makarovboy

Jeep, equal length headers are designed so the exhaust gases meet at the collector at the same time, creating a MINIMUM amount of back pressure, but back pressure none the less. Shorty's meet in the collector from backed up unequal lengths and produce more back pressure. I agree that the more air you can pump, the better off you are. But where are you getting torque? The type of cars most of us run would have lousy 60 ft. times and need a gazillion H.P. to pull every gear at 9 grand and run huge valves and humongous cams and 5" pipes. Fine for Bonneville, but back pressured is necessary for most of us.

SycoJoe247

I just decided to get in this great discusion to tell you old guys what I've learned. If were talking about 5.0 engines or 4.6 with 230 hp stock and 9.2 to 1 compression, back pressure is essential. It may not be as important in a 454 11.0 to 1 compression Chevelle pushin 24 lbs. dragger, due to the large amount of exhaust produced in such a LARGE engine. But to create good hp and torque curves on a SMALL 5.0 or 4.6., back pressure is essential to give your car the low rpm torque it needs to woop all those GM suckers. Long tubes on a nearly stock engine will kill low end torque and might produce a few more hp in the high rpms than equal length or standard shorties. So in the end it depends on the sized engine and the amount of hp ur runin through it. Thats why smart draggers put 6" tubes on their top fuel dragsters and why smart Mustangers go with equal length shorties an X and good 2 chamber mufflers.



I REST MY CASE.......

noslow50

no 1 it's 215 stock hp.... 2 full lenght headers r designed to give u low end torque...

jeep45238

Last I checked, long tubes were designed so they DON'T all hit at the same time. Usually the gases pass kind of like a river, in rapid succession. This creates a vacume which helps scavange exhaust gases from the other cylinders, which increases the VE of the motor and allows for more incoming air. It also increases the exhaust velocity.



Makarov, you are talking about minimizing backpressure....you're attempting to get as little as possible, which is nearly impossible for every RPM (as well as keeping high exhaust velocity).



Syco, An internal combustion gas engine is an internal combustion engine. You also have it backwards on the pipes, it will gain in every RPM (just not as much at certain areas as others). Even my lil satty benefited from it (hey, it was $20 and in mint condition, how can I pass it up?)





You really haven't provided ANY proof. The tubes on draggers are there to increase the exhaust velocity. Sure, running open heads will have no back pressure, but the exhaust velocity will suck. Smart 'stangers have equal length long tubes, when price and the area they live in allows (along with the X pipe and DynoMax mufflers...S shaped straight through that sounds nice and deep....with not even remotely close to the price or power loss. I remember seeing 25 HP/TQ gained on a turbo 'stang by switching to DynoMax from Flowmaster somewhere....)

makarovboy

Sorry Jeep, I meant equal length shorties. As for the top fueler, when you increase velocity, pressure increases (as in back pressure).



You mention long tubes, which I couldn't run due to my basically stock set up. But you also mention x-pipe and mufflers, which reduce the restriction but don't eliminate it, therefore causing back pressure. I agree that we're striving for less restriction, but it doesn't always mean zero in every application. When I put on the headers and cat back system, I noticed the difference, but if I were to run long tubes thru the collector my low end would go away bad.

jeep45238

Velocity doesn't mean pressure increases, as long as the tube DIA is sized correctly for the RPM's it will be used in.



Dude...you so screwed up. Reducing restrictions DOESN'T CAUSE BACK PRESSURE. Equal length long tubes don't kill your low end power.

makarovboy

I was wrong about the pressure. Bernoulli's Principle, which I learned many years ago states, "as velocity increases, pressure decreases". (the two brain cells I have left are having enough trouble just keeping each other company).



I've seen guys go to a long tube and lose the bottom end. But this could be due to using too large a diameter to fit the application. It would be a waste on low flowing stock heads. I don't believe any combo is perfect for optimum flow, but the fueler guys are close.



This argument could go on forever, but if the feds would allow car manufacturers and after market folks to continue to engineer the internal combustion engine, they might hit the perfect combo. (probably not in my lifetime).

jeep45238

They MIGHT eventually hit it......but the cost of the part will be so astronomically pricey to cover R+D nobody would buy it.



I've PERSONALLY never seen a single application that has lost low end power with headers, short, long, equal or un-equal. I've just always seen the best gains from equal length long tubes.



Nothing wrong with this debate, it's just that I keep hearing "you need backpressure", but I'm not seeing anything to back it up. I want to know why people think this.

makarovboy

A new exhaust can increase horsepower and torque, as well as change the exhaust tone. Although a free-flowing exhaust can increase power, too much flow is not always a good thing. Engines rely on some amount of back-pressure for desirable performance. A small engine with greatly-oversized exhaust will lose a significant amount of low-end power. With the proper size exhaust and muffler, most trucks can expect to gain 10 to 20-horsepower and similar amounts of torque. Adding a high-flow catalytic converter can net additional gains.



sportruck.com, on custom exhaust installations.



I say it's very healthy to have differing opinions.