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New Exhaust System: Is an X-Pipe Worth It?


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I am looking to get a new exhaust system installed in the next few weeks on my '70 SS454. I will be sticking with stock exhaust manifolds and exiting at the stock, under-the-rear bumper location with the factory-style chrome exhaust tips.

 

I have heard some good things about "crossover" pipes (either in an X or an H configuration), and was wondering if there are any negative aspects of these systems to consider? Is including an X-pipe in a new exhaust system actually worth the additional cost that it will add to a new system?

 

The sharing of any knowledge and/or first-hand experiences with these type of systems is appreciated. smile

 

Thanks,

Dave

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I've had both (currently an x-pipe) in my Monte. I have manifolds and 20" dynomax mufflers. The reason I switched to an x-pipe was to try to get rid of a nasty resonance at ~2000 rpm. It didn't help...

 

There are may opinions about what sounds good- the x-pipe has a higher pitch at full throttle.

Beyond that, I think I'm making pretty decent power through either system. I've used Torque Tech with good results- mandrel bent, fits well, durable. The x-pipe is supposed to be worth more power, but I haven't been to the track since I put it on. Seat-of-the-pants, it feels about the same.

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I've heard good reports about the crossovers. Claims are that it boosts the torque at lower speeds (what you like about a big-block, you will like MORE)and that they help quiet down the exhaust by smoothing out the exhaust pulses.

On the downside they can make it a little tougher to access stuff under the car, and you can't simply drop one exhaust pipe anymore.

I had a crude "H" pipe installed on my car, and it didn't cost but a few extra dollars to have it done when they did the rest of the system. Mine runs across just behind the trans crossmember....a little further back than optimal, but out of the way. I have heard that if you were to spraypaint your exhaust pipes, the crossover should go where the transition is between "burned-off" paint, and paint that stays.

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Dave,

 

I have the x-pipe on my car and it sounds great. I got the 2 1/2 inch mandrel bent kit from "Pypes". What I did was put flanges on the mufflers as well so that if I need to drop the system it's easy. In fact I have already taken it out once...no big deal. Check the pictures.

 

http://www.monteman.com/New%20Project%2020037.html

 

Steve

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Out of experience and over the counter knowledge we all know that connecting the 2 pipes makes for better performance, I had an H added for only $40, it sounds slightly different, I'd say a little quieter (barely noticeable though). The X is considered an improvement over the H as far as I know.

I've heard that an H or X pipe adds around 10hp+ is it true??

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Thanks for the information, guys. Overall, everything regarding a crossover pipe sounds pretty positive to me, so I'll probably end up going with one.

 

Thanks for including the link to the photo of yours too, Steve. A 2 1/2" system is what I'm thinking of going with as well - and yours looks fantastic!

 

Dave

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  • 6 months later...

Here is some pretty good info I think from another website , and pretty technical....

Professor Wizard

Section Moderator

 

With all this discussion about changing Mufflers and Exhausts I thought I would take a moment to explain why you have a cross over pipe (what we call an H or X pipe!), and the difference in concept between the two popular designs. This might help you decide if you which you want to go with!

 

The firing order of all production V8s, regardless of make, has one cylinder in each bank that will fire within 90 degrees of crankshaft rotation of another cylinder in the same bank. This occurs twice during completion of the entire firing order. These two cylinders will be exhausting almost simultaneously into the same exhaust manifold system.

 

Full-length four-tube headers help separate these pulses until the collector is reached. If this is a full race car running "open exhaust", you will notice the collector dumps into a short open pipe at least 2.5 times the size of the header pipes, or the header pipes dump direct without a collector. This is done to avoid the conflict of pressure caused by the timing of the 2 counter firing cylinders, which will create back pressure and degrade torque, horsepower and general performance, especially at higher RPM.

 

On a full exhaust system, after the header tubes dump into the collectors, the two close firing cylinders are fighting each other for space in the collector and exhaust pipe. The result is reflected pressure waves traveling back up the exhaust system, backpressure, lost power and poor economy.

