1988 Porsche 911 Turbo
Posted by Fclevelandwrx
John Vanlandingham Elite Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
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John Vanlandingham Elite Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
If you want to know things often you must not listen to fans and anhängers )which is actually 'trailers' but I like to joke. an auf Deutsch is same as Englisch 'on' and hänger ist from hang--something or somebody in this case who 'hangs-on'= and listen to those who have nothing to gain, they can--if they choose--speak honestly No really it was a typical German thickheadedness. Herr Doktor F Porsche designed the motor--particularly the head und it is darfür perfektes! Mit fantastisches "flow" thanks to very large valves considering the bore size Here you see the problem clearly: 
Look at zylinder eins und zwei zu rechts. See the nearly 90o angle zwischen die beide ventilen? Big angle like that meas a large open combustion chamber...to make any compression more than 7:1 you must put on the top of the piston a giant dome. Bad for flame front propagation Look at the combustion chamber: 
No attempt even at anything like a quench pad. Bad... And until 4 valve heads finally made it onto German vehicles very typical*... These thing limit what the motor can stand for compression and hot spots and detonation can only be held at bay in a adavance 1920s design like this via lower compression.. And as we all know, there is a direct realtionship between engine volume and torque Here is what was beating them even on clean dry asphalt and much less cylinder volume: 
That is as good a head made anywhere in the world for 1968---indeed it was basically one bank off a Ford Cosworth F1 V8 motor. Look at the valve angle. around 44.5 to 45o, nice compact combustion chamber, generous quench pads...detonation not a big problem with a head like that and pistons with little bitty domes like these: 
Ford had Cosworth make the iron block BDA in 1968, the 1800 in 75 and the all alloy BDG in 1976. Little difference to a Duratec head in this decade. Porsches' only option was to increase engine size since they insisted on retaining the archaic head design--as did BMW with their 2 valve junk---and Opel, and Mercedes.. In this history was repeating itself. Just30 years before their solution was 3 valve head VERY SIMILAR in design to the Porsche ideas and it became this: DB601 at 34 liters and alter DB603 at 44.5 liters against Rolls Royce Merlin at 27 liter... Ideed when they finally realised that they were too dogmatic, too rigid, too uncreative to design a good head, the Germans at BMW, Opel and Mercedes all with the Northhapton and paid Cosworth to save their schinken. John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
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For a rear-engined car, it seemed extra-appropriate.  KF7RWG 
http://www.utahrallygroup.com |
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