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| 996 FAQ |
In a similar vein to the suspension and tire pressure debate, intakes have generated some debate on the board. It may be a matter of philosophy - track guys vs. street guys. Or it may be that some of those who've tried alternatives to stock haven't allowed their OBDII to remap to the new set up. Powerflow have also slightly redesigned their intake (see below), which may have made a difference to peoples' experiences of it. In short, the jury's still out but it's looking more and more that this is a good performance modification to try out.
Powerflow inhalers (ZucZ): Getting more air into the engine should clearly increase performance. However, every engineer (or armchair engineer) knows that you rarely get something for free. The major downside to freer-breathing intakes is the likely increases in silicates entering the engine. Even very small differences in percentage filtering efficiency can result in significant increases in engine dirt. Also, the benefits of having more air enter the engine is also related to air temperature. Without a proper heat shield, freer-breathing intakes can actually reduce performance! Heroic pioneers on the list (Van's the Man!) have tried the Powerflow filter but so far several have decided to return it. The reasons given are noise (unpleasant droning like a bee hive between 3/4 and full throttle), a "hunting" at idle, a negligable power increase except when running over 5k, and a flat spot somewhere between 2-2500.
In response to this view, Mike Pumphrey had this to say:
"A few months ago I did a "test" of the Fabspeed exhaust on this site. Essentially it was a follow-on to Todd S's earlier test. In my report I mentioned that Joe Fabiano recommended the Powerflow as a compliment to the Fabspeed so I asked him to send me one. It was delayed nearly 2 months because, according to Joe, they were making changes to the 996 Powerflow unit. It arrived yesterday and I installed it.
It's an easy install, the instructions are clear except one spot where it talks about a piece of "black" hose that is actually orange, leading me to think I had the wrong parts (Once installed only black hose is visible). One caution - when you disconnect the battery (per the instructions) remember to hunt up your radio code so you can reenter it - otherwise, no radio. Also, the one touch window won't work until you run each window all the way down and back up the old fashioned way - by holding the switch down for each direction. The instructions state that the idle rpm will "hunt" by around 100 RPM for the first 60 miles or so as the computer "learns" the system. Mine did that for about 20 minutes and than stabilized at the normal rpm.
Sound: - To me the combination of the Fabspeed (FS) and Powerflow (PF) is THE SOUND for the 996. The PF adds a sort of growling-wail that at full throttle says, "Race Car" (did you know that "race car" spelled backwards is "race car"?) However, the PF does not add noise unless the throttle is essentially wide-open. Therefore, under any other driving conditions, the car is no louder than it was with the FS alone. I'm tellin' ya, ya gotta hear the FS/PF combination! At full throttle going from 5000RPM through 7300 it will make your hair stand on end!
OK, what about performance? Per recent advice from Joe Fabiano, I did a lot of acceleration runs to speed up the computer learning curve before any testing. If you don't give the computer time to learn the new system, your acceleration times will be SLOWER than stock. I learned this on my Fabspeed test where the car showed a loss in power until I retested several days later. I nearly returned the Fabspeed because I assumed the computer would instantly adjust to the new component - it doesn't. It learns the change gradually. The more full throttle runs you do, the quicker it learns. Install Note: You don't really have to disconnect the battery to install the system but it's safer and if you don't, the computer will take longer to "learn" the change.
Anyway, my "testing" showed a consistent .2 sec improvement in acceleration time from 3-7000 rpm in 3rd gear averaged over 10 tries. As in my FS "test" I can't claim it to be very scientific but the stopwatch times are pretty darn consistent so I'm confident I'm not doing the "louder is faster" thing. My overall differences stock vs FS/PF show a .4 second improvement. The only caveat is that the FS/stock tests were done in warmer weather several months ago. Since it was considerably cooler (20 degrees) yesterday when I tested the PF, the cooler air may have provided some (or maybe even a substantial amount) of the improvement. (Any air density/horsepower experts out there?)