 

At the same time two cylinders exhaust in one bank, there is no activity in the opposite bank. The traditional H-pipe equalizer allows some of the excess pressure to bleed over to the 'quiet side' of the exhaust system, resulting in some low and mid-range torque improvements. At high RPMs, however, in traditional exhaust systems, the gases cannot bleed across the H-pipe fast enough to help power significantly. Performance systems with the H pipe design, attempt to over come this by using a shorter cross over pipe which is also slightly larger in diameter as the main exhaust, then would be used in a standard exhaust.

 

To overcome the power loss of "over loading" the H pipe design, Exhaust manufacturers came up with the X pipe design, which features a tangentially Siamese crossover junction to synchronize exhaust pulses. The X-pipe concept is to split the flow in the crossover junction, so the pressures on both banks will be equal and pulse-free after the crossover, regardless of the rpm. Volumetric efficiency and power are therefore improved at all engine speeds. The negative aspect to the X pipe design is, because of the crisscrossing of the flow stream, harmonic pulsations will develop on some systems at certain RPMs, which will be perceived as a buzzing or humming sound.

 

A newer concept is a "Channel Pipe", where as two pipes are welded together in parallel with a baffle in between them which allows for mismatched pressures and pulses to cross to the idle side while allowing full, uninterrupted or redirected flow of the exhaust stream through the system.

 

Also... There is yet another option.... The MAC Prochamber.

 

It looks like a box, or a muffler where the 2 header leads enter one end and then exit the other in the location of the H or X pipe.

 

It is essentially a combination of all three basic designs I discussed, incorporating the crossover flow of an X pipe – the open buffer of an H pipe and the passive pulse control of a ported baffle channel pipe. MAC is the ONLY maker to have this design.

 

Basically it combines the exhaust into a single box, where the 2 inlets extend into the box a few inches to prevent reversion and open dumping exhaust into the box. The outlets are flush with the back of the box and there is a baffle between the sides with ported slots directing the flow of the inlets to cross to the other side. The Box holds backpressure at a steady rate, which eliminates scavenging.

 

There are many who believe the Prochamber will give increased performance values. Everyone using them will tell you they make a deeper yet quieter tone to the exhaust note.

 

===============================================================================

 

Some of you ask about a Cross Over on a V6.

 

In the case of the V6, with their “Even Firing Sequence… Having a crossover or not, is very dependent on the size of the exhaust and distance from the engine of the pipes placement. A cross over is not required if the exhaust is “tuned” to the engine. Tuned systems are nearly always without a crossover pipe because the length and diameter of the exhaust is specifically designed to work with your engine at a specified RPM Range to avoid reversion and scavenging.

 

On a V6 there is no need for a crossover due to the even firing engine. However, it has been proven that in some instances, a crossover pipe will decrease backpressure and allow for a higher flow. If the crossover pipe is too close to the engine, it allows the pulse timing of the opposing cylinders exhaust cycles, to crash into each other – that is to say, the pressure from a right cylinder will still be present in the left pipe when the left cylinder opens to vent. Too far a placement can create a “Pulse Vacuum”, causing diminished pressure on the venting opposing cylinder, causing decrease in torque (Called Scavenging). .

 

Proper design and placement of the cross over will allow a balance of pressures across the system and therein increase torque, especially at lower RPM.

 

Also, it has been shown that having a cross over pipe mellows out the raspy “ricer” sound that occurs above 3000rpm. So some people install them just for their “sound” value.

 

So, the bottom line is, you probably should have a cross over pipe on a V6 exhaust, even though it is not needed. There is minor performance gain and sound gain as well.

 

=====================================================================================

 

NOW - A couple of people ask about the Cross Over on a Motorcycle - They usually only have 2 Cylinders.

 

It is actually a little more technical but I’ll try to keep it simple.

 

In the case of 4 stroke motorcycle engines, the reason for a cross over is this...

 

After a cylindar fires and the piston cycles “up” - exhausts gas vents through the Exhaust valves, along with the remainder of the “explosion”, exiting the cylinder into the exhaust system.

 

This explosion creates 2 pulse waves… a Sonic Pulse - and a Thermal Pulse.

