[Tom Hand]

Here is my 3" offset center short bodied XLERATOR. Out of this family of high flowing, relatively quiet mufflers, this is the loud brother and I'll explain it below.

1) This one shows the basic layout and you can see how they chose to address high flow, low noise, and good tone. Goerlich, like Walker used to and like MagnaFlow does now, uses a perforated core surrounded by a stainless steel sock. This sock is critical to keep the same sound from the time it is installed until you take it off. The sock keeps the fiber from blowing out.

2) And contrary to the Aerochamber and non-packed mufflers, I believe Goerlich uses a continuous roving fiber for ultimate sound level control and tone. The case is large enough that in many places, it has at least one inch thick of the fiber which really absorbs the sound. Too packed, liked compressed fiber glass and it does not work, and too loose, and it does not work. This type, like Walker also uses, works very well.

3) And for anyone that wonders why these flow so well, this is why. You just can't beat this type of muffler with any chambered muffler or ones with a lot of pass tubes and restrictions and rough edges.

4) This shows the stainless steel sock but it also reveals why these 3" babies are loud. This perforated pattern is not very porous nor is it not very transparent. Both of the characteristics mean that there is not much way the exhaust gases' sound energy can creep out to be absorbed. Think of extremes; if it has no holes, it is a straight pipe and the exhaust screams through it unimpeded. If it has 100% holes, there is no pipe and the sound energy has lot of loss but the exhaust can't flow very well through the muffler.

The Aerochamber,the Ultraflow, the Dynomax Super Turbo, the MagnaFlow, PYPES Crossflow, Cliff's mufflers I built, the new Waldron Crossflow, and a few others work so well because they use the almost optimum pattern of perforation and they have the right amount and right size of holes, all staggered and spaced the right amount. There is lot of science to the perforated tubing and most now use very similar styles and types. And, the amount of fiber and type it is packed with affects the smoothness of the sound and the level.

How does this type of muffler work? Let's look at the numbers for an equivalent 2.5" offset offset version.

Goerlich's Xlerator, air flow as compared to straight pipe: 99%
Flowmaster 50 Series “Delta Flow”, airflow as compared to straight pipe: 53%
Hooker “AeroChamber”, air flow as compared to straight pipe: 73%

Sound level wise, the 2.5" XLERATOR was almsot 10 dBA quieter than the 50 series Flowmaster, and 8 DBA quieter than the Aerochamber. I said the 3" was very loud, it was only about five DBA quieter across the board than the Flowmaster, so it was indeed loud.

Not sure why they used this perf. pattern in the short XLERATOR but they did.

[71 T/A]

Have the 2.5 Xlerators but haven't installed them yet. Hope they're somewhat quiet compared to the Flowmasters my car came with from the previous owner. Like that 99% flow rate!

[Tom Hand]

Even the loud 3" short XLERATORs are quieter than most of the chambered mufflers so the 2.5" short and long ones should be fine. I suspect you have tailpipes because without them, all mufflers will rumble your guts and make you sick to your stomach after a while.
Tom

[goatnut]

I just put cat back duel exhaust on my pick up. The first muffler was a duel in / out cross flow magnaflow muffler with 3" pipes. That muffler sounded great outside the truck but terrible on the inside alot of resinance/drown litterly sounded like a helicopter behind my head when goin uphill around 2500 rpms. felt like I lost some low end torque also. Put on 2 flow master 40 series center in offset out LOUD as all get out but sounded good. Could only take that for two days now I am thinking why did I put duels on this truck. Put on two excellerators same size as the flow masters. Awe now I can drive my truck again no interior resinance sounds good on the outside not loud untill I get on it. Got my performance back also. I feel I did with the flow masters also but it was so loud I really didnt drive it. This is the only vehicle I have ever had this problem with???

[Z Code 400]

Originally Posted by Tom Hand

How does this type of muffler work? Let's look at the numbers for an equivalent 2.5" offset offset version.

Goerlich's Xlerator, air flow as compared to straight pipe: 99%
Flowmaster 50 Series “Delta Flow”, airflow as compared to straight pipe: 53%
Hooker “AeroChamber”, air flow as compared to straight pipe: 73%....

