Dual or single exhaust for my 360 swap?

[KYJ10]

I am wondering which way to go? I have access to a single 3" inlet/duel 2.5 outlet flowmaster, if I Y pipe from my headers, and run a single 3" pipe. Also have access to two regular single inlet/outlet flowmasters, if I decide to go dual. I figure with the 360engine,456 gears,T18-208 combo, I should have a ton of low end power when wheeling. So im thinking of going dual for more road power. What does everyone think and or what r u running and why? Thanks Dennis

[porkchop]

Go to the archives. There are a few topics on this. Also do a serch, you will be surprised. This is one of the biggest debates on here :D .

[porkchop]

Try this one http://www.ifsja.org/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=2;t=007790

[River Beast]

I have dual 2.25" right now with headers...I have made the choice of "Y" pipe and 2.5" single.

I have lost too much low end torque.... this is my choice after everything I have gone thru... the glass packs do NOTHING but hinder exhaust flow in the worst way but they were almost free and I needed exhaust.

Go single 2.5" for better low end... I have 4.89's with my 38's and I still want /need more low end torque

[Jerk]

glasspacks hinder flow? dude they're a strait shot through the pipe! how can that be a hinderance to flow?? you guys smoke too much wacky-weed here!

[ September 10, 2002, 10:18 AM: Message edited by: Matt W ]

[Rogue]

yea what riverbeast said, y-pipe allows the negative exhaust pulse wave of opposing cylinder to help scavenge its running mate's cylinder on the exhaust/overlap stroke, this in turn increases efficiency.........im sure you can figure it out from there

[Crazy_Jeepman]

glass packs do NOTHING but hinder exhaust flowPower robbing Junk there now. :eek: Only thing nice about glass packs is they do not get ripped off the rig as easy!!! :D

[Jerk]

I want some of you to try something regarding "real world" PROOF of small diameter pipe vs. large diameter pipe being good for power.
Get a 3/8" diameter by 8" long straw. Take a deep breath and blow through it as hard as you can. Now take a 1/4" by 8" straw and do the same thing. Now get a coffee stirrer, roughly 1/8" by 8" and do the same thing. which one is harder to blow through??????? now apply this DIRECTLY to the piston up stroke on the exhaust cycle. If the piston is using alot of its power( provided by the power stroke of a different piston) to push the exhaust out of restrictive pipes, how much surplus power is going to be available to spin the crank and produce "torque" and the "torque" at rpm (or a measuerd time interval) being horsepower? the answer is : not as much as their could be with low restriction/ open pipes/ large diameter pipes. The I.C. engine is an air pump, the quicker and more efficiently it can move the air the more surplus power is generated to motivate machinery. see the light?

[Crazy_Jeepman]

I think this subject has been beaten to DEATH!! LOL, I will run the pipes that Have proven performance. You can blow through the Straws!! There is more to it than just unrestricted flow.

[Jerk]

as far as y pipe scavenging anything, its not really making a big difference, if you run duels with an X or H pipe, then you'll get more scavenging, but 5 hp is a pretty pathetic return for the hassel of trying to figure out were to put X pipe on one of our rigs and have it live for more than 2 years.

[Jerk]

no there isn't. it all comes down to parasitic load.

[Sundowner]

actually,
it comes down to what I can get off the shelf at the local Napa:
"Hi Chris, I need more FSJ parts, got a Y pipe?"
"sure Rich, add it to your tab?"

[River Beast]

I have run single and dual....single has more low end torque.... duals have more high end power. I made the mistake of switching to dual and learned from realy world experience.... sure the pick up on the open road is GREAT with duals.... but that low end grunt is GONE!!! I'm going back to single...

As for Glasspacks... they are NOT straight thru... ever look on the inside? they have 'fins' that catch the exhaust and cause MASSIVE amounts of turblant air. No room for expansion either...

you talk straws, I 'll talk bottles.... fill 2 bottles of water... turn them upside down simultaneouly... swirl one to get a funnel effect in the water and hold the other steady... which one is free-flowing and empties quicker? You just answered the glasspack dilema... ;)

[KYJ10]

OK, so I guess most would go with single. The headers have 2.5" reducers on the ends, so I guess I'll get a Y pipe made and run a single 3" to my 3" inlet flowmaster and it has dual 2.5" outlets so I'll run them. Sound good? Thanks Dennis

[dnixon]

Originally posted by River Beast:
I have run single and dual....single has more low end torque.... duals have more high end power. I made the mistake of switching to dual and learned from realy world experience.... sure the pick up on the open road is GREAT with duals.... but that low end grunt is GONE!!! I'm going back to single...

