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My old man and me are haveing a debate I say that you don't need any such back pressure with like a muffle in an exahust system's. But I seen old gasser's drive (drag) with nothing more then just a pipe stickin out of the rocker panel. so how's would be right?
 

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Depends on what you use the engine for............Generally, if you shorten the exhaust, you may add horsepower, but you take away torque. Of course, there are many more factors too.....that is just a generalization.
 

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You can help torque by installing true duals, but don`t go too big on the pipe. Next, use paint, and paint a line down both pipes as they exit the headers or exhaust manifolds, let the paint dry, then take it down the road for several miles, check the pipes to see where the paint has bubbled, mark that spot and add a cross over pipe, make sure it`s 75% diameter of the main pipe. Also remember that exhaust gasses cool as they go further out in the system, so if the mufflers are more in the rear of the vehicle, the tail pipe diameter can be a size smaller which will help with velocity to keep the exhaust speed up.
 

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help on exhaust

Yeah Lil more complicated than that . Wide open exhaust generally delivers better performance . But Can also Cause motor too scavenge exhaust . Think of the Exhaust , as a Pulsation . faster the Pulsation is the more chance it will scavenge the exhaust back intoo the cylinders . A Lil back pressure will help too keep the motor from scavengeing exhaust , generally speakin. Better your head's flow << Less chance of Scavengeing ? Gas in Gas out ! Size of Diameter of exhaust , Tuned exhaust << all are designed too try too find a happy medium , within the perameter's of what your suckin in and puttin out . Better your head's flow . Usually the bigger the diameter of pipe, is needed .
It's even way more complicated than that??? Camm over Lappp ETC ? Be aware that open pipes . Leave, Allow cold air too reach the Valves after shut down . This has historically been blamed for Valve warpage .
Meaning You gotta keep a lott of Tennis Ball's around , too plug your exhaust , when you shut down , if you runn open header pipe .

Sean
 

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true duals doesnt really work though if your engine is a 22r whith only four inline cylinders though does it? thanks for that info i'll have to see how much of that i can make work
 

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Sean's said:
Yeah Lil more complicated than that . Wide open exhaust generally delivers better performance . But Can also Cause motor too scavenge exhaust . Think of the Exhaust , as a Pulsation . faster the Pulsation is the more chance it will scavenge the exhaust back intoo the cylinders . A Lil back pressure will help too keep the motor from scavengeing exhaust , generally speakin. Better your head's flow << Less chance of Scavengeing ? Gas in Gas out ! Size of Diameter of exhaust , Tuned exhaust << all are designed too try too find a happy medium , within the perameter's of what your suckin in and puttin out . Better your head's flow . Usually the bigger the diameter of pipe, is needed .
It's even way more complicated than that??? Camm over Lappp ETC ? Be aware that open pipes . Leave, Allow cold air too reach the Valves after shut down . This has historically been blamed for Valve warpage .
Meaning You gotta keep a lott of Tennis Ball's around , too plug your exhaust , when you shut down , if you runn open header pipe .

Sean
So you are saying that exhaust scavenging is a bad thing? :confused:
I must be mistaken, I have always heard that it is wanted to help clear the burn't gasses out of the cylinders.
Reversion is something you don't want.
 

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boggla500 said:
My old man and me are haveing a debate I say that you don't need any such back pressure with like a muffle in an exahust system's. But I seen old gasser's drive (drag) with nothing more then just a pipe stickin out of the rocker panel. so how's would be right?
All I know is that the Super classes started going faster when NHRA mandated mufflers. I think scientifically, it all comes down to managing the reverse pulse that helps to provide a low pressure area after the valve that pulls the exhaust slug out of the motor. You'll usually see those short pipes you're talking about on mechanically fuel injected cars, with collectors and equal length pipes used on carbureted cars. My dad always taught me that a motor needs a little back pressure. Sounds like your dad went to the same school.
 

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I think techy is sort of right. :mwink:

K I S S

No engine NEEDS backpressure, but ill tuned exhaust system might make more power with backpressure added.

What is important in tuning is scavenging which is affected by several factors.

One of which is the muffler acting as an expansion chamber in the otherwise "smaller" pipe. The placement and size of this chamber adjusts scavenging.

Hence, when some racers went to mufflers, the expansion chamber affect assisted their tuning, or complemented their system, and they made more power and went faster.

Many people erroneously concluded that "back pressure" is needed.

If you think of scavenging as one pulse sucking another out of the cylinder, that is not BACK pressure, it is sucking..... no back pressure involved.
 

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Paint marking of pipes for tuning header length as well as adding H pipe crossover was thoroughly disproven by actual dyno tests with full car exhaust systems on the dyno. The conclusion was that ANY variation of rpm or load changes the location of the H.

But the paint story is firmly imbedded in hot rod lore, and probably will remain.