Hmmmm.......A 2.5" diameter tube has a cross sectional area of 2.5 x 2.5 x pi / 4 = 4.9 square inches. Therefore, the most it can flow at 20.3" pressure drop is 4.9 x 124 which equates to 608 CFM, assuming 100% efficiency, yet in the real-world, about 75% is closer to the norm. Now, if we use the time-honored 2.2CFM/HP rule, when examining exhaust flow requirements, a 450 horsepower engine would need roughly 990 CFM.

3.50" systems now????

[6 Grrrs]

Not trying to get this thread too far off topic, but I'm looking for some direction here. If the Xlerators really flow that much more than a Flowmaster, I may need to try them out...

On my pickup I have 2" primary Hooker Super Comps into 3.5" collectors, smooth transitioned down to 3" into a magnaflow 3" x pipe, into 3" flowmasters & then full tailpipes to the back of the truck (all pipe is 3" stainless with mandrel bent u-bends used for all bends - welded together & connected with vband flanges). The xpipe & mufflers are on the pass side of the truck so the driver's side front pipe & tail pipe is longer than the pass side front pipe & tail pipe (see photo). This was all done for proper ground clearance because the truck is rather low. Actually the way it is done, the front air dam is the lowest point of the whole truck, which is plastic. This whole system was built by myself & a friend in his shop. We also modified the headers for ground clearance. The left side collector was moved back 4" & then the #5 & #7 tube rerouted to it. I'm sure this may hurt the header's performance, but it was necessary for driveability. When the headers were first installed, the left side header was 1.5" off the ground.

I ran it for a year or so with just turn downs out of the flowmasters. I added tailpipes & it seemed to hurt the performance big time.

Noise is not my problem as much as the loss of performance with the tailpipes. I don't have any hard evidence of a loss in performance other than seat of the pants. The truck is noisy outside, but completely acceptable inside. The whole cab was dynamatted by me 15-20 yrs ago. I have a little resonance at lower rpms, but with 4.56 rear gears & a T56, it cruises 70 mph at 2100 rpm. I typically do not get to an rpm range that it can resonate anyways. Even cruising on backroads in 5th gear, it pretty much stays above 2k rpm.

I actually love the sound of the flowmasters, but I'm thinking it may be time to change them out for performance reasons. I don't want obnoxiously loud exhaust, but I would be fine with the same level of noise I have now. Actually I would be upset if it got any quieter.

I'm looking at alot of work to replace them as they are actually mounted upright, then welded together. Then there is a piece of roughly 20" rod welded to the top of them, and then another which is run through a crossmember & supported by rubber cushions on either side, then the aforementioned vband clamps welded on either end of the mufflers for easy exhaust system removal. This is not just a 'remove & replace' install as would be on my GTO. I don't have the opportunity to swap out several different pairs of mufflers easily.

My motor made peak hp @ 5900 rpm on Lingenfelter's dyno. Torque is pretty flat across the rpm range - 427 at 1550 rpm & 535 peak tq at around 3200 rpm, still almost 500 tq at 5900 rpm. Not sure if any of this matters with muffler choice. What I'm getting at is I don't want to lose any of my low end tq for streetability, but I think I could gain some top end hp with a different pair of mufflers. The truck was on a chassis dyno before the tailpipes were added & it made a peak of 398 whp.

Sorry it is not a Pontiac, but I am a Pontiac guy at heart. I've owned more Pontiacs then I have Chevy's anyway. That should count for something

[Tom Hand]

Tod,
Very interesting and well thought out system you have. One issue I can see is it will be tough to get the same sound level you are used to since the mufflers you are running are about as loud as one can buy. A SpinTech or Flowmaster copy will be as loud but will gain you nothing power-wise so no need to look into any of them.

What you have in the photo looks to be two chambered Flowmasters. In our tests and our experience on the track and on the street, the X helps a lot on the perceived sound level and the interior sound level and it gets rid of resonation on Pontiacs. Not sure the Chevrolet engine acts quite the same but they sure sound smoother with eight cylinders blasting through the mufflers instead of only four.

If they are two-chambered, they should be 16" -17” bodied mufflers. If it were mine, I’d replace them with either MagnaFlow 18" long, 3" inlet and outlet, offset-offset 14264 mufflers or better still (cheaper and all USA made) Goerlich XLERATOR X123s which are also 3" inlet and outlet, offset- offset 18” long bodied mufflers.

