 Taken from the VetteNetters Forum
Back in Dec & Nov there was quite a bit of discussion of the K&N Filter. At the center of the controversy were questions about the K&N's filtering ability (i.e. though its performance enhancing features aren't in doubt, people wondered how good a filter it is?) The discussion even got a bit heated with someone on the anti-K&N side coming out and saying the K&N pretty much sucks as a filter and isn't good for your engine.
The only post I saw, pro or con, that backed up its statements with test data was one citing a 1992 British Motor Industry Research Association dust filtration efficiency test of the K&N air filter. While this test has been discussed previously, there are some things in it that need review.
The test procedure was done according to ISO standard 5011, an international standard for air filters of the type used on heavy-duty and commercial vehicles, using a K&N oil-impregnated, gauze media commercial type filter measuring 16.14" long, 10.43" diameter, with an air flow of 550 cfm. The test "dust" used was "coarse grade" as specified by ACDelco standards for testing their filters. Coarse grade dust is made up of the following percentages of varying diameters of dust particles.
The starting pressure differential across the filter was 26.45" of water and the test ran until it reached saturation (31.49" of water) and then the amount of dust trapped by the filter (5.1307 lbs.) was compared to the total amount of dust introduced during the test (5.1680 lbs.) It took 102 mins for the filter to reach saturation and the filtration efficiency was 99.28%.
So, how do I qualify this test to put it in the proper perspective for the street high performance engine in a Vette?
Another test of K&N filters was conducted by the British MIRA in 1983 but this time according to the SAE J726 standard which is a bit more familiar in the US. This test was done using "AC fine grade" dust which is more typical of what a street engine would encounter under normal driving conditions.
This test used a K&N three-layer motorcycle type filter with an airflow of 40 cfm. The initial pressure differential was .825" of water and saturation was reached at 6.85" of water. They introduced 15.6 grams of dust and the filter trapped 15.1 grams for an efficiency of 96.8% - very close to the 97% K&N claims for its street high-performance automotive filters.
Now, while a motorcycle filter is obviously "much" smaller than what a V8 would use, the efficiency should still be about the same and the bigger V8 filter should take longer to reach saturation.
In yet a 3rd MIRA test, using filters typical for V6 engines in high-performance sports coupes, two K&N oval filters (2.56"x7.48"x6.18" & 3.22"x7.05"x4.5") were tested. This test was run according to ISO 5011 using AC fine grade dust and the filter efficiency levels were 97.5% and 97.6% respectively.
All these tests showed efficiency levels well above the 95% most OEs claim and, in my opinion, convincingly show K&N, oil-impregnated, gauze air filters are not only capable of high filtration levels but also low airflow restricion. Many off-road racers must agree with me because a lot of them use K&N filters and, if they work in that kind of enviornment, they must be one heck of a good filter.
Also, Chrysler markets factory-approved performance kits for some of its US truck engines that includes a K&N filter and are covered under their factory warranty. You can bet they wouldn't warranty such a kit if the K&N filter didn't meet or exceed their OE filter efficiency standards!
In Japan, Nissan also markets similar factory-approved performance kits for a couple of their Japanese domestic models and, like the Chrysler kits, they include K&N filters.
Finally, one way a K&N filter can fail is if it's used - contrary to the manufacturer's instructions - without being oiled or with the "wrong" oil. If you use a K&N filter, you should clean it annually and reoil it every six months. If you operate your Vette in a dusty environment (the coarse dust) clean and reoil it more frequently. When you reoil, "only" use K&N's filter oil. Foam filter oil, engine oil, WD40 or ATF are "not" the proper oils and "will" significatnly degrade the filter's efficiency.
cYa
My D is a 98 SLT+, 5.9L with all options except rear air and is completely stock except for removing the factory molded running boards. I dropped the spare while racing to lessen the weight a bit but no other modifications were made.
I managed to make multiple runs under the same atmospheric conditions with the stock air filter, the K&N filter and "no" filter. Each run with the "same" air filter setup didn't vary more than .04 seconds and the averages were as follows:
I believe the difference between no filter and the K&N is just too small to lend any weight to the argument but the stock filter was definitely slower. It was also fun watching a Chrysler employee run his 5.9L JGC "company car" (it did 15.28 %40 88mph!!) I hope this may provide some kind of baseline for those of you with headers, cat backs, chips, intake systems etc.
