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Old 08-01-2007, 08:05 AM
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Why an H pipe ??

Why do i see everyone suggesting H pipes for their exhaust builds? Originally i was planning on headers with dual exhaust and two mufflers. Just run a header the pipe and the muffler independent of each other completely. Is this not a good idea? and if not then why?

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Old 08-01-2007, 08:27 AM
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H pipe balances pressures in both sides of the exhaust. It relay does help the motor make more power, and X pipe is better than a H pipe.

The way it works is this

One cylinder fires at a time, so its only able to use one side of the exhaust. With a crossover pipe, each cylinder can use EACH side of the exhaust. Witch results in less back pressure and a better sound (in my option)
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Old 08-01-2007, 09:25 AM
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right-on target! Brian
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Old 08-01-2007, 09:32 AM
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Ive run H pipes before and not seen any real noticable gains in power. It does tend to deaden some of the lower tones...but, overall I think it was not worth the expense and work involved...
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Old 08-01-2007, 09:37 AM
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I have seen two examples (my neighbor's 70 Chevelle w/454, and my street rod w/350) that have both benefitted in seat of the pants accelleration.

And yes, it sounds wicked!! Also makes it more comfy to cruise, cause it seems to tone the note down, take away some of the dreaded droning.

I think it's worth it!

H - pipes are easy to put in, X-pipes not as easy.
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Old 08-01-2007, 10:24 AM
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Quote:
Originally Posted by Holder350
H pipe balances pressures in both sides of the exhaust. It relay does help the motor make more power, and X pipe is better than a H pipe.

The way it works is this

One cylinder fires at a time, so its only able to use one side of the exhaust. With a crossover pipe, each cylinder can use EACH side of the exhaust. Witch results in less back pressure and a better sound (in my option)
correct, ive been putting H pipes on my cars since the 60s and the benefit is more power and quiter exhaust. X pipes are just an expensive way of doing an H pipe with the same benefits.
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Old 08-01-2007, 10:37 AM
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Quote:
Originally Posted by REALGONEKATT
Ive run H pipes before and not seen any real noticable gains in power. It does tend to deaden some of the lower tones...but, overall I think it was not worth the expense and work involved...

Well me either, I would never put in a X pipe......those look like a Pain in the
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Old 08-01-2007, 01:49 PM
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works on the same principal of 180* headers right
Shane
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Old 08-01-2007, 02:01 PM
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No, not the same as a 180 header because the adjacent cylinders are not cossed over in the collector to opposite sides.

My choice 100% of the time is to run the X pipe. They perform better and with a loud exhaust smooth out the resonance much better.
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Old 08-01-2007, 03:37 PM
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when I was a kid I always heard mostly SBCs poppin and kracklin when they would let off it. but if you tie the two sides together (H pipe) it equalizes the back pressure between the 2 sides and stops the poppin and kracklin. my uncle usta buy old 6 cylinder chevys to drive to work and he split the manifolds and run duals all the way back, and he loved the poppin kracklin (I liked the sound of the straight six too). even when I was a kid with headers and dual exhaust out the back, I tied the 2 sides together with a homemade H pipe. heck my Olds Cutlass has stock ex manifolds and duals out the back, and the two are tied together prob 18" to 24" behind the manifolds with a homemade H pipe, a exhaust shop did it. we were taught to always do it if it run out the back. if I run headers and a short chunk of pipe off each header to a turbo muffler and then turn it down, theres times we didn't tie the two sides together. my buddie has a 72 Chevy P/U we put exhaust on in early 90s. it has headers and a short chunk of pipe off each header to a turbo muffler and then it turns down off the muffler, and the two sides are tied together.......
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Old 08-01-2007, 03:40 PM
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Quote:
Originally Posted by Mustangsaly
when I was a kid I always heard mostly SBCs poppin and kracklin when they would let off it. but if you tie the two sides together (H pipe) it equalizes the back pressure between the 2 sides and stops the poppin and kracklin. my uncle usta buy old 6 cylinder chevys to drive to work and he split the manifolds and run duals all the way back, and he loved the poppin kracklin (I liked the sound of the straight six too). even when I was a kid with headers and dual exhaust out the back, I tied the 2 sides together with a homemade H pipe. heck my Olds Cutlass has stock ex manifolds and duals out the back, and the two are tied together prob 18" to 24" behind the manifolds with a homemade H pipe, a exhaust shop did it. we were taught to always do it if it run out the back. if I run headers and a short chunk of pipe off each header to a turbo muffler and then turn it down, theres times we didn't tie the two sides together. my buddie has a 72 Chevy P/U we put exhaust on in early 90s. it has headers and a short chunk of pipe off each header to a turbo muffler and then it turns down off the muffler, and the two sides are tied together.......
My camaro has cherry bombs welded to the collectors

lotsa noise
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Old 08-01-2007, 04:56 PM
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Quote:
Originally Posted by Holder350
My camaro has cherry bombs welded to the collectors

lotsa noise

I had a 67 GTO and when I 1st started taking it to the strip 55mi away, we would pull in and unbolt the purple hornies and run. at the end of the day, bolt um back on and drive home. (sometimes limp home) when I got into the high 12s I trailered it to the drag strip, mostly cause more things could and did go wrong. man them were the days. we were young and we loved it. my wife even enjoyed it when we 1st met. I sold that Goat to buy a house, well to put a down payment on a house. as my 1st daughter was on her way. I miss the car, but still have my daughter & my wife. my daughter is 26 now D: man time flys.............................