As for Glasspacks... they are NOT straight thru... ever look on the inside? they have 'fins' that catch the exhaust and cause MASSIVE amounts of turblant air. No room for expansion either...

you talk straws, I 'll talk bottles.... fill 2 bottles of water... turn them upside down simultaneouly... swirl one to get a funnel effect in the water and hold the other steady... which one is free-flowing and empties quicker? You just answered the glasspack dilema... ;) ooooooo... bottles or straws... is the glass half empty or half full... i think i am leaning towards the bottles argument.. think of it like this if the glasspack was a straight shot then why would you have them on there?? It wouldn't muffle anything and it would be just a fancy piece of straight pipe. Therefore you know there is exhaust going through those fins and it is causeing turbulance to muffle the sound. Its all about disturbing the sound and sound has to travel through a medium and if that medium is restricted so will that sound.. this is just my thinking... (I don't know if that makes sense or not but I just finished a quater of physics dealing with sound and i just wanted to try to apply something i learned..haha)

[Chero77]

The way I understand it is that anything you do to improve breathing improves efficiency and thus increases both horsepower and torque. So if you go with dual pipes you will get more horsepower and more torque, BUT, the rpm range at which peak power and torque occur will be shifted upwards. If run really big dual pipes this shift will be enough to notice. Now, if you have a manual transmission, no big deal, you will just naturally shift at higher rpm where you feel the power. However, if you have an automatic you have a problem, the auto still has the stock shift points which are now to low to take advantage of the increased power and torque. In fact, at the stock shift points, torque may be less than with the old exhaust. Its not that torque has actually decreased with the big exhuast, its actually greater but its a few hundred rpms higher in the range than the stock auto will shift at. So one needs to get a shift kit and move the autos shift points upwards.

As I see it the only other thing that could happen is if you went to something like 3" dual pipes in which case the flow capacity of the stock 4-barrel will probably be exceeded and you will end up with a real dog of an engine until you get a bigger carb.

All of the above being said, most of us have low output smog motors and a 3" single pipe or a 2.25 dual set up is just about all the exhuast we can use. Also, a straight 2.5" pipe will flow 600 cfm, about the max a stock motor would need. So if you ran a straight 2.5" pipe into the muffler and a 3" pipe over the axle, you should be fine.

[River Beast]

Right the HP/Torque curve is adjusted into a higher rpm range..... therefore you don't have the same torque on bottom end with duals as you would with a single....

[FSJeeper]

It is not just one component that makes an engine run better, it is the matching of components. Most people over cam. A lot of people over carburate. And still more put headers and large exhaust tubing and kill lower rpm exhaust velocity and scavenging effect. You all know who you are.

It is the combination, not any one single item that make it run well.

Chrysler has a book out for modifying AMC engines with lots of proven combinations from mild to wild. These are all based on dyno work, not guessing. This book is worth a look at. Also the AMC guys have been documenting combos for years.

Bottom line is you do not want larger diameter intake runners cause they kill intake velocity at lower rpms and thus torque. You do not want large primaries on your carb for the same reason. That is why the Qjet is considered the best off road carb, it has the smallest primaries for best low rpm intake velocity of ANY carb. Large dia headers have the same effect. The cam needs to be from stock to mild or you move the power curves out of the useful range for four wheeling.

These highly scientific straw and bottle tests are hard to compete with, but I have one. Cut 1 straw in half. Put both straws in your mouth and blow. Try to remember how it easy flowed. Now, restrict one straw 50% buy placing your finger over half the end. Blow. Feel the noticable back pressure and restriction? For you guys running the factory log type and header type pairs of manifolds, your engine is using your power to compensate for the poor flow coming from the log type manifold. The engine is fighting itself with unbalanced flow from both banks of cylinders. First mod you guys should do is fix this! Any other power mods you make to the engine just make this problem worse.

[Gladi8r]

I just want to know one thing... Do I pour the water directly into the mufflers or use a straw?? :D :D

[Rogue]

there is absolutely no doubt that a larger pipe will flow more volume but at a lower velocity - thus the loss of low end torque, forget it i'm not even gonna try but i will say this I have in my possesion and have read countless times in HOT ROD magazine with DYNO tests that they proved on a DYNO a single 3" y'd exhaust with 3 - 5 lbs of backpressure made more horsepower than a dual system period. to achieve the piston speed and airflow demand that a dual 2.5 exhaust would require is going to require an engine spinning in excess of 6,000 rpm

[porkchop]

What if you take the straw and suck up the water from the bottle and then blow the water out facing up hill on a windy day in June?

All this shadetree mechanics is making my head swim :D . Does anyone here work on engines and exhuast as a profession? Duals have there place and A single pipe has it's place. It all depends on what you do. If you mud bog are you going to want low end torq or torq at higher RPM's? See my point?

[River Beast]

Where is VEEPSTER WHEN YOU NEED HIM!?!?!? HE's got the Dyno!!!!

EVERYBODY>>>>> LET's GO TO OCEANSIDE ,Calif and invade Veepster's shop!!!! :D

[243]

All the "reported" blowing and sucking has the hair on the back of my neck standing straight up :D

What fins are ya'll referring too? Every glasspack I've seen has a perforated core wrapped with glass with that assembly encased in another steel tube.

[Damage, Inc.]

Bottom line is duals will flow better, providing better high-end response.
A single exhaust with a y-pipe provides two things; scavenging and increased back pressure. Back pressure is *CRITICAL* for low-end response. Let me go ahead and say that again...back pressure is critical for low-end response. There is, of course, a fine line between good and bad back pressure!

