Question regarding HP

[DByers]

While reading through the July issue of Panorama I came across the article “ The Early 911 Development Evolution” and it raised a question, Why such modest HP gains between 2.2 and 3.2 engines? (Looking at a 71S 2.2 @ 180hp, and 83SC 3.0 @ 180hp, and finally the 89 Carrera 3.2 @207-217hp.) Was this do to US emissions, to much money to have the factory increase the HP not making it viable in the market during those years, or am I off base thinking that the 3.0 should have more HP than the 2.2S built 12 years prior? In my quest to learn more I ask the board for any input.
TIA

[emcon5]

Emmissions restrictions and noise rules would be my guess.

Tom

[A Quiet Boom]

If I remember right, the torque ratings of both motors is radically different with the 3.0 having much more. Also the early style exhaust is said to be worth as much as 20HP on an SC and it's still likely a little restrictive. The rest I can would also assume was emmisions and fuel effficency related.

[Paco Anton]

In the late 70s, Porsche wanted the 928 to replace the 911, so they could not have a 911 (SC) run faster than a 928 and detuned it to 180 hp.

In 1980 they realized that they were keeping the 911 and increased power to 188 and then 204 hp (in Europe). The 3.2 had 231 hp in Europe so I guess there is also an US emissions issue.

[jluetjen]

As I see it, in general terms cc's = torque. Because of such things as ram tuning, torque will increase a bit with well tuned high RPM engines (such as the early S's), but the affect is secondary to cc's. So the more cc's that you have the higher the torque reading.

Torque * RPM = HP. If you have a small engine, you wind it up to make HP. But unfortunately high RPM engines are noisey and not very clean when they are "off cam". So Porsche (as well as most other auto manufacturers) went the route of low rev'ing, larger capacity motors.

Porsche's early strategy was to wind their engines tight to develop HP. So engines like the early S's and E's had redlines of 7000 RPM and above. With the advent of emissions controls (often measured at idle or low RPM's), Porsche adopted the strategy of larger motors with lower rev's. Examples of these engines are the 2.7's through 3.6's. I wasn't in the room at the time, but I suspect that they chose their HP targets keeping in mind that they wanted to preserve or improve upon their car's existing performance with gradual increases in the car's weight. Since rev's were not required, it allowed them to go to longer strokes and milders cams which allowed the use of CIS and later EFI systems with air flow sensors to meet pollution requirements.

Only with the advent of Variable valve timing and variable intake lengths has it been possible to develop engines that are clean and efficient at low RPM's, and still generate a lot of torque and HP at higher RPM's. This is why Porsche and Honda can now produce engines (VTech and VarioRam) which make HP like early S's, while still meeting the emissions requirements of the new mellenium.

[Jim Richards]

Hey John, or others, I've seen the terms "off cam" and "on cam" used from time to time but I really don't know what this means. Can you explain this for me? Thanks!

[jluetjen]

The terms are relative. I guess I'd say that an engine is "On-Cam" if it is making more then the average of it torque over it's total rev range. An engine is "Off Cam" if it is making less then the average torque over it's rev range. Check out the attached where I've marked up the HP chart for a 2.2 S with the approximate areas of "off cam" versus "on the cam".

[Jim Richards]

Thanks John!

[silverc4s]

It was also part of the 911 engine development philosophy that improvements in power could not be made if they sacrificed fuel efficiency!
It would be much easier to improve performance of these engines, if one did not care about fuel mileage, but Porsche overall, has not done that..

[DByers]

Thanks for the info, and thanks for helping a rookie learn more about his car.

[Roland Kunz]

Hello

The early 911 was driven by Mr. Piech and the idear to race down every competition in the 2,0 L class.
Piech then decided that he needs a new midengined chassis to push even further and to avoid conflicts the 911 moved up in the class to the 2,5L cars or got turboed to compete in the 3L class.
In the 70´s Porsche dominatet most sport car races worldwide.

However in the 70´s the Oilcrisis hit the world ( At the same time when the Street Turbo was lounched ), Piech moved to Audi and the club of Rome showed the end of progress.

This was when the company focused more on other things.
As sportcars had a very bad mouth in puplic ( useless for transportation and why to have fun ? ) Porsche developed the "friendly sportscar" to keep the Porsche cars acceptet by the "normal" people. So since the 70´s the 911 was the most clean sportscar and every Porsche developed since then was the pacecar for enoviroment friendly, social acceptet fast driving.

In the mid 70´s Porsche had so much work with there own cars and the development for external companys that they just didn´t have enough manpower to keep everything at the top level.

If you look at the world car marked you will find Porsche was still on the top loosing some 10% power output due the emmisions.
If you look at a Vette in the 70´s you will find a 50% powertrop trough the line. And even the american supersportscar was hard to sale.

The GEO then Mr Fuhrmann who was in charge as tecnical leader for the 930 and also the 928 was a cool engeneer who decided on facts rather then on feelings. He just had seen that the 911 would need massive engeneering while it is a old concept only to sale to "backdatet" people. So the only thing happend to 911 in the 75-79 timeframe was to make the needed things to keep the car on the road and to keep the status qou on the powerlevel.
Maybe Porsche was hopeing that the 911 sales would trop or sleep in. Fuhrmann did know that the 911 driver was very bad infectet and not easy to push into other cars. The 928 was made to achive sales in new markets and had maybe some costumers coming over from the 911/930 but the 924 turbo was launched to get the 911 drivers inhouse behind a waterpumper

Things worked a other way as always some ill orientatet 911 dye in the wool fans ordered new cars, some bought only as they had been scared by rumors of the final run.

Grüsse