12

What's the benefit to Formula 1 using engines like a 3.0L V8 or a 2.4L V8?

I read this Reddit discussion on why it's not practical to put small many-cylindered engines into production cars. Cost mostly, due to the many additional and higher-quality components that must go into it.

Just because race teams can afford to produce engines like that, what is the benefit to using these engines instead of 6- or 8-cylinder engines with higher displacement?

8

The answer to why F1 teams use a certain engine displacement and cylinder count is not a technical one; it's governed by the rules of the sport.

You can see the history of F1 engines here. From the same source, for 2014/2015:

1.6-litre, six-cylinder single-turbos with energy recovery and fuel restrictions to replace 2.4-litre normally aspirated V8s, Fuel efficiency to increase by 35%, Power of energy-recovery systems to double, Overall power to remain at approx 750bhp.).

  • 3
    One thing I might add is that such prescriptive regulations are quite a recent thing, an attempt to level the playing field for teams with smaller development budgets. Previously there would only be a limit of capacity (one limit for normally aspirated, one for forced induction). Engines like BRM's famous supercharged 1500cc V16 were't as far out as they might sound today. Very roughly, more cylinders make a more balanced engine, and the shorter the stroke the easier it will be to reach high engine RPM. In turn, high RPM roughly means more power, as power is a product of torque and RPM. – Sam Jan 6 '16 at 22:48
  • @Sam you should make that comment an answer – Zaid Jan 7 '16 at 10:43
  • I wish there more F1 style questions. I'm a fanatic too. – DucatiKiller Jan 16 '16 at 15:46
14

Race and high performance road car engines often have a higher number of cylinders in relation to overall capacity, compared to engines designed to optimize cost and reliability over ultimate performance.

The reasons multiple cylinder engines produce more power for the same cubic capacity are:

  1. Smaller bore x stroke = smaller pistons + smaller connecting rods + lighter crankshaft = less mass to accelerate on each stroke = quicker revving/higher max R.P.M. = more power = higher top speed + faster acceleration.
  2. More cylinders = more valves = higher rate of fuel throughput = greater power output.

Downsides to multi-cylinder engines include:

  1. Greater complexity of manufacture.
  2. Greater expense.
  3. Increased difficulty of servicing and shorter intervals between services.
  4. Greater complexity and difficulty of setting up and tuning engine to optimize performance.
  5. Reduced reliability and robustness.

Nowadays there are fairly stringent reliability regulations in Formula 1 and there are penalties for teams who have to replace too many engines in one season in order to control costs, but as a general principle the ideal racing car engine is one which disintegrates immediately after crossing the finish line!

Of course it's impossible to design an engine that precisely, but historically you'll find that racing engines are extremely strong when used within their intended design envelope (eg full rebuild every few dozen miles, scrapped after a few thousand miles) but tend to blow up spectacularly if they exceed the envelope by even a small amount. (eg if under serviced, over-revved etc.)

The reason for this is a combination of weight saving + trying to extract the absolute maximum power output and also a result of the compromise between those two goals and reliability. Racing car success can depend on the tiniest of margins. If your car is consistently 0.1 of a second faster than its nearest rival on a particular track, then that equates to a 5 second lead at the end of a 50 lap race. That is why racing car designers will attempt to use any possible means available to them in order to make their cars just that little tiny bit faster.

Weight is also incredibly important on a racing car. You might think that saving 1 gramme of weight on one component wouldn't make any difference, but if you can save 1 gramme on each of a car's 1000 components, then you've saved a total of 1 Kilogram, which on a lightweight racing car, can make a measurable performance increase. On a racing car, a V16 engine, may well be more expensive, more complicated and less reliable than the same capacity V8, but all other things being equal, if it weighs 2% less and produces 2% more power and is still reliable enough to finish races, and the team have the budget to build and run it, then (regulations permitting) they're going to use it.

The engine is not the only component on a racing car, but it's one of the most important for determining the car's ultimate performance. In Formula 1, the added cost and complexity of multiple cylinder engines is far outweighed by their performance advantage over a same capacity straight 4 for example.

In modern Formula 1 there are many complex regulations, governing engine design, reliability, energy recovery, fuel consumption, overall weight of cars, etc etc. and the number of cylinders and layout allowed may sometimes be defined by regulation rather than performance, but in general, a well designed and built many-cylindered engine will out perform one of the same capacity, but with fewer cylinders.

5

In addition to @Andrew Kerr's answer: for a given engine capacity, adding more cylinders increases peak power.
But it also increases losses in several areas:

  • more moving parts means more friction.
  • smaller cylinders means the ratio of volume versus wall area goes down, so heat losses increase.
  • there's a potential loss of reliability die to the extra moving parts
  • more cylinders often also means a longer engine block, which makes it difficult to build a block that doesn't flex when it is used as a structural part (as is usual in Formula 1).
  • with more than 12 cylinders, it becomes difficult to build a crankshaft that's strong enough. Some straight-8 engines used a gear in the middle of the crankshaft to transmit power to the clutch and gearbox.

This means there's an optimum number of cylinders for a given capacity. In 1989, Formula 1 banned turbocharged engines and mandated a 3.5 litre naturally aspirated engine. The number of cylinders was limited to 12.
Several manufacturers used computers to find the optimum number of cylinders, and built V10 engines. It turns out, at that capacity a V12 would be less powerful than a V10.

Oh, and the #1 reason not to use many-cylinder engines in small cars: fuel consumption goes up with the number of cylinders.

And specifically to the last part of the question:

Just because race teams can afford to produce engines like that, what is the benefit to using these engines instead of 6- or 8-cylinder engines with higher displacement?

Formula One and other race classes have a hard limit on displacement. This is done to limit engine power, which is done to keep performance below the design limits of the circuits they use (the faster a racecar is, the larger you need to make the runoff areas).

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.