Proof? Take a HD exhaust. The SuperTrapp exhaust has a stack of baffle plates that can be removed to fine tune the exhaust's back pressure for maximum performance.
More Proof? When porting heads, the efficiency between the intake and exhaust doesn't even remotely have to be equal; 75% is MORE than enough. That's why exhaust valves are so much smaller in diameter.

Personally, RB, I wouldn't go back to a single exhaust. A dual with smaller dia tubing would work just as well. Forget the scavenging effect...I doubt that the way AMC's y-pipe is shaped that one gets much benefit from this.

[Stangerize]

Originally posted by dnixon:
</font><blockquote>quote:</font><hr />Originally posted by River Beast:
I have run single and dual....single has more low end torque.... duals have more high end power. I made the mistake of switching to dual and learned from realy world experience.... sure the pick up on the open road is GREAT with duals.... but that low end grunt is GONE!!! I'm going back to single...

As for Glasspacks... they are NOT straight thru... ever look on the inside? they have 'fins' that catch the exhaust and cause MASSIVE amounts of turblant air. No room for expansion either...

you talk straws, I 'll talk bottles.... fill 2 bottles of water... turn them upside down simultaneouly... swirl one to get a funnel effect in the water and hold the other steady... which one is free-flowing and empties quicker? You just answered the glasspack dilema... ;) ooooooo... bottles or straws... is the glass half empty or half full... i think i am leaning towards the bottles argument.. think of it like this if the glasspack was a straight shot then why would you have them on there?? It wouldn't muffle anything and it would be just a fancy piece of straight pipe. Therefore you know there is exhaust going through those fins and it is causeing turbulance to muffle the sound. Its all about disturbing the sound and sound has to travel through a medium and if that medium is restricted so will that sound.. this is just my thinking... (I don't know if that makes sense or not but I just finished a quater of physics dealing with sound and i just wanted to try to apply something i learned..haha)</font>[/QUOTE]I used to work for a company that had a line of "mufflers" so to speak for turbine engines used in industrial applications. They were straight through just as glass packs are and lined with "fiberglass" insulation. Hence the term "glass". Now the mufflers we made were about 8'x8' and not only were they lined but they had internal panels approx. 8" wide filled with dense fiberglass insulation as well.

The sound deadening came from the fact that sound waves do not pass in a straight line but in waves. The waves would die out or muffle into the insulation. That's what a sound proof room is also, a well insulated room.

[Jerk]

would any of you mind explaining to me how exhaust forced out of a smaller pipe at higher pressure is increasing torque at a low rpm and slower moving exhaust being forced out under lower pressure is going to kill torque. I'd really like to hear how fast, high pressure exhaust is making me more torque.

I would also like to say, yes, I have looked through a glasspack. I just put one on and believe it or not, it had no restriction in diameter all the way through. it was the same ****ing internal diameter as the inlet and outlet. The "screen" material has holes in it to act as sound baffles, it isn't supposed to allow exhaust to flow into and around it to magically come out quieter. its to trap and muffle sound waves. all mufflers are designed to do this, not just alter flow. all of them do alter flow,that's pretty unavoidable, but the overall intent is quiet the gasses. oh and by the way, if the fiberglass is rotted out or burned out, the glass packs running around here in Redneck-ville, Wyoming sound amazingly loud and just like strait pipes. hm, imagine that.

thirdly, the straw is a perfectly scientific experiment, meant to show that the AIRFLOW going through the different diameter straws is restricted every time you go smaller causing you to exert MORE power to blow the SAME amount of volume through it. if its harder to blow through the small one and easier to blow through the big one, simple logic (which apparently is in extreme short supply around here!) would dictate the big one needs less parasitic load (muscle effort) on a piston (your diaphragm) to empty a cylinder (your lungs) of waste gasses. Those that scoff, obviously are afraid a simple straw might disprove their "old wives tales" about stinking tiny pipes making huge lowend torque.

Let's try this, the higher rpm you have a torque rating at, the higher horsepower you will have. torque and horsepower are limited by the amount of air the engine can move efficiently and at the same time spin the crankshaft with whatever power is left over from pumping the air into and out of the engine. Now, horsepower is present at any rpm, from less than 1rpm to beyond 5,000. try to differentiate the difference between "torque" and horsepower" when you are driving. ITS ALL THE SAME- POWER. if the vehicle moves, then it has power, if it moves fast it has more power, if it can get to moving fast very quickly it has even more power. its as simple as that. you people, and YOU know who you are, that think torque and horsepower are 2 different things in an I.C. engine are being misled. torque is the measurement of physical power needed or exerted to move an object once. horsepower is the measurement of how many times that work can be done in a certain amount of time. you can't have horsepower without torque in the formula. so instead of whining about your puny lowend torque numbers with your new bigger pipe, why don't you try looking at the whole picture and actually findout what in the formula is really out of balance. 44" tires and a weak 360 and high gears, matched with very little air at high elevation, yep, must be the pipe!
and since when does a larger door (exhaust system) demand that a larger person (increased exhaust flow) HAS to go through it. It is simply there when the need arises.

