998 - 8 cylinder
#46
In the states, the weight problems are because of the saftey standards for road cars and the luxury items buyers want today. If they were able to stip the cars down to the saftey standards of the past, etc., they would probably be lighter...just a thought.
Look at the jumps in weight from the 70's to the 80's. In one of my pcar books they make reference to the saftey standards, weight issues.
PK
Look at the jumps in weight from the 70's to the 80's. In one of my pcar books they make reference to the saftey standards, weight issues.
PK
#47
Originally posted by brh986
Yea I see the error in my logic now. Where is there a straight six of the same displacement as a ferrari v12 to use for comparison? BMW's 3.2L inline six does fairly nicely with 8,000 rpm redline doesn't it? Ferraris' 575M has a 5.75 liter V12. 5.75 / 12 = .4791 3.2 / 6 = .5333
I'm pretty sure the 575 has an 8000 rpm or lower rev limit. WHat's going on there?
Yea I see the error in my logic now. Where is there a straight six of the same displacement as a ferrari v12 to use for comparison? BMW's 3.2L inline six does fairly nicely with 8,000 rpm redline doesn't it? Ferraris' 575M has a 5.75 liter V12. 5.75 / 12 = .4791 3.2 / 6 = .5333
I'm pretty sure the 575 has an 8000 rpm or lower rev limit. WHat's going on there?
"All other things being equal", similar cylinder displacement size results in similar rev limits. That is, Ferrari engine with a swept volume of 480cc/cylinder has a rev limit fairly close to the BMW engine with 530cc /cyl..
But the proviso "all other things being equal" is important.
A lot more factors come into the equation:
- The effort put into maximising the rev limit depends on the application.
An F1 engine is tuned for max power at max revs, with no regard for low-end torque, because F1 cars are not driven much at the low end of the rev range.
An SUV engine would need high lugging torque at low revs, but would hardly ever be driven at max revs, so a high rev limit is not a priority.
An engine with a very high rev limit and very high torque at low revs has yet to be developed.
- The bore/stroke ratio. Long stroke means high mean piston speed for a given engine speed and swept volume. There is limit to the possible max mean piston speed, which depends on the quality of lubrication and piston ring and cyl. bore materials, among other things.
I could go on and on..... There are books on this subject, so I won't.
#51
I was told yesterday by a Porsche salesman that the 997 would only be produced for two years as a transition model, then the platform would switch to the 8-cylinder 998. First time I've had a Porsche salesman tell me so (though I still have my doubts).
#52
Originally posted by Sean
I was told yesterday by a Porsche salesman that the 997 would only be produced for two years as a transition model, then the platform would switch to the 8-cylinder 998. First time I've had a Porsche salesman tell me so (though I still have my doubts).
I was told yesterday by a Porsche salesman that the 997 would only be produced for two years as a transition model, then the platform would switch to the 8-cylinder 998. First time I've had a Porsche salesman tell me so (though I still have my doubts).
I bet that, whilst well informed on the 998, he couldn't reliably tell you when you could take delivery of a 997, right?