Which exhaust makes the most horsepower

[todd86]

On a 5.0 w/ H/C/I which exhaust makes the most power? An H-pipe, an X-pipe, or a MAC Prochamber?

[Walter]

I would say x.

[redfirepearlgt]

Got this article from mustang forums. It was a good read. hope it helps. - Chad

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.

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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.

[todd86]

Sound is not an issue w/ me. Just wanna make the most power. Thanx for the info.

[85_SS_302_Coupe]

It usually comes down to sound preference because any HP differences are very minor unless you're running very high RPM. Typically from what i've seen/read/heard, an X gives better peak HP with a slight loss in low RPM torque, whereas an H is just the opposite with more torque and slightly less peak HP. The Pro Chamber, personally i think it sounds retarded so even if it gave 10hp more i wouldn't run one. It's an over priced POS.

Oh...another note, SVT/Shelby installed X pipes on all their serious cars going back to the '00 Cobra R. There's a good reason for it and it's not just sound.

[todd86]

Power is my main concern. Sound I don't care. Motor is gonna rev to at least 7000. Any guys that run NMRA have a preference?

[bbfstanger]

bullets dumped at the axle with pipes as big as the collector.
3in collector 3in exhaust.
there are some really short mufflers out there like the bullets but are only 6-9 in. long, im gonna try them this year.
it would essentially be like running straight pipes.
stay away from the flow junk's they hurt power.
ive had both h and x pipes ,couldnt tell the diff powerwise between the two.
i did some experimenting on hpipes to change the tone of the exh.
alot of them come with a smaller pipe for the h with just a small hole in the pipes, if you go to the same 2 1/2 pipe for the crossover and inlarge the holes it gives it a much deeper tone and takes away the raspiness, is that a word? lol!

[SpoonyGT]

I would say x but I prefer my H pipe and I would love a prochamber

[85_SS_302_Coupe]

If you really want max power then you need to think about scavenging and what you'll find is that ultimately you'll have something like an 18 inch pipe coming off the headers and that's it. Obviously you won't get away with running that on the street.

[5.0calypso93lx]

I remember seeing a dyno comparing midpipes a while ago in one of the mustang mags, and I believe everyone is dead on except I think that the pro chamber really really hurt power across the board.

I personally think the pro chamber sounds the best, but I'm just gonna run an h or x, whatever I find cheapest :lol:

[rmracing]

Power is my main concern. Sound I don't care. Motor is gonna rev to at least 7000. Any guys that run NMRA have a preference?

I run in the NMRA and alot of racers use x-pipes and some also use h-pipes or straight pipes with no crossover . I dont think too many if any run the pro chamber . I used to run a pro chamber until I did some testing and found that the pro chamber made the least power of all the setups I tried . They may work for some apps. but I wouldnt put one on a competive race car .

[todd86]

Thanks for ithe info guys!

[boostanggt]

The easiest way I distinguish between buying the two is that if you have a chambered style muffler system, run an H pipe. If you have a straight through design, run an X. IMO those are the combo's that sound the best. It's all personal preference though. Go on youtube and you can find which one sounds the best to you.

[todd86]

Sound isn't mt concern. Just lookin for power. Gonna go w/ an x-pipe and bullets. I guess that'll make the most power and still sound good. My combo is an edelbrock performer rpm 2 intake, ported performer rpm heads, and a custom cam that I haven't decided the specs on yet.

[85_SS_302_Coupe]

The reason people keep mentioning sound is because you MIGHT be looking at 5hp extra with an X. That much of a difference could be made depending on the weather, how good your gas is, how fresh your plugs are etc. It's not like putting an H on is going to rob you of seat of the pants power. Unless you're building a dyno queen, being a better driver and having better traction will get you further than whatever power extra that an X might give you.

By the way unless something has changed i'm pretty sure NASCAR uses H pipes...and how much power are they making?

[todd86]

When I ran NMRA I would have spent $500 or more for 5 hp. I get what you're saying but I'm the type to sacrifice sound to pick up 5 hp.

[Buckeye]

Most power gains I have seen from exhaust are ones that include a turbo in them :)

[5.0calypso93lx]

The reason people keep mentioning sound is because you MIGHT be looking at 5hp extra with an X. That much of a difference could be made depending on the weather, how good your gas is, how fresh your plugs are etc. It's not like putting an H on is going to rob you of seat of the pants power. Unless you're building a dyno queen, being a better driver and having better traction will get you further than whatever power extra that an X might give you.

By the way unless something has changed i'm pretty sure NASCAR uses H pipes...and how much power are they making?

I didn't even think they ran midpipes? I just assumed it was open longtubes with some small muffler at the end like dirt track cars haha.

[85_SS_302_Coupe]

Like i said things have probably changed since i followed NASCAR, and i didn't much follow it really. I know back in at least the late '80s or early '90s they ran basically straight pipes off the headers that had an equalizer tube between them (technically making it an H) and then they 45'ed out to side exits. I'm sure now they probably run something totally different...don't both exit out the same side now?