(X) or (H) PIPE



(X) or (H) PIPE

Postby grumpyvette » April 4th, 2009, 9:43 am

INSTALLING AN (X) PIPE IN THE EXHAUST ON A DUAL EXHAUST CAR

theres a good deal of info here in the sub links that might help, including some dyno results
btw, learning to welds , a bit like GREAT SEX, if youve never been involved you don,t see the advantages but once you are, you wonder how you could ever have gone without having constant access!
(and an exhaust system is a great place to learn)
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These three circles illustrate the difference in internal square-inch area between 2.25-, 2.50-, and 3-inch exhaust pipes. Weâve calculated the area based on a wall thickness of 0.065. The 2.25-inch pipe has a flow area of 3.80 square inches, a 2.5-inch system increases the area 25 percent to 4.7 square inches, and a 3-inch pipe pumps the area up to 6.8 square inches.

Understand the different concepts ,adding an (X) pipe effectively doubles the exhaust cross sectional area , as your effectively allowing both sides of the dual exhaust to carry only half the flow that the single side of the exhaust can flow, this is cutting the resistance to exhaust flow restriction nearly in half and increases scavenging, this blends and smooths the exhaust flow, remember you get a pulse of exhaust every 90 degrees of engine rotation,
Since V8’s fire unevenly, exhaust exits in pulses rather than a steady flow. While one pipe is filled with pressure the other pipe is at far less , or lower pressure, or relatively low pressure.
but the connecting of the two pipes in a Siamese pattern with an (X) pipe allows pressure to be released to and equalize to the other side, this instantly doubles the exhaust cross section and blends the pulse,and reduces flow restriction,. This action allows the exhaust to pass through the pipe quicker and this better ‘breathing’ increases horsepower, but it also effectively extends the low pressure at the other exhaust ports if the length is correctly calculated or tuned. THUS a properly set up exhaust can SCAVENGE the cylinders increasing intake flow efficiency significantly.
the "drone, sound you hear with some exhaust systems " has a great deal too do with muffler PLACEMENT and pipe diameter,and distance from the header collectors and use of an (X) pipe or (h) PIPE placement ,AND MUFFLER DESIGN USED, all of those factors will effect the rpm level or frequency that "DRONE" may occur at with almost any exhaust, ADDING AN (x) PIPE OR ADDING A SECOND (x) PIPE OR MOVING ITS LOCATION OR ADDING LENGTH TO THE TAIL PIPE CAN OFTEN REDUCE OR ELIMINATE THE DRONE IN AN OBJECTIONABLE RPM RANGE

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Id also point out that cam timing matched to the exhaust scavenging has a huge effect on potential intake flow rates
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HERES A GOOD EXAMPLE OF A CUSTOM FABRICATED EXHAUST
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looks like a well done job CONGRATS!
heres a video of it,running
http://www.youtube.com/watch?v=EGqRfsqf ... e=youtu.be
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DUAL X-PIPES TEND TO RESULT IN MORE EFFECTIVE CYLINDER SCAVENGING,BY BLENDING EXHAUST PULSE DURATION, AND A BROADER TORQUE CURVE AND MELLOWER EXHAUST TONE
I did dual x pipes similar too this picture , on four different muscle cars and corvettes so far with good results,it tends to mellow the tone noticeably


http://www.summitracing.com/parts/sum-642030

http://static.summitracing.com/global/images/instructions/sum-642025.pdf
one more in an endless list of reasons you NEED a good MIG or TIG WELDER
in an ideal set up the exhaust system beyond the header collectors has a very low restriction to flow, and there will be an (X) pipe to effectively double the exhaust cross sectional area to significantly lower resistance to exhaust flow restriction still further, to increase the header,s ability to scavenge the cylinders efficiently in the intended power & rpm band, keep in mind your goal is or should be in most cases to maximize the torque in the intended rpm range that your engine combo produces.
every change you make, or part you select either enhances or restricted the engine power potential, at some point in the power band
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WATCH THIS VIDEO
http://www.youtube.com/watch?v=yMyKv_P8 ... re=related

viewtopic.php?f=60&t=77

http://www.circletrack.com/enginetech/c ... ewall.html

viewtopic.php?f=60&t=1594

http://www.spintechmufflers.com/x-pipes ... t_139.html

http://www.carcraft.com/techarticles/ex ... index.html

http://www.pontiacstreetperformance.com ... haust.html

viewtopic.php?f=60&t=72

viewtopic.php?f=56&t=1166

http://metalgeek.com/static/cope.pcgi

http://www.pontiacstreetperformance.com ... haust.html

viewtopic.php?f=56&t=1503

a simple basic exhaust system like these 3" pipes bolted to the header collectors, and leading too an (X) pipe and dual 3" or -3.5" dual mufflers can produce excellent results if you have room under the car