Happy D'ing
Will a TB spacer help my performance? The principle behind such spacers is increasing the distance between the throttle body, or carburator on older vehicles, and the intake values so the fuel/air mixture takes a "little bit" longer to actually reach the cylinder and ignite. This "slight" delay allows the fuel and air to mix more thoroughly so it achieves more complete combustion and thus more power and better mileage.
This idea has been around for quite some time and is a "well proven" means of gaining a few extra HP and slightly better mileage from a carburator or TBI (Throttle Body injection) setup where the fuel is sprayed into the air flow "before" it enters the intake manifold. However, newer MPI (Multi-Point Injection) setups - like what's on the D - have separate fuel injectors for each cylinder and the fuel is sprayed into the air flow at the "end" of the intake manifold just before everything gets sucked into the cylinder for combustion. This means increasing the distance the air flows in a MPI setup, which is the "only" thing a spacer really does, doesn't help the fuel and air mix any better because the fuel doesn't even come into the equation until everything's ready to enter the cylinder for ignition!
So, the answer is "no", a TB spacer won't help performance or mileage on a D - or any other MPI equipped engine!
The general conscientious is add-on chips don't work very well and are eventually "learned around" by the factory computer. Many have posted they didn't notice any difference with an add-on chip installed, or it disappeared after a few months, and one group even did some before & after dyno testing and actually "lost" HP with the Jet chip installed! The best options for permanent performance gains seem to be replacing the stock PCM (the engine computer) with a Mopar Performance one (if your D is pre 2001 model) or having a custom program flash applied to the stock PCM.
Mopar sells Performance PCMs with +15 HP and +10 ft-lbs of torque but only for 98, 99 & 00 Ds. They warn that "add-on" chips aren't very good because the PCM eventually learns around these chips and you'll lose any performance gains. Their Performance PCM uses different intenal fuel and timing curves so the gains are permanent and but it requires you use premium fuel (although some owners have gotten away with using 89 or even 87 octant with it installed.)
Actually, it's not like either because, unlike the chips which simple plug into the stock PCM, the Mopar Performance PCM actually "replaces" the stock PCM! Also, unlike the chips, it raises the engine's rev limit and removes the electronic top-speed limiter. - Mike Leach's flash, available from KRC performance, is better for people with superchargers who need custom fuel maps to support a supercharger's higher compression.
- ASE Performance Chips and Kenne Bell have decent flashes, but they don't add anywhere near as much performance as the B&G one.
- B&G offers 2 levels of programing:
Regular flash
Martel Brothers Racing Products (800-882-7223, FAX: 281-391-7772) sells Stage II Jet chips for the 5.9L ($229.95) as well as the 180ºF thermostat ($10.95)
To achieve maximun effect, this chip requires headers, cat-back, 180ºF thermostat, preferably a K&N filter and requires you use premium fuel. I received my Jet Stage II chip and the 180ºF stat from Martel Bros. Racing and installed them over the weekend. The installation of the chip is "very" easy and the stat would be relatively easy - as long as you have right tools.
INSTALLATION
REVIEW
Hope this info was helpful.
Bob C.
Tire size & speedo calibration? There's been considerable debate on what can and can't be changed with respect to tire sizes and the speedo. This was posted on the Dak list and, after some "quality time" with my local Chrysler service computer I came to the same conclusion. There are "no" speedo pinion gears in our "D"s and the only "adjustability" is via the vehicle computer. According to what I was told by the service manager, the computer can "only" be programed for OEM tire sizes and axle options. The text from the MDS II as posted to the Dak list is:
1998 & newer
The instrument cluster circuitry calculates the proper gauge pointer position based upon a vehicle speed message from the PCM (Powertrain Control Module) recieved via the CCD (Chrysler Collision Detection) data bus. The PCM uses a speed pulse input received from the CAB (Controller Anti-lock Brake) and internal programming to decide what vehicle speed and distance messages to send to the instrument cluster circuitry via the CCD data bus. The CAB uses an input from the rear wheel speed sensor and internal programming, which includes a programmable pinion factor to compensate for different axle ratios and tire sizes, to determine what speed pulse output is sent to the PCM via a hard wired circuit.