[Stangerize]

OK, the thing here is that everyone is right. In some applications a single exhaust will make more power and in others a dual setup will make more power. It boils down to "what fits your application". When you need more CFM to exit is when you have more CFM entering. An engine is like a big air pump, air in air out. When you have gobs of compression or a blower or nitrous, then you definitely have to increase your exhaust flow. A stock motor with a stock cam even will run just fine on a single exhaust. Depends on your app.

[Damage, Inc.]

Velocity = Torque. PERIOD.
Believe it or don't...

LOL....'quiet the gasses'...

[Big Daddy aka.redwoodsignman]

Just when I've finally made up my mind, I just have to read one more thread!!! I'm lost for sure maybe the next thread will help!

[Jerk]

LOL...Velocity = Torque. PERIOD.
Belive it or don't..."
nice reasoning, VERY scientific. lends one to believe your point of view just from pure authority. is it based on anything scientific you can explain here, or just your godlike "engineering" omniscience?...."Damage"?

[Big Daddy aka.redwoodsignman]

I just jumped in as a joke I didn't realize this was serious. I want out.

[Rogue]

Does anyone here work on engines and exhuast as a profession? ASE Master Technician, built more engines than I can count, spent 8 years of my life as a Late Model crew chief, anyone else ever build a 800 horsepower alcohol burning 358 cubic inch engine?

[Rogue]

and oh yea we used a merged exhaust with a single 4" pipe on the late model

[oddfire]

Dude, when I went to plumb my built 401 with exhaust, I took some time to talk to the local muffler guy. I wanted dual 3", cant beat the sound of duals on a strong v8, but the muffler guy sold me on a single 3". He said the same thing that has been said here, for low end torque you need adaquate back pressure or you will lose the bottom end torque. Now since my cherokee is built for trails and low rpm grunt,it barly saw 1500 rpm on any of the trails at Ouray, even at 13,114 ft,I chose to go with the wisdom of the lowly muffler man and have not regreted it.It is what he does for a living after all...phil

[River Beast]

Originally posted by Matt W:
would any of you mind explaining to me how exhaust forced out of a smaller pipe at higher pressure is increasing torque at a low rpm and slower moving exhaust being forced out under lower pressure is going to kill torque. I'd really like to hear how fast, high pressure exhaust is making me more torque.Go to a dyno shop....ask them.. they will show you...If you NEED ALL your torque on the bottom...say 1500rpms or lower.... go with a single... the HP/torque curves are lower on the graph...

Use the same motor and LARGE duals and at 1500 rpms... you are NOWHERE NEAR the maximum torque output of the motor...therfore you have 'lost' your torque

When I said LOST my bottom end.. it's a figure of speech... I KNOW I didn't 'LOSE' it... it's just MOVE to where I don't NEED/WANT it.

IF you set up your 4x4 correctly, I 100% agree...nothing would be lost....

I hope you weren't referring to me as having a wrong setup...as I said in the past(maybe not in this thread).. I KNOW I have the wrong cam for what I do and the dual exhaust I have(somewhat)enhance the performance of the installed cam... but it's all TOP END. As for the rest of my setup...I am set just right for gears/tires.

***Let's remember that these debates are for all to learn, share experience, and get ideas...not to get upset and frustrated...its all a learning process....let's not get crazy****

[Crazy_Jeepman]

Way to funny, how some people get their Pipes Bent out of Shape on this Subject. Several FACTS were made about how torque is created, Velocity and Back Pressure, Smaller Valves. Only way to get that is a restrictive system. I can say I have never run a rig on a Dyno nor have I blew into straws or emptied bottles of water. Ever watch how the exhaust exits a Dual System in the Cold Weather? PUFF PUFF quite possibley with Smoke rings even. Single Pipe just long steady stream.... Wonder what system has the velocity in this comparrison? Big Torque monster engines had several things in common large CC heads Small Valves and restrictive systems. Torque developed through the use of HIGH RPMS and Torque Developed with Low off idle RPM would require two different systems in my way of thinking, both would require Velocity and back pressure. I believe it depends on where your engines operating range will be. If you are going to run it below 5000 RPM the single system will provide the needed back pressure and velocity. If you are running in excess of 5000 RPM well then I guess duals may be the way to go, maybe. Doubt I would but maybe. If someone wants to run Dauls over singles...So be it. Who really cares. Just get the tail pipe(s) to the rear of the rig so you do not kill yourself :D

[Big Daddy aka.redwoodsignman]

OK now that everyone seems peaceable can you single system sound good I don't want to break windows but I would like to turn a head or two?

[River Beast]

Originally posted by Big Daddy aka.redwoodsignman:
OK now that everyone seems peaceable can you single system sound good I don't want to break windows but I would like to turn a head or two?Yeah you can...a good flowing muffler such as the Flowmaster Delta Flow and Dynomax Super Turbo can give you a suttle mean sounding single exhaust..that's just to name two... ;)

[Damage, Inc.]

