I was reading Urbanhunter's (too) technical post about the science of exhaust - it's all fine if you want to know too much. (Nothing against the post mind you).

A few questions come to mind:
1. Do X-pipes gain HP, & if you think they do, how much?
2. What happens if you omit mufflers & just run straight pipe?
3. Who makes the best flowing mufflers on the market?
4. Why are Flowmaster mufflers SO popular?
5. Are "performance" aftermarket catalytic converters better than OE? Why?

It'll be interesting to see different responses.

 

X pipes can gain hp if your exhaust is a restriction right now. It is actually the highest flowing system compared to true duals with an H pipe.

 

That's why it's "More than you'd ever want to know.."

1. Yes they'll give you a performance boost over straight pipes and an H pipe. The only problem an X pipe has than an H doesn't is that occasionally at a very certain RPM (different in each car) you'll get a harmonic reasonance through the pipes (usually heard as a strong humming sound). It's nothing really to complain about though and the power gain is well worth any momentary annoyance. Personally I like the sound.

2. It gets really loud? All a muffler does is slow down the exhaust and create a restriction. Less restriction = less backpressure = higher RPM tuning (good for racing) = MORE POWER.

3. Best flowing TRUE muffler would be (in my opinion) something from the Spintech line. Something single in/single out. They flow very well. If you've got some cash check out Dr. Gas. Magnaflows also flow very well. Stay away from Flowmaster. The best flowing reasonator (outflows the best muffler, usually by alot) is something like the Dynomax Bullet.

4. Advertising and the fact they've been around far longer than any other company. Personally I think they sound awful and it's been proven they flow horrible. Many people swear by "The Flowmaster Tone" but quite honestly the drone gets VERY annoying. Plus every car/truck/minivan seems to have one nowadays, what's the use in sounding like everyone else?

5. Yes, slightly. The difference in an aftermarket "high-flow" converter and a good, new stock one is probably 2 HP and $250 dollars. No joke - aftermarket is MUCH cheaper. The only reasons I'd recommend a high-flow over a stock cat is either you're in a restricted class and you need every pony, or your stock cat blew up and you want to replace it.

 

If one has the "factory style dual cat system" where would you put an X-Pipe. Would it be worth it?

 

Granted the late model Camaro/Firebirds have REAL funky exhaust systems - because of the floor pan arrangement, so they are not even fair to talk about dual exhaust on.

In short, X-pipes have been shown to increase HP & "performance" either ZERO, or maybe as much as 4-5 HP. They do create a different sound, some people hate the sound, others don't mind. The sound changes with different mufflers too. One thing the X-pipe will do pretty effectively is cancel out some sound waves (quieter than an H-pipe or no crossover at all). Personally, I much prefer an H-pipe to an X, simply based on the resultant sound. The H-pipe helps to equalize pressure between the two banks.

Spintech mufflers being the best flowing? I'd bet against it - there's restriction in the internals like on a Flowmaster - walls to hit. They probably flow better than the FM's, but not as well as an Ultra Flow. Magna Flow mufflers are knock-offs of the Dynomax Ultras. I'll try to find out flow #'s on the Spintechs & I'll post my findings.

OE catalytic converters are much better quality than aftermarket, & the honeycomb substrates are all designed very similarly. There's a reason the OE cats are WAY more $$ than aftermarket. Durability.

Question: When your converter gets red-hot or has a meltdown, is it because the converter is defective?

 

An X-pipe flows better than an H pipe, that's its advantage over it. They both accomplish the same thing (equalizing the pressure between banks), but the X does it better. Over seperate pipes you'll see a good increase. 4-5hp increase is only likely if your motor is only making 250 hp to begin with. On any decent sized motor (350+ rwhp) you'll see a 3x that gain over seperate. Over an H pipe you'll see a little less (the job of equalizing the banks is already done..) but still a gain.

Well my choosing of which muffler is going to flow the best is based on personal experience at the track and with friends switching mufflers. I havn't actually flowed them but if you can produce a flow chart that would be neat and would be something I could learn from. Quite honestly if you're worried about power changes between individual mufflers, just get a cutout or go with a straight through bullet design.

And I own a magnaflow on my car.. it sounds nothing like a dynomax ultra? The dynomax ultra is very quiet, the magnaflow is anything but. Of course I usually drive around with open headers but when it's connected it is loud. If dynomax is affiliated with Magnaflow then they definetly changed something.