In other words, there's no tranny gear to replace on newer trucks!
Craig According to the ABS section of the manual, the CAB is programmed with an specific RPM (Revolutions Per Mile) number for each different tire size. This would "seem" to accomodate any tire size/axle ratio combination but, the manual doesn't mention the actual procedure for inputting this number.
Matt "the" D
Which Cat-back’s are good and will they help my mpg? The general conscientious of most exhaust experts is the OEM system on the D is "more" that adequate! It's already mandrel-bend stainless and includes a high-flow catalytic converter so the best "bang for your buck" is simply replacing the restrictive OEM muffler with a fee-flow version.
Borla. It cost me $500 installed in the San Francisco Bay area, has a single, round, intercooled tip and the muffler is smaller than stock giving more ground clearance. It's got a deep, throaty tone on acceleration but once at speed is very quiet and almost can't be heard on the freeway. One problem, the system didn't fit exactly right! It hit the trailer hitch so the muffler shop had to kinked the pipe, which I didn't want but it would have rattled otherwise. I called Borla, and they said they designed it for a D with the small tires and no trailer hitch.
I later put on Edelbrock Headers, which pulled my whole exhaust system forward and made the pipe hit the hitch again, so I had a Flowmaster two chamber muffler installed with dual exhaust pipes and love the sound and look. It gets a little annoying on the freeway, but makes you look forward to that green light and the sound of a '69 muscle car. I had the Borla, installed by a local off road shop. Their opinion was the Gibson (they sell both) might have too little back pressure and I'd lose my low end grunt. The price for the stainless Gibson was only $8 less than the stainless Borla (Gibson does sell an aluminized version for around $300.) I don't have definitive answers as far as performance increases, but I did notice a 2 mpg improvement in mileage.
I had a Borla installed by a local off-road shop. Getting it to fit seemed pretty straigh-forward, but the installer did have to trim about an inch off of the tow platform, in back of the bolts, to keep it from rubbing on the pipe. I haven't noticed any mpg gains yet, but, subjectively, there does seem to be better low end response.
The guy who installed my Borla had to cut a small corner off of the hitch platform. After that, it fit better than the stock one!
I realized a 1-2 mpg gain with a Borla & JBA headers, but I'm not convinced the improvement was from the Borla since, after the cat-back installation, I didn't notice much of an improvement in mileage - just a slight "seat-of-the-pants" improvement in acceleration. Nice sound though!
I personally believe the Eldebrock RPM series 3" cat-back is the best. Their design should have less turbulence and better flow than some of the other chambered versions like the Flowmaster - I don't know about the design of the Gibson or the Borla. I do know the Gibson hangs to low and the Borla is too expensive! I also talked to a performance shop and on their modified pro stock Nova they said the Borla killed their performance.
I ordered mine from a locate performance shop for $279 for both my D and RAM 1500. The cat-back part# was 5760 and the stainless turndown tip was 5598. This should be a good addition to a D. I got the Gibson cat-back and am very pleased. It cost me $384 plus tax installed by a place called Conversion Xtra's here in Houston. It looked like a straight forward, simple install (very "factory" look) but I didn't have the tools to DIY. I've only noticed minimal performance gains and mpg improvements, but the sound and looks of the chrome tip are extremely cool. The shop owner recommended the Gibson over Borla, saying it has much less resonance (which I didn't want) and was better designed for the application. They sell Borla and do a lot of high-performance work, so I took his word for it.
I got the Gibson stainless cat-back performance exhaust and have been very satisfied with it - I still enjoy hearing it whenever I start up my D! I know Gibson designs its systems to fit the OEM hangers, their stainless system comes with a lifetime warranty, and when I called their toll-free number with some questions I found them to be friendly and helpful. A local franchise called Trick Trucks charged me $90 for the installation and as far as I can tell, they did a fine job. If I recall correctly, the Gibson is 3" pipe while the Borla is 2.5" and both are mandrel-bent. The Gibson comes with a "giant" polished stainless tip.
I have Gibson stainless headers and their 3" cat-back.