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an (x) pipe effectively reduces the flow restriction by increasing the cross sectional area of the exhaust system, and by BLENDING the individual exhaust pulses,remember a cylinder fires every 90 degrees of engine rotation, meaning the pressure and volume in the exhaust comes down the exhaust in pressure waves, thus an (x) pipe splitting and blending the pulse pressure wave is effectively reducing the strength and noise levels, as the gasses rapidly expand to double the previous pipe cross sectional area, and by reducing the pressure, velocity and resistance to flow in each side of a dual exhaust, an (H) is LESS effective , because it doesn,t blend the exhaust pulse it only allows the pressure to equalize to some extent, between the two sides of the engine, but its not nearly as efficient at reducing the pressure difference but its still an improvement over having no connection between cylinder banks, it should be obvious that having a PROPERLY tuned exhaust header mounted between the cylinder heads and (X) pipe and exhaust pipe sizes matching the displacement and intended rpm range of the engine will increase cylinder scavenging

http://www.pontiacstreetperformance.com ... aust3.html

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SHORT H PIPES LIKE THIS ONE ABOVE that are full pipe diameter are FAR more effective than longer cross over versions, (LIKE THE LONGER H-PIPE BELOW)but they still don,t blend the exhaust gas pulse inertia nearly as effectively as a true (X PIPE)
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http://www.mustang50magazine.com/techar ... index.html

http://www.automedia.com/Exhaust_XPipes/pht20011101xp/1

http://www.superchevy.com/technical/eng ... index.html

http://www.boyleworks.com/ta400/psp/exhaust3.html

viewtopic.php?f=56&t=495

http://www.burnsstainless.com/crossoversmain.aspx

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there are mufflers with internal x pipe designs
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placing two 3" x pipes in sequence seems to work well at both mellowing the exhaust note, and increasing the exhaust scavenging of the cylinders as it blends and smooths out the exhaust flow by allowing the individual cylinder pulse strength to dissipate rapidly, the first (x) reduces flow restriction, the second allows the exhaust pulse to run into itself further disrupting the individual pulse strength


READ THRU ALL THE SUB LINKED INFO IN THIS THREAD ALSO

viewtopic.php?f=56&t=185&p=219#p219

http://home.flash.net/~ivc1/cobra/xpipes.html

keep in mind installing an (X) almost increases the effective cross sectional area,of the dual exhaust ,to double what it had been behind a single header collector, by doubling the area that the exhaust flow sees, dropping the restriction to flow almost in half

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buy this TOOL and custom fit the (X) INTO YOUR EXHAUST SYSTEM youll want to use a decent welder but its fast and a no-brainer AS LONG AS YOU REMEMBER TO CAREFULLY MEASURE BOTH THE (X) AND THE PROPOSED OPENING TO BE CUT,BEFORE CUTTING AND HAVE THE (X) BE A BIT LONGER THAN THE OPENING BETWEEN THE OLD PIPE WHERE ITS INSTALLED FOR AN OVERLAP NOT A BUTT WELD

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?function=Search
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ITEM 37354-9VGA

$10.99 YOU CAN,T AFFORD NOT TO HAVE THIS TOOL IF YOU DO EXHAUST PIPE MODS, PERSONALLY I LIKE AN OXY-ACETOLENE TORCH FOR THIS TYPE WELD BUT ALMOST ANY WELDER WILL WORK, this is one area those little 110 volt migs are great for!

http://www.autoanything.com/exhausts-mufflers/69A2672A0A0.aspx

http://store.summitracing.com/partdetail.asp?autofilter=1&part=MPE%2D10792&N=700+115&autoview=sku