Overall, Although I generally liked the FS alone, the combination is fantastic and is definitely better than the sum of its parts.
Now for the the disclaimer: one man's music is another man's noise so don't blame me if you spend the 450 bucks and don't like it. (Todd, ignore the disclaimer, you gotta buy this thing) "
Mike added a little later:
"In the interest of fair reporting, I have some items to mention concerning the Powerflow intake system that I reported very favorably on a week ago.
1. Today I noticed a scratch on the Powerflow that is caused by interference with the engine compartment fan. I didn't notice it on installation although I checked it carefully. There is a manufactured "dimple" in the Powerflow that is probably there to clear the fan; but the dimple does not align with the fan strut. It would take very little adjustment to rotate the Powerflow slightly and match the dimple to the fan however...
2. The bracket that holds the Powerflow to the same bolt that held the OEM airbox does not allow any "shifting" of the Powerflow position. It should have elongated holes to allow this. I may fabricate a new bracket or elongate the holes in the supplied bracket - 1/2 inch of adjustment would be plenty. The bracket should be able to adjust height and angle.
3. Several days after the installation I noticed that when the engine is cold there is some surging at part throttle - such as going downhill with just enough throttle to hold the speed. It's not particularly bad and when the engine is warmed up it is essentially gone. I noticed this occasionally with the OEM airbox but it seems more noticeable with the Powerflow.
I'm still extremely pleased with the powerflow sound and performance and would never consider going back to stock but the bracket must be improved to allow adjustment which would resolve the fan clearance issue. The surging is only noticeable under cold-engine part throttle conditions and I haven't found it to be objectionable at all but I wanted everyone to know about it. "
Update, Update! Mike now adds: "There is a mod to the 996 Powerflow that corrects an occasional part throttle surging condition. The mod can be obtained free from Zuczs, the maker of the powerflow. Call Todd at 480-317-9911 for specifics if you have a Powerflow that either exhibits any surging or triggers the "Check Engine" light." [Ed: The modification is a spacer that correctly places the unit with regard to the Mass Airflow Sensor. I have also heard that the unit has been slightly redesigned to fit the compartment better.]
Here's a picture of James' (of Atlanta, soon S. Florida) install:
One of the listers, Robert Sirico, justifiably unhappy with shelling out $450 for some tubing and a filter, built his own intake. Here's his write up:
"I read some posts about the Power Flow and felt I should write you about what I've accomplished. I manufactured my own intake after reading the article in excellence magazine. I went to a local auto parts store and purchased a K&N cone air filter, a big one, I had to cut off about 2" in length than re-attached the metal end cap on it to make it fit into the area it needed to go. Next I used 2 - 3" PVC fittings, a 90 degree street el and a 45 degree street el and lastly a no hub 3" rubber gasket and 1 hose clamp. I came out of the throttle body with the 45 facing down than attached the 90 facing left than added the air filter. I added the MAF sensor to the right side of the 45, sprayed it all black with hi temp paint and installed it. Looking at the photo in excellence my filter ended up in basically the same spot as theirs. Upon start up the idle was smooth and off I went. The car seemed fine and I did notice an improvement for a while but as the engine compartment heated up I felt the power taper off. I drove back home and popped the engine compartment and touched the metal end cap on the filter and almost burnt my hand. Way to much heat from the engine was being transferred to the intake and I remember reading something once that said for every 10 degrees of temp you pick up you loose 1 hp. Not good. So I decided to make a heat shield that would keep the hot air away and help divert the cool air directly towards the filter. I manufactured it out of aluminum and foil type insulation. A cut here and a tuck there and it was done. I went for a good long ride and never noticed a decrease in power, in fact the engine felt perkier than it did before the heat shield. When I got back I popped the engine compartment and again touched the metal end cap and it was just barely warm. It worked, I was getting cool outside air to the filter. The whole project probably took me 3 hours and cost me $40.00 for the K&N, $9.00 for the two PVC fittings and no-hub gasket, and $17.00 for the 2'x3' sheet of aluminum, 2'x2' aluminum insulation and aluminum tape. Total cost $66.00. I spend money freely when it comes to my cars. I race an SCCA T2 BMW M3 that is a MONEY PIT but I couldn't go along with $449 for an air intake. I get intake noise but only at wide open throttle."
