Car for high hills

[LeonOfTheDead]

In 'drive' my old Merc V8 idles at 550~600 rpm, with good oil pressure!

ok, but how old and large that engine is?

As long as we're discussing supercharged engines I have a question that's been bothering me for a while. As was mentioned earlier they don't work as well at high rpms, so why does the Caterham Levante with a 10,500 rpm redline and the Lotus Elise/Exige with close to it use a supercharger? I understand the fact that it minimizes lag but it seems like effeciency at those higher rpms would be a bigger issue, yet it does seem to work fine.

Good question, that's the case of the Caparo T1 as well.
To be precise, SC systems don't have a weak efficiency at high revs in general, but only after the rpm of maximum power.

Point in case, the MB SLR, which has an SC. Here comes its power curve:



As you can see after the point of maximum power, the power itself decreases quicker than how much it was increasing just before of that point. This happens in all engines, but it is even more stressed if an SC is present.
Another thing to notice is that on an SCed engine it isn't possible to use much of the revs range after the point of maximum power as it (the power once again) drops significantly and pretty soon. You can notice that in the same graph as the higher rpm is just 500 revs after the point of maximum power. Not only that, but those are 500 additional revs at just 6.500 rpm, so a relatively low regime.

On naturally aspirated engine, in this case the Porsche 997 GT3, the power decreases slower than on an SC engine, and you can still use the engine for 1.000 additional rpm after the maximum power, and from 7.500 to 8.500 rpm, definitely higher.



On cars like the Caterham or the Atom and Caparo, the engine revs a lot, true, but being more of racing cars then road going ones, I wouldn't be surprised seeing the gears and the red line are set so to not use many revs after the maximum power.

Would have been cool to compare the power curves of a NA Exige and of an SCed one, but Lotus had the great idea to cut the graph right after the maximum power was reached, so to not appreciate the decreasing curves...

[HuisZi]

depends on how much you wanna spend? I'm driving a '85 range rover, with 2800 isuzu diesel.. and its great in rough terrain and in asphalt roads.. how far you wanna go? Mine was 950pounds.. came from uk.. the only negative point is that the steering wheel is on the 'right side'...