As would be expected, just as with the Isuzu community, there is quite a bit
of debate concerning what particular type and which brand cat back exhaust
system works best on the Chevrolet Cavalier and Pontiac Sunfire. We have
already terminated this debate among the Isuzu community with our dyno test
comparison of 2 1/4 inch Pacesetter and 2 1/2 inch Iperformance exhaust
systems for 1990-93 Isuzu and Geo Storm cars. We decided to go ahead and run
the same test comparison on the 1996-2005 Chevrolet Cavalier and Pontiac
Sunfire, so that we could test a couple examples of cat back exhaust systems
for these vehicles, side by side, on a dynamometer, and establish which
system worked better.
To accomplish this, we came to an agreement with Mustang Muscle Performance
and Dyno Service in High Ridge, Missouri, to use their DynoJet Dynamometer to
We were lucky enough to find a volunteer locally, Lenny Kean of Wentzville,
Missouri, who graciously donated the use of his 2001 Chevrolet Cavalier Z24
car for the testing. Lenny's car is basically stock, the only modifications
being a fiberglass hood, Eibach lowering springs, and a polished stainless
steel straight through type muffler spliced onto the stock piping in place of
the original equipment chambered muffler. We would return the car to the
stock pipe with the stock muffler for the baseline numbers, but not after we
ran the car on the dyno with Lenny's setup which we quickly named "the loud
The exhaust systems to be tested were the stock cat back exhaust system, the
RK Sport / Magnaflow brand single muffler cat back exhaust system, and the Iperformance
brand cat back exhaust system.
Dyno testing involves parking the vehicle with the drive wheels and tires on
the rollers of the dynamometer and then strapping the car down to the ground
so that it will stay on those rollers while the drive wheels and tires spin
An inductive electrical current sensor is placed around one of the ignition
wires so that the machine can measure information on power produced at each
specific engine speed. For the Cavalier with the Quad Four engine, we quickly
learned that we would have to un tape the wire loom where it plugs into the
ignition coil pack and place the inductive sensor around the black wire which
triggers the firing of the number one cylinder.
The settings of the machine are adjusted to match the gear ratios of
transmission of the vehicle by correcting engine speed and roller speed to
Once the machinery is ready, the vehicle is accelerated through first,
second, and third gears, to fourth gear, and the engine speed is held at
2,000 RPM by the operator. The operator then hits a button to begin the
measurement and presses the accelerator pedal to the floor. Engine power
usually is measured by the machinery at wide open throttle from or just above
2,000 RPM, all the way just short of the rev limiter. The Cavalier and
Sunfire, though, have a speed limiter programmed into the engine control
computer, which cuts off the ignition once the car reaches a point just about
105-108 MPH. The car, will, of course, easily reach this speed in fourth
gear, and our testing was limited to the engine speed just above 2,000 RPM to
5,600 RPM, where the speed limiter kicked in when the tires reached 108 MPH
on the dyno rollers.
The machinery measures the air temperature, humidity, and barometric
pressure, so that it can correct the results for the atmospheric conditions.
This corrects the results to SAE, which is what we have used in all of our
In order to avoid any possible impropriety, as we are the exclusive
distributor of one of the products being tested, all of the testing was
conducted by Daryl, the owner of Mustang Muscle, or Matt, his son. They both
have many years experience running dynamometers and had no interest in what
the results of the testing were.
Dyno Chart Showing All Three Exhaust Performance Results
We were fortunate that Lenny had his original equipment muffler and allowed
us to use that for our baseline tests. We did purchase a new exhaust pipe
from Chevrolet to go between the muffler and the three bolt connection behind
the catalytic converter.
The stock exhaust system consists of 2 inch diameter pipe with a rather
unique resonator neat the front end and a relatively common chambered muffler
at the end, terminating in a Y and two steel turned down tail pipes. The pipe
is squeeze bent. The resonator is interesting because from the outside, it
appears to be a standard bullet style glass pack as is commonly used by auto
manufacturers for resonators. This one, however, is hollow on the inside, and
has a 2 inch diameter cylinder positioned lengthwise, so that the exhaust
flows both through the center as well as around the sides, reducing the harsh
sound of the exhaust without causing a great deal of turbulence.
