| Quiet Bird - Testing the new Dynomax VT Mufflers |
- By Mike Noun
Vehicle.................... : 1969 Firebird
Engine.................... : Pontiac 455
Camshaft............... : Comp Cams 305H
Approx. HP............ : 525 hp
ET range................ : 11.60's @ 116 mph - full exhaust, street tires
Exhaust................. : Indian Adventures headers 2" primaries,
3.5 collectors, tapered 7" long reducers
down to 3" pipes, Dr. Gas X-pipe,
3" Torque Tech 2-piece tailpipes exiting
behind rear wheelwell.
Engine.................... : Pontiac 455
Camshaft............... : Comp Cams 305H
Approx. HP............ : 525 hp
ET range................ : 11.60's @ 116 mph - full exhaust, street tires
Exhaust................. : Indian Adventures headers 2" primaries,
3.5 collectors, tapered 7" long reducers
down to 3" pipes, Dr. Gas X-pipe,
3" Torque Tech 2-piece tailpipes exiting
behind rear wheelwell.
| Thanks to Nick at Walker Dynomax, and an HUGE thank you goes out to Tom Hand. For those that do not know Tom Hand (and his father Jim), they have been a blessing to the Pontiac community with their generosity and their willingness to share information. The data they provided years ago, with their extensive testing of mufflers, exhaust system flow restrictions, etc., have been instrumental in helping hundreds of enthusiasts select the proper exhaust system.... |
Comments? Please contact Mike at : mnoun@yahoo.com
| Favorite Links Dynomax Exhaust - click here MusclecarFilms.com - Vintage Drag Racing, NASCAR, Promo Films - click here Mike Noun's Ponti-Archeology Articles - For hard core Pontiac fans! - click here How To Build Max Performance - Pontiac V8's - The Pontiac Bible Book - click here Performance Years Forums - click here Classical Pontiac - click here Pontiacs Online - click here |
| Mufflers Tested Dynomax VT (Valve Technology) #17959* (see note) - 3" offset/offset, 16" shell, 19" overall. Dynomax (Ultra Flow Welded ) #17229 - 3" offset/offset, 14" shell, 19" overall. |
| Sound Level Test DB Meter placed 10 ft. from tailpipes Dynomax VT's Dynomax 17229 800 rpm - 81 db 800 rpm - 84 db 2000 rpm - 87 db 2000 rpm - 93 db 3500 rpm - 106 db 3500 rpm - 105 db Dynomax VT's w/18" long Dynomax 17229 w/18" long Dynomax bullet mufflers Dynomax bullet mufflers 800 rpm - 78 db 800 rpm - 82 db 2000 rpm - 84 db 2000 rpm - 90 db 3500 rpm - 103 db 3500 rpm - 102 db DB Meter placed inside interior, on center console, all windows closed Dynomax VT's Dynomax 17229 800 rpm - 75 db 800 rpm - 77 db Dynomax VT's w/18" long Dynomax 17229 w/18" long Dynomax bullet mufflers Dynomax bullet mufflers 800 rpm - 72 db 800 rpm - 74 db |
Additional notes
1) At cruising speed (40 mph @ 2000 rpm), there is hardly ANY drone or resonation from the Dynomax VT's, while the Dynomax
17229's had a slight drone, and the Pypes Race Pros had a significant drone.
2) Accelerating away from a stoplight, under light load, the quietest mufflers by far were the VT's. The VT's actually had a slight
hissing sound, almost like a stock GM muffler! While the Dynomax VT's were indeed quieter than the Ultra Flow Welded 17229's,
they still retain some of that low end rumble we like to hear on our old cars. The most noticeable difference between the Dynomax
VT's and the Dynomax Ultra Flow Welded mufflers are when you're driving down the road. The VT's are significantly quieter than
the Ultra Flow Welded mufflers, and much quieter than the Pypes Race Pros.
4) Quality of construction on all 3 mufflers is excellent, however the Dynomax mufflers seem to use much thicker metal than the
Pypes Race Pros (see comparison photos above). Also, the perforated internal tube on the Dynomax mufflers lines up perfectly
with the inlet/outlet. There is no overlap or mismatch.
5) As you may or may not know, the 1st Gen Firebirds have small indentations in the floorpan, limiting us to 14" shell mufflers
(unless you don't mind having your mufflers show from the side of the car, and you do not care if the mufflers hang down, then the
sky's the limit as far as muffler length is concerned). The Dynomax VT's I installed had 16" shells, and the inlet/outlet pipes,
normally 3" long each, were cut down to 1.5" each, so the overall length of the mufflers were 19", the same length as a standard
14" shell muffler. With this modification, any 16" shell muffler WILL fit under a 67-69 Firebird, but it's tight!