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HED%2D18830&N=700+115&autoview=sku

http://www.edelbrock.com/automotive_new ... ipes.shtml

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WHY INSTALL AN (X)???
The lower your restriction to exhaust flow the better, past the headers collectors
An (X) basically allows BOTH sides of your exhaust system to share and split the exhaust flow, a 3” pipe has approximately a 7 sq inch cross section, splitting the flow doubles the area and tends to reduce the back pressure a good deal as your now using 14 sq inches vs 7” to allow the gases to both expand and cool, remember as hot exhaust gases cool the volume shrinks, and an added benefit is a mellower exhaust tone.
exhaust flow is NOT constant its in pulsed slugs as the piston on the exhaust stroke and the high pressure in the cylinder try to rapidly exit the cylinder of the previously burn fuel/air mix, if the headers are designed correctly the previous rapidly exiting mass tends to drag the next intake charge into the cylinder and a small percentage out the exhaust, thus clearing and filling the cylinder for the next compression stroke.
yes I strongly advise upgrading a corvettes exhaust on a performance build to 3" from the header collectors and back!most guys I talk and deal with,seem to think that slapping a set of headers on their car is all that's required to boost performance....ANY HEADERS! ...and they fail to realize that both the header design and the exhaust system behind them require a good deal of thought if you want the maximum benefits, and that simply hooking a restrictive exhaust system to the collectors on the best headers will negate most of their potential benefits.
most commercial headers are designed mostly for ease of manufacturing and ease of installation,little thought goes into maximizing the cylinder scavenging which is their main function.
your fooling yourself if you think headers will provide a big boost in hp/tq without the low restriction exhaust behind them,and in most cases that requires a larger diam. exhaust system and adding an (X) to the system and extending the header collectors at their full diam. up till at least the exit of the (X) so the twin exhaust pipes cross sectional area can provide that reduced restriction to flow, rather than the reducers many guys install to the collector exits to adapt them to the stock exhaust system.

With an 'X' type crossover arrangement, design ( the angle of convergence, tubing cross sectional size, volume, or area where they converge) and placement or distance from the header collectors are very important. If possible, an 'X' type crossover should be placed at the exact point in the system (measured length) that you would terminate tuned collector length in an open header system having no mufflers nor tailpipes, as the correctly sized (x) provides a sudden reduction in restriction similar to having open header collectors exit to the open air in some respects




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[b] heres a great example of really crappy quality install, done by a muffler shop ,and one reason an (H) pipe that is not installed correctly will tend to have a rather bad reputation, as too equalizing the exhaust flow rates or pressure, keep in mind at higher rpms you might easily have 50 exhaust pulses per second, making an (H) pipe all but useless,, especially if the connecting passage is far smaller than the pipe diameter, while a properly installed (X) pipe blends the pulses very efficiently


[color=#008000](H) PIPE


[/color]example of a well laid out exhaust (MELROSE)[/b]
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on most SBC or LS based high performance engines of at least 350 cubic inches, designed to exceed 400 hp, the GREEN ARROW primaries should be 1 3/4" and at least 33 -38" long the RED ARROW or exhaust will usually perform well with a 3" diameter

if you look closely youll see the major difference is how easily exhaust flow pulses can move into the adjacent pipe to balance flow, the (H) pipe requires two 90 degree turns while the (X) pipe can easily balance with only part of a pulse expanding as it passes the (X) PIPE) merge point, the ease in balancing pressure, and reducing restriction greatly favors the (X PIPE DESIGN)

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notice the X pipe design has several variations, the type above is more effective than the type below at blending and equalizing the pulse volume from either side but even the more restrictive version below still works well.
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heres a good example showing why an (X) pipe is very efficient at equalizing and blending exhaust pulse flow rates
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Heres a fairly standard (H) pipe exhaust lay out (above)
one lesson most guys don,t usually learn right away, that I constantly try to point out is that buying a few CAREFULLY SELECTED,QUALITY COMPONENTS usually is a far better route to take when building an engine than buying a greater number of lower quality components, like a decent roller cam, heads and a good low restriction exhaust

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but even that system could be hurt if you slap restrictive mufflers on it

bjhines posted these and their good examples
looking thru an (X) pipe
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mocking it up, this type of (X) pipe generally provides a noticeable reduction in the restriction to flow that helps hp
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http://www.fordmuscle.com/archives/2000 ... ndex.shtml

"X Versus H
It's long been known that connecting the two sides of a dual exhaust system, shortly after the headers, increases power and reduces sound. However in a traditional "H" pipe,its mostly, only sound and pressure waves that cross through the connection. most of the Gasses take the route of lowest pressure, which is straight out the pipe, rather than making a 90 degree turn in to the H.
Indy and Nascar teams have been using "X" type crossovers for quite some time. In an "X" pipe the gasses from both cylinder banks actually pass through a common area. This not only provides the benefits of some sound wave cancellation, but also increases the scavenging effect, helping draw out spent charge from the combustion chamber.
So how much of an increase does an X gain over an H? It's hard to say, especially considering that every combination will yield varying gains. In theory an X will work better as rpms go up. Considering the Flowtech X-Terminator pieces are priced under $50; you're much better off getting that, rather than having a shop fab up a crude 'H' piece."



