Any benefit besides sound?

[fitn217]

Hey guys....I'm new here.....great site.....lots of good info.....did the zip tie trick on the throttle cable...wow!!!!
I would just like to maximize the power and mpg of my 04 fx4. I've got a K&N drop in and was planning on getting the SCT X cal. I've searched just about every exhaust thread and can't find what I'm looking for. It seems that most here are changing their exhaust to make it sound louder....I'm not interested in sound I'm only looking for performance gains....not high end gains either......prefer it to be more ballsy down low...under 3000rpms...where I drive most often.
I've always known that more air and fuel in and a free flowing exhaust lets an engine create more power and run more effeciently. I wanted to see if stock is too restrictive and get everything done before purchasing the x cal.

This truck is a daily driver...I don't do much offroading....maybe the occasional beach...but use the 4wd often when going on ski trips. I'm just interested in overall driveability being improved and wondering if a new exhaust and xcal would do that for me.
Thanks

 

[Fast Fords]

An open exhaust with mandrel bends is your best scenario..anything over 2.5" inside diameter is pointless unless you are planning to supercharge (or any other plans of forced induction), or if you have a v8. Dual exit exhaust is great for sound, but the best is tru-duals. Basically, the least amount of bends possible is the best. The quickest exit will really open it up.

Just remember, replacing your muffler only replaces the sound. Doing all the piping is the best way to get the best intake/exhaust combo. There are LOADS of kits for the ranger. Look up some sites; summitracing.com or autopartswarehouse.com are my favourite.

 

[Yellowsplash]

Anything over 2.5 is pointless even if it is supercharged. A little v6 isnt going to be able to scavenge correctly with anything over that. Turbocharged would be a different ball game. True duals is pointless on a v6 too. If you need an explaination of this, you dont understand the fundamentals of scavenging.
What you want is a mandrel bent 2.5" catback with highflow muffler. That in combination with the Xcal should help but dont expect miracles.

 

[Wicked_Sludge]

this thread is full of a lot of

if increasing power and mileage were as simple as using a .5" larger pipe, ford would have done it from the factory...remember, power and MPG sells.

the stock 2" pipe is MORE than sufficient for a stock 4.0's needs. also keep in mind that the larger the pipe used, the higher the powerband will climb...since the OP is looking for LOW end power, he would be much better off sticking with the SMALLER 2" pipe in order to maintane exhaust velocity with the lower CFM's experienced during lower RPM..

the only constriction in the stock exhaust are the stock log manifolds...this was an economy move on fords part and exhaust flow suffered for it. a good set of headers would definitely help economy and power...but at over $500 for a good set of headers, its going to take you a LONG time to recoup the cost.

when people talk about fuel economy savings, they fail to consider the initial cost of increasing said mileage. yes a tuner will help mileage, but it also costs $300. say gas is $3.00 a gallon, and the tuner nets you 3MPG (a generous estimate), its going to take you 15,000 miles just to break even. just something to consider...

 

[Yellowsplash]

Interesting that you said that....the SOHC engines don’t have log style manifolds. They actually flow quite well for a factory manifold...much better than the OHV manifolds. The size of the exhaust piping isn’t going to make that much of a difference to "change" the power curve when the only thing you are changing is the catback (or the last 3-4 feet of the exhaust) with piping only marginally larger. If you look hard enough, you'll actually find out that the catalytic converter extension pipe assembly is actually 2.5" in diameter (and even bigger just downstream of the y-pipe joint entering the cats). Cutting off the flange for the tailpipe where it reduces to 2" and continuing it 2.5 to an aftermarket high-flow muffler will help the engine to breathe. I have this setup and it DID help the whole power curve, including down low, off idle torque. Either way, if you don’t agree, install a 2" and be on your merry way....it’s your truck. Do what you like...