It only took me 20 mins to install the complete Cat-back and there was absolutely no clearance problems by either the rear tire or my tow hitch! Earlier reports of the close proximity to the tire and hitch worried me, but if you push the muffler and tail pipe forwards far enough it clears just fine. I think maybe those other people's systems just weren't installed correctly as Dave Hoot of Automotive Accessories Connection checked with the Gibson factory and was told there've been no reports of such problems with Gibson systems installed on hitch-equipped D.
Afew notes to preface this bit of info which was taken from an article in Super Ford magazine. The test vehicle was a 1991 Mustang 5.0L convertible with an automatic transmission and this information is not meant to be the "gospel" on mufflers; simply a tool to aid in comparisons between some of the major brands available.
For reference, 60 dB represents normal conversation levels, 90 dB is considered the threshold for pain and a 14 dB increase effectively means the sound level has doubled.
The reviewers noted during the test drives there was a noticeable improvement over the stock mufflers but not between the different aftermarket mufflers (performance wise).
All installations used DynoMax Easy Seal clamps - a stainless steel band clamp that forms a 360 degree seal.
Overall, Borlas were among the quietest we tested. Definitely a quality package. Stainless steel throughout, which accounts for the high cost.
Comments: 40ish: Very quiet. Sort of a stock-sounding growl at idle. There's some roar during acceleration, but it's mellow. Hardly any sound at all at low cruising speeds and deceleration. At full throttle, they're more like the stock mufflers. Barely audible at 65 mph. These are probably the best mufflers for the guy who likes to hear his stereo. I'm not a real fan of the Borla exhaust tips. 20ish: These are really soft on acceleration. They don't build up the roar that's so common with most of the other mufflers. You actually hear more convertible wind noise than you do the mufflers. They're real quiet on deceleration and don't have that popping as you let off the throttle. Just enough sound that you know they're there.
These mufflers have a more conventional design with three perforated tubes, flow directors and fiberglass matting.
Comments: 40ish: Idle has a lower rumble. They roar too, but not quite as bad a some of the others. Not as ear piercing. These get louder as the rpm rises. Still fairly objectionable at 65 mph cruise. At lower speeds, you can barely hear them, almost like stock. At full throttle, more of the sound seems to be coming out of the tailpipes. It has a pretty mellow acceleration sound, I wouldn't say they were loud at all inside the car. 20ish: They aren't as loud as I expected. The roar is in a lower range, so they're not as obnoxious. They sound fine to me at cruising speed. For this car, they're probably quieter than what I would like. People usually want to make their cars louder when they are this close to stock.
Billed by Dynomax as "the ultimate muffler", the Ulta Flo mufflers are a straight-through design with a single inner tube with large perforations, for maximum sound absorption and minimum turbulence, according to Dynomax, and stainless steel mesh wrapping. The interior of the bright stainless steel casing, which make the Ultra Flo one of the better looking mufflers, is filled with fiberglass for a deep performance tone. According to Dynomax's John Brubaker, the Ultra Flo is designed for excellent flow characteristics with a quieter tone than the super Turbo.
Comments: 40ish: Seems louder but growlier at idle. A deeper tone. But they still roar, although it's deeper. Sounds as loud as the Super Turbos, although more of the sound seems to be coming from the tailpipes, not inside with you. The deceleration seems louder. I expected these to be quieter than they are. 20ish: they're pretty loud through the 2000 rpm range. They sound really good at idle. Under normal acceleration they seem quieter than the Super Turbos. To me, they sound quieter at full throttle. They're not, according to the dB meter, but they sound quieter.
At first, we weren't sure about including these "straight pipes with crimps" in our muffler sound-off. Looking very much like the chambered exhaust for mid-'60s Camaros, the Turbo Tubes are labeled for "off-road use only", and after installing them we can see why. However, most of the sound stays outside the car, keeping the interior level somewhat tolerable. Of all the mufflers we tested, these were the most fun! Trouble is, they make you want to hit the throttle all the time just so you can listen to them. Definitely no clearance issues with these.