Oh, and for the record, I've ran 2100 hp blown alcohol motors on the dyno. I spent 3 years working for SuperFlow, the best engine and chassis dyno ever made.
SuperFlow's customers include Vance & Hines, Edelbrock, HD, D&D Exhaust, CompCams, Ernie Elliot, Inc., Yates Racing, Bosch, Polaris, etc. These are ALL customers I've worked with and whose shops I've been to and worked at.
smile.gif

[redwilly]

I like the low end torque of the y pipe and the fact that theres half as much shiat to get torn off on rocks, trees, and small passenger cars.

[Panoscopic]

Matts missing the point. Exhaust tuning is affected by multiple dynamics of sound waves and venturi effect of the gas from the other cylinders. Exhaust tuning for your power band is complex and not limited to just providing unrestricted flow.

Now, its off topic, but is really interesting is the exhaust dynamics of two-stroke engines....tuning them a black art if there ever was one.

Check out this cool animated gif at the bottom to see what I mean...

http://w3.one.net/~jschust/animations.html

[Crazy_Jeepman]

Panoscopic that is great!! LOL :D :D Here is the Animation ;)
http://w3.one.net/~jschust/two-stroke_c.gif

[Panoscopic]

I just loooooove two stroke motorcycle engines!

The smell, explosive power bands, and yes...

rrrrring ding ding ding ding......

[Chero77]

Matt W. is pretty much right on the money with his analysis. Better breathing equals more horsepower and more torque. The tradeoff is that the torque and horsepower curves shift upwards in the rpm range. With a manual transmission or a properly setup automatic this is not a problem, whatever your application.

A simple example will explain the situation. If you look at a stock 401, the torque peak is 320 ft-lbs at 2800 rpm. That's acheived with a 2 1/4 single pipe. Now lets say you decrease the pipe diameter to a 1.75" single pipe. What happens, well the obvious, peak torque will DECREASE, but what little peak torque you have will occur at a lower rpm, maybe at 2400 or thereabouts. Now what happens if you go to a 3" single pipe, well again the obvious. Peak torque will INCREASE, albeit it will now occur at a higher rpm, possibly 3200 or thereabouts. To get actual numbers one would have to run the different systems on a dyno, but I think we all get the point.

By the way, whether its a single or dual system doesn't really matter, its the flow area that counts. I.e., a 3" single pipe has about the same flow area as 2.25 dual system. The exact numbers are 7.06 square inches for the 3" single and 7.95 square inches for the dual 2.25 system. One caveat, a single pipe is little more efficient than a dual system with the same flow area.

The fact is that we have very heavy beasts which are very underpowered by modern standards. We need all the power we can get.

[ColeTrickle]

Dag'gum guys, I stopped reading after the first page!
How 'bout just good 'ole resonating sound...the sound of a good 'ole fashion V-8.
Why so technical?

[tuckers89GW]

i don't know about you guys, I'm getting a headache just reading this post. smile.gif

[Jerk]

Originally posted by Crazy_Jeepman:
...I can say I have never run a rig on a Dyno nor have I blew into straws or emptied bottles of water. Ever watch how the exhaust exits a Dual System in the Cold Weather?

(yep, and this don't happen, it comes out in big clouds and is moving pretty fast itself!)

PUFF PUFF quite possibley with Smoke rings even.(Hah! never seen smoke rings coming out of my jeep!)

Single Pipe just long steady stream.... Wonder what system has the velocity in this comparrison?

(in your little "comparison" here? OBVIOUSLY the small pipes, they have to have more pressure for the same amount of x-haust gas volume! that's a no-brainer, MY point is if you open the pipe, you can have MORE gas volume flow without overpressuring the x-haust system.
If "Back Pressure" = pressure pushing against the piston in its exhaust stroke. Then you definately want less back pressure. THIS IS WHY!: The power stroke of another piston is causing the x-haust stroke of the piston that has the x-haust gas pressure against it. DO YOU SEE THIS? more energy/power generated by the combusting fuel/air and driving that piston down the cylinder, used to push out waste gas is energy/power not available/surplus to provide power to the wheels.)

Big Torque monster engines had several things in common large CC heads Small Valves and restrictive systems.

(like the 426 hemi, 440 dodge, 454 chevy? I'd say they made pretty **** good torque AND HP, they did not have little valves and exhaust!)

Torque developed through the use of HIGH RPMS and Torque Developed with Low off idle RPM would require two different systems in my way of thinking, both would require Velocity and back pressure.

(not true. how much torque do top fuelers make? enough to not be dyno'd w/out breaking the dyno! they don't have little valves or small exhaust. and they make huge amounts of idle torque AND high rpm Torque)


I believe it depends on where your engines operating range will be. If you are going to run it below 5000 RPM the single system will provide the needed back pressure and velocity. If you are running in excess of 5000 RPM well then I guess duals may be the way to go, maybe.

