Why no 5 Valve Engines?

[NDR008]

This is a bit of a deviation but still related, it is also not common to see 5 valve per cylinders. The only one i can recall is the 4A-GE black/silver top version which for of you who don't know, the 4A-GE is one of toyota's most legendary cast iron road car engines, known to be 'abusable'. The first series and supercharged series where all 16valve, but a later generation was released with 20valve. Not sure if the Atlantic series 4A-GE was a 20 or 16 valve though.

[skyripper]

abusable...?? you really sure about it?
from the "suck squish bang blow" series aritcle wrote by mike kojima and other pratical experience heard from my friends, 4AGE's short block is just weak as honda D-series engine.

the latest version of 4AGE even comes with the ITB, but frankly, it doesnt really produce reputable horsepower as other high-revving engines, like all those honda DOHC VTECs, SR16VE engine from nissan, or even the 3SGE motor made by toyota itself. high revving engines require stronger rods to withstand tremendously inertia load, so just take a look of the 4AGE's redline and you will have a idea. when you say "abusable" toyota motors i personally think 3SGE(T), or 2ZZ engines, are the ones should be referred to. not the 4AGE.

other 20 valves street engines, like VW 1.8T, is a masterpiece too.
this motor has the maximun torque output @ 1,950-5,000rpm, simply but just amazing powerband. since the common myth is, 5 valves valvetrain is only good for huge air flow at high rpm, so i really dont understand the theory behind this, why VAG adopt the 5 valves system on their 1.8t? it's not a high revving motor. its turbo compressor is small too, does it really flow that much?

so come back to the topic, anyone here knows the old V6 F1 engines use 4 valves or 5 valves? will the 5 valves fit turbo better? with 3 inlet valves, will a turbocharged engine acquire more flat powerband? (at such high rpm, high boost condition?)

[tommi]

I think the reason four valves are used is due to the stiffness that can be achieved of the thixotropically cast al alloy cylinder head at high temps. Incidently it is this thixotropic cast technology derived from f1 that enables honda to bring us the first all alloy diesel engine.

PS whats this crap on the website about transmissions operating at 1000deg.C. I'd like to see the modern gearboxes with polymer/carbonfibre composite components operate at that! one to many 0's I think.

[Guest]

just a question

who have the best engine in f1 ?(top four) the most powerfull engine

[Stas]

Its simple 5 valves= less reliability

[Reca]

Its simple 5 valves= less reliability

I wouldn’t be so sure about that.

[Monstrobolaxa]

He's looking at it from a statistics point of few.....more moving parts....the higher the probablitiy of something breaking...

[Reca]

I know that common sense would lead to that conclusion, but with 3 intake valves instead of 2 each valve is lighter and the valve lift is lower so you have lower mass and lower accelerations, that’s more important in term of reliability and wasted power than the increased number of parts, actually these are probably the biggest advantages of the solution.

[riff_raff]

There is a very interesting technical paper published by Yamaha (SAE 860032), regarding the optimum number of valves. They evaluated various valve configurations, from 4 valves to 7 valves. They came to the conclusion that 5 valves was best, with regards to VE and BTE.

Of course for production cars, as opposed to race cars, Mercedes has determined that a 3 valve configuration is best, when considering both cost and performance.

Who knows?

[Mehmet]

Simply because this is an FIA restriction.

Engines can have no more than 4 valves per cylinder.

Cheers

In the big cylinders, they can use up to 8 valves per cylinder but it's only in diesel engines. because the air and fuel are not good mixed together so they put an injector everywhere in the cylinder. but in the petrol engine they couldnt use this much of valves because the fuel is good mixed with the air, so the preignition and detonation could occures.......

[riff_raff]

Monstrobolaxa is right....

With regards to statistical failure analysis, for a given function, a mechanism with fewer parts will always have a higher reliability (statistically) than a mechanism with more parts, performing the same function under the same conditions.

It boils down to "X" number of parts times "X" failure rate per part. Thus, more parts means a greater probability of failure, all other things being equal.

Of course, this theory does not take into account redundancy of function.

[Reca]

It boils down to "X" number of parts times "X" failure rate per part. Thus, more parts means a greater probability of failure, all other things being equal.

And the point is exactly that all other things aren’t equal, as I already said :

with 3 intake valves instead of 2 each valve is lighter and the valve lift is lower so you have lower mass and lower accelerations

This means that you have less stress on the valve springs, and, as you said in another thread :

Back when high-rpm race engines had metal valve springs, the fatigue life of the highly stressed valve springs was usually the limiting factor with regards to race engine life.

Many people designed heads with 5 valves instead of 4 mainly for this reason, with 2 intake valves they weren’t able to increase the rpm without taking too big risks, with 3 valves they were. The valve were lighter and due to lower lift also the accelerations were reduced, the required spring rate was lower => the spring itself lighter (not negligible advantage since the spring itself is part of the equivalent mass of the system) and here it goes the usual vicious circle of weight reduction that all the engineers, especially aeronautical ones, learn to appreciate since day one at Uni : lighter airplane, less lift required, less drag, less power required, lighter engine, lighter airplane etc... Incidentally, the main problem the Wright brothers had to solve was exactly to find an engine with a power/weight ratio high enough, the engines available at the time were heavy hence requiring more lift hence more... Ok, no need to do it again...

[bcsolutions]

Surely the main benfefit of 5 valve per cylinder heads is with regard to total valve circumference x lift. Lift is obviously restricted by the need to avoid the whole valves hitting pistons problem so valve circumference is the way to go. Of course then you encouter the problems, like spark plug placement, increased port angles, combustion chamber shape, valvetrain complication etc. 5 valve per cylinder is obviously superior in some applications, just not F1, yet.

the latest version of 4AGE even comes with the ITB, but frankly, it doesnt really produce reputable horsepower as other high-revving engines

The later spec 4AGE is good for 160bhp+ on a standard bottom end. Formula Atlantic use the (allbeit modified) 4AGE and they manage 250bhp.

[Guest]

Although 5 valve engines are allowed by fia regulations, and is and efficent intake system, it is impossible to run pentroof cylinder heads with more than four valves. Therefore, the gain in compression from the pentroofs is more valuable than the marginally better air inlet. Hope that helps explain something!

[abisec]

what you are goin to leave out from a f1car....is not goin to add on to its weight and is not going to give you problems...besides the universal definition of a racecar would be......