Performance On The Dyno
Baseline performance was measured at a peak horsepower of 127.3 and a peak
torque of 136.7 ft-lb.
The average power across the range of engine speed was 95.7 HP and 130.9
ft-lb of torque.
The real surprise was the torque curve, which stays very high across the
entire range of engine speed, never falling off like other four cylinder
The RK Sport / Magnaflow Single Muffler Cat Back Exhaust
Note: This exhaust system was originally branded as "RK Sport made by Magnaflow" and
was available exclusively through RK Sport. It has since been made available to all
retailers from Magnaflow as Magnaflow PN 15761, with a suggested retail of $821.45.
We purchased a single muffler cat back exhaust system directly from RK Sport,
at retail, for this test.
The packaging was one of the more interesting aspects of this product. The
pipe and muffler had all been placed into a plastic bag and insulation foam
sprayed into the box around the parts in the bag.
This did a very good job protecting the parts from anything that might
puncture the box and damage them, but since the parts were not individually
wrapped or padded, the pipes banged against the polished muffler and tip for
probably the entire trip from California to Missouri while in transit by UPS,
and as a result, the muffler was dented and there were scratches in the
finish of both the muffler and the tip.
The RK Sport / Magnaflow cat back exhaust consists of four main pieces, three pipes
between the three bolt flange connection and the muffler, and the muffler and
tip assembly itself. Hardware included several pipe clamps, two nuts and
bolts, and a gasket for the flange connection between two of the three
sections of pipe.
The pipe is 2 1/4 inch diameter mandrel bent and is described by RK Sport as
being stainless steel. However, if anyone was expecting the pipe to be as
shiny and polished as the muffler and tip, they would be disappointed, as the
pipe has the same appearance of any new exhaust pipe, unpolished, and dull.
This is not of concern, it's exhaust pipe, it goes under the car, and it
doesn't have to be shiny. In addition, the flanges and most of the hardware
(except for two of the three pipe clamps) and the hangers, are mild steel,
instead of stainless, making for a rather interesting combination of that
which arrived with a bit of surface rust on it and that which will not rust.
The muffler is a Magnaflow brand muffler, with straight through design and
perforated core. It is of very high quality, as are all of Magnaflow's
products. The tip is rather interesting, in that it is a double wall tip,
which has a 2 1/4 inch diameter inlet and gradually expands at an angle to
four inches at the end of the tip, and then folds back on the outside to give
the appearance that it is four inches from the muffler out. This will have
some interesting implications on the sound of the exhaust system.
Something that is rather interesting is the pipe assembly which bolts to the
three bolt flange at the beginning of the cat back exhaust system. For some
reason, Magnaflow flares the 2 1/4 inch pipe out to 2 1/2 inches and uses a
three bolt flange designed for use with 2 1/2 inch pipe. It is almost as if
Magnaflow planned for their customers to use their exhaust system with headers
that have 2 1/2 inch diameter collector pipes.
Overall, it's a pretty impressive exhaust system, much higher quality than we
There are no written instructions, but installing an exhaust system is fairly
straight forward. Remove the original exhaust system by unbolting each piece
starting from the tail pipe forward. Hang the new pieces in place from the
catalytic converter to the tail pipe, but do not tighten the bolts or clamps
until all the pieces are in place.
Something that RK Sport and Magnaflow might have warned us about is that they do not use
the OEM muffler hanger to hold the muffler of their exhaust system in place,
and, instead, the muffler bolts to the rear bumper. Everything goes into
place once you figure that out, and the only real concern about the hanging
of the muffler is that there is no rubber hanger to dampen the vibration of
the exhaust pipe where it attaches by way of bolting the bracket onto the
rear bumper stud.
Overall fit of the exhaust system is pretty good. The exhaust system being
four pieces instead of three means the installer must do some juggling
maneuvers to position and secure the pipes before they fall out of position.
The exhaust system seemed to hang down a lot lower than necessary, though
Lenny did not say it hit anything while he was driving around with it on the
One big concern was that the stainless steel pipe is very stiff, and the slip
joints that secure the exhaust pieces together are rather shallow. This
combination led to very leaky connections and no amount of tightening in the
world would stop the leaks around the connection between the second and third
pipes and the third pipe and inlet to the muffler.