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read thru ALL the sub linked info in this thread, and ITS SUB LINKED THREADS
its not at all rare for a swap from 2.5"-to-3" exhaust on a sbc or mild bbc or from 3"-to-3.5" on a radical big block to add 5-15hp,OR MORE, depending on the restriction that was removed behind the collectors or exhaust manifolds, back pressure reduces the effectiveness of the exhaust cylinder scavenging, and once you tune the engine to take full advantage of that reduced restriction and better cylinder scavenging factor you get the full benefits that the reduced back pressure tends to provide.
keep in mind the lower rpm TORQUE LOSS thats occasionally reported is FREQUENTLY a tuning issue as the more effective scavenging tends to lean out the effective fuel/air ratio
what most guys don,t understand is that your results will depend to some degree on the cam timing and engine displacement, intake runner design, and the rpm range the engines run in,its the length and diameter. of the header collectors ,entering the point where the (X) or (H) is located AND the flow restriction in the exhaust system in the collectors and primaries that will effect the cylinder scavenging,and the restriction to exhaust flow rates BEYOND that point, that the mufflers provide that will effect the results, and some those factors will change as the rpms increase.
HAVING the ability to test the vacuum or back-pressure, at the x or h pipe and beyond, will usually give you some indication of the exhaust system efficiency, what your trying to do, in most cases is increase the volumetric efficiency of the engine thru more effectively scavenging the cylinder in your intended power band, by reducing the exhaust system back pressure at and beyond the (H) or (X) pipe by splitting high pressure pulsed flow from each collector into the lower restriction , blended flow into two exhaust, pipes sharing the flow which at least in theory cuts the restriction, past that point noticeably.
if you can increase the rpm range, that the cylinder scavenge effectively at, with a low restriction beyond the tuned collectors, thru higher volumetric efficiency in the upper rpm band, power tends to increase


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here above is a rather typical (X) pipe, the exhaust pressure pulse splits its flow and significantly reduces back pressure as the pulse enters the (X) as its effective cross sectional area almost DOUBLES , dropping that back pressure almost in half at that point, which usually increases cylinder scavenging potential of tuned headers, and increasing higher rpm power if used, and usually reducing noise as the frequency is disrupted, inducing a mellower tone.

EXHAUST flow is not at a constant pressure, its in pressure waves
an (X) and to a lesser extent an (H) pipe in an exhaust doesn,t BALANCE the flow, it effectively DOUBLES the area each separate PULSE of high pressure exhaust, in each cylinder, sees as its dumped into the collectors,each pulse in the header primaries introduces a high pressure wave into the collector as it enters the collector and introduces a low pressure reflective wave back up the header primary, if the size and length are correctly calculated that negative pressure reaches the exhaust port at time the exhaust valve from the next following exhaust cycle exits the cylinder to increase the scavenging of the cylinder ,helping to draw more of the intake charge from the intake runners during the overlap period and into the cylinder to increase volumetric efficiency in the intended rpm band.
in a correctly designed system the header collectors feed directly into the junction of the (X),or (H)at the same diam. as the collector diam., and only after the junction point is the exhaust pipe diam. reduced (IF THEN)
remember the goal is to increase the cylinder scavenging to increase the volumetric efficiency and thus extend the torque curve, by reducing back pressure and increasing the length and strength of the negative pressure wave that helps scavenge the cylinders, and that pulse helps draw in the intake runner charge of fresh f/a charge, as its fast exiting inertia drags the intake charge along with it.
in fact its not unusual for a correctly designed exhaust with a matched cam timing to draw a small percentage of the intake charge thru the intake and out thru the exhaust valve as the piston descends on the intake stroke during the cams overlap period.
The idea behind an exhaust header is to eliminate the exhaust manifold's back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. The individual pipes are cut and bent so that each one is the same or nearly the same length as the others. By making them the same length, it tends too guarantee that each cylinder's exhaust gases arrive in the collector spaced out equally so there is little or no effective back pressure restricting flow generated by the cylinders sharing the collector.

