906 - RSR - 908 - 917 Engines? More the same then different?

[jluetjen]

Anyone care to comment on the following thought:

Porsche really only had one race engine concept from 1966 through 1974. They varied the materials, cylinder count and capacity, but conceptually the engines were more alike then different. My data:

Engine.....HP/Liter.....Torque/Liter......Peak HP Speed.....Peak Torque Speed
906:........110..........76.............8000 RPM.........6600 RPM
911ST......108..........79.............8000 RPM..........6200 RPM
911RSR.....110.........78.............8000 RPM...........6200 RPM
908............117.........78.............8400 RPM............6600 RPM
917 4.5......129.........80.............8400 RPM............6800 RPM
917 5.0.......120.........81.............8400 RPM.............6400 RPM

It's possible to see the painful price of progress given the amount of magnesium and titanium in the 917 motors. But all in all, I guess this is just another reason to love a 911. There really is a connection between Porsche's race cars and the 911.

[Early_S_Man]

No disagreement, here!

The only missing data frpm your progression is the 916 engine of '68/'69 ... and, it really was the bridge/link between making the step from 906 to 908 ehgine and beyond!

916 ...... 115 ...... 76 ...... 9000 rpm ...... 6800 rpm

[mskala]

One other engine that was different was the 2.2L 8-cyl used I think mainly in the 907. These things are very rare, and apparently not a lot like a 911 motor, since I'm told there is
virtually no one qualified to build them. They made about 275HP, too!.


http://members.rennlist.com/marks/eng-1.jpg
http://members.rennlist.com/marks/eng-2.jpg
http://members.rennlist.com/marks/eng-3.jpg
http://members.rennlist.com/marks/eng-4.jpg
http://members.rennlist.com/marks/eng-5.jpg

Mark S.

[Early_S_Man]

Mark,

No, that was from a much earlier engine family ... Typ 804 Grand Prix car that Dan Gurney drove to victory. It started as a 1.5 liter, maxed out as 2.2 liter, 275 hp endurance-racing engine ... but, had absolutely nothing in common with the 901-family engine descendants John is talking about!

[michel richard]

Sure is a lot of composite material on that 8 cyl engine ! . . . and that injection pump is nice. dohc too.

[mskala]

Originally posted by Early_S_Man
Mark,

No, that was from a much earlier engine family ... Typ 804 Grand Prix car that Dan Gurney drove to victory. It started as a 1.5 liter, maxed out as 2.2 liter, 275 hp endurance-racing engine ... but, had absolutely nothing in common with the 901-family engine descendants John is talking about!

That's kinda my point. There was not just one type of porsche race motor (with major upgrades) used during that time period. I had forgotten where the type 771 came from, though.
Mark S.

[TRE Cup]

You should see the new 907 motors sitting on the shelf at Carl Thompson's in Long Beach- complicated suckers- drool!

[jluetjen]

To revive an old thread...

I just picked up the book "Classic Racing Engines" by Karl Ludvigsen. It's a great book. They review a number of Porsche's great race engines (some of which weren't even Porsches!) such as...
* 1936 Auto Union C V16
* Cisitalia 1.5 liter Flat 12
* Porsche 547 Carrera engine
* Porsche 753 Flat 8 1.5 liter F1 engine
* Porsche 912 (917) 4.5 liter Flat 12 engine.

Looking at the 917 spec's, the valves were a little bit bigger then the 911 ST's 46i/40e at 47.5i/40.5e. The interesting thing is that the cam appears to be the exact same 906 cam profile that had been around since the -- well -- 906. The only difference is that the exhaust appears to have been advanced by 5 degrees.

Once again it supports what we all believe -- that the 911 motor is similar in many respects to a SOHC 6-cylinder version of the 917.

BTW - There are some other cool engines in the book...
* The BRM H16
* Honda's 230 HP, 12000 RPM 1.5 liter V12 with integral gear box from 1965
* Honda's 774 HP, 14000 RPM 3 liter V12 from 1992.

[Wayne 962]

Right - common folklore has basically said that the 917 is really not much more than two 911 motors connected together. The systems are very similar.

Although they did have some interesting differences:

- Transmission driveshaft lowered from crankshaft
- Dual camshafts on each side

-Wayne

[Thunderbolt]

The cams were also gear driven off the center of the crank. Most of this along the the driveshaft being driven off the center was due to the amount of flex(whip) measured at the end of the very long crank.

[Wayne 962]

Right - the 908 is the most similar to the 911 that I know of. It's chain driven, and the only huge difference is that it has four camshafts instead of a single one like on the 911. Oh, and it has an extra cylinder bank too!

-Wayne