Dyno run question

My stock 02 996 C2 with Tip was on the dyno the other day and I ended up with 252 HP at 6800 RPM and 238 ft lbs of torque between 4500 and 5000 RPMat the rear wheels. These are advertised as 320HP cars. Now I do know they probably take those numbers at the crank. Is it normal to lose that much HP and power through the drivetrain? Could there be something wrong with the car? It runs great and strong with no flat spots. Any comments?

15% loss is what i've heard

In my case its more like 20% but the car has some miles so your post makes sense then. Thanks Sparks

Everyone is always looking for a larger diameter TB for better breathing and top end HP and I understand that. What if you dropped the diameter in size would it create more low end torque and better throttle response(I understand at a sacrifice to top end performance and breathing) ? Would this be something to try for around town driving? Im curious, does anyone have any experience with trying this?

20-25% is a normal drive-train loss for hydraulic automatic transmissions. Then you have to adjust for elevation, temperature, humidity etc. 252 at the wheels is a good number for a tiptronic. Porsche N/A 3.6 motor is already very efficient at squeezing all of the power out. You will not see any significant power improvements from most bolt on mods (FI and nitrous oxide systems being only exceptions), but you will see your bank account balance decrease substantially.

My NA 3.4 6 speed did at the flywheel CEngPw Max of 288 for an engine rated 296. CEngTq was 246, rated 258. At the time, they mentioned that 50HP is normal drive train loss as a rule of thumb. So i guess 60 is reasonable. Added IDP plenum since.

What kind of dyno, what altitude, what temperature, what octane, how many pulls, what correction factors? Chassis dyno's can be great for tuning and before/after comparisons, but trying to use a chassis dyno to determine accurate peak engine HP isn't what they do well.

Most dyno operators have their machines set to reat high so cutomers would like the numbers and come back for more. So, dyno readings should only be used as a comparison for upgrades. And always on the same dymo under similar conditions. Keep that in mind.

We have both engine and chassis dynos on site here. We haven't ever experienced a factory engine making the flywheel HP that the factory states, its always less. We always see an 18-25% (tiptronic soaks up more power) drivetrain losses with these engines in our own lab between the engine dyno and chassis dyno. We see these differentials with all Porsche engines, both aircooled and watercooled, not just the M96. Most factory HP statements are made with a DIN correction factor as they are tested in Europe. Here the standard correction factor is SAE. I can select a DIN correction factor for tests, but since we are not in Europe, this is not done. This means an engine stated with a DIN correction factor is not compared "apples to apples" with an engine tested at SAE correction factors. For a better understanding, see here: http://www.google.com/url?sa=t&rct=j...52164340,d.eWU 252HP for that car (tiptronic) is considered within the top 5% here at our facility, where I have several hundred vehicles to compare the results to. Bigger wheels (heavier), different tires and suspension settings all impact the power put the rollers of a chassis dyno. Most tiptronics like yours don't break 250 RWHP here in my world, and the majority are in the 245-248 range. Also, don't look at those peak numbers, average power under the curve is what matters. Too many people look at dyno graphs the wrong way. I should re-word that to say "too many people focus their eyes at peak power values when viewing a dyno graph". Developing an engine for months on the engine dyno, then finally installing it into a car for a back to back run is a truly alarming experience. Taking that engine from one car and installing it into another on the same day for another test is even further alarming. Your car is strong. I don't use the dyno for power output as much as I utilize it for gathering other data that I'd kill myself trying to attain on the street. In 90% of the dyno runs that I do I don't even choose peak power or even horsepower as a plot on the X or Y grids. Often times people tune for big peak numbers and THE CAR IS SLOWER! I have personally lost 6HP (purposely) peak with my Wife's Land Speed 996 and the car went faster. In fact she set 4 standing records in a single weekend with a mechanical combination I developed that lost 6 peak HP, but picked up mid range and acceleration. This resulted in picking up 4 MPH and setting the records that she had been .5 MPH from breaking for the past two events in a row. A dyno is just a tool and you can use it incorrectly, just like you can use a wrench incorrectly, or a ruler. Hell, just this past week we found a bad knock sensor (actually a mouse had chewed the wire in half leading to it) by using our comparatives. This was due to the bumpiness of the graph and the reduced power, and the best part was there were ZERO fault codes in the ECU, and none pending for the failure. The owner had been driving around losing over 20HP the entire time that he owned the car. Leave it alone and drive it. :-)