In formula one motor racing, the construction rules for engines are:
Engine capacity not to exceed 3 litres (183 cubic inches)
Engines must be four stroke
Engines must be naturally aspirated (no turbos, superchargers, intercoolers or similar)
and:
maximum of ten cylinders
fixed length exhaust manifolds
I understand the first three restrictions, but if the capacity is fixed, why the restriction on the number of cylinders? What advantages would a 12 cylinder 3 litre engine have over an 8 cylinder?
I don’t have the faintest idea what restriction (5) is all about. I know the manifold is the the bunch of tubes which carry the exhaust gases from the the cylinders to the outside world. But what advantage would you have by allowing their length to change? How, mechanically, would this be achieved? Why have a manifold at all - why not let the cylinder exhaust ports just vent into the air? (I’m assuming racing cars don’t bother with mufflers.)
Just a WAG here, as I’m not a racing fan. Also, I just woke up, so I can’t stop myself.
WAG: If the manifold was adjustable, you could tune it during the race to extract more power. I know that you can significantly boost an engine’s horsepower by using a tuned pipe. Maybe you can tune a manifold? (But you can’t tuna fish! rimshot)
Not much of a technician though. But I do know that a 3 litre 12 cylinder produces more power than a 3 l. 8 cylinder. It has something to do with the momentum of the crank-shaft being better because it is driven by more piston. More, smaller, combustions are more power, I suppose.
All F1 teams use 10 cylinders these days. In the early 90’s, engines ranged from 8 to 12. The 12 cylinders (Ferrari were known for them) were more powerful, whereas the V8’s were more economical. On slower tracks, a V8 with a decent pit strategy could in theory beat a 12 cylinder.
I have heard that they’re gonna lift the 12 cylinder ban, since a few teams have declared that they have developed 12 cylinders with better economy now. Ferrari being one of them.
And who DOESN’T want to hear a Ferrari V12 screaming through Eau Rouge (true race fans know what “Red Water” is)?
The reason for the limit on the number of cylinders is to limit the maximum RPM’s that an engine can spin at. Smaller pistons are lighter, and smaller cylinders can fill with fresh air and empty of exhaust faster than larger ones can. So if you had two engines, both three liters each and one with 4 cylinders and the other with 12, the 12 will be able to turn higher RPMs, producing more power. While burning more fuel, but that’s another problem. - MC
What I mean is trying to have a “style” as to how the engines are configured. My understanding is that F1 and other racing bodies do try to keep a “common” engine configuration, to avoid really outlandish or unusual designs, as part of the aesthetics of the sport (like the good ol’ V8 in NASCAR, which I believe is mandated - I don’t think they allow the Chrysler V10 or other V12’s in there for instance). Some sports ban gas turbine cars (although it’s a moot point, since they can’t usually compete).
I’m sure I may be wrong, but do you see what I’m getting at?
Ah, I see. I think, however, that the main reason is to keep the speed down to an acceptable level. In the last 15 years, I can recall the following restrictions on F1 engines/cars:
Turbos were banned after 1986;
Enngine capacity went from 3.5 to 3 liters (1993?);
Wings are more and more restricted in size every year;
The introduction of the grooved tires (1997?).
All with the purpose to reduce speeds. Which works, really. Apart from Senna and Ratzenberger, who both died at Imola in 1994, there haven’t been any fatalities in F1 since the early 80’s.
When a cylinder fires and the combustion products are released into a tube it creates a wave of pressure as the pulse is fired out.
When the firing is continuous there are a series of pressure waves travelling up the exhaust tube in pulses, but in between there are regions of low pressure.
The tube length can be arranged so that at a certain firing speed there will be a region of low pressure at the outlet valve just as it opens which helps enormously to evacuate the cylinder and if the design has been careful can aid the induction process.
The tube length is critical to the frequency of engine pulses.If the engine changes revs the the scavenging effect is reduced.
What some manufacturers do is to join all the exhaust tubes into one or two pipes and borrow the pulses of one cylinder to scavenge another.
This is one of the reasons that an engine will suddenly pick up, this is especially noticeable on 2 stroke bikes.
There is always a compromise and there are times when you want to increase the torque of the engine rather than its power output.