(The engine's power band can be tuned wider so you get low rpm power, what every on calls torque, and high rpm power, what everyone calls horsepower, by tuning the intake side to the low to high rpm band and the exhaust to the mid to high rpm side. this is pretty common on rigs these days were the owner of the vehicle/engine doesn't want all their power to occur all below 3000 rpm or all above 3000 rpm. This allows power to be less peaky and more broad and flat, from 1500 to 5000 rpm. My engine is set up like this, no single-plane highrise and 850 cfm carb are sitting on my engine, nor is there a huge lumpy cam that makes power only above 3000 rpm. I have a highrise duel plane, with a 600 cfm carb with smaller primaries and bigger secondaries, and a 1500 to 5000 rpm cam with 204*/214* duration @ .050" lift and .448"/.472" lift. This motor gets around pretty well and if I put it in lowrange it idles up hills with 3.73:1 axles, 2.48:1 1st gear and 2.56:1 lowrange with 32" tires in a 5100 lb truck. AND yes I do have hedmans and duel 2.5" short pipe running into "Turbo" mufflers. Obviously I don't have huge low rpm torque, but I also don't have 500 cubic inches. If I did though, I'd put the same setup on it. I can beat the mid to late 90's 454 chevy 3/4 ton trucks off the line and they have more cubes than I do!)



[ September 11, 2002, 10:48 AM: Message edited by: Matt W ]

[sandmanb]

ky j-10, what did you start here? if this is my fault for sugesting you take this to the board i'm sorry. buy the way, what have you decided on, or has your head exploded?

[Crazy_Jeepman]

UH HUH I see. Well I guess you are a professional exhaust annalist. I concede all my opinions to you amazing gospel on the subject. You go through great lengths to prove your opinions. I personally do not care what anyone decides to use for an exaughst system, or for what reasons. However you do, so I will leave all the exaughst system advice to you. OK EVERYONE MATT IS RIGHT, HE HAS ALL THE DUCKS IN A ROW ON THIS!!!!!!
LOL Thanks for showing me the way.........Now where is my Y pipe and 3" pipe :D :D
ROTFLMAO WOW :D

[243]

Matt,

Have you every run your rig with "un-capped" headers?

[KYJ10]

Well, I was thinking of maybe running quadruple exahst! I might also run some straws and bottles of water. Yea, this is more info than I can sort through. I was hoping there was one exact answer, but I see differenlty. I think Im going with the Y pipe and use you flowmaster. Pulled engine last night and hopefully will get the tranny stuff out today. Dennis

[Jerk]

243, I ran the j20 with headers and no pipe once. It was for 8 miles on the way to the exhaust shop. I didn't rev it above 2000 rpm (which was around 50 mph or so) for fear of the cab glass exploding. It was loud!
I have started the Cher, with stock manifolds and stock Y pipe and no cat/muffler/tailpipe. it wasn't all that loud, but it did stink somewhat. I just welded the 24" glasspack on and kept it like that, mellow and sorta loud but not bad at all- My wife loves the rig! Why do you ask?

[Jerk]

Originally posted by KYJ10:
Well, I was thinking of maybe running quadruple exahst! DennisI wanted to do a Cobra Daytona Coupe setup for a while, just for kicks. its got 4 into 2 headers and twin sidepipes on each side of the car. So I guess that would be quadruple exhaust. Hey, it worked for them. they even beat the 427 GT40s with their little 289s. All high rpm power and and great handling versus the ford's bigger high end AND lowend power and looser handling. Go figure, maybe torque isn't the only answer. Got any lame opinions on this, "Crazy"?

[Nagy]

I don't mean to stir this up any more but what effect would adding a free flowing Cat do to this scenario? Assuming a single 3" exhaust, would it be better to run with or without the cat?

[Damage, Inc.]

Top fuellers DO NOT have gobs of low-idle torque. They have NO torque at low idle. They're designed for WOT action, only.

Tell you what...you go ahead and cruise that high-torque, low-idle TF around town. If you can do it, I'll buy you one. ****, man. Some of the stuff you say is partially correct, but somewhere, you've been lead wrong.

It's not for me to tell you. Go pick up a book. Then come back and apologize to everyone.

[Jerk]

OF COURSE they're set up to run at W.O.T.! They ain't gonna go 0 to 350 mph in 4.5 seconds in a 1/4 mile by idling! It's an acceleration thing, you go as quickly as you possibly can! The point is they don't run cast iron manifolds and 2" single exhaust and I don't think they are suffering from it! they still have more torque at low rpm than anything you or I drive- 401, 340 or 440!

[Damage, Inc.]

Ummm...okay.

Anyone else want to try? I'm done....

[FSJeeper]

ROTFLMOA!

[bvibert]

Room spinning..... eyes burning.... to much... must stop reading post..

All I know is I love how my duel exhaust sounds :D

[River Beast]

LMAO!!!

[jeepstruck]

I just did a 258 to 360 swap on my 1980 J-10. I have headman headers with duel exaust all the way out. Duel high-flow cat's and turbo mufflers. It sounds great!! Go with the duels.

[River Beast]

Originally posted by CT FSJ Fan:
Room spinning..... eyes burning.... to much... must stop reading post..