theres a great deal of info on the site about selecting or building headers, but one major factor is that a NON-RESTRICTIVE exhaust system MUST be installed with ANY HEADERS to allow them to work correctly. for headers to work correctly they require an exhaust pulse to allow its inertial energy to drag the following charge along with it out the exhaust.
if you can,t visualize that it might help to find a 3 ft long section of 2.5" pvc pipe and wrap a bit of tape around a full coke can so it slides easily thru the PVC, pipe but fills its interior diam., now place the pipe horizontally insert the coke can and drop the opposite end strait down while you hold your hand over the end the coke can was inserted into, as the mass of the coke can falls you'll feel air dragged with it , the same basic thing happens with an exhaust pulse, its mass is far less but its traveling much much faster, and depending on the rpm and displacement it does generate significant energy that can be used to draw the next intake runners charge into the cylinder as it draws out the next exhaust charge during the cams overlap duration (LOOK INTO CAM TIMING)
keep in mind the LENGTH of the header tube effects the rpm levels and energy transferred as it takes time for that mass of hot exhaust gas to travel thru the primary tube, naturally a longer distance tends to require a longer time and the longer duration tends to impart a longer and stronger negative pressure wave to assist the next pulse IF ITS TIMED CORRECTLY and the header primary tube is the correct diam. and length for the engines displacement,compression, cam timing, and several other factors, but again, it works far more effectively if the exhaust system is a low restriction design that doesn,t reduce the scavenging effect of the pulse waves, and the tubing is long enough to work effectively


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http://www.slowgt.com/Calc2.htm#Header

http://www.bgsoflex.com/auto.html

these threads might help

http://www.pontiacracing.net/js_header_length1.htm
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: (X) or (H) PIPE

Postby grumpyvette » January 29th, 2010, 5:03 pm

ISKY CAMS POSTED THIS RELATED INFO

Longer Exhaust Duration: Is this really necessary?

Most stock camshafts from American production V8, V6 and 4 cylinder engines manufactured today are ground with the longer exhaust lobe duration. Or, another way of looking at this is that they are ground with shorter intake durations! The former embraces the viewpoint that either the Exhaust Ports or Exhaust Pipe system is somewhat restrictive, and is in need of an assist. The latter suggests that the intake system is rather efficient and cam timing can be trimmed back a bit with out much sacrifice in power, in order to maximize throttle response and cruising efficiency.

Take your pick here. There is no absolutely correct viewpoint - because both are probably true! In a stock engine running at conservative RPM levels, for the sake of overall efficiency, fuel economy and a quiet smooth running engine, this staggering of intake and exhaust duration is quite common and appropriate.

However, High Performance is another thing entirely. Change one factor, let's say in this case, the exhaust system (installing headers and larger pipes) and you have just negated in most cases, the need for that longer exhaust lobe. Now couple this change with a different intake system and camshaft and you have really scrambled the equation. But, wait just a moment. Why is it that so many people (racers & cam grinders alike) insist on running a cam with longer exhaust duration regardless of what equipment is employed? The answer is "habit". Most of them have been somewhat successful in doing it their way and will probably never change unless virtually forced by circumstances to do so.

Before we go any further however let's review what it actually is we are trying to do with an engine when we attempt to make more power. Our best result comes when we are cognizant of the fact that an engine is basically an air pump. We pump it in and out (although in a different form) and we have problems when one side or the other is restricted. Balance or the equilibrium or flow should be our objective, unless of course we are not trying to make more horsepower!

Example #1 (Oval track racing) Here, I have often observed that the most experienced drivers are those who are most likely to run a single pattern (equal on intake and exhaust duration) cam. Why? Because such cams always, I repeat always make more torque! These veterans have a more educated foot and greater experience in feathering the throttle in the corners. They can therefore, utilize the benefit of added torque, in the lower to mid RPM range, to their advantage.

Their counterparts, the younger drivers on the circuit, generally are not as experienced and may at times actually get "crossed up" in the corners especially with a lighter car or when they are learning the ropes. In their case, a longer exhaust duration is often the more appropriate choice. It will often help them to drive better, more "flat footed" if you will, without consequence. But please for the sake of accuracy, let us be truthful. The benefit comes from an actual bleeding off of low to mid range torque, which is always what happens when Exh. Duration is lengthened, not from any improvement. The improvement, (if any) would come because of an improvement in scavenging at the extreme upper end of the power curve and would usually be marginal at best. Yet the so-called "extra power" potential of a longer Exh. Duration cam is most often why they are touted - power most people are backing away from at the end of the strait away!

Example #2 (Drag Racing) At the drag strip it's a little different and I feel more honest. Here, racers have long enjoyed longer exhaust and longer durations across the board (If I may add specifically for the purpose of "killing" low-end torque) to keep the tires from too easily breaking lose. This has been successful and sometimes actually results in a slight increase in top end power - something you can actually use in drag racing since it is a full throttle endeavor through the lights. Keep in mind here though, it's quite possible that a longer duration cam overall would have done just as well or better. In other words if you needed that longer exhaust for top end, perhaps the intake could have benefited from such a lengthening as well.