So the answer is to do something that Yamaha have been doing for a while now and what Honda has started doing just lately, and that is to swap the way that the exhaust pipes are connected by using a diverter valve.
What happens here is that depending on the revs, cylinder ones exhaust might be connect to cylinder 2 or 3 or 4 oultet to take advantage of the low pressure pulse at differant engine revs.
The absolute best way to do it would be to actually change the length of the exhaust pipe depending on the revs so taking advantage of the scavenging pulse all the time.
This would increse low down torque and peak output power but it would also be very expensive to do beause the whole engine would probably have to be redesigned.
This would make F1 even more expensive than it already is and we would end up with even less competition.
I don’t know anything about formula one. But among naturally-aspirated engines in street-legal passenger vehicles currently in large-scale production, the best specific output is achieved by the 4-cylinder, 2.0 litre, 240 hp engine in the Honda S2000 coupe. That’s an astounding 120 horsepower per litre. By comparison, the 6-cylinder 300hp engine availible for the Porsche 911 coupe produces only 88 hp/litre. Sadly, my truck produces only 48 hp/litre. I have no idea how these figures compare to formula-one racers.
Coldfire is correct, if all other things are equal. While the Honda engine’s output is admirable, the comparison between the Honda and the Porsche is not really comparing apples to apples.
We could also go into the difference between peak horsepower, and the area under the horsepower curve, and torque, and so forth. Like I said, one cannot look at just the peak power and compare directly.
The S2000 is so “power efficient” partly because it can be revved so high(9000 RPM). Even at 7500RPM, it only generates 153 ft-lbs of torque. It may have very impressive performance for such a small displacement; but the need to really rev the car for any kind of performance is a major downside.
The 911 generates its peak torque of 258 ft-lbs at 4600RPM. That’s much closer to normal driving engine speeds, and you aren’t abusing the engine either.
Taking the engine to redline(where the S2000 shines) is fine for the racetrack and car magazines, but it’s not practical or a common practice for most street drivers.
I test-drove the S2000, and I can confirm this. It has this Honda V-Tec technology. Variable valve timing, or something. Anyway, it means it can rev much higher than the regular 4 cylinder engine.
However: it’s pretty dull at normal revs, as described above. You REALLY have to push hard to make it jump.
Top Gear shared my opinion, so I must be doing something right
That aggrees pretty well with my experience. My 3.0L 911SC had good pick-up until it reached about 4,500 RPM. Then it was like igniting an afterburner! I had a lot of fun zooming around in that car, and it was quite comfortable even in the triple-digit speeds. Unfortunately it was not at all a practical car. Sometimes I have a need to actually carry more than one passenger and a verbal message. I sold it and got a Jeep Cherokee. Much more practical, but not as much fun (except off-road)!
The engine in the Honda S2000 doesn’t violate what I said; it’s an engine with small-displacement cylinders. Sadly, there are only four of them; 8 would have rocked. - It’s difficult to compare multi-cylinder engines because to be fair they should have the same types of intake and exhaust systems, valve arrangments and bore/stroke ratio.
And I seem to remember that a few years back Cadillac wanted to field a 16 cylinder engine, and at the same time introduce a 16 cylinder passenger car motor (probably not the same engine for both). Their argument was that they had built 16-cylinder cars/engines in the past. It might have just been board-room chit chat, and I can’t remember if that was Formula 1 or something else however.
There’s two reasons that turbine cars are banned: building turbine engines from scratch is way more expensive than building piston engines from scratch, and the different powerbands of the two engines makes it difficult to do any “real-world/track” comparisons. Turbines are extremely light and make massive amounts of power, but mostly only at ~95% max RPMs. Unlimited hydrofoils haven’t done too badly with them, but for that sport they use modified helicopter engines - building from scratch would give better results but it would cost too much. As far as being competitive goes, most civil helicopter engines produce about 4 times their weight in horsepower, as sustained output. Piston engines can’t do that for very long. - MC
One reason my Mustang feels so powerful with “only” 225 hp - it has 300 lb-ft of torque, and it’s torque band is decently fat. I can cruise around at 25 mph in 5th gear, and it will pull away from there without lugging if I step on it (slowly, but without lugging). It really runs out of breath at above 4500 rpm though…that will change somewhat when I put on the SVO Blower.