Some may try to convince you that airflow does not matter but it does. At WOT, it looks to me like you are making some power (at the higher rpms you listed) and your engine may see the restriction the mufflers you have create in the exhaust. Those 3” offset-offset mufflers flow about the same as 2.5” Dynomax SuperTurbos or most 2.25” straight through mufflers. The straight through 3” ones I listed above will provide more than enough air flow capacity for your wide power band engine but unfortunately, they will not be as loud as what you have now. They will have a nice tone and the X will smooth the tone even more.

Whatever you choose to use, it looks as if you have about 10 to 12" in front of the mufflers so the extra 2" of the mufflers’ body length of the ones I mentioned should enable you to fit them on. PYPEs also sell some straight through ones; MVR36 is the right one.

Or, to get more sound with only one muffler, you could run the Dynomax Welded UltraFlo 17231 (14”) or the 17525 (20”). Both are 3” internal tubes so you only need bump the inlet and outlet up to 3” to make them fit right on. Both will support the power you are producing and you might be able to flange both sides, and angle it up and fit it right on. It looks like you may have about 6” to 7” center to center on the pipes you have in the mufflers now and these may only be 5” to 5.25” but they might work.

These are my thoughts. Not sure how much money you want to spend on it but even any of the race straight-through small round shell mufflers will give lots of sound and a lot of air flow but they may be too loud for your taste.

[Tom Hand]

Tod,
I went back to some of our data from a few years back to get a bit more to share with you.

Assuming the mufflers you have are 3" two chamber or the Delta Flow versions, the stock 99-'00 Ford truck muffler or the 17749 Dynomax SuperTurbo (2.5") will allow the same amount of air to be passed through them. Interestingly, the old favorite stock 2.5" turbo Corvair muffler flows only 18% less than the 3" mufflers you have now. BUT, none of these will meet your desire of not dropping the sound level significantly from your current set-up.

From my experience and our testing, the X does enable you to get away with more restrictive mufflers so your engine "sees" the setup you have as on the edge of needing more airflow for the power output you have. One 3" offset-offset XLERATOR, (5" by 11" by 22" or the smaller case-sized X123)will just about equal the air flow the two mufflers (combined) you have now provide but you lose the added capacity benefit the X provides; I'd still run two mufflers or one large dual in-dual out muffler it it were me. The ones I listed above are still ones I'd consider.

Take care,
Tom

[6 Grrrs]

They are the regular 2 chamber Flowmasters. It is interesting that they flow so poorly.

I do have a little room in front of them, but no room behind them. That is a shock that is next to the outlet of the mufflers & the reason that the tailpipes route towards the frame, instead of the mufflers being closer to the frame rail.

How much improvement do you think I could see? Is it something that the cost/time may outweigh the benefit? Before I built this system, I still had cast iron manifolds & the original y pipe was cut & then ran back to 2 2.25" flowmasters & then turn downs. It made 348 hp at the wheels. Basically I picked up 50 whp with my headers/exhaust.

Am I gonna see another 2-3 whp or maybe as high as 10-12 whp improvement? Just looking for an opinion on whether it is worth the trouble. I may need to get it on a dyno again to see what the tailpipes really cost me at the wheels.

In the back of my mind I have been thinking that cost wise, a 150 shot of NOS may get me my desired ET. It currently runs 12.68 @ 109 mph. I'd like to see trap speeds of 115 or more & get into the 11s. It weighs 4700 lbs + driver.

[Tom Hand]

Tod,
Here is how I would approach it if I had access to the chassis dynomometer you do. When you go back,

1) drop the tailpipes off and run it. If it loses only a few HP, the tailpipes are not the real issue.

If not, then,

2) drop the mufflers off.

If it picks up quite a bit, you can decide. A change may come in a small power increase from low to high RPM but not sure the chassis dyno will show it like the dragstrip does. However, I see lots of chassis dyno tests regarding muffler and air induction systems that do show incremental changes from low to high RPM and you know this will make a difference in dragstrip performance. In fact, on the car we use to test things, when calculating power based on speed and weight, the X pipe made only six (calculated peak) HP at the track yet it made almost sixteen when you calculated the ET decrease. This indicates clearly an across-the-board increase in torque/power, at least in the power range it was being operated in at the track.