One of my favorite expressions is how "The Drag Racing mentality has infiltrated the ranks of Oval Track". Many have crossed over and made the switch in the past 10-15 years and some have brought their preconceived notions about how to cam an engine with them. A few may actually read these concepts and if they do so will at least come away with a better understanding of what they are doing. On the other hand they also could find that this information might actually help their cars to run just a bit faster!
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: (X) or (H) PIPE

Postby grumpyvette » January 29th, 2010, 5:05 pm

Intake Restriction and Over Scavenging: "Waste not...Want not!"

It is certainly an over simplification to make the statement "that which is not wasted, should be inducted". However, in the case of restricted intake systems and in particular 2-BBL carb rules, it is not far off the mark. Engines with such restrictions are "choked off" to the point where they will not run much past 6500 RPM (if even that high) without dropping off sharply in power. You might have trouble running very fast yourself if someone had your windpipe choked down to say 50 or 60% of it's normal capacity. Under such conditions, would you volunteer to give blood at the Red Cross? Of course not, but without knowing so, racers often do the equivalent with their engines by running a camshaft better suited for a 4-BBL class! How So?

If you'll recall in last months tech tip: "Longer Exhaust Duration: Is This Really Necessary?" I discussed how, through habit, many racers and cam grinders alike are predisposed to running camshafts with longer exhaust durations, whether they need to or not! Well, in the case of restricted intake applications, if there was ever a situation in which you'd want to avoid the longer exhaust "trap" it's here! Especially the 8, 10, 12 or even longer degree spreads, I often discover people employing.

Use such a cam at you own risk - and don't be surprised to find that your exhaust temperatures are unusually high. Your headers in fact may even glow cherry red. There is a very good reason for this. Raw (unburned) fuel is burning "late" or in the pipe (header/manifold). You may have a good equilibrium of flow going here but there is just one problem. Much of what should be inducted into the cylinder is being scavenged out the exhaust! You see, although back pressure in an exhaust system can be restrictive, the only thing that could be even worse is a reduction of it to the point where you are now, in effect pulling a vacuum. In the case of an intake restriction, very slight back pressure is preferable to avoid "over scavenging".

Yes, Yes I know. You are probably thinking "what's wrong with a little scavenging?". Well, nothing if you can afford it. But with intake restrictions (either small 2-BBL carbs and/or restrictor plates) you must be very careful. You already have reduced intake potential and therefore simply cannot be cavalier about valve overlap and scavenging or you'll be way down on power and have those nice bright cherry red pipes to show for it! Case in Point: One racer who called me was in this exact situation and was running, not surprisingly, a 14 Degree longer exhaust duration. It was Friday afternoon and he needed a cam the next day for the last "points race" of the season and UPS had already picked up at Isky. "Too Bad" I said, "You don't have a set of those low ratio break-in rocker arms because they could really help in this case". " I do have some" he said "but they are only 1.2:1 ratio - is that okay?" I told him to use them (on his exhaust valves only of course) and he finished the race 2nd having come from the back of the pack. Later we made him the right cam so he could avoid this make shift approach.

Unfortunately, the symptoms are not always as obvious as in this case to allow for a speedy diagnosis. Also, it's not only longer exhaust duration that causes the problem. Although it is usually the primary offender, it is often coupled with too close a lobe separation angle of say 104 Degrees. A widening to 106 Degrees or preferably 108 Degrees (some go even wider) is usually prudent.

I am not absolutely dead set against a slightly longer exhaust duration in these cases as a 2-4 Degree longer exhaust lobe is permissible under some circumstances (if your running a completely stock exhaust system including mufflers for example). Each case is different, depending upon the equipment employed. I might even recommend shorter exhaust duration to some; if I feel they have "overdone" their exhaust ports and or exhaust system a bit. What matters is the end result and if you're out of balance on one side simply employ what I call the "Great Law of Compensation" to bring you back to that equilibrium of flow.