6) Just an additional note: I tested my 2005 Pontiac Bonneville GXP (Northstar V8) with the DB meter. My GXP has the original
exhaust system, low mileage, factory 4 chrome tips out the back. With the meter 10 ft. from the tailpipes (exactly the same as my
tests above), my Bonneville GXP, which has a little 'growl' out the back (like any Northstar, LT1, LS1, G8, etc. has) was
71 db @ idle. Looking at my previous tests (the quietest setup on my 1969 Firebird being 78 db @ idle with the VT's and bullet
resonators) shows the 1969 Firebird being 7 db louder than a 2005 Bonneville GXP. Not too bad, considering the 1969 Firebird
has a 455, radical cam, huge tubular headers, and a 3" exhaust!
1) At cruising speed (40 mph @ 2000 rpm), there is hardly ANY drone or resonation from the Dynomax VT's, while the Dynomax
17229's had a slight drone, and the Pypes Race Pros had a significant drone.
2) Accelerating away from a stoplight, under light load, the quietest mufflers by far were the VT's. The VT's actually had a slight
hissing sound, almost like a stock GM muffler! While the Dynomax VT's were indeed quieter than the Ultra Flow Welded 17229's,
they still retain some of that low end rumble we like to hear on our old cars. The most noticeable difference between the Dynomax
VT's and the Dynomax Ultra Flow Welded mufflers are when you're driving down the road. The VT's are significantly quieter than
the Ultra Flow Welded mufflers, and much quieter than the Pypes Race Pros.
4) Quality of construction on all 3 mufflers is excellent, however the Dynomax mufflers seem to use much thicker metal than the
Pypes Race Pros (see comparison photos above). Also, the perforated internal tube on the Dynomax mufflers lines up perfectly
with the inlet/outlet. There is no overlap or mismatch.
5) As you may or may not know, the 1st Gen Firebirds have small indentations in the floorpan, limiting us to 14" shell mufflers
(unless you don't mind having your mufflers show from the side of the car, and you do not care if the mufflers hang down, then the
sky's the limit as far as muffler length is concerned). The Dynomax VT's I installed had 16" shells, and the inlet/outlet pipes,
normally 3" long each, were cut down to 1.5" each, so the overall length of the mufflers were 19", the same length as a standard
14" shell muffler. With this modification, any 16" shell muffler WILL fit under a 67-69 Firebird, but it's tight!
6) Just an additional note: I tested my 2005 Pontiac Bonneville GXP (Northstar V8) with the DB meter. My GXP has the original
exhaust system, low mileage, factory 4 chrome tips out the back. With the meter 10 ft. from the tailpipes (exactly the same as my
tests above), my Bonneville GXP, which has a little 'growl' out the back (like any Northstar, LT1, LS1, G8, etc. has) was
71 db @ idle. Looking at my previous tests (the quietest setup on my 1969 Firebird being 78 db @ idle with the VT's and bullet
resonators) shows the 1969 Firebird being 7 db louder than a 2005 Bonneville GXP. Not too bad, considering the 1969 Firebird
has a 455, radical cam, huge tubular headers, and a 3" exhaust!
The following article documents the differences between two Dynomax muffers: the Dynomax Ultra Flo
Welded and their new Dynomax VT mufflers. This is not a test of flow capabilities, but a sound comparison.
Welded and their new Dynomax VT mufflers. This is not a test of flow capabilities, but a sound comparison.
Comparison of a Pypes Race Pro (top) and the new Dynomax
VT (bottom). The Pypes Race Pro is a standard 14" shell with
2.5" length of connector pipe on the inlet/outlet. The Dynomax
VT has a 16" shell and the same standard 2.5" length
inlet/outlet, but the inlet/outlet pipes in this case were cut back
1.5", so both mufflers have an overall length of 19".
VT (bottom). The Pypes Race Pro is a standard 14" shell with
2.5" length of connector pipe on the inlet/outlet. The Dynomax
VT has a 16" shell and the same standard 2.5" length
inlet/outlet, but the inlet/outlet pipes in this case were cut back
1.5", so both mufflers have an overall length of 19".
Here we see one of the new Dynomax VT mufflers (right)
compared to a Pypes Race Pro muffler (left). As you can see,
the Pypes Race Pro is oval-shaped, similar to a standard
muffler shape of the 60's and 70's, while the Dynomax VT is
more shoebox shaped. Also note the Dynomax muffler is about
1/2" taller, so they will sit a little lower under your vehicle.
compared to a Pypes Race Pro muffler (left). As you can see,
the Pypes Race Pro is oval-shaped, similar to a standard
muffler shape of the 60's and 70's, while the Dynomax VT is
more shoebox shaped. Also note the Dynomax muffler is about
1/2" taller, so they will sit a little lower under your vehicle.
The Dynomax VT mufflers are well made, and use an
innovative internal valve to control exhaust drone. The valve
is spring loaded. When open, the muffler is a
straight-through design. When closed (at idle and part
throttle), the sound is much more subdued.
innovative internal valve to control exhaust drone. The valve
is spring loaded. When open, the muffler is a
straight-through design. When closed (at idle and part
throttle), the sound is much more subdued.
Comparison of a Dynomax Ultra Flow Welded (left) and
the new Dynomax VT (right). As you can see, the case
shapes are identical.
the new Dynomax VT (right). As you can see, the case
shapes are identical.