 

[Wicked_Sludge]

you'll actually find out that the catalytic converter extension pipe assembly is actually 2.5" in diameter (and even bigger just downstream of the y-pipe joint entering the cats).

there is a reason that ford used smaller pipe behind the cat converter. cat converters use heat from the exhaust to perform their duty, thus heat and energy is removed from the exhaust stream, meaning the exhaust coming out of the downstream side of the converter is cooler and denser than the gas flowing into the converter. in order to maintane the velocity of this cooler and denser gas, it needs to be contained in a smaller area...hense the 2" pipe. replacing it with a larger pipe will slow the gas down and reduce exhaust scavanging.

i dont care what your "butt dyno" says, your fighting physics and its a losing battle.

the stock SOHC manifolds are a far cry better than the old pushrod manifolds...but they are still manifolds...headers will out-perform them.

 

[Yellowsplash]

It’s actually thermodynamics...And yes, as the exhaust moves further away from the engine it does condense, or more specifically, an example of thermal contraction. A smaller pipe would be help to keep velocity up and is great for stock applications, but that’s the extent of it. If ford engineers (who by the way don’t engineer their products strictly for best power, but rather a compromise of emissions and other factors) were soo worried about maintaining perfect velocity, why would they have implemented piping larger than 2.5" BEFORE AND THROUGHOUT the cat. Wouldn’t that cause a velocity drop and cause the engine to have to push the gases through the cats rather than the previous pulse pulling them behind via vacuum from scavenging. Point is, factory equipped parts aren’t always best for power...that’s why aftermarket performance exists.

As I said before, replacing a piece of piping that’s only marginally larger than the factory piping long after the cats isn’t going to cause any kind of issue with velocity. For best volumetric efficiency where more power is obtained, this step down hinders flow. Most people who modify their 4.0 exhaust go with 2.5" piping, including aftermarket suppliers who specialize in exhaust systems. If it were to reduce velocity and flow, don’t you think that everyone would have noticed this decrease and consequently went to smaller piping.
Also, I wouldn't recommend a 2.5" exhaust for a 4 cylinder or a 3.0 like your truck as it isn't producing as much volume per exhaust pulse to keep velocity constant.

...And I never said headers wouldn't help. Of course they would. I was just correcting you on your claim of the SOHC using log style manifold like the OHV engine does. They do flow better than a log style, but headers will outperform. Unfortunately, not as drastic as on an OHV. In other words, they flow pretty good in stock form.

 

[Wicked_Sludge]

merriam-webster defines thermodynamics as "physics that deals with the mechanical action or relations of heat". but thanks for adding another pointless dimension to your debate.

as i explained in my last post, larger pipe before the cat is used because the exhaust gases have not yet lost a large portion of their heat to the cat converter. the exhaust is still very hot, and thus, it takes up a lot of room (fluids expand as they are heated). if you were to use 2" pipe before the cat, it could prove restrictive at higher RPM's.

an ideal exhaust system would start out large, and gradually taper all the way to the tailpipe, which would produce even velocity throughout the entire system as the exhaust gets cooler and cooler toward the tailpipe. however such a system would be difficult to engineer and the gains would be negligible.

the original poster is looking for maximum fuel economy and maximum low RPM power. since most driving occurs at a relatively low RPM around 2500 or so, tuning the engine for this RPM range will produce both best economy (because we all know an ICE produces its lowest BSFC near its peak power for a given throttle setting), and best power in the range he wants. going with a pipe any larger than stock (which ISNT restrictive in the lower RPM range) will move the powerband up...INCREASING peak power, but reducing low RPM torque.

 

[Yellowsplash]

"A system undergoes a thermodynamic process when there is some sort of energetic change within the system, generally associated with changes in pressure, volume, internal energy (i.e. temperature), or any sort of heat transfer, such as thermal expansion and contraction" You cant label that as pointless...

as i explained in my last post, larger pipe before the cat is used because the exhaust gases have not yet lost a large portion of their heat to the cat converter.

You do realize that there are cats in the downpipes of newer trucks...so your theory would mean that the gases would lose heat before it even gets to the main cats. Why doesnt this loss of heat cause velocity issues in the main cats? And further, if all 3 cats had taken extreme amounts of heat away from the gases, why is the piping throughout (yes, completely throughout) the both mains cats, including the fourth, in some cases larger than 2.5"? Wouldnt the exhaust gases have lost too much heat and consequently velocity to flow unrestricted through the fourth cat without causing the bumper car effect with the pulse behind it?

going with a pipe any larger than stock (which ISNT restrictive in the lower RPM range) will move the powerband up...INCREASING peak power, but reducing low RPM torque.

