So I've been reading around on various forums and I've noticed something that is pretty common. People have a tendancy to say "if you install that muffler that way, you lose horsepower and torque or both." Nobody ever has any data on this, its usually just "this one friend of mine dynoed his before and after" or "a friend of mine owns a muffler shop and this is what he says".
To me common sense dictates that the less resistance to flow, then the engine has to use less horsepower to expel the exhaust out the tailpipes therefore making more horsepower at your disposal. I understand that if you go to the extreme and have no backpressure it can in fact be harmful and have negative effect on horsepower, however this really can't be achieved with a simple swap of mufflers can it? It doesn't make sense, there really isn't that significant of a change in flow properties.
So I set out the challenge to anybody to prove me wrong. Show me numbers, before and after an exhaust setup.

 

I've never dyno'd my truck, but after the exhaust install, and according to my Edge, I picked up 7/10's 0-60. I verified this with 4 different runs. As far as the numbers, I'd love to see dyno sheets as well, not just peak numbers. You can hack the exhaust off and gain peak numbers, but you'll lose torque most everywhere else....

 

Think about it this way... If it was better overall to change the diameter of pipes, or put hi flow cats, then ford would have done it from the factory. Some people are looking for increased torque, some for faster 0-60 times, some for max hp. It's according to your needs as to what you want to do to your truck. I, personally don't think that ANY exhaust system helps enough to justify the cost. If simple things like hi flow cats helped gas mileage while increasing performance, don't you think Ford would have put them on from the factory?!

 

Not necessarily, there is the problem with cost effectiveness. It would bring the overall price of the truck up, with out adding much value. I'm not saying they are cost effective, I'm saying they do help.

 

Well that isn't entirely true. Ford has to pass certian emissions, pass by sound tests, and keep things down to a certian cost. I understand that most hi-flow cats and aftermarket mufflers will pas your local sniffer but they probably would be cutting it really close on the goverment testing Ford has to go through.

On the other side of the coin is these items will add power depending on application. Alot of them aren't gaining power through the acctual muffler but more through the piping. If you look at your factory exhaust piping any bend in the system is crimped. So in that spot you go from a 2 1/4" ID pipe down to sometimes as low as a 1" ID pipe. Aftermarket systems are mandrel bent, so even in the bends you still have 2 1/4" pipes. Welding in a Flowmaster will give you a better sound but you still have to contend with the bent up piping so the gains will be minimal. A high flow cat will reduce some back pressure freeing up some of the power it takes to push the burnt fuel out, but it still is a cat so even though it flows better than stock it isn't flowing as good as a straight pipe.

Another thing to look at is the car is built to run with the current exhaust system, once you start changing it, in turn it will change the way the car runs. Alot of times exhaust modifications will cause the car to run rich which will reduce some of the power you might have gained from the system almost canceling them out. Now if you put the exhaust system on then tune the car on a dyno adjusting the a/f ratio then you will see the gains you are getting from it.

If you run too big of an exhaust system what people commonly refer to as backpressure will be lost, what this is is a pressure difference between the inside of the cyl. and the headers. The pressure difference sucks the spent gasses out of the cyl and in turn sucks in the new air charge from the intake. If you loose this pressure difference by running too big of an exhaust setup you will not get all of the spent gas out. So now you have some bad air so to speak taking up room that otherswise could have been filled with a fresh air charge. Not only do you now have unburnable air taking up room in the cyl that left over air is also hot which heats up the new intake charge creating even less power.

A big free flowing exhaust will increase your peak hp numbers up top as scavengin isn't as important in the higher RPM's but you will loose gobbs of torque below the curve. Example I had a Grand Prix GTP that I put a ture dual exhaust on from the headers back. 2 1/4" pipe all the way back to the mufflers. Since I was supercharged and the supercharger forced the air in and the old air out scavenging wasn't that big of a deal to my car. I picked up almost 30rwhp. A guy I know who had a non s/c GT tried the same setup, he gained 5hp peak to peak but lost as much as 20lbft of torque under the curve because the exhaust system was too big for his application.

 

[QUOTE=01TruBluGT]he gained 5hp peak to peak but lost as much as 20lbft of torque under the curve[QUOTE]
5 hp is an insignifigant ammount when you're talking about a pickup truck. That 5 hp is almost immeasurable. From day to day, your truck gains and looses 5 hp just from changing atmospheric conditions. You're talking about a waste of time and money. If you want to irritate everybody with a loud exhaust system, fine. But think of it this way.. If Neal was to put a muffler on his truck, would he loose 40 hp? I don't think so! People come on this site for advice about their trucks and I think that they recieve a lot of bull crap about increasing hp and gas mileage. It just doesn't make that much of a difference!!!

NOW. If you're racing your truck, then by all means, 5hp here and there may be signifigant. If you drive your truck back and forth to work or school, 5 hp is useless.

I don't want anybody to get offended at me. I just come on this site and see kids soaking up everything that is said here. They leave this site and go buy new exhaust, cold air intakes (which are stupid cause they take hot air from under the hood!!), underdrive pulleys, e-fans, and amsoil oil cause it will make their truck last longer and give them better fuel mileage.

 

That was my point. For certain applications an exhaust will add power, some it won't add enough to make it worth it other than the sound factor. As I stated in my s/c'ed application I gained allot of power where as my friend with the same exhaust only gained a bit of hp and lost allot of torque.


Well I don't know Neal's setup so I really couldn't say, However for the sake of argument if you take a stock 4.6 n/a motor and swap out to a 3" exhaust system under the notion that bigger is better I would bet you could easily give up 20-30lbft and probably 15-20hp under the curve. Now peak to peak you might pick up some but unless it is a dyno queen that 5hp on the top will not make up for the loss down low.