All I know is I love how my duel exhaust sounds :D ME too... but I can't find my torque in 4 lo... SOMETHING STOLE IT!!!! :D ;) Or 'MAYBE' I misplaced it HIGHER on the graph...hmmmm

[ September 11, 2002, 01:26 PM: Message edited by: River Beast ]

[J20fan]

Ummm...okay. Anyone else want to try? I'm done....
Blah,Blah, Blah........As the piston approaches top dead center, the spark plug fires igniting a fireball just as the piston rocks over into the power stroke. The piston transfers the energy of the expanding gases to the crankshaft as the exhaust valve starts to open in the last part of the power stroke. The gas pressure is still high (70 to 90 p.s.i.) causing a rapid escape of the gases (blowdown). A pressure wave is generated as the valve continues to open. Gases can flow at an average speed of over 350 ft/sec, but the pressure wave travels at the speed of sound (and is dependent on gas temperature). Expanding exhaust gases rush into the port and down the primary header pipe. At the end of the pipe, the gases and waves converge at the collector. In the collector, the gases expand quickly as the waves propagate into all of the available orifices including the other primary tubes. The gases and some of the wave energy flow into the collector outlet and out the tail pipe.

Based on the above visualization, two basic phenomenon are at work in the exhaust system: gas particle movement and pressure wave activity. The absolute pressure differential between the cylinder and the atmosphere determines gas particle speed. As the gases travel down the pipe and expand, the speed decreases. The pressure waves, on the other hand, base their speed on the speed of sound. While the wave speed also decreases as they travel down the pipe due to gas cooling, the speed will increase again as the wave is reflected back up the pipe towards the cylinder. At all times, the speed of the wave action is much greater than the speed of the gas particles. Waves behave much differently than gas particles when a junction is encountered in the pipe. When two or more pipes come together, as in a collector for example, the waves travel into all of the available pipes - backwards as well as forwards. Waves are also reflected back up the original pipe, but with a negative pressure. The strength of the wave reflection is based on the area change compared to the area of the originating pipe.

This reflecting, negative pulse energy is the basis of wave action tuning. The basic idea is to time the negative wave pulse reflection to coincide with the period of overlap - this low pressure helps to pull in a fresh intake charge as the intake valve is opening and helps to remove the residual exhaust gases before the exhaust valve closes. Typically this phenomenon is controlled by the length of the primary header pipe. Due to the 'critical timing' aspect of this tuning technique, there may be parts of the power curve where more harm than good is done.

Gas speed is a double edged sword as well, too much gas speed indicates that that the system may be too restrictive hurting top end power, while too little gas speed tends to make the power curve excessively 'peaky' hurting low end torque. Larger diameter tubes allow the gases to expand; this cools the gases, slowing down both the gases and the waves.

Exhaust system design is a balancing act between all of these complex events and their timing. Even with the best compromise of exhaust pipe diameter and length, the collector outlet sizing can make or break the best design. The bottom line on any exhaust system design is to create the best, most useful power curve. All theory aside, the final judgement is how the engine likes the exhaust tuning...............and furthermore......Blah,Blah, Blah,

Use what works for you and what you like :D :D :D :D :D :D

[ September 11, 2002, 01:31 PM: Message edited by: J20fan ]

[bvibert]

Originally posted by River Beast:
</font><blockquote>quote:</font><hr />Originally posted by CT FSJ Fan:
Room spinning..... eyes burning.... to much... must stop reading post..

All I know is I love how my duel exhaust sounds :D ME too... but I can't find my torque in 4 lo... SOMETHING STOLE IT!!!! :D ;) Or 'MAYBE' I misplaced it HIGHER on the graph...hmmmm</font>[/QUOTE]Thats funny, I can't find my 4 lo... must be an epidemic or something ;)

...nevermind I found it :D just have to climb uner the truck to turn it on...

[tuckers89GW]

Just to add fuel to the fire

http://www.modernmusclecars.net/articles/exhaustdynamics.html

[FSJeeper]

So does that mean we can forget about a top fuel engine that does 350 MPH in 4.5 seconds but with the rock crawling off idle torque of a 440?

[porkchop]

ME too... but I can't find my torque in 4 lo... SOMETHING STOLE IT!!!! Or 'MAYBE' I misplaced it HIGHER on the graph...hmmmm
It was mostly altitude. Have you tried the 4 lo since you have been home? I rode with Mike and he had the pedal all the way down and he didn't seem to have much power, but it was due to the altitude and the vapor lock.

[River Beast]

Originally posted by porkchop:
</font><blockquote>quote:</font><hr />ME too... but I can't find my torque in 4 lo... SOMETHING STOLE IT!!!! Or 'MAYBE' I misplaced it HIGHER on the graph...hmmmm
It was mostly altitude. Have you tried the 4 lo since you have been home? I rode with Mike and he had the pedal all the way down and he didn't seem to have much power, but it was due to the altitude and the vapor lock.</font>[/QUOTE]Yes I have... and I can remember MUCH more pull from before my duals... even without my front shaft... ;) I understand about the altitude...but I want more low end that I have... I want it back!!!

[ September 11, 2002, 02:34 PM: Message edited by: River Beast ]

[porkchop]

OK just checking, but before the duals you were also running with 33's and the 3.54 gears. Correct? If I can remember correctly you didn't get the duals on until after the Bronco tank. And the bronco tank didn't go on until after the shackle flip. At that time you put on 39.5's. The wag set for about 10 months before you drove it. I am going from Memory.

