BigHeadDennis

Hmmm... I'm still confused. I was completely incorrect in my confusion, where I wrote "brake HP" I really meant "HP at wheel", as measured on a chassis dyno. The rest of what I wrote about power measurement, however, is still correct, I believe.

As you noted, SAE Gross power ratings haven't been used for over three decades, and AFAIK, Porsche has either never used SAE Gross power or hasn't used it for a very long time. The power figures that Porsche releases in the US are in either SAE (net) or DIN. So why would you say that, with respect to the official factory GT2 power number, "The GT2's SAE HP is less than 400" when the official HP number is 477 **SAE**?

As measured on a chassis dyno (putting the car on rollers), the GT2 may well generate a reading of less than 400 hp, but considering that driveline and frictional (and other) losses usually average 15-20%, an SAE (net) 477 hp engine would result in a <400hp reading on that dyno.

So Todd's claim of "378 HP (SAE)" is actually a full 99 hp less than the official Porsche claim of 477 hp (SAE) for the GT2. And looking around on this forum reveals that the 477 hp claim is actually really conservative, and one owner states that the 477 hp does not include the 30-second "overboost" feature.

Do you know if Todd's claim of "378 HP (SAE)" was measured with an engine dyno (engine out of the car) or measured on a chassis dyno, and calculated backwards (e.g., getting 304 hp on the chassis dyno and adding back 20%)?

Considering that the GT2's official weight is 3175lbs., and the 1999 996 C2's official weight is 2910 lbs., that's only a 265lbs. difference, before adding the weight of the supercharger and other parts. Turbo lag for 0-60 acceleration shouldn't be too bad, given that the engine is always at boost from the beginning. And the GT2 has wider tires to put the power down. So gearing differences and the slight weight differential makes up for a 99hp deficit?

Maybe your car is more powerful than Todd believes?

vty,

--Dennis

1999Porsche911

The GT2 AND the other porsches are advertised by their bhp horsepower and NOT by their SAE NET. Therefore - reduce that figure by 15 - 20% (depending on car) to get the SAE net. The 320 HP of the new Carerra is bhp horsepower.

You can argue all day with the various ways of figuring HP. However, my car dyno'd by Todd with 250 SAE net HP before the supercharger and 378 after. Regardless of what that measures...the supercharger increased my power by more than 50% to give me a bhp of just shy of 450.

Using the same reduction of 18.6% from the bhp of 296 of my stock 996 as measured by Todd....the GT2's 477 would have a SAE net of 388 hp. That's 10 HP more than mine.

BigHeadDennis

My intent is not to argue, just looking for clarification. Your response above isn't helping to clarify much...

the official Porsche HP number for the 1999 996 is 296. That is SAE NET. And the official Porsche HP for the GT2 is 477 HP SAE NET. Not BHP (SAE Gross). Remember, NO ONE USES SAE Gross, and hasn't for 30 years. All car manufacturers list a HP as measured with the engine on the bench (the difference between SAE Gross and SAE Net has to do with the accesories on the engine while it's on the bench, and the testing method). Tuners typically provide power numbers from a chassis dyno, sometimes they extrapolate backwards to get an approximate SAE Net number for comparison purposes.

And, in case you don't believe me when I say that the GT2 477 HP number is in SAE NET, check out the official Porsche website:
http://content2.us.porsche.com/prod/...usaenglish/gt2

It says, "Horsepower (SAE) 477 hp @ 5,700 rpm".

Sceond, the rolling dyno that Todd uses for the stock 996 would indeed result in 250 HP **AT THE WHEEL** and NOT SAE net. SAE NET is measured with the engine OUT OF THE CAR. The 18.6% difference is because the engine is in the car, and the measurement is taken at the tire.

If Todd used the same dyno to get 378 HP from you car, using the same 18.6% power loss calculation would result in an approximate SAE NET number of 464 hp, which would be much closer to the official GT2 figure of 477 hp, and would explain a similar 0-60 acceleration time.

But I'm curious as to where that 378 hp number came from, as Todd himself advertises less HP. Maybe your car is just more powerful? His website provides a dyno chart for his supercharger system:
http://www.evoms.com/P%20996%20SC%20dyno.htm

As you can see, his peak power is 352.4, compared to the stock 996's 249.6. Which, using the same 18.6% extrapolation, means that his supercharger is getting ~433hp SAE Net, which is still a 44 hp deficit to the GT2.