RK Sport Retail Price: $599.99
Magnaflow Suggested Retail Price: $821.47
Driving Around With It On The Car
Once installed, we started the car, and the sound of the engine running at
idle was totally imperceptible, even in a quiet, residential neighborhood.
The tone was deep, but could not be heard unless a person knelt down beside
the exhaust tip to listen.
This was rather disappointing, as we expected that big chrome muffler and big
chrome tip to emit a more noticeable sound at idle speed, as opposed to
sounding quiet to the point that a driver in another car might pull up next
to a Cavalier with the RK Sport / Magnaflow exhaust at a light and assume the car had
nothing more than a chrome muffler and tip on the stock exhaust.
The exhaust sound above idle was a bit more noticeable, but not as pleasant
as would be expected.
From about 2,000 RPM through 4,500 RPM, the sound is only slightly deeper
in tone than a chain saw. Lenny seemed more upset with this than anyone else,
saying his car sounded like a rice car. We didn't think it was quite that
bad, but not as deep a tone as we are accustomed to with Magnaflow mufflers.
Lenny also commented that the exhaust was loud at highway speed when he ran
the car up in gear, and that the tone at higher engine speeds remained
higher in pitch than he desired.
We attribute much of the higher pitched exhaust sound as being caused by
the smaller, 2 1/4 inch diameter of the pipe, which is too small for an
engine of this size, and the angled walls of the exhaust tip, which do
not result in as deep a tone as tips with parallel walls.
Lenny also commented that the car did not feel as strong with the RK Sport
/ Magnaflow exhaust system as did the stock pipe with his loud muffler. A little
better than stock, but not a lot.
Performance on the Dyno
The RK Sport / Magnaflow cat back exhaust system was measured at a peak horsepower of
132.3 and a peak torque of 142.6 ft-lb. That is a increase over stock of 5.0
HP and 5.9 ft-lb of torque.
The average power across the range of engine speed was 99.4 HP and 136.2
ft-lb of torque. This is an increase of 3.7 HP and 5.3 ft-lb of torque.
The graphed performance curves on the chart show relatively consistent
performance over that of the stock system from 2,100 RPM through 5,600 RPM.
The Iperformance Cat Back Exhaust
This is the exhaust system we offer for the Cavalier and Sunfire cars. The
part numbers for this cat back exhaust system are SHBILL09BP (single muffler,
There are actually several new part numbers for this exhaust system for the
various 2.2 and 2.4 liter cars.
This particular exhaust system was the prototype for our 1999-2001 exhaust
Although we did not ship this product to ourselves for testing, we do go to a
great deal more effort to keep the Iperformance system from being damaged in
shipment. The box is sized to match the product.
Each piece is wrapped in either bubble wrap or corrugated card board. The
insides of the box walls and ends are lined with additional layers of
corrugated cardboard as the product is being placed into the box, and any
extra space is taken up with more cardboard or packing material to keep the
pieces packed tightly and prevent any damage from pieces hitting each other
or from the pieces breaking out the sides of the box itself.
The Iperformance cat back exhaust system consists of four pieces, a forward
pipe, a center piece which goes over the rear cross member, a muffler
assembly, and a turned down tail pipe. Hardware included is a three bolt
catalytic converter gasket, and three U style 2 1/2 inch pipe clamps. As a
result of this testing, we are going to start including three sets of nuts,
bolts, and washers, to secure the exhaust system to the down pipe assembly in
front of it, because the OEM system has threaded holes, requiring new nuts
and bolts be used to install the exhaust system.
The pipe is 2 1/2 inch diameter aluminized steel finish.
The pipe itself measures .082 inches thick, or 14 gauge for durability and
expected long life span.
The Magnaflow brand muffler is a straight through design with sound deadening
material wrapped around a perforated core.
Long ago, we learned that no two Cavalier or Sunfire owners wanted the same
type of tip on their exhaust system, so we resolved this by including a
simple, turned down aluminized tip, that the owner could replace with
anything they desired.
Again, there are no written instructions, but installing an exhaust system is
fairly straight forward.
Remove the original exhaust system by unbolting each piece starting from the
tail pipe forward.
Hang the new pieces in place from the catalytic converter to the tail pipe,
but do not tighten the bolts or clamps until all the pieces are in place.
