Road vs Rally vs F1 engines comparison

Question and answer direct with GC. Competition engines and 'live' projects only. Good photos to illustrate your post are expected.
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Road vs Rally vs F1 engines comparison

Post by Nobby » Fri Jan 21, 2011 4:35 pm

I’ve often thought (and been asked), what’s the difference between my engine and an F1 engine?

Even if it’s not a petrolhead asking me I don’t find it easy to articulate the answer. I try to summarise it as follows - A major manufacturer spends a fortune on development, but specifically the engine is limited so the final product has to be affordable, economical and has longevity. A formula one team must spend equally huge amounts, but its drivers are entirely different – performance & its delivery, weight and a specific lifetime. But this still doesn’t really say much.

I’d love to see a few basic comparisons with 3 common engines. Lets keep it Italian obviously….for example a 1400cc production Fiat engine, a 2000cc Rally spec TC Fiat engine and a full on F1 v8 engine.

Capacity is the obvious first difference: 1400, 2000 and say 3000cc. Number of cylinders next: 4, 4 and 8. Number of valves: 4, 16 and 32. Number of cams: 1, 2 and 4 etc…. I could go on forever.

Aside from all the obvious stuff it’s very hard to know the major differences in the components of the engine. I’ve never worked in the Industry (much to my dismay) so I don’t have any knowledge on the following but I’d love to find out.
- Overall clearances
- Production tolerances
- Degree of engine balancing
- Weight of items to within 0.n percent
- Comparative weights of components
- Materials used (superalloys, inconel, titanium, iron…)
- Production method (forged, cast, hand made)
- How long they take to make
- How long will they last
- How much they cost

The other side to this is actual engine design. VE, head design, Max RPM, fueling, ignition etc

Many thanks

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Re: Road vs Rally vs F1 engines comparison

Post by TomLouwrier » Sat Jan 22, 2011 12:24 pm

hi Chris,

Now there's a question.
Road and F1 engines are not something you can compare. Both are 4-stroke and use petrol and that is it, really.
F1 engines are built for maximum power and minimal weight. All other things like noise, emissions, assembly and maintenance come way low on the list of specs. Fuel consumption has only recently become an issue, apart from team strategy, car weight (tank full and empty) and pit stops.
A road engine is built for street usability (balance between power and torque), emissions control, fuel consumption, noise control. It must fit inside the engine bay of a range of cars and be compatible with several transmissions. The driver may be alone or have the entire family with him including holiday stuff for two weeks and a caravan on the tow hook. He may be steaming down the highway with it or pull up an Alpine pass. In hot summer. In winter.

Both engines need to be very reliable during their entire working life, but that working life is quite different:
- you don't want to loose WC points because of an oil leak or failing plugs, but you can rip it apart every other weekend and overhaul.
- you don't want to have your engine taken out every 5000 miles, but you may have minor repairs during routine services.
A competition engine only lasts so many weekends, qualifying engines lasted just several rounds.
A street engine will carry you everywhere without fuss, from day one and then some 200.000 kms (or miles).

Street engines are built in very large numbers. When I was at Peugeot in Poissy some years ago they had 2 lines running, pushing out a car every 80 seconds or so. That is 100 cars every hour, 24x7, each of them with an engine in it.
This means that you will spend very much time and effort in you design to make it easy and profitable to produce and assemble the engine. Materials and tolerances have to be so that it is always right, the first time. Matching parts, shimming out or adjusting on the lines are not possible, you will go bankrupt. Also: good enough is good enough. Finer tolerances to make things 'better' or 'fit always' will cost you. Bad design practice.
Scrapping more than half a percent of your parts because they are out of tolerance will see you jobless quite soon too.
You will use production machines (lathes, mills, etc) that are designed and built for just that job, and can not make another part without lengthy and costly changes to them. These machines cost a fortune, but spread over the number of engines produced it is worth it because once they're running, they're really running.
If you find a way to build the same engine for 1 euro less, you will earn €100 an hour (and of course the other way around...). Ask Ford or Toyota, they are quite good in the bean counter department.