So, how can you tell if you may need to make some of these changes in your camshaft? Well, short of trying a lower exhaust rocker arm ratio, you can increase exhaust valve lash .004" - .008" temporarily to see if there is any improvement. You can also try and increase restriction (smaller headers or pipes, or in the case of open headers a longer collector) and simply observe the results. Remember, "One test is worth a thousand expert opinions". Keep this old axiom in your "tool box" and you'll be ahead of the game. How do you think Smokey's shop got to be "The best Damn Garage in Town" anyway? Yes, he had those country smarts, but his experiences in racing and his willingness to test are legendary!
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: (X) or (H) PIPE

Postby grumpyvette » May 16th, 2010, 11:41 am

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heres a good VISUAL shot to show why an (X) pipe is far less restrictive to balanced/ blended flow
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BTW on my last BIG BLOCK C4 swap I had TWO 3" (X) pipes and got a bit creative and well built a DUAL (X) exhaust that was similar to this PICTURE BELOW. the result was a rather unique exhaust tone, a nice smooth rumble note in the sound and a very nice smooth low and mid rpm torque curve, now Im not sure if the exhaust mod added or subtracted from the power curve because I didn,t try it with a different exhaust config. but I got the strong impression that it helped, I know it made the sound distinctive and more mellow, bye having the exhaust pulse blending twice the scavenging effect in the cylinders seemed to noticeably increase efficiency, keep in mind the benefit of an (X) pipe is your effectively doubling the flow area and cutting the pulse strength into two roughly equal pulses, a second (x) allows those pulse to collide, further reducing potential noise and further smoothing flow in each pipe

Image

Image

http://www.jegs.com/i/Hooker-Headers/52 ... oreDetails

Image

when selecting an exhaust you can refer to the linked info for sizes, but
a basic exhaust laided out similar to these pictures above with headers feeding 3" exhaust and an (X) pipe tends to provide excellent results, on most cars if matched to low restriction mufflers,keep in mind the idea is to reduce flow restriction and increase cylinder scavenging, thru the design.
just remember the main goal is improved cylinder scavenging and low restriction to flow while reducing the noise level, in roughly that order but obviously theres compromises that are made due to clearances and noise ordinances
a well thought thru design on an (X) pipe and cut outs
keep in mind headers loose a great deal of their potential horsepower gains if there matched up to a restrictive exhaust

Image

Image

btw adding an (H) pipe
Image

http://www.jegs.com/i/Flowmaster/389/15921/10002/-1

the question often comes up about use of mandrel bends vs crimp bent exhaust pipes, in designing an exhaust system, well it should be noted that its the cross sectional area much more than the shape of the pipe thats the more important factor, while its true that mandrel bends do maintain a more consistent cross sectional area, simply selecting a slightly larger diameter non-mandrel bent exhaust pipe size with its larger cross section can frequently be the less expensive route. as long as you've got an (X) pipe in the system and the tail pipes are nominally the same diameter IE lets say 2.5" or 3" the type of bend at that point will be all but meaningless due to the fact that by that point the exhaust pulse strength and velocity has been significantly reduced thru cooling distance, the effect of the (X) pipe splitting the pulse,and the lack of significant restriction.
every test Ive ever seen shows that an (x) pipe mounted near the header collectors and mandrel bends on collectors do help flow, but youve effectively almost doubled the cross sectional area after the (x)and because the engine fires every 90 degrees the pulse of exhaust past the (x) is significantly reduced in exhaust pressure, your exhaust will normally require an exhaust pipe that will handle the flow based on the engines air flow rate and horse power
you can use the info posted
Image



knowing a few constants in engine pressure and flow helps


an engine usually requires approximately 2.257 cubic feet per minute per horsepower to maximize intake flow and exhaust flow at about 115 cfm per square inch

so assuming your building a 500 hp engine / 2 (divided by 2 as there's normally two header collectors on a v8) we have 250hp per header collector, (open header collectors) multiply that by 2.257 cfm and you see you need 565 cfm and divide that by 115/square inches and we see we need a 4.9 square inch minimum exhaust collector pipe, per side (open header collectors).

as a cross check 500hp /8=1129/8=142 hp per header primary , 2.257 x 142/115=2.76 sq inches 0r a header primary a bit larger than 1 3/4 and smaller than 2" or a 1 7/8 to maximize peak hp, per header primary, but keep in mind you'll spend most of your time below peak rpms so a slightly smaller 1 3/4" primary on a street strip engine that sacrifices a bit of peak hp for better mid rpm torque makes sense, and once you install longer exhaust pipes and mufflers you'll need to steep up the exhaust pipe size cross section past the header collectors or they will tend to be restrictive at the minimum size the formula predicts

viewtopic.php?f=56&t=1730&p=5392#p5392

viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=1503


Image
just in front of the muffler entrance point can slightly further reduce noise and mellow the tone

related info


viewtopic.php?f=56&t=1303

viewtopic.php?f=56&t=495

http://www.boyleworks.com/ta400/psp/exhaust3.html

http://www.boyleworks.com/ta400/psp/exhaust.html
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: (X) or (H) PIPE