There are, naturally, a bunch of after-market exhausts on the market for the 996. They include Tri-Flo, Gemballa, B&B, and an outfit called Fabspeed. Bottom line is that Fabspeed ( www.fabspeed.com ) is the darling of the 996 web community, closely followed by a small band of happy B&B customers (at least one of whom prefers the tip shape of the B&B). I have not seen a single bad report on Fabspeed and lots and lots of good ones. Although the primary motive for most seems to be sound and looks, the Fabspeed muffler does seem to give slight increases in performance. However, it is essential with OBDII cars to allow plenty of driving time for the system to adapt and make any gains it's going to - don't expect immediate and dramatic changes. Also, it's always a good idea to hear a car that's been modified with a new exhaust. I have one 911 friend who scrapped his aftermarket muffler because he couldn't live with the sound. I heard the Fabspeed muffler recently and, to be quite honest, couldn't really tell much difference in sound when inside the car, either at standstill or at speed. Outside, the sound is somewhat richer than stock but not a huge difference -very tasteful actually.
Todd Serota has been helpful in documenting his Fabspeed install and the following is his summary of tests he did against his stock exhaust:
"Ok. I’ve finally gotten around to putting together the numbers from the comparison I did between the stock exhaust on my 996 Cab and the Fabspeed exhaust I added. All tests were done on the same stretch of road, with the same driver (me) and the same timer (a friend). Times of day and air temp, fwiw, were also essentially the same. Obviously, the tests involved full throttle acceleration. The car had about 1500 miles on it when I did the stock exhaust test, and about 4000 miles when I did the Fabspeed exhaust test. The results appear below:
2nd GEAR - 3k-6k RPMS (approx. 32 mph to 63 mph indicated)
Stock exhaust:
Fabspeed exhaust:
2nd GEAR - 4k-7k RPMS (approx. 42 mph - 73 mph indicated)
Stock exhaust:
Fabspeed Exhaust:
3rd GEAR - 3k-6k RPMS (approx. 45 mph - 89 mph indicated)
Stock exhaust:
Fabspeed exhaust:
3rd GEAR - 4k-7k RPMS (approx. 60 mph - 103 mph indicated)
Stock exhaust:
Fabspeed exhaust:
It’s clear from these results that putting on the Fabspeed exhaust added some hp. I’d guess that about 5-10 hp, which is what Joe claims for the exhaust alone, seems about right to produce this kind of gain. The only odd thing is the result in the 2nd gear, 3k-6k test - the times were essentially identical. In all of the other ranges, there was a definitive, consistent, approx. 0.2 second gain with the Fabspeed. At this point, I don’t have an explanation for it, but I don’t think it invalidates the results in the other ranges.
Let me close by saying that whatever hp gain there is, I consider it a bonus. I got the exhaust to enhance the visceral enjoyment of the sound of the car, and in that regard, the Fabspeed exhaust is a 100% success. It’s been on for a few months now, and I still love listening to it as I get on and off the throttle. Of course, having a Cab really helps - on those rare occasions when the top is up, the effect isn’t as dramatic. Either way, it’s one of the best sounding aftermarket exhaust I’ve ever heard on ANY car. Highly recommended.
[Ed: The OBDII unit takes time to re-map. Driving hard for a couple of hours helps speed this process. Some on the list started out with flat spots and other disappointing results after installing their after-market exhausts, only to find that later the power came back with just a hair more to boot. I think it reasonable that the Fabspeed muffler can make an additional 5-10HP. However, it is also lighter than the stock system, which may help a little to create the positive impact noted above. The PowerFlow/Fabspeed combo is reported to be properly sporty and bannishes the luckluster sewing machine exhaust notes!]