General questions: 1. what is the difference between an x-pipe and an h-pipe and true dual exhaust? I know what they look like, I mean performance-wise. Which one is better for street/highway? 2. does larger diameter pipe=louder? Maverick/Comet specific questions: 1. I'm putting a 99 Explorer 5.0 and AOD in my Maverick. I have Hedman shorty headers. Will a cat back exhaust system for a Fox body Mustang work with a little tweaking? The reason I ask is because last week I saw a complete fox mustang exhaust with x-pipe and mufflers for $120, and I only have headers so far. 2. Flowmaster recommended the 70 series to me in an email, I understand they are very big, is space an issue with our cars? 3. Borla recommends the AT-S, which one is more bearable for hours at a time? All of the comparisons I saw were of the Flowmaster 40 and super 44 and the Borla AT-K which are both louder than the 70 or the AT-S. (and a Magnaflow that made me want to choke someone..raspy and buzzy as hell.) would I be better off with a 2-in 2-out single large FM70 series, or 2 smaller Borlas? For my build, exhaust sound level and tone are more important than horsepower gains. Has anyone run the Flowmaster Delta 70 or the Borla AT-S on a 5.0 in a Mav/Comet that can tell me what the ride is like?
lol.. look away, Frank. These aren't really "general questions" but I will help fill in some blanks until you have time to study the physics of exhaust flow and system design. Basic answers in red below. Nothing wrong with many of the older OEM case designs like the old school Walker Dynomax super turbos or Cherry bomb turbos. Here's a quick youtube search. Search around to find cars with similar engine exhaust designs to yours and listen. Tons of Turbo style mufflers out there. They don't last as long as some of the other premium designs but they are cheap enough to replace every once in a while too. Hope all this helped.
Thank you, groberts101 that is the information I was after on the X vs. H pipes. By "general questions", I meant ones that apply to any make or model, as opposed to questions specific to Maverick/Comet. I was looking at chambered designs only. I've had several glass pack mufflers and I am familiar with their sound levels. I'm not after a stock sound, it just can't be overwhelming after 4 hours in the seat. I owned a 77 Mercury Marquis Brougham with a 400M/C6 that the muffler exploded on when it backfired once. I replaced the cheap stock muffler with a Thrush Magnum glass pack. It sounded cool for about 30 minutes, after a 7 hour drive, it wasn't so cool anymore.
No problem. Keep in mind that any OEM style crimped case muffler will be subject to splitting open on a heavy backfire. I've split a few Walker Super Turbos open through the years when the tune suddenly goes away and fuel builds up in the exhaust for whatever reason. Pretty rare nowadays though as most of those issues were related to points style ignitions.
Ah, memories. I wasted two mufflers when I had a bad coil. Split them right down the seam. Scared the hell out of me. Micah
A "H" pipe is simply a pipe that connects the left and right exhaust pipes in an effort to equalize the pressure. In my experience, it makes the exhaust somewhat quieter and gives it a more balanced sound from the two tailpipes. A "X" pipe basically accomplishes the same thing, but the left exhaust crosses over to the right pipe and the right exhaust crosses over to the left pipe. You get the equalization of the "H" pipe but with less turbulence. I would say the difference in the two performance wise is probably negligible for a daily driven street car. A larger pipe does not necessarily equate to a louder exhaust, but it can have a detrimental effect on performance in a street car. Pipes too large can slow exhaust gas velocity and increase exhaust pressure to the point of hurting low end performance. A 2.25 diameter pipe is good up to around 350 h.p.. A 2.5 diameter pipe is good up to around 450. If you want to get technical you can estimate the intake CFM of your engine and then multiply by 1.5 to estimate the exhaust CFM of your engine. The result will dictate how large the diameter of the pipe should be for the volume of exhaust gases taking into account gas expansion due to heat. The pipes from the collector to the muffler are the most critical for sizing correctly. The pipes from the muffler to the exhaust tips can actually be slightly smaller due to the exhaust gases cooling and condensing. From what you posted, 2.25 with a "H" running to the mufflers would be more than adequate with either 2.25 or 2 from the muffler to exhaust tips. Others please feel free to correct and post as I only have a rudimentary understanding to pass along.