The conclusion was made that the location is not important but the size is. The area of the H should be equal to the size of the main pipes.

They also concluded that X pipes are better at smoothing and balancing the pressure waves since the flow does not have to go so far across the H. well, duh.
 

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Posted by xntrik:
"But the paint story is firmly imbedded in hot rod lore, and probably will remain."

The paint story was actually originated by the Ramchargers and had to do with the placement of the collector on headers, not the "H" or "X" pipe. At least that's the story I get from a dyed-in-the-wool Mopar buddy. Where the paint stopped burning off the primaries was where to put the collector and dictated the length of the primaries.

For you youngsters who don't know the history of the Ramchargers, here is a short story of them:



The Ramchargers

The Hemi was gone but not forgotten by some at Chrysler. Around 1958, a small group of Chrysler engineers formed a club to share their interest in cars in general and high-performance cars in particular. Tom Hoover was one of the men in this group. Having received his masters degree in physics in 1955, he entered Chrysler through the Chrysler Institute and in 1957, went to work in the area of fuel injection. He got to know like-minded engineers over the next year, and what first started out as casual gatherings eventually evolved into one of the most aggressive drag-racing teams in the United States.

"In the cafeteria in Engineering at lunchtime," Hoover recalls, "a number of us who had performance vehicles, which was rather rare in those days among the Chrysler cars, would get together. There were six or eight [of us] initially. Wayne Erikson and myself were the two primary instigators. The idea was to have just a group so that we could go to the drag races together, cooperate and help one another out."

This group called themselves the Ramchargers. At night, they would demoralize other drag racers on North Woodward Avenue in Detroit and on weekends, set records at Detroit Dragway. These engineers had access to the research and development work that had been done on the Hemi and they applied it to their personal cars. Then they concocted a plan to build an altered vehicle for the B/Altered class in sanctioned drag racing, and the High and Mighty started to take shape. The car they used was a 1949 Plymouth Business Coupe, and it was extensively modified in the home garage of Jack Mc-Phearson, one of the Ramchargers.

"Dan Mancini and I built the engine," Hoover says. "Gale Porter over at Dodge got for us a 354 Hemi truck engine that had dropped an exhaust valve. It became the engine for the High and Mighty. It was a joke with us at the time because we had roughly $200 invested in it. We bought a new set of Jahns pistons. Jim Hider had a place over near the Detroit Airport. We came up with a camshaft profile and ol' Jim would do it for a reasonable price. Jeff Baker at Chrysler designed the plenum-ram manifold, and we used reinforced radiator hose for the trumpets. The High and Mighty was the grandaddy of the tunnel-ram manifold."

Getting all this new-found horse-power to the ground was a problem due to the limitations of tires in the late fifties. Troy Simonsen joined Chrysler in 1958 and the Ramchargers shortly there-after. He relates how they solved the problem of traction.

"With the High and Mighty, we sat down and thought about the vehicle dynamics of drag racing. The problem was getting all the traction you can. We wanted the car high, to get weight shift. We had a unique suspension that was intended to transfer the weight equally to both the rear wheels so that the torque of the driveshaft and the tendency to lift the right wheel was offset.That car," Simonsen remembers, "was tall enough that you could crawl under it on your hands and knees, almost."

This impromptu club grew from its rather inauspicious beginnings over the years to race the Max Wedge and 426 Hemi engines, and the Ramchargers became one of the biggest draws in sanctioned drag racing. More importantly, the Ramchargers had a dramatic impact on Chrysler Corporation's racing engine development. The company's racing success and attendant public image were a direct result of the enthusiastic efforts of these engineers. Some of the others who joined the Ram-chargers included Dick Maxwell, Dan Knapp, Tom Coddington, Jerry Donley, HermMoser, Jim Thornton, Mike Buckle and Gary Congdon.

"I doubt that there would have been a drag-racing program withoutthe Ramchargers," Hoover says. "I really believe if the company had made an attempt to do drag racing as they did, I doubt they would have been successful at all if the Ramchargers cornerstone had not been available."

The ability of the hemispherical-combustion-chamber cylinder head to make power would prove itself again when the new Wedge-head engines showed their limitations on the high-banked ovals of NASCAR racing around the country. The Hemi was momentarily eclipsed by the Wedge head until it became clear that something more-much more—was needed.
 

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Discussion Starter #13
I see that summit got some thing to keep a little back pressure, then again flow master got that like muffler thing I don't know the name of it off the top of my head but all it has is metal welded in diffrent spots. Probley have the same Idea what I saw in summit racein. Now I under stand more how it's supoze to work thanx
 

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In surfing around looking for the "paint" thing, I have found evidence that the procedure was used to determine collector length, not primary tube length, so my buddy may be wrong. Who knows? And what does it matter anyway?
 
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