Well you kind of contradicted yourself there:
"If you're racing your truck, then by all means, 5hp here and there may be significant."

Well if it would be significant for racing why would it not be on the street. 5 here 10 there, another 5 or 6 here, after a few bolt ons you could add 20hp or so which you WILL notice. If I were to take your advice verbatim then I should only stick to mods that in themselves would give me enough to feel and make a difference.

Well I agree with you about the cold air intakes that put the filter under the hood open to the hot engine bay temps, U/D pulleys I have never been a fan of, they might give you 3-4hp but for one you will never feel it and two the way the 4.6 & 5.4 is setup with the oil pump on the crank I have seen too many oil pump gears shatter because u/d pulleys were not capable of damping the vibrations like the stock one does. Electric fans and waterpumps are proven and I use them whenever possible. They take parasitic drag off of the motor increasing h/p and tq at no real disadvantage. You have to look at it like this if you take belt driven devices off of the rotating assy then you will loose less power and your engine will perform at a higher efficiency level, which will save gas and add to the motors longevity.


One more thing to add just for future reference. My Mustang is rated at 305fly wheel hp from Ford. The only modifications I have done is an off road midpipe, SLP catback exhaust, JLT cold Air intake(It puts the filter inside of the fender not under the hood), and had the car tuned and I am pushing 330hp/338tq to the tires. So the little things add up in the end.

 

I am pretty confused here...

It seems some of you are basically saying to add a freer flowing muffler/piping would actually decrease horsepower and torque. What it seems to me is that by adding a free flowing muffler and piping that you would decrease backpressure, which would in turn allow burnt gas to expel much easier, which would decrease strain on the engine, resulting in increases in torque and horsepower.

I do not have dyno evidence to back this up, but it seems some of the above posts insinuate that adding a freer flowing muffler (or system) will not make an engine perform better. If this is the case, why have so many dyno tested magazine articles and tv shows (Horsepower TV, Trucks) show contrary.

I personally do not think there is some huge conspiracy to sell mufflers and hurt performance and efficiency. The simple truth seems (again, I am not an expert) that Ford does not install free flowing mufflers due to several factors (demand for louder exhaust not being very significant, costs of said mufflers being high, and possibly regulations).

 

Well a properly sized exhaust system will increase power. If you put too big of an exhaust system on you could loose more power down low than you will gain up top. Like I said earlier, on my GTP I added 2 1/4" pipes from the headers back and gained almost 30rwhp. A friend with a n/a GT tried the same exhaust and gained 5hp peak but lost as much as 20lbft down low. If he would have stuck with the stock size pipes from the headers to the muffles he wouldn't have lost all of that torque and would have gained more HP.

A free flowing exhaust will make the car preform better. From a muffler swap alone you might gain 5rwhp which isn't noticable. On the other hand switching out to a properly sized mandrel bent catback could probably gain you 10hp which is noticable.

No there is no conspiracy. Like I said a free flowing muffler will gain you some power, enough power to make it worth it other than sound..not always. You will not feel 5hp. You also have to take into account that on the TV shows, and in magazines they are somewhat paid off. Not to the point that they would lie, but to the point where they would exagerate results to keep the companies giving them free gear and paying for add spots. Example they always show you them putting an exhaust system on and then dynoing the car right. They don't tell you that they probably tuned the car, or that it is ice cold so naturally it will make more power than when they baselined it before the install when it was hot. If you drove your car to a dyno today and made a pull, then let it sit for about 2 hours cooling off, then made another pull, you would probably see about 5-7rwhp gain by just letting it sit.

 

ok if you want exhaust get one...if you dont then buy one for me i got mine more so for the sound. i really didnt care if i lost or gained 5-10hp because it wont be noticed.

 

I went extreme. Custom 3" dual all the way, and it sounds like an effing NASCAR baby!

 

im yet to hear any kind of exhaust on navigators around here. its like the bastards that buy them think they spent all the money on car and now it has to stay that way

 

Exhaust systems don't help you a signifigant ammount to justify the cost. They do make your truck louder, and if it's what you want, then go for it. If you don't believe me about how much it helps, just run your truck in a drag strip, and then unbolt your exhaust system, and run it again. It won't help your times. I tried it.

What I meant by racing, was that if your truck is putting out 700 hp, well, then the small diameter pipe and muffler might be a bit restrictive. But with a relatively unmodified engine, it's not going to be that much.

 

I added a Volant SISO for looks as well as sound... Didn't consider performance #'s for that purchase since I was installing an Edge Advantage at the same time.

Here is a post on my (good) experience with the Volant Cat Back.
https://www.f150online.com/forums/sh...d.php?t=236748

 

I beg to differ. In certain applications, they may not, but in others they will. For example, in my case (although I have been scolded by several for this mod) I add a true dual 3 inch system with hi flow cats and Flowmaster 40 series mufflers. All that piping is exhaling what the powerdyne is huffing down its throat, sometimes upwards of almost 6000 RPM. At 6000 RPM I am sending around 7psi quite forcfully down the throat of this big bastard, and I am sure that with a total of 6 inches of pipe, she can breathe as freely as she wants. Now, the question of torque loss under say 3000rpm, well in my case its really irrelevant. I built this thing to cruise around town and at my own accord, stomp on the throttle and chit out the fools who elect to run against me. Most of the powerband that I care for is well above 3000rpm. Could I benefit for daily driving from say 2.5" pipe? I am sure I could, but my chit sounds mean, acts mean, and scares the hell out of those who are enshrouded in its unspent fuel from behind. And by god I like it that way