I've heard conjecture of stock cats doing better in smog tests but I've never talked to anyone personally that had a problem and most of my friends (that actually still run cats) have high-flows and have had them for a long time. Factory cats are a scam imo, they rape you on prices when the aftermarket can do just as well.

If you knew all the answers yourself, why did you ask?

 

Video - 85 tpi IROC camaro take off
i like my magnaflow.....

 

or it could be along the lines of they charge more for everything you get through them then aftermarket.

hell I know of a few things aftermarket wise you get cheaper and it works better then OEM stuff

as an example. my spark plugs through mazda 7.99 per. I get the same heat range plugs through local autostore and pay 4.99 a plug.
same people make the plug (NGK) same heat range. they seem to last the same either way. so why the difference?

dealers don't use vasoline

 

I'm running the Hedman long tubes, S bends, and dual classic chambered mufflers at the moment and am definetly going with an H or X pipe. My question here is the engine is a stock 1987 TPI that has bested a 13.84 and I'm curious if the added cost of an X pipe would be worthwhile. The exhaust is unreal loud at the moment so I'm looking to the H pipe to quiet it down but I realize with the cam overlap and vacuum there's performance to be had if the crossover's done right. Sorry to jack the thread but hopefully I can get some track time to show what an H or X pipe will do.

P.S. The motor is stock cam with 1.6 roller rockers, completely ported and siamesed plenum, ported runner entries, and a ton of bolt ons to boot.

 

Urbanhunter, the reason I started this thread is because I've read a bunch of threads over time here about exhaust & I see a bunch of different theories at work & a lot of different ideas & opinions. I've worked in the aftermarket performance exhaust field now since 1998 - in engineering, product development, & manufacturing. I am now manufacturing the Powerstick mufflers as one of my involvements.

I learned about the X-pipes from engineers at Ford that spent over a year testing them. I learned about different flow rates while working for one of the really big performance exhaust manufacturers. OE converters cost more because they are built to endure - they must not fail for 8 years or 80,000 miles. To do this, the internals (bricks) have a much higher concentration of precious metals in the washcoat that is applied to the bricks. There is not much of a performance advantage - the school of thought that OE converters flow worse than aftermarket is pretty much false. Changing inlet/outlet diameters is a different matter however, it's not legal though. SOME car owners want to do legal upgrades.

By knowing what you guys think about different options, I can help to support or debunk some of the theories at work on these cars.

 

What I've read is that with some cam overlap you get a suction on the intake because of the exhaust gas pulling it into the cylinder. This is what the Vortec is based on from what I understand. The science makes sense but I'm worried about getting this right the first time and not throwing away money. I can see that an H pipe would equalize the tone but would it provide the same ammount of exhaust scavinging suction on the opposing bank? I've also read that the best way to do an X or H pipe is to paint the pipes and install the crossover where the paint burns off first; I'de love to do this but I don't know if my exhaust is long enough to. I may try painting the S bends and see what results I get. Good thread btw, thanks to everyone who's responding to this.

 

I think what would be of interest to a lot of us here is what can be done with the factory style routing of the exhaust system. I know dual pipes is an answer but I would like to stay out of that conversation for now.

Things of interest would be a X or H pipe in front or after the cat(s). Maybe a small terminator box inplace of the X or H pipe or other ideas.

We know that headers are a good thing. Installing larger than factory exhaust pipes is good depending on the combination. Say going from 2 1/4" to 2 1/2" mandrel bent pipes. Maybe even 2 3/4" or 3" in some cases.

So Chambered, urbanhunter44 I would like to draw on your experiences and what you have seen on the dyno and strip.

 

I've heard this but to install the crossover right where the paint stops burning off.

 

1. Purely subjective. They change sound more than anything else. HP numbers between the two are negligable at best.

Lets take a trip on the wayback machine

2. Purely (my) opinoin... it sounds like ***. Or, compare it to a crappy old 70's farm truck that the exhause has rotted off.

I personally equate running the loudest or, no mufflers (on a stock or near stock car), to no more than import cars with the 5" exhaust. 'I hope it sounds fast enough to scare you so we don't have to race and I get my *** handed to me'

3. Depends on the sound you're looking for. Dynomax/Walker makes some great flowing mufflers but, they are quiet. There are pleanty of others too (Hooker comes to mind).

4. Sound.. it's very distinct.

5. Anything is better than OE. Why ? Most aftermarket is designed for better performance. OE or replacement is designed to mimic the tune of OE standards... just good enough.