F1 engines are built by hand, counted in tens or hundreds per year, not thousands per day. Many parts are made from billet materials on regular, universal machines. These are flexible but cost per part produced is high. The staff needed to do this will have to be very skilled and hard to get. People like Guy.
Some parts just can not be made from billet and must be cast. The moulds for this are really expensive and they will only be used to produce several hundreds instead of several hundred thousands.
The materials in these engines are very high grade and expensive, yes, and so are the tolerances and finish. But compared to the costs of tooling and labour this is not very important. Gain a kilo and you may win, throw a rod and you will not.

Design effort for both sort of engines would be more or less equal I estimate. Street engines will then have to go through a very intensive phase of testing, in order to be proven reliable, within specs of power, torque, emission and fuel consumption, and then of course to be certified by all sorts of official bodies so that it will be allowed on the roads. More time and money spent.

As for maintenance: most competition engine designs have very little or no respect for the guys who will work on it once it is out there. The mechanics are supposed to be very skilled and work all night to get it running again next morning on racing day. Come on, this is Formula 1!
A street engine must be serviced as little as possible, by average grease monkeys (sorry!), in the shortest time. All to ensure that you won't have to spend thousands on an 'oil & plugs' service and the garage owner can still make a living off it. We all know some engines and engine bays that are pigs to work on and we also know the language we use when we're in there.

Finally: rally engines. These are most like what us folks on this forum work with. Competition engines, grown out of street designs.
Power and torque demands are different, considering the sort of use they will see. Reliability and serviceability are high on the list.
They really get punished. Events last several days, service and repairs are done in tents with mechanics lying on their backs, under the car. If the gearbox jams in 3rd, the driver will push on anyway to finish the stage.
Most classes require for a car to be homologated that it is based on a production model that is built and sold to the general public in reasonable numbers.
So, based on regular street engine designs, what you can do with them will be limited all the time by the dozens of compromises that were made by the designers in order to meet the criteria in their design brief (power, fuel, cost, package, emissions, cost, cost). Making the most of what you've got takes a lot of investigating, testing and labour. Some parts you will modify (like heads) others you replace (rods). Sometimes the factory does a run of specials, like cranks out of better steel, produced on the regular production tooling. By the time you have a winner, the cost of the original core engine is completely offset by those of development and special parts.
On the other hand: it is from these engines that we're most likely to see the results of the lessons learned in our own cars next season. Racing improves the breed.

Bottom lines: it's bhp for courses, and money makes the world go round.


Guy Croft
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Re: Road vs Rally vs F1 engines comparison

Post by Guy Croft » Sat Jan 22, 2011 2:28 pm

I think this is amost interesting thread and well done both so far.

Look forward to joining in next week..


Rich Ellingham
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Re: Road vs Rally vs F1 engines comparison

Post by Rich Ellingham » Thu Jan 27, 2011 9:23 pm

Chris in addition, the origin of the design is of significant importance, your list of questions even if answered won't go far to highlight the different world that is a true race engine. Tom has mentioned a number of aspects but an easy way is to consider a full race bred engine from its block. Around the internet there are all kinds of tales regarding blocks used in F1 which were from used production cars, namely BMW. However, these stories are folklore BMW did try a used production block it didn't even get up to temperature on the dyno before it failed. So with that in mind full ground up race engines are designed for a power, torque and output from the start an many have little in the way of excess material, look on the outside of a race block and you will see the outline of the water jackets. Every inch is FEA analysed and very complex casting will be made to ensure no excess weight is carried. In addition to this many blocks especially in single seater make up the rear part of the chassis and are load bearing from the tub to the engine to the gearbox onto which the suspension will be mounted, thus they are taking additional loads beyond that of just combustion related forces. A true race engine has significant thought put into about centre of gravity and crank centre line as the unit will often need to be placed as low a possible in the car to assist the entire vehicles CofG position. In addition to comparable things a full race unit might have to power another hydraulic system for the gearbox.