So maybe you just got lucky with the system, or maybe you're running more boost, to get an extra 26 hp. Maybe Todd should advertise with YOUR dyno run?



vty,

--Dennis

1999Porsche911

As I stated in one of my first posts on this subject...Todd was able to get the extra power because I do not have e-gas. The 1999 C2 is sill a cable cobtrolled accelerator. Apparently the e-gas computer control limits some of the parameters that can be modified in the computer. Todd still set it up for less than 5 lbs of boost.

Additionaly, Todd was able to increase my torque from the expected 275 ft lbs to 290.

1999Porsche911

The fact is that the 320 HP contributed to the new Carerra is NOT, repeat NOT, repeat again...NOT SAE NET. It is SAE GROSS. The 477 GT2 HP rating is also SAE GROSS. The Z06 HP Rating is SAE GROSS...need I go further.


Rather than argue...do a little research and rather than throwing out alot of "maybe's", call Todd directly and see what he can do for your car.

BigHeadDennis

Argue? Hey, I'm just quoting from the OFFICIAL PORSCHE WEBSITE. Do you really think that Porsche would choose to use a standard that went away back in 1972?

Everyone still reading this thread can decide for themselves: choose one of the following:

1. Do you believe that the 320 hp attributed to the new Carrera is measured in SAE GROSS, a measurement of horsepower that fell out of favor over three decades ago, to the point that not a single car manufacturer in the world uses this measurement, and hasn't for over thirty years OR

2. Do you believe that the 320 hp attributed to the new Carrera is measured in SAE NET, as specified by Porsche itself on its website: "The 911 engine is a six-cylinder unit displacing 3.6 liters and developing 320 hp (SAE) at 6,800 rpm. "
http://content3.us.porsche.com/prod/...ineperformance

Would you have us believe that Porsche's website is incorrect when it actually says that the HP measurement is in SAE?

Tell you what. If Todd says that the official Porsche power figures of 320 and 477 for the C2 and GT2, respectively, are in SAE Gross, I will publicly go over to John Dunkle and Jen's house and eat a bug. A big bug. Seriously.

vty,

--Dennis

Tbred911

sounds like we've found our next contestant for FEAR FACTOR...

ben in lj

"I believe you do care about 1/4 mile and 0-60... isn't this a standard measurement that is valid for our cars?"

believe what you want - apparently you're gonna anyway.

btw, even the fatest buttometer available is going to feel a 50% increase in power.

1999Porsche911

The horsepower is bhp, and if bhp is the same as Gross HP, then it is gross Hp. You can search all day and you'll find an equal amount of people that state that BHP is gross and BHP is net. What is true..I now have more than 50% more power than before the supercharger.

1999Porsche911

For 30 years...bhp has been the same as Gross HP. If they have changed the definition, it is news to me. The current z06 is advertized as "bhp" which is defined as hp at the flywheel with minimal accessories attached.
Gross HP is defined as the same.

http://www.supercars.net/cars/2004@$Chevrolet@$Corvette%20Z06%20Commemorative%20Editiong.html

Like I said....it's a confusing subject and the agruments will continue longer than I will.

Tbred911

Ben,

why won't you post your 60 and 1/4 mile times? were all curious dude



regards,
Pete

ben in lj

"why won't you post your 60 and 1/4 mile times?"

because i have never timed either which is strange since as you say they must be important to me!

Tbred911

Actually, by your statement above in a few posts back... you do care cause the other SC 996 has a faster 0-60 time and that's why you want to know how it was measured... cause you can't pull a 0-60 in 3.8

BigHeadDennis

Ok. I need to retract my admission of error previously - I was right after all! Ok, well, mostly right. I stated that BHP was equivalent to HP measured at the wheel on a chassis dyno. Then I said that I was wrong, and agreed with 1999Porsche911 that BHP = SAE Gross.

Well, it turns out that I was right. AND 1999Porsche911 was correct in that BHP used to be used as the equivalent of SAE Gross. **TODAY**, BHP is shorthand for what I said it was - it is used to indicate an HP measurement taken on a chassis dyno.

I stand by everything else I wrote - SAE Net is different from SAE Gross, SAE Gross hasn't been used by the manufacturers since 1971, and SAE is the standard North American measurement of HP from the factory (measured on an engine dyno, on a bench, with accessories attached). Porsche's HP numbers are SAE Net. Todd's #s are from a rolling chassis dyno. BHP can be used to describe EITHER SAE Gross OR power measured at the wheel on a rolling chassis dyno (yes, confusing, I know).