I run these bolted to the header

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Old 08-01-2007, 05:06 PM
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Quote:
Originally Posted by tinman386
Why do i see everyone suggesting H pipes for their exhaust builds? Originally i was planning on headers with dual exhaust and two mufflers. Just run a header the pipe and the muffler independent of each other completely. Is this not a good idea? and if not then why?
This is one of those places where there's a lot of "Rocket Science" going on.

Basically, it's hard to get pipes and mufflers with enough capacity for a V8 at WOT. 800 CFM carbs or bigger are easy to get while 800 cfm capacity in an exhaust system takes some careful parts selection. Most mufflers, especially cheap ones don't come close (usually about half or less that for a good muffler) so it takes two in order to provide the needed flow capacity.

When duals are tied together, it allows both mufflers to be used by the engine at any given moment, essentially doubling the flow area any cylinder sees. This reduces back pressure which improves fuel efficiency and power. Surprisingly, with no other changes to the engine, a typical mild OEM V8 will pick up a mile or two to the gallon and 5 to 10 hp when duals are installed on a vehicle that's used in a mild cruise operating area of its power band; where you'd think duals wouldn't have an impact on engine performance. Of couse they're even more effective for an engine that works hard like a turck needing lots of throttle opening or a high performance engine spun up to a lot of RPM.

However, one of the problems with duals at slow to moderate speeds is keeping the exhaust velocity up so that it pulls a negative pressure in the cylinder during the cam's overlap phase. This allows for complete blow down in the combustion chamber space which the piston can't positively force evacuation of like it does the cylinder. Also, the resulting negative pressure launches the intake mixture into the cylinder as the intake valve just starts to open.

Here's where you get into some Physics of pipe design. An H pipe is typically close to the front of the system because space permits it to be there. At lower RPMs where the extra area/volume of the the duals isn't needed, the exhaust slug pretty much ignors the crossover pipe, keeping velocity up in the primary pipe into which the slug was exhausted. As RPMs come up, back pressure rises to a point where the exhaust slug will begin to use the H pipe as an additional path to more evacuation area/volume. The flow here becomes fairly turbulent as the H pipe presents nothing but sharp edged, right angle corners, this causes efficiency of the pipe to drop as RPMs get really high. The X pipe's crossover is always located further back because it needs a lot of space and the transmission is in the way up front. But as it turns out for "RS" reasons it needs to be further back so things just work out right thru no fault of our own. The X pipe with its smooth transition presents the total area/volume of both pipes and mufflers from the crossover point back to all the flow all the time. At low and moderate engine speeds any exhaust slug entering here can't escape seeing all the area/volume because of the smooth transition. This requires the head pipe to be longer to provide time where the exhaust flow is speedy in the smaller pipe at low to moderate engine revs so that cylinder blow down is evacuating the combustion chamber and intake is starting properly during the overlap phase of the cam. The upside is that the X transition doesn't develop high speed flow interference the H pipe does because none of the flow is forced to make right angle turns which generate a lot of turbulence resulting in the pipe looking smaller to the flow trying to get thru it. The disadvantage of the X pipe is that space is a premium under the car and the X pipe uses a lot of it.

Both pipes will tend to reduce exhaust noise as sound waves take advantage of twice the pipe and muffler area/volume which dissipates them more effectively. This lets you get away with higher flowing mufflers which tend to be noisier than quieter but lower flowing mufflers.

Bogie

Last edited by oldbogie; 08-03-2007 at 11:55 AM. Reason: sentence structure
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Old 08-01-2007, 06:42 PM
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Quote:
Originally Posted by Mustangsaly
I run these bolted to the header

Yeah I was gonna get the purple hornies, but they were $40 a peice and the unpainted cherrybombs were only $15

cheap skate that I am I made some.....er.....rusty hornies!!!
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Old 08-01-2007, 10:12 PM
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Actually, with exhaust X-pipes the almost seamless connection between the two exhaust pipes allows sequential firing cylinders to salvage any spent exhaust gases from the combustion chamber more efficiently and creates more room in the cylinder for a fresh intake of undiluted fuel and air. When you have two exhaust pipes, as the velocity in one header tube increases, the pressure in the adjacent tube is lowered causing the exhaust to be sucked out of that cylinder. X-pipes are simply better at doing the job, especially at higher speeds. It's not so much the extar volume of the exhaust system as it is the scavenging effect of the adjacent power stroke.
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