Dyno testing a Porsche 917

this was posted by a member of the GPMA (grand prix modelers assoc), thought I'd share.



> The last of the 917 long tails were dyno tested at SwRI's Engine Test Facility 15, 20 years ago -- where I work.
>
> Rather, the engines and trannies were.
>
> They were by far the most powerful engines that had ever been tested at SwRI. Special dynos were built with computer controlled, simulated road course loading. The test cell shifted through the gears and loaded up the chassis dyno to simulate side slip, hills, etc. As a result, the engines were able to be run through entire LeMans events without leaving their test cells. The purpose was to stress test the transmissions through real race stress.
>
> Because they were so loud, exhaust pipes made from insulated barrels were made to transport the sound up and out of the building. As a result, the sound of a road racing 917 could be heard anywhere on campus when the tests were running. Remember, this is a twin turbo 1200 hp 917 engine...
>
> SwRI sits on 880 acres or so between three major roads and a highway. The only other facilities on the same block of land are a fire station, a major police station, and some fast food restaurants along the highway. These are all at the farthest corner of the quadrangle, very distant from the labs.
>
> SwRI has a test track, but it's parallel to one of the major roads and entirely visible, just down the street from the police station.
>
> And so, for many months, intermittantly, the sounds of road racing 917s were audible through the woods....
>
> Vroom....vrooommmmm....wroooooooooommmm....VROOOOO OOOOOOOMMM... Bra-ra-ra-ra-rappppppp..... Vroom... vroom... VROOOOOOOOOOOOOOOOOOOOM...
>
> Round and round the simulated road racing track. Upshifting. Engine braking. Blasting out of corners. Over and over and over again. Usually at night, because it was so loud the noise interfered with other work.
>
> About the same time, we noticed an odd increase in police activity, patrol cars tearing around the roads around the institute, almost like they were running laps. Sometimes, we'd see three or four sets of cars, going in opposite directions.
>
> Then, one night, someone had the bright idea to turn on a police scanner.
>
> What we heard: "No, damnit, I STILL can't see them! They must have turned onto Commerce again! They didn't pass you???"
>
> "Negative, negative. They must have turned north on the access road. I can't acquire them. I'm still behind them. I can hear them just ahead."
>
> "DAMN! What IS that thing??? Sounds like some */$3%^ race car!! Are you sure it's not on the SwRI track???"
>
> "Negative, negative... the track is empty. I just passed the loop of their test track on Culebra. It's dark and the gates are secure."
>
> "How'd they get past both of us???? We GOTTA CATCH THESE GUYS!!!!"

I think the person who gave you this quote is a little misled. The term "long tail" refers to a body style, raced primarily at LeMans. The more common 917 is the shorttail. The drivetrain wouldn't be different between the two. The 917 was developed and raced in the late 60's and early 70's, so there'd be no reason to be dyno testing an impossibly scarce and expensive 917 motor in the 80's.

Also, the turbo engine was only fitted to the 917 Spyder, which is an open cockpit car, not a langheck (longtail) I saw the 917 spyder race at Watkins Glen in 1973, like all turbo cars, it's relatively quiet. The normally aspirated engine would have been quite loud, like a Formula 1 car, though with a much lower tone since it turned less than 10,000 RPM.

If you'd like to read up on the development of the 917 for endurance racing, get the book "Porsche Racing Cars". Also in "The Unfair Advantage", Mark Donohue gives his side of the development story of the 917 turbomotor for the Can-Am Spyder.