the eternal exhaust debate
05-30-2006, 12:04 PM
#16
Racer
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Location: New York
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Originally Posted by icon
they dyno for sound?
ridden all types of motorcycles!
if i were going for performance i would get a sportbike.
a 250 could lap your harley!
ridden all types of motorcycles!
if i were going for performance i would get a sportbike.
a 250 could lap your harley!
05-30-2006, 02:12 PM
#17
Originally Posted by Bob Rouleau
I am very skeptical aboout claims made by aftermarket exhaust system suppliers. I have been burnt by several in the past. Great sound - yes. Weight reduction - yes, power increase - NO! In fact at least one was a power reduction.
More noise does not equate more power. Since the 993, a cat-back exhaust has had a lot of trouble extraing more power. I have read that Porsche uses noise cancelling techniques to meet sound pressure levels without overly restricting the exhaust.
Headers are another matter. They usually deliver a power increase although a retuned ECU may be needed to get the benefit.
It is also interesting that Porsche makes no claims of added HP with the PSE. It sounds nice but no power gain. How is it that non factory, low volume suppliers manage to extract more power ... or, are they simply promoting?
I also find it interesting that the 996 GT3 makes only 9 HP less than the 996 GT3 CUP car which uses high flow cats and no mufflers at all. Nine out of 380 ...about 2.5 percent. Just another data point to consider.
Best,
More noise does not equate more power. Since the 993, a cat-back exhaust has had a lot of trouble extraing more power. I have read that Porsche uses noise cancelling techniques to meet sound pressure levels without overly restricting the exhaust.
Headers are another matter. They usually deliver a power increase although a retuned ECU may be needed to get the benefit.
It is also interesting that Porsche makes no claims of added HP with the PSE. It sounds nice but no power gain. How is it that non factory, low volume suppliers manage to extract more power ... or, are they simply promoting?
I also find it interesting that the 996 GT3 makes only 9 HP less than the 996 GT3 CUP car which uses high flow cats and no mufflers at all. Nine out of 380 ...about 2.5 percent. Just another data point to consider.
Best,
05-30-2006, 03:09 PM
#18
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Originally Posted by Eggplant Cab
Dunno about that. Lotsa people noticed my Ducatti Monster more than my heritage softtail. Now I just have a moped and a mountain bike
I think Ducati Monster is a great design. you should have kept it
05-30-2006, 03:49 PM
#19
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Originally Posted by Bob Rouleau
I also find it interesting that the 996 GT3 makes only 9 HP less than the 996 GT3 CUP car which uses high flow cats and no mufflers at all. Nine out of 380 ...about 2.5 percent. Just another data point to consider.
Hi all, this is my first post!
Been scanning the forum from behind the scene for a while now though
05-30-2006, 04:44 PM
#20
Race Director
Originally Posted by gpjli2
Then there is the R&T"Tuner Cars" shootout (5/06). TechArt entered a 2CS with every known bolt on engine mod. Intake,filter, headers, manifolds,exhaust,ecu, etc. The car ran a 12.6 @ 112.2 which is an average result for this roadtested car. No great hp increase there. But people want to believe the ads. I'd rather put the money into lightweight wheels to lower unsprung weight and a muffler that took 30-40 lbs off the rear of the car. You can believe in the laws of physics.
05-30-2006, 05:22 PM
#21
Originally Posted by mdrums
Absolutly...could not agree more! To add more power, even a 10-20hp on a 997 you have to spend some major money, not just a little muffler exchange. I am not a Porsche guru but I know this.
Air is power. The more air that moves through the system the more power. Now, IF a motor had unused intake capacity at the throttle body and unused intake valve capacity at the heads, THEN maybe opening the exhaust alone would add power. But I doubt Porsche has more intake air capacity then they utilitze. That's what new heads are for.
It is a pretty common rule of thumb (and the x51 powerkit highlights it) that air flow MUST be increased at the intake, the heads, and the exhaust to get more power. Unfortunately it is just that simple and that expensive.
I do believe that the least expensive way to get more power from a Porsche motor is to simply run 93 octane in it. Noticable difference to me.
06-01-2006, 02:10 PM
#22
Three Wheelin'
Originally Posted by Eggplant Cab
Robbonds
The problem with testing against another car is that you didn't go against him before to get a baseline. Out of the box engines can differ a lot. My 1st Porsche 911 targa was dynoed at 261 rwhp with 8k miles. After exhaust (with cats intact), airbox and chip, it pumped 276. The 2nd 964 had 255 at 4k.
So your method is abit inaccurate. A dyno takes out the driver and other variables except environmental. Even if there's a 20°F or 10% humidity change, the dyno is accurate to show an increase or decrease to a point.
The problem with testing against another car is that you didn't go against him before to get a baseline. Out of the box engines can differ a lot. My 1st Porsche 911 targa was dynoed at 261 rwhp with 8k miles. After exhaust (with cats intact), airbox and chip, it pumped 276. The 2nd 964 had 255 at 4k.
So your method is abit inaccurate. A dyno takes out the driver and other variables except environmental. Even if there's a 20°F or 10% humidity change, the dyno is accurate to show an increase or decrease to a point.
true - but if we are both traveling 60 in 3rd and punch it and go through the gears - if i continue to pull away from you in every gear i have a faster car....the modified boxster i raced continued to pull away from me - no driver in the world could have caught him in my stock car - his car was faster
06-01-2006, 03:20 PM
#23
Originally Posted by robbonds
true - but if we are both traveling 60 in 3rd and punch it and go through the gears - if i continue to pull away from you in every gear i have a faster car....the modified boxster i raced continued to pull away from me - no driver in the world could have caught him in my stock car - his car was faster
The Ducatti is nice but impractical for this boy. The garage is already filled with stuff I won't get rid of, my 964 cab mainly. Plus I like the electric moped (it's unplug and play) plus the bike makes sure I'm not slowing down the cars too much with unwanted weight.
Robbonds
My point was that different cars from the factory can have different outputs. My older porsche came with higher than spec by as much as 11hp. My E39 M5 came under spec by 10hp, quickly addressed by a few days at Dinan(with pre and post dyno of course). My Maserati Coupe was 12 hp over spec etc etc. So your faster car may not mean the exhaust performs as promised. But with respect to the faster car, in a straightline, sure the faster car is the faster car, doesn't matter what mods or not there are in it.