Cylinder heads as I'm sure Guy will discuss will include significant downdrafted angles and valve train capable of the high rpm and rapid changes in rpm when using sequential transmissions. Full race engines need to work to certain rules and the design may work around those rules, for example in F1 the engine development freeze states the intlet ports cannot be revised, to get round this the heads are designed such that the actual port is very short and most of its is part of the manifold, allowing changes to be incorporated without breaking the rules (although the rules changed further to combat that). The Full race engine will have critical control of lubrication and cooling, radiators cause drag so the designers need to know what is the minimum size they can get away with in order to cool the engine at race speed (consider the F1 problems when running under the yellow flag), to know the minimum size of radiator knowledge of the heat creation and dissipation characteristics of the engine must be known to a level far beyond production.

Rebuilds are another area which are very different, a road car rebuild will involve replacements of moving parts or bearings, while in top end racing blocks and heads can be considered replaceable for reasons of fatigue, or the likelihood they would finish a race.

The conversion of road units to race was probably its most extreme in the super touring car years, with most money being spent on working around the rules, for example the TWR Volvo 850 was a 20v design similar to that of the Fiat, but in race guise it had custom made cam boxes and the head face was machine at an angle to increase inlet downdraft, I struggle to remember the figure quotes in Racecar engineering regarding this but something like £20k worth of machining alone was done on each head before any assembly.

I hope to add more soon to this discussion, but I’ve no doubt Guy’s experience of all levels of the sport will prove to be the best insight.

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Re: Road vs Rally vs F1 engines comparison

Post by Nobby » Fri Feb 04, 2011 11:39 am

Thanks for the response chaps - its really useful to see a simple breakdown of how certain things are different.


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Re: Road vs Rally vs F1 engines comparison

Post by TomLouwrier » Fri Feb 11, 2011 10:18 pm

hi guys,

Right, let's bump this one a bit. There's more to be said about the subject.
Reading back on Chris's original question I feel we missed the point a bit. Everything so far has been mainly qualitative, but there is hardly any quantitative information about engines in it.
So I've set up a very limited sort of benchmark in the form of a spread sheet.
Before you go downloading it, let me explain what I did.

In the rows:
Below each other I've listed a number of engines, each on its own row, with their data.
The first group are production engines, mostly familiar examples from Fiat/Lancia. I included the BMW M1 because that is known to be one of the best developed atmo engines ever on the streets.
The second group are engines I like. Why? Well simply because I happen to own them :-)
In the third group you find engines built buy Guy, the numbers taken from this site and his second book (the first still being someplace up in the attic since I moved house).
The fourth group are true Formula engines. It is not so easy to find accurate figures about things as max torque and rpm's, but I got some in. The Matra V12 is listed as LeMans engine, but actually they used it in both LM and F1 with only a small difference in BHP due to tuning, max rpm and 3 piston rings (LM) vs 2 rings (F1).

So over to the columns.

The first set are engine characteristics. You will recognize all of that: valves/cylinder, atmo or turbo, rally or street. I'm using these just to describe the engine a bit. DOHC on a V-engine means 4 cams in total of course.
The next set are also given data, but these are used in calculations so whatever we put there should be accurate. They are marked in *bold*. Here we see things like: # of cylinders, bore and stroke. That gives us swept volume in cc's and bore/stroke ratio.

Next set: power figures. Max power, @rpm. From these we can get the torque at that rpm which gives us BMEP (brake mean effective pressure). BMEP is actually the main key to what's going on in the combustion chamber. The higher it is, the better the engine is doing. With BMEP you are not bothered by differences in swept volume or engine speed. This is important is you want to compare a 1600cc 4-cylinder running 6500 rpm to a 3-litre v12 running 10000 etc. (Otherwise just look at the power column, pick the highest one and you have your winner).
After BMEP we have specific power (BHP/litre). Also engine weight, so we can have a look at BHP/kg. Very important in all competition, but in aero and marine applications as well (especially military).
For the same reason that BMEP is independent of both engine size and speed I've been using something I call 'state of tune' for years. It is quite simply the max power in BHP, divided by the engine volume in litres (aka specific power) and that divided by the number of revs in (1000's). The effect is very much like BMEP, but easier to do if you're quickly comparing engine performance numbers from eg a magazine, sales brochure or conversation.

After power comes torque. Same approach as before: max torque and @rpm give power at that rpm and BMEP, and specific torque (Nm/litre).

Finally: flexibility. This is N_power_max / N_torque_max. The closer these numbers are together, the less flexible an engine is. This means the more peaky it will behave. High number means flexible engine.