From these two tests you can make, you can decide how much more you want to spend to modify your exhaust for more power. No performance muffler will make a huge difference unless something is drastically wrong. But if you are looking for max performance, certainly, higher flowing ones will make a difference if your engine needs that potential.

[6 Grrrs]

Tom,

Thanks for your suggestion & input. That's a good idea to put it on the dyno & run without the mufflers/tailpipes. With the vband clamps, it really would be a simple test. The whole system comes apart with a few bolts.

[Tom Hand]

And this way, if yours acts differently than most every other one I have ever seen, you will not have wasted a dime buying anything that will not help.

Not sure where you are but it is nice that you can go out and tinker. We received three more inches of snow today here in KC, it is 5 degrees F, and there is no no sun on top of the 12 or so inches of snow we still have from late December. Tough to tinker on anything here in these conditions! Even the heated garage is too cold to play in.

Stay warm!

[74 SD455 Formula]

I am running a 2 1/2 in Ram Air Restoration's " X " pipe set up on my 72 HO455 GTO with these exact muffler's.I took off a Gardner 2 1/4 stock set up and it was like nite and day.The muffler's are quite until you get on it and they flow like there's no tomarrow.There are a few other people I know that have made the switch with similar result's.Nobody around here has complained.

[71 T/A]

Originally Posted by Tom Hand

Even the loud 3" short XLERATORs are quieter than most of the chambered mufflers so the 2.5" short and long ones should be fine. I suspect you have tailpipes because without them, all mufflers will rumble your guts and make you sick to your stomach after a while.
Tom

I have the 2.5" short Xlerators to go on my 72 Formula and will retain the tailpipes. I'll swap them out when I drop in my new motor, which will be in a couple of months. I was wondering how they compare to Pypes RacePro because I had heard that Pypes incorporated the Xlerator design in that muffler.

[Tom Hand]

71, this is good question for Chris and the guys here at PY since they sell/sold both of them.
Chris, if you or DM Fan are free, can you comment on these for 71 T/A?
Thank you,
Tom

[6 Grrrs]

We have been getting about 3-4 inches daily here. I can go & tinker in my garage, but neither of my toys has a reason to be out in snow. It is currently 9 degrees here. I can't wait for 40 degrees again

Originally Posted by Tom Hand

And this way, if yours acts differently than most every other one I have ever seen, you will not have wasted a dime buying anything that will not help.

Not sure where you are but it is nice that you can go out and tinker. We received three more inches of snow today here in KC, it is 5 degrees F, and there is no no sun on top of the 12 or so inches of snow we still have from late December. Tough to tinker on anything here in these conditions! Even the heated garage is too cold to play in.

Stay warm!

[lust4speed]

Tom, how does the 3" 50 series 3-chamber perform comparred to the 3" 40 series 2-chamber? Just wondering whether they are a little better or a little worse. I've had the 3" 50 series Delta Flow mufflers on the car for about nine years and just wondering where they fall on the list.

[Tom Hand]

Mick,
Instead of repeating advertisements or reprinting articles on dyno tests of smaller engines, please allow me to share with you what we saw in our tests and then I will make some predictions for you based on established data, manufacturer’s statements, and impacts we saw on other cars and our own tests.

First, a bit of background info for you. The Delta Flow series was created to get a higher sound level and resonation reduction from the unpacked, reactive-style Flowmaster mufflers. The Delta Flow improvement helped these chambered, unpacked mufflers by turning them into a more tolerable driving muffler, especially for cars with catalytic converters. If you look at cross sectional images of the mufflers, you see they added a large Helmholtz tuning chamber (one could consider this as a sort of “anti resonation chamber). Instead of one "V" after the center port/passage in the muffler, the Delta Flow has a series of multiple "V"s, carefully spaced to help react/reduce the sound frequencies and levels and at the same time, they got some of the backpressure under control which corresponds to increases in the air flow capacity. Indeed, it works very well and we saw right at a 10% increase in air flow between the competing size 2.5”, traditional 40 series, 13” long muffler and the longer 17” Delta Flow muffler. Keep in mind that length in a muffler shell provides increased volume which gives a reduction in sound level and an increase in air flow which corresponds to a lowering of backpressure. So, how much air flow increase is created by the extra "V"s or how much comes from the extra 4” in case length? I have my thoughts but can't base it on fact so I will not comment. Sound-wise, on the 455 we used, the level reduction was about 1% to 3% depending upon rpm.

