I have a 2004 Carrera 2 with the Sport Exhaust option (the button on the dashboard that cuts in a "silencer" but otherwise let's the car sound "like a Porsche." ((When the light on the switch is "on", the sport exhaust is de-activated, of "off.")))

I have wondered since I bought this car (new, only 8 weeks ago, but it now has 3000 miles on it ) if there is any difference in power output just because of the noise.

I looked on the web and found little: on the PCA site the topic is addressed and answer seems to be "Porsche says no, but then they would for legal reasons. of certifying just one engine tune." Not sure if that is the case but I decided to find out. I had to take my (very modified) 'vette in for dyno testing and tuning today so since I was buying dyno time I just had my son drive the Porsche along and we tested it after we ran the 'vette.

To get valid on what I assumed would be a small difference at best (I expected nothing), we ran quite a number of dyno runs: A series of warm up runs to track "heat soak," then a cool down for half an hour, then two runs, one with it on (light on, sport exhaust off) and then with the light off (i.e., noisy), then let it cool down half an hour, then two more runs with the light off and then on (i.e., oppsite order from the first test), then let it cool for 30 minutes, a run with the light on and then off, then let it cool another 30 min, then another with it off and on, etc., all afternoon, to get a set of dual back to back readings that eliminated as much chance as possible that we were just seeing differential heat soak making the HP difference. Then we averaged all the results into the two sets

Air temp was 98 deg F, the machine was a recently calibrated Dynojet 640 with recently updated software.

Heat soak runs. With the sport exhaust light "off" (i.e, the sport exhaust is on) and the engine cooled down for about 75 minutes, the first of six dyno runs in a row netted 265 HP at the rear wheels, the next 263.5, the last, only 260.5. (Each run takes the car at full throttle from 2000 RPM to redline, all in 4th gear and takes about 11 seconds.

Comparison of average of all the runs to compare sport exhaust on and off (after and excluding the heat soak runs):
There is no difference in power output from 2000 RPM (lowest RPM plotted) to 5500 RPM: the average curves lay down within a plotted line's width of one another, except for two "blips" from 2500 to 2750 and from 4450 to 4650 where the "light on" (i.e., sport exhaust off -- in quiet mode) produces about 4-5 more HP. From 5900 RPM on up to the redline the "light off" (sport exhaust is on, i.e., in noisy mode) produces an average of about 5 more HP: 263.9 vs. 258.6. A similar difference appears in every set of two runs no matter which order on-off or off on it was done and it averages that -- this includes the difference and the top end and the two "blips" (which I think are due to exhaust resonance), so I believe that a conclusion that the sport exhaust loses 4-5 HP at the top end when in silencer mode is real.

By the way, the 'vette put down 595 RWHP - so close but still no 600 RWHP cigar.

 

By the way I forgot to add that the car has a Tiptronic, so this is why HP is a bit lower than one might think.

 

hey Lee!

i still havent gotten my car to the dyno, but im not expecting anywhere near 600 rwhp...im hoping for more like 500 ghp...

 

That's still an awful lot of power. 500 HP is about all you can ever use on the street.

 

Stephen kaspar runs 809 crank in his TT and it is his daily driver in the sun, rain, snow...year round. And he isn't the only one driving around with over 600.

 

The thing about the 'vette is that it is every bit as well behaved as stock, and easy to drive despite the power. Idles smooth, starts and runs fine -- even gets 20 mpg around town and 29+ on the highway (at legal speedser. That and around 600 RWHP was the goal -- and while I can double the boost (too 12 lbs) with nothing but a pulley and re-porogramming change) I don't plan to because I think 600 RW is about the limit. Its very difficult to put more than about 600 controlable HP through just one axle.

Do you mean by "TT" a Porsche Turbo or a Lingenfelter Twin Turbo 427? I know the latter goes up to 825 flywheel if you spend enough, but its also supposed to be very difficult to control under full power. The advantage a Porsche Trubo would have is the four wheel drive.

 

2001 Porsche 996 Twin Turbo, obviously upgraded and yes, AWD. You get on it even half throttle and you can have it sideways, but i guess it is just knowing the car and where the limit is. We just finished an 04' GT2 (RWD) about a month ago that put down 640 to the wheels, and is a daily driver as well as track car. In the GT2 we used a tilton triple disc clutch, which felt amazingly like stock, so it was extremely driveable. Stephens twin has a puck clutch in it that is a little difficult to drive if you don't know the car, but after seeing what the triple disc is like, we will be putting that in the car in the near future. The 996's and even the 993's put down the power and control it very well, a 930 on the other hand is pretty nasty trying to drive around with over 500hp.

How does the vette hook up between shifts when laying the power down? They run around with some fat meats on the rear, but i would think 600 and RWD breaks them loose pretty easy? Do you track it at all, or just street?

 

while im sure that it is awesome to have 800+ BHP, it really isntr practical, and im sure that guy doesnt drive like i do, if he drives it that much...at least not without constantly replacing things, which i cant afford to do..figure, that im pushing a 3800+lb car down the quarter mile in the mid 12s, before the new springs and tranny...which still isnt together...those compurer dynop programs arent good to base things on, but its an idea, and it puts me mid-to-high 400 range..something like 470 or so.,..not bad for a car running on 87 octane...

 

I'm not sure how much power is practical for the street. I remember in the late 60s, when I thought anything in the 13s was God-like. I struggled to get my 689 327 Camaro in the high 14s. Now, my daily driver is an automatic transmission Porsche Carrera that will do 13.4-13.5. the bar keeps moving . . who knows where it will be in a few years?

I have 345x18 drag radials on the rear of the vette. They are big, which helps, and they are drag radials, which helps a whole bunch: I tried 345 Michelin Pilot sports and they were not nearly as good under acccerlation. These tires work really good when its dry, but: 1) I get a bit less than 4000 miles per $675 set and I don't burn them up, they are just soft as erasers and they don't last, and 2) the car is TOTALLY undriveable on wet roads above 20 mph (and I mean just "wet" roads -- there does not need to be any standing water, even a film if its damp, I'm toast. This is its downfall.

And they behave better in corners than I expected: no problems there as long as its dry. Franly I could not tell a difference from the Michelin Pilots.

I make a point of telling people that "I drive fast cars, but I don't drive fast." I really don't use the power often. And since I'm in my late 50s and look totally harmless, I've actually talked my way out of several tickets that way (okay, maybe I drive a little fast). I take the 'vette out about an hour each weekend and drive it around on the street. I talk about "terrorizing the natives" but actually I don't abuse it. Except there is always some jerk who has to **** me off, and then . . .

I always take it out on a long backroad US highway (but not interstate) where I can make sure it still performs "to spec" -- I know that my G-techsays it will do 100 in 7 flat and 150 in under 16 seconds: that's my weekly benchmark that its still in tune.

 

Quote: They run around with some fat meats on the rear, but i would think 600 and RWD breaks them loose pretty easy? Do you track it at all, or just street?

As I said, I have 345s., but that just mitigates what would be imposdsible otherwise. It is total wheelspin in 1st gear - it will snap the tires lose on dry and perfect pavement just by slamming the throttle open-no need to drop the clutch. On the other hand it doesn't crab badly - a little creep to the side but it is amazingly well behaved. It ps the tires badly going into third and gets a bark into fourth, which is pretty amazing.

I used to track it occasionally, letting my son drive, when I had a Magnusen supercharged stock block. 480 RWHP roughly. It had stock tires then but would still do 11.6s and 11.7s all day. But then with the new engine,naturally aspirated, my son drove it to a 11.46 and they told usI had to have a roll cage to come back, particularly with a SC now. So, that's it.