the overall power curve compair between the two? Was the overall power curve higher or just around peak?

 

Plus, at least for me, a really loud exhaust makes me feel like I'm moving slower than I really am. A while ago, I was testing for an exhaust obstruction and removed everything from the hollowed cat & back. I got on the turnpike (away from other people) and hit the gas. I felt like I was barely moving and when I looked down at the speedometer, I was in the triple digits.

 

Id like to see you fit this under your car. Good Luck

Hve you taken a tape measure out latley and seen exactly how much 6 inches is?

Info On The Pic Below:

540 c.i BBC
10-71 Blower
12.4:1 CR
1,024 HP on 12 lb/s Boost w/Pump Gas

2.5" Primarys w/6" Dump ONLY FOR DYNO
Heres a Vid if you want to compare to your 355.
1024 Hp 540 Dyno Pull

 

Notice that the primarys are bigger/same than most peoples full exhaust.

 

wow, thats amazing

 

Go 6" so in the future some bigger fool will show you up with 8", 10", or 12"....
The next "Fast and Furrious" movie will explain to have your exhaust the same size as your subs.

 

It appears that the general consensus is that unique is cool only when it is practical and improves performance and a six or five inch exhaust crosses the line between unique and foolish. I'd have to agree. Perhaps you can find some other way to be UNIQUE and COOL. Just keep in mind that the fur headliner's been done.