So here is something to think about. When one compares the actual air flow through each of them, the longer one is capable of supporting up to about 130 HP per pipe it is used on (260 HP total) without starting to affect the power output of the engine. This statement is based on the accepted value of 2.2 CFM of air flow required per HP, tested at 20.3 inches of water pressure. Now before anyone gets too sidetracked and argues that air flow through a muffler does not matter and that you can’t use the airflow figures to predict horsepower output, I got the power/size/flow figures from Flowmaster’s published literature. With this out of the way, let’s move on.

You asked me about your larger diameter, 3” longer-case Delta Flow offset-offset or offset-center mufflers compared to the shorter 3”, 40 series mufflers. You definitely did the right thing going with the longer case, Delta Flow technology mufflers. You have a higher flowing muffler with some reduction in sound level (over the shorter 40 series) but even more so, you gained a reduction in resonation, assuming you paid close attention to Flowmaster’s statement: “A cross-over pipe is strongly recommended in all dual exhaust applications”. We saw the "X" crossover reduces the sound level at least 75% of the time, the "H", not as often. Again, based on air flow versus potential unaffected power output, the 3” Delta Flow can safely support 150 HP per pipe for a total of 300 HP, assuming the rest of your system is up to snuff.

So, if you are wondering if your car will run much faster with a change; I would first like to make one comment based on your signature data. I see you are not trying to be full time drag racer so that tells me you are not as worried about every tenth of second or every MPH. If you were, and if you were making 350 HP or more, a change to higher flowing mufflers would make a difference and by using a packed muffler, like any of the ones I shared in other posts, you could also kick some of the sound level down. You would lose that distinctive Flowmaster sound but your engine would be able to force a lot more exhaust out of your system, doing so more easily, thereby making making more power and torque.

Mick, I trust this makes sense but if not, please, feel free to email me or ask again, I’ll try to clarify anything that does not make sense.
Tom

[Z Code 400]

Originally Posted by Tom Hand

"You definitely did the right thing going with the longer case, Delta Flow technology mufflers. You have a higher flowing muffler with some reduction in sound level over the shorter 40 series. Again, based on air flow versus potential unaffected power output, the 3” Delta Flow can safely support 150 HP per pipe for a total of 300 HP, assuming the rest of your system is up to snuff...Tom"

Here is something to consider with any chambered muffler. The vacuum flow testing cannot create the pulsation effect of the exhaust gas flow in a running engine. This is the single most common flaw in the evaluation of any muffler that channels, accelerates or otherwise re-directs exhaust gas flow. Vacuum testing cannot produce the scavenging effect of accelerating the pulsating exhaust gasses, period.

For example, let's examine Cliff's ventura. With headers, 3.0" inlet 40 series Flowmasters, an H-pipe and 2.50" compression bent tailpipes, he ran a best of 11.58 @ 116.39 mph with around 500 horsepower and 573 lbs.ft of TQ at the crankshaft. We know these facts to be well documented and not reflective of any 'brand loyalty' or corporate sponsorship activities.

Now, if, by your deductions, a 3.0" Flowmaster can only support about 150 HP per pipe, then how do you explain Cliff's consistent, well documented 1/4 mile performance???

[lust4speed]

Thank you Tom. My exhaust kit was ordered from Torque Tech before the invention (or at least introduction) of the X pipe so the old H pipe is in place. I believe what you are saying is my system will support 150 horsepower per side without restriction, but will become more restrictive as the horsepower goes up. The system is on the blue 4-speed street car that produced 405 rear wheel horsepower through the mufflers on Harry K.'s chassis dyno. The engine was done at 5,200 RPM and with the roller cam and such really should have developed max horsepower at about 6,100 RPM -- probably a sure sign the mufflers were taking their toll. I didn't want to be tempted running it at the track, so I purposely didn't install cutouts - but that also stopped me from making a good A to B comparison on the dyno.