Comments: 40ish: More of a '60s sound to them, almost like an old glasspack. Idle outside the car is throbbing, like the car wants to go. Obviously loud, but not a lot of resonance inside the car. At low cruise, you hear the rumble but not obnoxious. Definitely louder, with more rumble on deceleration with popping. Actually, not as loud as I thought they'd be. Loud, but mellow. These make you want to drive fast. Twenty years ago I would have loved 'em. 20ish: They don't sound bad outside at idle, not what I expected. I expected them to be louder. I'm pleasantly surprised. I think they sound pretty good at full throttle.
Edelbrock's RPM Series muffler uses a totally different design from the other mufflers. Inside the stainless steel casing is Edelbrock's "Tru-Flo" core, a split-channel design made from perforated stainless steel with surrounding ceramic packing. Unlike mufflers with baffles, the exhaust passes through the core with minimal turbulence.
Comments: 40ish: Idle seems louder, has a little bit of a flippity-flap to it. Roars, but the sound is coming out the back. not in the car. The roar seems to occur at a lower rpm. Loudest at around 1700 rpm. Quiet at lower cruise speeds, you can hear the rearend whine. Very quiet on deceleration. Really pretty quiet just tooling around. At full throttle, it's quiet, with all the sound coming from behind the car. Sounds real good, more like a '60s musclecar. 20ish: Dead quiet at lower speeds. They're throaty when they're loud. They're quiet, then they all of a sudden jump out at you, then go away real fast. They do sound good at full throttle. Sound like the stereotypical TV car. Overall, they have a pleasing sound.
Now fully aluminized for durability, Flowmasters come either two-chamber or three-chamber. The two-chambers are designed for race applications, so they offer less backpressure with accompanying higher sound levels.
Comments: 40ish: I like the idle. Lower, racier. The roar is still there at 2000 rpm inside the car, but it seems to go away real quick. Then you've got a real throuty sound. At low cruising speed, there's a nice rumble out back. On deceleration, there's a popping, or cackling, sound. The roar doesn't have that ear-piercing tone to it. There's a bit of a roar at 65 mph, but because the tone is lower it's not as objectionable. I can see why so many people like these because they have a real powerful sound, all the way across, not just at idle or full throttle. 20ish: Sounds like a street race about to happen. Has a racier sound at idle. The cats help a lot with the sound levels. A lot of guys run two-chambers with off-road pipe and they're pretty loud. The roar at 65 mph seems more pronounced, more powerful. The sound seems to increase, swell up until the roar, then it goes away at the shift.
Designed for stock or mildly modified vehicles, the three-chambers still have that Flowmaster sound but it's not as pronounced as with the two-chambers, thanks to the use of an additional V-shaped chamber inside the muffler casing.
Comments: 40ish: Idle is sort of a low rumble with a growl. I'd say these have the lowest tone overall. Has a real low rumble at low cruising speeds - a powerful rumble from the back of the car. Deceleration is fairly quiet but you still hear the rumble and a little cackling. Loud at 65 mph but not obnoxious. Good sound overall, not too quiet and enough of a rumble for a performance sound but not too objectionable except a little bit in that 2000 rpm range. Sound is great at full throttle. 20ish: The roar doesn't seem to be as pronounced with these. One of the quieter mufflers at 65 mph. Looks like we're not going to get away from that 2000 rpm roar with any of these mufflers. I think these are the best so far in that range. Good at idle, not very pronounced.
Marketed as the "Bad Boy of Mufflers" the Flowtech Terminator mufflers reminded us of Flowmasters, both in sound and appearance. Definitely heavy-duty, the Terminators are fully welded thoughout and use 12 and 14 gauge aluminized steel, with the casing painted black. For sound control, the Flowtech mufflers utilize short, perforated tubing both front and back with a baffled chamber in the center.
Comments: 40ish: Throaty idle outside the car, sounds very much like a '70 Mach I. Idle inside the car is kind of throbbing. More of a deep roar at about 2000 rpm, with a deep rumble at low cruise. You can hear them, but they're fairly quiet on deceleration. A real good full throttle note, with some popping. Pretty loud at 65 mph, with lots of noise on deceleration from 65 mph. I give them pretty good marks all around except for the 65 mph cruise. 20ish: They sound like Flowmasters! They sound really good on full acceleration, but a little smoother overall than Flowmasters.