Here's a good description of everything I wrote above:

>There are basically two differences between a DIN and a SAE horsepower rating: One difference is in the parameters for a measurement: Horsepower is defined as work done over time. One SAE horsepower is the amount of power necessary to lift 550 pounds 1 foot in 1 second, or 33,000 lb.ft./minute. One DIN horsepower is the ability to lift 450000 kg one cm in one minute. For the same power the SAE measurement is thus 98.629% of the metric DIN measurement. 100 SAE hp = 101.42 DIN hp = 74.6 kW If you see the term bhp, it just means "brake horsepower", which is the actual usable horsepower delivered to the rear wheels of the car. It is so named because a brake is applied to determine how much pressure is needed to stop or absorb the power. Bhp could reference either DIN or SAE horsepower. Often, however, brake horsepower is measured with no load from a chassis or any accessories attached to the engine whatsoever. It’s also called gross horsepower. In vehicles, torque measures the turning force generated at the wheels. A high horsepower rating generally indicates the ability to sustain higher top speeds, while torque signifies a vehicle's acceleration and ability to pull heavy loads. Horsepower is effectively torque times rpms, with the exact formula being HP = Torque x 2 x Pi x rpm (Pi=3.1416…) so if you keep the same amount of torque and double the revs, you double the effective horsepower. This is why most engines have the highest horsepower rating at higher RPMs. And along those lines, you can have an engine that has lots of horsepower at higher RPMs, but not much energy at lower RPMs where it counts off the line, so often torque ends up being a more interesting measurement than horsepower. The other difference is in the engine configuration for the test: While DIN (Deutsche Industrie Normen) 70020 and thereunder DIN 6270 requires the efffective HP to be measured on an engine in standard production configuration, i.e.: with stock intake and exhaust, fan and waterpump or cooling blower, fuel pump, fuel injection pump and no electric load alternator, in the U.S.,vehicle manufacturers can test for horsepower and torque in a variety of ways. SAE J1349 Engine Power Test Code – Spark Ignition and Compression Ignition – Net Power Rating Standard specifies a basis for net engine power rating, and a method for determining net full load engine power with a dynamometer. A dynamometer places a load on the engine and measures the amount of power that the engine can produce against the load. The current test, which originated in the early '70s and was last reviewed in 1995, allows OEMs to claim horsepower and torque figures higher than what most owners will actually experience. The SAE –Society of Automotive Engineering - Power Test Code Committee , is currently revising its standard for measuring horsepower and may suggest that OEMs have an independent observer verify the numbers they claim for horsepower and torque. The standard will also set a procedure for how to test torque, which is also heavily advertised by car manufacturers. According to SAE, the revised standard is expected to be written by the end of 2003. An SAE advisory committee will then decide whether to adopt the procedure and the use of outside witnesses, such as Underwriters Laboratories Inc., to verify OEMs' claims.

vty,

--Dennis

ben in lj

"Actually, by your statement above in a few posts back... you do care cause the other SC 996 has a faster 0-60 time and that's why you want to know how it was measured... cause you can't pull a 0-60 in 3.8"

????????? are you ms. cleo? you have no clue why i want to know how it is measured. but, i will tell you it is simply CURIOUSITY since i have nothing but a dyno and buttmeter measurement on my car to go by. additionally, claims that an SC'd 3.4 C2 running with a GT2 seem unbelievable so the source of measurement would have been interesting. further, his car is a coupe weighing 200 lbs less than mine. he "should" be getting better times, and this isn't a dick measurement anyway.

again, the buttmeter and dyno were all i really cared about. the dyno was an independant and factual comparison of apples to apples (ie: before and after) of just how much incrimental power was added and the buttmeter is how i enjoy it. do you really think that just because you (and others) like trite little measurements for bragging rights, that i have to too? on the contrary, during our mountain drives i kick the schit out of poseur TT owners who bought their car for bragging rights and haven't a clue about how to drive it correctly. these little measurements on .10s of seconds on 0-60 times are a farce. unless you are at the dragstrip with lights, etc and the drivers are similarly capable, there can EASILY be a .5 sec (or more) difference between two drivers of the same car. this is why in addition to inquiring as to how the unbelievable time was measured, i asked if he had swapped cars with his buddy to see if the outcome was a result of his buddy not knowing how to drive.