For most 'specific' values I have added a column that gives a % relative to the lowest one. The poor Spider 2000 USA is our 100% mark here.

Now what do we read in all these rows of numbers? Just a couple of my own conclusions:

- 4 valves give a good advantage over 2 on a similar engine, with BMEP around 10.5-11 versus 9-10 in street engines.

- turbo charging is very effective, bumping performance by nearly a factor 2 on both 2 and 4 valve engines.

- compression is an important factor for having a well performing engine.

- the BMW M1 was indeed a racer in street guise. I'm pretty sure it could do much more than the quoted 6500, especially given the N_max_torque of 5000/min.

- the very short stroke X1/9 1500 is actually one very flexible engine. Must be breathing well at lower revs (or: could do better at high revs).

- the simple Simca OHV was in fact a very good engine, dating from 1959.
Apart from the camshaft the head is quite similar to the Fiat SOHC: alloy head, cross flow / 8 ports, tilted parallel valves and a wedge shaped chamber. Too bad it was never fitted with valves big enough for anything over 1.3 litre. Ah well... it was originally designed to be 900-1200 cc's and not much more, so you can't blame them really.

- bike engines are usually in a higher tune than car engines. Remember that they have far less weight to push along, so they can do with less torque and flexibility.

- Guy's engines are -as expected- considerably more powerful than standard, reaching F1 levels in BMEP. You're not going to get higher than this.

- F1 BMEP hasn't gone up much over the last 30 or so years. Power has come down recently because the regulations limit engines to V8, 98mm bore, max 18000 rpm and min 95kgs. That was done to help make the sport safer (?) and less expensive (??). All is relative of course.

- F1 engines make their power from revs. Anything running 18000+ rpm is really screaming. This is essentially what F1 engines are built for. And given the strict regulations each team does the same homework and finds the same limits, so all engines give pretty much the same performance. Boring, isn't it?

- the higher the BMEP, the more powerful the engine is. But once you're over about 12 bar you're most likely to get more power from upping the revs. This will shift the N_max_torque up as well, and give you a less flexible engine.

Apart from comparing existing engines you can also use this to play 'what if'.
You may set and evaluate your goals when thinking about improving an engine. Fill in whatever power and torque @rpm's you'd like to achieve and see what sort of BMEP, BHP/L and Nm/L that would mean. If your numbers go way beyond those of the F1 engines, forget it. When they are somewhere near the examples it should be do-able.

NB: Not all data is completely correct!
- I'm pretty sure that engine weights are more than 10% off for most. I guesstimated some.
- Torque figures for some of the F1 engines are not readily available.
- There might be some confusion about power figures: is that SAE or DIN? Dunno, but the difference between the two is not that big.

By all means, use this sheet and add engines you like. Correct errors you find and post it back here.

I'm very interested in what you come up with.

engine comparison.xls
(34.5 KiB) Downloaded 182 times

Guy Croft
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Re: Road vs Rally vs F1 engines comparison

Post by Guy Croft » Tue Feb 15, 2011 6:48 pm

Now that is a 'job of work', Tom, well done you!

Some blanks for me I see!

Sorry but partly to the ridiculous amount of 'background' work this firm requires and partly due to the exceptional calibre of responses so far I have not joined in the discussion - for which I am sorry.

I might perhaps add (sorry if it has already been said) that the principal difference betw F1 and anything else is budget - which to all practical intents 9as far as we understand it) is, well, unlimited. this means that anything is possible, quite literally, even if the current engine regs are restrictive and, er, rather dull.

Again, not sure if it's been mentioned but F1 engine are scratchbuilt thoroughbreds against which all other engines are hybrids - good or bad. Moreover F1 is the trendsetter. Today's trend may be tribological losses and tomorrow's windage losses - all other forms of motorsport copy F1 but no-one will ever actually overtake them in terms of the design (far less manufacturing) response time and the sheer indeniable excellence of the designs. Any F1 engine firm could redesign any core component in 24hrs (head, crank, crankcase) in 24hrs and have it ready to test in 10 days. No-one on the planet can match that capability. I say redesign and I've seen it done. Design from scratch is another matter.


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