Postby grumpyvette » July 6th, 2012, 10:58 am

http://www.wholesalemarine.com/p/MOE-02 ... nQod21jA7Q
Image
spraying a corrosion reducing spray on your exhaust system welds with zinc chromate spray tends to significantly reduce the formation of rust on welds, this tends to extend your exhaust system life expectancy and is highly recommended after welding even on stainless exhaust welds.
IF YOUR WELDING STAINLESS USE A MINIMUM 16GA 18 GA is too THIN, FOR STAINLESS HEADERS OR EXHAUST PIPE, AND DON,T FORGET TO PURGE THE BACK GAS WHEN WELDING , and 321 is superior to 304 stainless
it would be difficult to over stress how important having the correct tools and the skill to use them are on modifying parts, frankly I can,t imaging a shop without some basics like a couple welders and a drill press and a belt sander, air compressor
and die grinders etc.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: (X) or (H) PIPE

Postby grumpyvette » October 3rd, 2013, 10:44 am

Spezzy wrote:Hey guys,

Have a '76 daily driver, approx 250k in 7 years. Only has Custom Image 1 7/8" headers and Edelbrock Performer RPM Air gap intake. Waiting to install Procharger later.

I recently had a true dual 3" exhaust made, no mufflers or cats. It was very loud, just what I wanted in sound. I had always read about X-pipes and such quieting exhaust a bit, but sound clips on YouTube made it seem very minor.

I was surprised when I started up the car after the X-pipe install. I used a Flowtech unit. Start up wasn't drastic, but all drone was gone. Can easily have a conversation inside now.

The sound is MUCH quieter.. Inside it is like a Corolla (seriously..) Outside it is no longer deafening as it was before, but the tone is deeper. It also sounds like it is revving much higher than it really is. 3500 RPM sounds like 5500.

I'm still waiting to see if I like it as much or not. No popping on decel, brap brap sound..

The main thing holding me back from removing it is the fact that it drives SO much better. Kick in the pants feel. Definitely more torque.

I'd liken the true dual to a Harley in loudness.. X-pipe not sure in loudness yet, but it isn't deafening in the least, even revving in underpasses.

Maybe it will grow on me more. Thinking of trying a different style of X-pipe as well, like the Magnaflow Tru-X. The Flowtech unit is similar to the Dr. Gas, NASCAR looking.
Image
I'll upload videos soon. Unfortunately I never did a rev video with true duals, but have an idle one.


ADDING the (X) pipe reduces the EXHAUST flow restriction,by effectively doubling the internal pipe cross sectional area, and tends to INCREASE the cylinder scavenging efficiency,by blending the pulses effectively extending the low pressure scavenging the cylinders, plus it tends to mute, and smooth out and lower the noise levels and tone

https://www.holley.com/types/Maximum_Flow.asp

http://www.dynomax.com/mufflers?muffler ... ameter=171

http://www.jegs.com/p/Flowmaster/Flowma ... Ntt=744765

http://www.summitracing.com/parts/wlk-1 ... 7AodgW4AYg

http://www.summitracing.com/parts/sum-638270

http://www.summitracing.com/parts/pye-mvr70

I don,t know the size mufflers used ,theres dozens of similar ones sold by several manufacturers
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: (X) or (H) PIPE

Postby grumpyvette » July 24th, 2014, 11:01 am

CORSA came out with a more efficient DUAL (X) PIPE exhaust and headers for the c7 corvettes, the increased scavenging effect of dual (X) pipes is something I've promoted for decades
MY c4 vettes exhaust looks similar to this
Image

Ive always been amazed at the number of guys who think the only options they have in components , they can use on a car, involve buying and installing parts listed in a catalog.
adding a dual (X) to the exhaust system has proven to reduce the decibel level and spread the torque curve on several corvettes, Ive done that mod to the exhaust on,as it tends to increase the cylinder scavenging efficiency,and reduce the exhaust back pressure, and I read that modifying headers in a similar manor is worth .05 seconds on several cars, so don,t think a bit of thinking outside the box as they say won,t pay off in a bit more power or power over a wider rpm band.

Image


http://www.pfyc.com/pc/C75003/C7EXH/Cor ... ngray.html

http://www.pfyc.com/pc/C75005/C7EXH/Koo ... ngray.html

heres the new corvette dual (x) pipe
Image

https://www.youtube.com/watch?v=f61NC3It8Jc
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: (X) or (H) PIPE

Postby philly » August 4th, 2014, 7:46 pm

oh thats fancy! sounds incredible by the way on the c7
-phil

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