Dynomax Ultra Flo Welded #17229, 3" offset inlet/outlet. Another
great muffler from Dynomax, these have been on the market since
the late 1990's, and are the benchmark for high performance
mufflers. They are a total straight-thru design, and offer the best
flow possible with very good sound control.
great muffler from Dynomax, these have been on the market since
the late 1990's, and are the benchmark for high performance
mufflers. They are a total straight-thru design, and offer the best
flow possible with very good sound control.
Dynomax Ultra Flow Welded (bottom) and Dynomax VT
(top) are the same height and width.
(top) are the same height and width.
Dynomax Ultra Flow Welded (bottom) is the exact same
overall length (19") as the modified Dynomax VT (top).
overall length (19") as the modified Dynomax VT (top).
Dynomax VT's installed under a 1969 Firebird. Note the
X-pipe just in front of the mufflers.
X-pipe just in front of the mufflers.
...but the outlet side of Dynomax VT is where the new Valve
Technology is seen. The spring loaded valve stays closed at idle
and at low cruising speeds, diverting the sound and exhaust
gases back through the body for additional sound deadening.
Under WOT or heavy loads, the valve is open, allowing
straight-through unrestricted flow.
Technology is seen. The spring loaded valve stays closed at idle
and at low cruising speeds, diverting the sound and exhaust
gases back through the body for additional sound deadening.
Under WOT or heavy loads, the valve is open, allowing
straight-through unrestricted flow.
The inlet/outlet pipes on a Dynomax Ultra Flow Welded,
and the inlet side of the Dynomax VT, are identical....
and the inlet side of the Dynomax VT, are identical....
Regardless of what exhaust system you're working on, I strongly recommend slotting any slip-fit pipes (left photo). This will allow
you to use far less torque on a muffler clamp to achieve a seal, and will prevent pipe crush. As we all know, once a muffler clamp
is torqued down to a point where the outer pipe crushes the inner pipe, the only way to get the pipes apart is with a giant
hammer, lots of sweat, and some cursing. And after they're apart, unless you have an exhaust pipe expander, reusing the same
pipe and muffler is nearly impossible. Slotting the pipe is simple and quick: use a reciprocating saw (center photo), cut 4 evenly
spaced 1.5" slits into each slip fit outer pipe. I also strongly recommend Walker Acousti/Seal (right). I bought a tube of this
tar-like sealer years ago, and it's well worth the price. It provides an absolute air tight seal, and allows pipes to be easily
disassembled later. I've also used this stuff on slip-fit header collectors, it's good to 900 degrees.
you to use far less torque on a muffler clamp to achieve a seal, and will prevent pipe crush. As we all know, once a muffler clamp
is torqued down to a point where the outer pipe crushes the inner pipe, the only way to get the pipes apart is with a giant
hammer, lots of sweat, and some cursing. And after they're apart, unless you have an exhaust pipe expander, reusing the same
pipe and muffler is nearly impossible. Slotting the pipe is simple and quick: use a reciprocating saw (center photo), cut 4 evenly
spaced 1.5" slits into each slip fit outer pipe. I also strongly recommend Walker Acousti/Seal (right). I bought a tube of this
tar-like sealer years ago, and it's well worth the price. It provides an absolute air tight seal, and allows pipes to be easily
disassembled later. I've also used this stuff on slip-fit header collectors, it's good to 900 degrees.
As you can see, the end result, 78 db at idle using the Dynomax VT mufflers and a pair of 18" length bullet mufflers, is quite
remarkable for a big cube, 500+ hp vehicle that uses large 2" primary tube headers and a radical camshaft. As stated earlier, the
most noticeable difference between the Dynomax VT's and the Dynomax 17229's (and the Pypes Race Pros) was at idle, light
acceleration, and cruising.
At wide open throttle, the Dynomax VT's appear to sound exactly the same as the Dynomax 17229's and the Pypes Race Pros.
remarkable for a big cube, 500+ hp vehicle that uses large 2" primary tube headers and a radical camshaft. As stated earlier, the
most noticeable difference between the Dynomax VT's and the Dynomax 17229's (and the Pypes Race Pros) was at idle, light
acceleration, and cruising.
At wide open throttle, the Dynomax VT's appear to sound exactly the same as the Dynomax 17229's and the Pypes Race Pros.
| Copyright 2011 MusclecarFilms. All rights reserved. |
* Dynomax lists the #17959 muffler as a 2.5" muffler. The #17959 version I tested was a 3" version, and considered a
prototype. The 2.5" version uses a 3" inner tube, but has a 2.5" inlet/outlet. The inlet/outlet was expanded to 3" by
Dynomax, making the mufflers 3" all the way through. At the time of this test, we were not aware that Dynomax would
not offer a 3" offset/offset, so I apologize for the confusion. Please see Dynomax's website for further details.
prototype. The 2.5" version uses a 3" inner tube, but has a 2.5" inlet/outlet. The inlet/outlet was expanded to 3" by
Dynomax, making the mufflers 3" all the way through. At the time of this test, we were not aware that Dynomax would
not offer a 3" offset/offset, so I apologize for the confusion. Please see Dynomax's website for further details.