 

Seeing that Hot Rod Magazine gained 40lbs of torque just by tuning a set of collector dumps I'm sure there's something to be had in an X or H pipe. I'm thinking of just having an H installed right before the mufflers in the S bends (and have them tuck that exhaust more, the tips hang low). The other option would be to get an X pipe but that would involve having crush bent 2.5 pipe put in, I have no crush bends as of now. Anyways I have no dyno but I can give you track results and tell you about the sound, stay posted.

 

Hmm well most of what I know is based off of technical works I've read, real experience at the race track, the dyno shop and the good old butt dyno. I'm friends with a couple dynoshops locally and I've had the opportunity several times to see an X pipe make power over an H. Not a LOT mind you, but a decent increase. Usually it's mustangs that I see and typically 5.0s don't see good gains because they don't make any power in the first place - stock anyway. But there's a gain of 4-6 hp. On higher powered motors (one S/C 5.0 in particular) the gain was (i think) 15 hp/29 ft-lbs. That's a decent gain imo!

I guess we'll have to agree to disagree on that point

As for OE converters longevity, have you considered the fact that MOST of the people on this forum either won't own/havn't owned their car for 8 years or if they do, probably don't drive it that much because it's a show car or drag car? For almost everyone on this board I'd recommend a high-flow over OE 100% of the time. I'm going high-flow in a year or so when my smog rolls around. They pass smog fine and they'll last the life of the car (in 95% of circumstances). Performance wise, no there isn't much difference. Maybe 1 or 2 hp.. Maybe.

Powerstick eh? Thats what I want as my next exhaust. Know of any good deals?

 

Urban any idea on how far back an H pipe should be mounted on a TPI engine? I've read the farther back the lower in the power band it will scavenge, I don't know if this is a big deal and if i'll see any gains from making it to short and therefore putting the tuning in a higher RPM band than it should be. The s bends are 18.5in long and the plan was to put the H at the ends of the S bends immeidatly before they enter the mufflers. I used a header design program that stated the optimal length before the crossover was 14in on an engine producing 300hp, hopefully this was for tuning around 5500rpm and the extra 2 or so inches will put it around the TPI's sweet spot. Also will it make alot of difference if I use 2.25in pipe on 2.5in primaries? Or should I insist they make the crossover out of 2.5in tubing? I'm going to talk to the exhaust shop tommorow and make sure they can do an H without it intruding into the exhuast stream and i'll see what my options are there.

 

Dropped my car off at the muffler shop to get the H pipe put in and my turn downs redone so they won't scrape on everything in the world, I'll post results if we make it to the track this Friday

 

Got the car back and finally got a chance to get on it Sunday. Throttle response is up and the car feels like it pulls better at part throttle and full throttle. The sound is much better, quieter and smoother; it actually gets louder as it builds revs as opposed to being ***** out loud and somewhat monotone from 2500 to redline. If weather permits I'll have it at the track Friday and see if I get any gains from it.

 

I will be interested in seeing what the results are.

 

Could you tell me what those two things have to do with each other?

Deadbird, loved your comment about the 5inch muffler import guys. Classic

 

If you read Urban Hunters post on exhaust resonant tuning it will make sense. The H pipe basically acts as a termination end kind of like the opening on an open header collector. If you can find the article on the exhaust length tuning it will also make a little more sense because each muffler type changes the apparent length of the collector. It's not really hard to explain, just kind of hard to put into words. I did alot of research on this before I did the exhaust I have on my car. That's why I asked about the length of the collectors to tune into a TPI. I can tell you right now the H pipe helped even though it's a tad too short (at least I'm pretty sure it is), the car takes so little throttle now to move it's awesome. Full throttle sounds way better but I'll have to strap the slicks on before I can tell you anything (street tires = massive spin).

 

Ran the 8th mile tonight with my slicks and the car was a tenth faster on and off spray. This is the great part about it though; my friends kept asking me why I let off because the exhaust is so toned down now compared to the last time they'de heard it run. It definetly reduces the ammount of noise, and it helped out pretty substantially considering the cost (20 dollars). I have only one complaint, when I first start the car it gives me a weird little airy sound (no it's not a leak) I've heard the same sound on a friends Mustang after his X pipe, but it does it while driving, mine only seems to do it on start up.

 

Does anyone have sound clips of their car with an X pipe installed?

 

It could be a slight leak somewhere that goes away after things heat-up & expand.

 

That's a possibility, I'm using the ball and socket flanges and I think they may leak for a split second.