So this now breaks into the weight to power thread.

Does it matter if you have a dual with a 4bbl or a 2bbl? I am wonder where that comes into play with this whole torq thing.

[ September 11, 2002, 02:37 PM: Message edited by: porkchop ]

[Rogue]

Originally posted by Crazy_Jeepman:
UH HUH I see. Well I guess you are a professional exhaust annalist. I concede all my opinions to you amazing gospel on the subject. You go through great lengths to prove your opinions. I personally do not care what anyone decides to use for an exaughst system, or for what reasons. However you do, so I will leave all the exaughst system advice to you. OK EVERYONE MATT IS RIGHT, HE HAS ALL THE DUCKS IN A ROW ON THIS!!!!!!
LOL Thanks for showing me the way.........Now where is my Y pipe and 3" pipe :D :D
ROTFLMAO WOW :D rotflmao !!! :D i'm no engineer just a mechanic repeating what i've been taught i find no love in argument i think the whole point was lost long ago

[River Beast]

Originally posted by porkchop:
OK just checking, but before the duals you were also running with 33's and the 3.54 gears. Correct? If I can remember correctly you didn't get the duals on until after the Bronco tank. And the bronco tank didn't go on until after the shackle flip. At that time you put on 39.5's. The wag set for about 10 months before you drove it. I am going from Memory.

So this now breaks into the weight to power thread.

Does it matter if you have a dual with a 4bbl or a 2bbl? I am wonder where that comes into play with this whole torq thing.I had dual with the OEM tank but just before the
SOA and ran straight pipe... the loss was felt then but I thought nothing of it due to not having mufflers.... I just wanted duals!!! what was I thinking!!!... the main reasoning behind the duals was to unobstruct the front shaft.. the 'Y' pipe was in the way of the front shaft.... remember?

[Big Daddy aka.redwoodsignman]

Some of you out there are taking all the fun out of the purchase exhaust stuff! How's that for technical?

[tuckers89GW]

hey big daddy, I think your jeep is on fire. smile.gif

[Big Daddy aka.redwoodsignman]

That's why I keep reading this thread, I'm thinkin' I'm running a little rich with a single exhaust and blowed up cat and muffler. besides the floor pan is a little warm. will duals cool my floor pan or should I just run in reverse?
hehehehe

[FSJ Thing]

I think I'll just lift the p*$$ out of my wag and leave the engine alone until I convert to propane. Like FSJeeper says, it's the matching of components. You have to do it all at once to get to work, and 9 times out of ten, we ALL forget something and are out of money by the time we find it, leaving us with a 1/2 Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley rig with lots of mods to brag about but nothing to back it up with exept "next I'm gonna"s. I figure I'll just leave the engine stock and compensate with lower gearing for now. Who we got to impress anyway?

[tuckers89GW]

I say drive in reverse. at least you will scare the h#ll out of the people behind you, or is it in front..............

[Big Daddy aka.redwoodsignman]

Does anybody sell an adapter to turn the drivers seat and steering to face the rear. Thats goota be cheaper than some of those new fangled x or y pipes, and then I can just use what i have.

[Ernzo]

INteresting link
http://web.tampabay.rr.com/redroby/3liter/exhaust.html

[FSJ Thing]

YOU CAN DO EET!!!

[Jerk]

RB, did you tune the carb when you added the duels? this will make a difference. I think your case is like a whole bunch of little problems adding up into a big problem. and remember for every 1000ft elevation over sea level you lose like 3.5% of your power due to less air in the at-mos-fear. I'm at 4400 feet above sea level, and 14% drop in power from what I'd have if I were tuned/driving at sea level. :(

[River Beast]

Yeah.. carb is tuned with duals and re-tuned upon arrival to Ouray...I wheel here locally as well... on step inclines it's still not what I want... I have ALOT of wieght

I'm holding off on modding the exhaust for now anyway... the 360 is prolly going away anyway... so I can deal with the exhaust issues later.

[krob725]

Get the diesel!

krob725 :D

[RamJetFSJ]

Wait, Todd, the 360 is going away anyway??? What will be replacing it I might ask??? smile.gif smile.gif

Ben

[kjax]

Todd said:

"I have dual 2.25" right now with headers...I have made the choice of "Y" pipe and 2.5" single.

I have lost too much low end torque.... this is my choice after everything I have gone thru... the glass packs do NOTHING but hinder exhaust flow in the worst way but they were almost free and I needed exhaust."

The glass packs should be working to your favor, then, if you are sure that the less restrictive exhaust has shifted your torque curve too far up the rpm band.

Ya know, for all you guys that are sure your less restrictive exhaust systems are killing your bottom end performance, you could always just add some restriction back in. It's a real popular fix for two stroke sleds that come from the factory set up more for sea level than the mountains. Simply add a restrictor to the end of your pipes. Should make figuring out if your pipes are too big or not easy.

[ October 06, 2003, 01:59 AM: Message edited by: kjax ]