Hooker's Aero Chamber mufflers use a "step" baffle design that, manages the individual exhaust pulses of each cylinder. Constructed from aluminized steel and painted black, the Aero Chambers resemble Flowmasters in appearance.
Comments: 40ish: They've got a mellow tone. My only complaint is at the 2000 rpm range where it reaches 90 dB. Every time you accelerate, you have to go through that. You almost need one of those Corvette radios that adjust the volume. The idle is kind of throbby, but mellow. 20ish: Inside, they're pretty quiet except right there at cruise speed. They are kind of irritating there. The car sounds close to stock at idle. It has a growl but it's not obnoxious.
Conceptually similar to Dynomax's Ultra Flo, the Hooker Max Flow mufflers use a straight-thru tube surrounded by a high-temperature packing material. Almost identical in exterior appearance to Hooker's Aero Chambers, the Max Flows are made from 16 gauge aluminum and stainless steel, with the casings painted heat-resistant black.
Comments: 40ish: Outside idle is quiet, with a metallic sound. Very quiet idle inside the car, almost like stock but with more of a rumble from the back of the car. Very quiet at low cruising speeds and deceleration, almost can't hear them. At 65 mph, there's a bit of a roar but not too obnoxious. They don't sound real powerful, almost too quiet, especially at low cruising and idle. These have a nice, unobtrusive idle and off-idle sound. I'd really like these if it wasn't for the resonance between 1800 and 2000 rpm. Almost perfect mufflers from idle to 1700 rpm, and from 2000 rpm to 5000 rpm. 20ish: Much softer than Flowmasters at low cruising speed and deceleration. They're smooth. In a hardtop, you might not be able to hear them at low cruise or idle. Would be interesting with off-road pipes.
With 18" of case length, the Pacesetter TFX Power mufflers were 3-4" longer than the other mufflers, which made them slightly more difficult to install. We later discovered that we had received a "universal-fit" pair of mufflers. Regardless, the sound should be the same (Sean: I disagree here as a longer case length will quiet the tone). These are constructed from aluminized steel and come with a low-restriction internal design that does not require packing material for sound control.
Comments: 40ish: Nice burble at idle from outside the car, with deep tone inside the car. Roar is pretty muffled. Fairly quiet at a low cruise and hardly any sound at all on deceleration. Good, throaty tone coming out of the tailpipes on full acceleration. Bit of a roar at 65 mph. The roar between 1700 and 2000 rpm is fairly mellow, not ear piercing. Like the Borlas, these are for the guy that wants to listen to his stereo. 20ish: They sound better than I expected. They've got a real nice, deep idle to them, and they sound good under full throttle.
A relatively new player in the market. A straight-thru design, the Rhino mufflers use a trio of perforated tube baffles in the center to control sound, along with all aluminized construction.
Comments: 40ish: From inside the car, these are really quiet at idle. On normal acceleration, the roar is still there, coming on at about 1800 rpm. The roar is not as ear-piercing because it has a lower tone. Low cruise is pretty quiet. Can still hear them; there's a rumble back there, but still quiet. Sounds good at full throttle, not loud inside the car. Pretty good roar at cruising speed. These sound like louder stock mufflers. 20ish: They really resonate inside the car, like they fill up the backseat. Seem louder to me at full throttle, even louder then the two-chamber Flowmasters. Also seem a little bit louder on deceleration, especially coming down from 65 mph. These are loud, not irritating, but they don't sound as good as the Flowmasters to me. They don't have that tone to them.
For those of you considering the DJM 3" drop kit available for 4x4 Durangos.
I just got back from the dealership working with the mechanic trying to figure a way to get my 17" wheels to work and it's not gonna happen. The lower ball joint gouged a grove in the wheel as we tried to move it over to do the front end alignment. After much tugging and readjustment of the settings, we managed to clear the wheel enough to roll the vehicle but it's completely undriveable because each bump in the road would gouge the wheel again. I now have a new set of 18" wheels and tires on order due to be delivered Wed.
Interesting note, DJM developed this kit for the Shelby Durango, which was originally going to have 18" wheels but, due to a supply problem, was delivered with 17". I would not suggest installing this kit on on a 4x4 D without 18" or larger wheels!
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