You cant change the power curve by changing an exhaust pipe size .5" by the axle. Only the cam, intake manifold and exhaust header primaries can do this. In no way, shape or form, is this going to happen. If that were the case, those guys running 2 foot long 4" inch diameter tips would gain top end horsepower

Im not debating that modern day thermodynamics, as a portion of physics, wrong in any way....your correct in your logic and great for a stock vehicle not concerned with power. If 2.5" piping were an issue, why is everyone still using it on their 4.0s?

To the original poster....If your concerned with power and fuel economy, dont lug your engine at lower rpms. A SOHC engine is made to rev freely. It was designed to make its power higher up in the rpms. Its not a 300 straight 6...restricting it to 2 grand is only going to limit the power and use more fuel consumption. If torque is what your after (and probably is), replace your gears with a lower (numerically higher) set and drive on...

 

[Wicked_Sludge]

"A system undergoes a thermodynamic process when there is some sort of energetic change within the system, generally associated with changes in pressure, volume, internal energy (i.e. temperature), or any sort of heat transfer, such as thermal expansion and contraction" You cant label that as pointless...

my point was, thermodynamics is a branch of physics..."correcting" me when i wasnt wrong was pointless.

You do realize that there are cats in the downpipes of newer trucks...so your theory would mean that the gases would lose heat before it even gets to the main cats. Why doesnt this loss of heat cause velocity issues in the main cats? And further, if all 3 cats had taken extreme amounts of heat away from the gases, why is the piping throughout (yes, completely throughout) the both mains cats, including the fourth, in some cases larger than 2.5"? Wouldnt the exhaust gases have lost too much heat and consequently velocity to flow unrestricted through the fourth cat without causing the bumper car effect with the pulse behind it?

like i said before, an ideal system would gradually taper from start to finish. being that the insignificant gain from this type of system would not warrant the cost and complexity of a continually tapering pipe, ford simply tapered the pipe once, after the largest loss of heat: the cat converters.

You cant change the power curve by changing an exhaust pipe size .5" by the axle. Only the cam, intake manifold and exhaust header primaries can do this. In no way, shape or form, is this going to happen. If that were the case, those guys running 2 foot long 4" inch diameter tips would gain top end horsepower

you DO change the power curve by changing the tuning of the exhaust system. an engine is nothing more than a glorified air pump. changing the length and/or diameter of either or both the intake and exhaust systems WILL change the flow characteristics of the engine, thus manipulating its power curve. those guys with the 2 foot long, 4" dia. pipe DID increase their top end...they just increased it to the point that its no longer usable by their engines (unless they built such a beast that could spin XX,000 RPM and move sufficient CFM to fill those pipes)...and they cost themselves bottom end, of coarse.

Im not debating that modern day thermodynamics, as a portion of physics, wrong in any way....your correct in your logic and great for a stock vehicle not concerned with power. If 2.5" piping were an issue, why is everyone still using it on their 4.0s?

"everyone" is running 2.5" pipe because when most people are looking for power after a mod, they run out, floor it, and wind the engine up to see what it'll do...thus PEAK power makes a difference to them. the OP is not looking for peak power, hes looking for low RPM power.

To the original poster....If your concerned with power and fuel economy, dont lug your engine at lower rpms. A SOHC engine is made to rev freely. It was designed to make its power higher up in the rpms. Its not a 300 straight 6...restricting it to 2 grand is only going to limit the power and use more fuel consumption. If torque is what your after (and probably is), replace your gears with a lower (numerically higher) set and drive on...

i do agree with you on this point. SOHC motors are high revving engines. being that your motor already makes peak power over 5200 RPM, it would be in your best interest to keep the revs up.

 

[fitn217]

Hey guys......wow I'm impressed with the responses so far. One thing I've noticed...I didn't have a caliper or sewing tape to measure but it seems that the exhaust coming from the 1st cats tapers down....maybe to 2" for about a length of 5 or 6 inches or so....before the two pipes enter the 2nd main cat. Just kinda weird because it would be going from bigger pipe to smaller(for that 6" length), to cat, to bigger, to smaller pipe, to muffler and continue with the 2" out till the last few inches of the tailpipe tip.