With three main pieces and deep slip joints, the Iperformance system did not
involve any juggling and there was no worry of pieces falling.
The deeper slip joints sealed much more easily.
It was sort of odd that the larger pipe of the Iperformance exhaust system actually
hung higher with more ground clearance than the smaller pipe of the RK Sport / Magnaflow
Driving Around With It On The Car
The Iperformance cat back exhaust system had a more noticeable sound at idle
speed. It was not overbearing, and was about the same volume as the original
equipment exhaust, possibly a very little bit louder, and very deep in
tone. It was very evident at idle speed that the car did have a
performance exhaust system on it by the tone.
The exhaust sound is authoritative when the engine is above idle speed. It
is deeper in tone than the weed whacker import sound and also noticeably
deeper in tone than the RK Sport / Magnaflow exhaust.
Lenny was grinning from ear to ear. He said it was a little bit quieter than
his loud muffler on the stock pipe, but that the car felt like it had a
lot more power.
Lenny also said it sounded very good on the highway and that the car felt
like it pulled much harder.
Performance on the Dyno
The Iperformance cat back exhaust system was measured at a peak horsepower of
134.9 and a peak torque of 146.9 ft-lb. The peak power gain is 7.6 HP and
10.2 ft-lbs of torque.
The Iperformance cat back shows a maximum increase of 9.0 HP at 4,600
RPM and 10.7 ft-lbs of torque at 2,600 RPM.
The average power across the range of engine speed was 101.6 HP and 139.2
ft-lb of torque. This is an average increase of 5.9 HP and 8.3 ft-lb of
The graphed performance curves on the chart show consistent performance over
that of the RK Sport / Magnaflow system from 2,100 RPM through 5,600 RPM, on the measure
of more than 1 1/2 times the improvement of the RK Sport / Magnaflow exhaust.
There was no loss of low or mid range torque or horsepower, and the
performance increase is even across the entire range without any dips below
either stock level or the level of the RK Sport / Magnaflow system.
In fact, with the Iperformance cat back, there was a minimum increase of 7.4
ft-lbs of torque from 2,100 RPM all the way through 4,800 RPM, showing that
low and mid range torque is precisely the area that was most improved with
We expect the performance increase to widen past the tests limited engine
speed of 5,600 RPM, where the speed limiter kicked in, and that the gap
between the 2 1/4 and 2 1/2 inch pipe would widen as is typical, at higher
engine speeds, at and above where peak horsepower occurs.
The Iperformance cat back exhaust system outperformed the RK Sport / Magnaflow cat back
exhaust system by a rather healthy margin.
The Iperformance system picked up more than 1 1/2 times more peak
horsepower and nearly double the peak torque as compared to the RK Sport /Magnaflow
The Iperformance system shows almost double the increase in average HP
and 1 1/2 times the increase in average torque as compared to the RK Sport / Magnaflow
Comparing the two on the basis of dollars spent per peak horsepower gained, the
RK Sport / Magnaflow system costs $119.80 per horsepower, while the Iperformance
system costs $44.33 per horsepower.
The design of both systems is nearly identical, both using mandrel bent pipe
and both using Magnaflow brand straight through mufflers. The performance
difference being that the 2 1/4 inch pipe can not keep up with the flow
requirements of the engine and can not match the results of the 2 1/2 inch
Yet again, our testing has shown that 2 1/2 inch is the proper size
for any naturally aspirated four cylinder engines and 2 1/4 inch is too
*We have demonstrated once more, that there is no loss of mid or low range
torque or horsepower when comparing 2 1/4 inch exhaust systems to 2 1/2 inch
The Final Word
What is the difference between the RK Sport / Magnaflow exhaust system and the Iperformance
brand exhaust system?
2.6 Peak Horsepower and 3.5 Peak Ft-Lb of Torque.
Daryl and Matt at Mustang Muscle Performance and Dyno Service have stated
that they are more than happy to discuss their testing and equipment with
anyone who has any questions, and they are more than happy to help if you
want to dyno test your own car at their facility. They can be reached at:
Mustang Muscle Performance and Dyno Service
High Ridge, MO 63049
TEL: (636) 677-9987
FAX: (636) 677-3632