 

When the faster Sonic Pulse leaves the exhaust it has created a vacuum in the pipe behind it, which air pressure will enter the pipe to fill the vacuum. This air will collide with the Thermal Pulse and cause it to reverse. The timing of this event causes exhausted gases to be returned to the cylinder while the exhaust valve is still open therein not allowing all the spent gas to escape and also polluting the environment for your next stroke cycle with fresh air/fuel mix.

 

This “Event” is call Reversion and seriously degrades performance and lifetime of valves and cylinder heads.

 

The Cylinders fire opposite of each other – or nearly so on a Harley. So when One side is firing, the other side is idle. Having the cross over pipe allows the pulses to dissipate back and forth between the tubes instead of - or before exiting the exhaust and therein greatly diminishing the effects of reversion and so improve performance and engine life.

 

Yes - you see a lot of bikes with duels and no cross over. These are usually "Tuned Pipes".. meaning their length and size are tuned to work with the S/T Pulse in such a way that reversion can not return to the engine before the exhaust cycle has ended.

 

===============================================================================

 

So you ask - "Which is the BEST one to have?"

 

I am sorry to say - the answer to that question is purly subjective.

 

The anwer is... It is best to have a cross over pipe instead stright pipes... Which one purely depends on what performance and audio improvements your looking for. There are positive and negitives with both the X and the H cross overs. Each option improves HP and Torque over not having one. But each one creates a very different sound, and effects different RPM powerbands.

 

Personally, I am sticking with the H because I don't like the harmonics the X creates.

 

Seems like a lot of blahblahblah.gif , but very interesting!

 

I know Rice Racing is quite tech familiar so I would be interested in what he says if so inclined.

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I've had both "H" and "X" designs. The "H" was on a 450hp small block and the "X" is on my current 600hp big block. The small block had 2.5" pipes and the big block has 3.5/3.0" pipes. I hated the drone of the "H" pipe and there didn't seem to be any added benefit in terms of HP/TQ. I initially started with the "H" when I switched to my big block and the droning was worse. I bought the Torque Tech "X" pipe exhaust system I currently have on my Monte and I immediately noticed a difference in tone, resonance, volume, and power. The tone was deeper, the interior resonance was much lower, the lower resonance means that the volume was lower a lower db under normal driving, and both low end torque and upper rpm HP increased. If you want my opinion call Torque Tech and ask for Keith. They will sell you the right system to maximize what you already have and be sure to include any details of further performance modifications. With a big block using manifolds I feel you are robbing yourself of some noticeable power. Especially HP. If you are worried about low end torque, don't be, it's a big block and with headers you probably won't even know the difference. Torque might even increase. It all depends on your combination. As far as header tube diameter goes I'd get with Don on this one. I run 2" Hooker Comps with a 3.5" collector, but that doesn't mean that is the right one for you. Don will steer you in the right direction. As always just my two cents.

BB

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If you are talking about Torque Tech, the number is (800) 408-0016 and ask for Keith. If you mean Don, he goes by the user name RiceRacing1 in here. Torque Tech's web address is http://www.torquetechexh.com/gmaheader.htm Torque Tech can also steer you in the right direction as far as header tube diameter goes.

BB

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Hey Adam, I would ask if you know your stuff about pipes but I'm afraid you would say "no, but I did stay at a Holiday Inn Express". lol I read that whole thing and it was very informative. Thanks for taking the time.

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Thanks for the info 600, I'll keep that info handy.

 

And savva....yeah, it's not my own data :-) I know enough to understand that dual exhaust is a good idea, and turbo mufflers provide the best airflow. But then there are many styles out there from different companies.

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  • 1 year later...

there is one more option.. it's expensive and a hassle.. but it truly is the best option smile use 180° headers.

 

instead of all the odd side cylinders going into one exhaust pipe and all the even ones going into the other...

 

the header tubes are aranged so that with the firing order, the cylinders alternate exahust pipes..

 

so 1, 4, 6, 7 go into one pipe

and 8,3,5,2 go into the other pipe. it creates a real spagetti mess of primary tubes, but it solves all the back pressure problems smile

 

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