6 replies to this topic

[PeaQ]

I know this has been up before, but is there a max limit on how many bhp's you can pull out from a 3 litre engine?

[desmo]

There appears to be a limit of something like 90 ft./lbs. of torque per liter (sorry about mixing metric and English measurements here) with a naturally aspirated 4-stroke on petrol. bhp is torque x rpm x a constant so the only theoretical ceiling is how fast one can turn the engine. Nobody knows how high that figure can be made to go. With the bans on materials in F1, even F1 motors do not define the upper limit any more. At one time F1 engines were true state-of-the-art designs. This is no longer the case, and is becoming less the case each time new regulations are imposed on the sport.

[MacFan]

It is my understanding that the frictional losses become critical at the sort of revs F1 engines are running now. I think (correct me if I'm wrong) that these losses increase with the square of engine speed, in a similar manner to aero drag v. car speed. Obviously the rotating parts need to be mechanically strong and light, but would friction not become the limiting factor on how much more power you could produce from increasing revs?

If this is so, then future increases in power may not come as easily, and may rely on breakthroughs in materials technology.

[MrAerodynamicist]

There has to be a limit: for a given volume of fuel there is a maximum amount of energy stored within. Secondly, there is a limit to how much fuel you could reasonable get though. [eg no supersonic flows etc]

[TNSFH]

There is also a limit on how fast a paticular mass will spin. I have been looking franticly for a trade magazine with an article about a completly composite materials engine. The thing I remember about the engine was it developed amazing RPM but becuase of the the lack of mass there wasn't much torque.

[Nathan]

I agree with desmo on the torque per liter limit. I have always thought 85 or so was the limit, but have found that Honda Civic N1 race cars make it into the 87 ft./lbs per liter area. Simply what is comes down to I think is the RPM limitations of the engine design and the intake limitations in which an intake system can supply 100% cylinder filling at that RPM limit. But Im sure it will be the limits of how much energy can be releases from the fuel before the other max out.

[Yelnats]

As mentioned earlier on this topic, the limitation on power output will probably be related to flow velocities in the inlet ports and supersonic effects there-in. Accelerating masses of air from a standstill to near sonic velocities must place some theoretical limitations on ultimate power output as a near vacuum will be produced at the inlet ports at some point high up in the rev band.

We must be cautious with predictioning such limits because I'm sure that current engines vastly exceed any forcasts that could have been made earlier in this century before the appearance of the enhanced materials available now.