I was thinking of the Gibson Catback system.....single to single...I'm definately not going to go double from the muffler.......Are these catback systems mandrel bent??
I also checked at Midas and they said they could do a custom job.....don't know if it would be Mandrel bent though....guess I'll have to go back.

Since researching on this forum about the SOHC I have started to let it rev more. Where I used to get to cruise at around 2000 rpm I now leave it in the lower gear and cruise around 2250 - 2600 before it feels like its in too low of a gear and really slowing down fast when you take your foot off of the gas. It seems to be getting better mileage. Also I almost never rev it over 3000 except for the occasional time when shifting so I definately don't need an exhaust that gives me more rpm's.

Quite honestly that simple zip tie trick really made it feel like a different truck. I used to have to mash the pedal down to get decent performance.....it really felt like a pig. Now I just push it a bit and it instantly responds...I guess it's twofold from being in a lower gear and tightening the slack on the throttle cable...Funny how I didn't think of that myself since I just did it on my softail a few months ago.

So with all this I was even considering just doing nothing and waiting till the current exhaust falls off as paying a lot to save a few sometimes isnt the smartest thing sometimes.
At least it seems to be a decent thread that maybe some others in my situation might get some use out of.

Thanks for all of your responses.

 

[Wicked_Sludge]

your going to be waiting a while for the factory exhaust to fall off as its either stainless or aluminized (i cant recall which).

doing nothing but keeping the motor properly tuned up is by far your best bet. there arent many mods out there that will pay for themselves in a very reasonable amount of time.

one thing i do suggest doing is purchasing and hooking up a vacuum guage, as this gives you a real time example of what kind of load your engine is experiencing. the driver is by far the single biggest variable when it comes to fuel economy and a vacuum guage will help teach you how to drive for best mileage.

 

[motohead771]

Im glad I read this thread. I have been interested in getting an exaust system for a while now, but didn't know much about it. Whats the best cat-back kit from any of your past experiences?

Also fitn217, don't expect your exhaust to rot out any time soon. My truck is a '94 and has close to no rust. I have lived in CO most of my life so that explains why, (not much salt on the roads).

 

[fitn217]

The exhaust system looks good as a whole...but...the connection between the cat and the muffler is rusted to sh**. There's a lot more rust then there should be. I had to replace the brake rotors after the surface started disentegrating. Guess it's from the salt air, running the beach and the fact that NYC starts salting the roads if the forecast calls for 2 inches.....besides the fact that everyone runs to the store to stockpile for "the storm".

If I do decide to change the exhaust what's a good cat back system that sounds more like stock....it could be a hair louder.....just a hair ....no more.....if the performance gain would be worth it.....& don't forget no loss of torque....as I've heard here that some cause.

 

[Gotta_gofast]

You mentioned the gibson single side swept exhaust. This is a 2.5" mandrel bent aluminized steel system that will give you a mellow tone without annoying anybody. You'll probably feel a slight seat of the pants difference in acceleration and a marginally better fuel economy. Is it worth 300+ bucks? I think so. But if your only in it for the economy then probably not.

An X-cal will give you a definate gain. You'll have the best results when running premium fuel though. BUT!!! running a torque tune on premium fuel will often give you 1-2mpg increase when your not hard on the gofast petal. So, the increase in economy often outweighs the extra $0.20 a gallon for the extra octane. But, most people purchase a tuner for extra power, tire/gear changes, and shift points/firmness. In my opinion, a "fuel economy" tune is BS on a gas engine.

Either way, you'll find a lot of people on both sides of the fence about A LOT subjects. Things such as E-fans, underdrive pullies, CAI... you'll get some strong negative feedback from them. But, there's a guy on explorerforum (I believe) with a 4.0L sohc that build his for mileage. He used all the devils tools that defy physics and all other "logic"-I'm talking about those e fans, pullies, intakes, ect-and claims an increase in over 5mpg. He's got quite a big list, so I'm guessing the cost outweighs the mpg increase (unless you put a lot of miles on your vehicle a day). I'll post the link if I can find it.