The exhaust moving through each pipe creates pulses of high and low pressure. Moving gas is lower pressure, static gas is higher pressure. By equalizing the pressure in both pipes with each other, it makes the system more efficient by allowing the exhaust system to assist, through lower pipe pressures, in pulling the exhaust from the engine.
No "pressure" is ever needed in the exhaust system. What is needed is velocity (speed), and a pipe that is too large slows the gases down.
Exactly right. Each exhaust pulse has distinctly different pressure zones in front and behind the individual pulse. What volume of mass that gets displaced as the pulse heads out of the engine will need to be replenished or filled back in once the speed and energy dies down enough for the flow to be reveresed. So, slower gas flow allows for a quicker slowing and easier reversal of direction to cause the next pressure pulse to have to overcome before it can again continue on its way out the tail pipe. The slower the pulse.. the less vaccum is created behind it to help pull the next intake charge into the cylinder on the next firing cylinder. Smaller pipes = more vacuum and less reversion. At least until they reach a point that they can no longer flow the needed amount and backpressure increases to points beyond where that level of scavenging can be beneficial to power output. Ideally it should be matched to the airflow/rpm potential and intake manifold and exhaust manifold sizing of the engine. A simple physics test is to put your hand on the end of the tail pipe. You will first feel it push away as the pulse exits the pipe.. quickly followed by you hand being sucked back towards the pipe as the negative pressure is created behind the pulse. This "negative pressure" is what we call scavenging but unfortunately it can also lead to contamination of the chamber during intake and exhaust overlap. This is why bigger cams tend to lope so hard at idle as the manifold is becoming contaminated by this backwards flow/reversal of pressure waves. As for the true nature of flow through and H or X pipe.. it's not so much about the transitional area changes that allows them to produce more power over completely separated L&R exhaust banks.. but more about the paired firing of each bank over saturating each banks individual pipe and muffler thereby causing an increase in backpressure as rpm/piston speed increases. So, for instance. On our motors with the newer HO/351 firing order of 1-3-7-2-6-5-4-8.. you can easily see that cylinder #1 & #3 are firing only 90° apart from one another on the same right side/bank 1. And on the other left side/bank 2 we have cylinder #6 & #5 firing back to back 180° later. This inherent pairing(unless you're lucky enough to own a new Boss Mustang with a 180° flat plane crank design) becomes even more problematic with lower flowing mufflers and a simple balance tube can help to effectively allow those paired pulses to be shared between both mufflers to reduce backpressure. This flow increase and sound reduction capability is why you see them on many V8 powered OEM exhaust systems. Simple and cheap.. yet highly effective. As mentioned above, an X pipe can allow this bank to bank pairing as well but tends to have an additional scavenging action due to the lower pressures created as one bank of cylinders fires the pulse past the shared opening which is set at a considerably reduced angle compared to the H pipes abrupt 90° turn that the flow will have to navigate. In essence, an H flows less than an X and falls off quicker as rpm goes up. I won't even get into the reverse flow damping and acoustic tuning effects caused by the reflected sound waves. Pretty complex stuff and there's plenty of info around the net if you're that into learning about it. About all the time I have right now.. hope it helps paint a better picture for those inquiring minds out there. lol
Just a footnote .. NASCAR has been using the " X " pipe setup on their cars for decades now .. I've got it on all our cars here in Florida . ( Works great !) Cometized (Chip)
yep.. Dr Gas was the one who started and perfected building them. Remember the crash when everyone got a good view of that top secret design? He once told me that he couldn't have afforded advertising as good as that and his business took off. The spintech style mufflers and boomtubes work pretty well too. Mr Butler is one smart dude when it comes to the physics of hot exhaust gas flow and I have learned a lot from him through the years.
