Why did Ferrari revert to 4-valve engines?

5 valves per cylinder was a "solution looking for a problem" probably led by the marketing dept. Fortunately they wised up and went back to 4 valve heads.

 

The five valve configuration was because they used it in racing right? I think we could check out the horspower per litre of the five valves vs the 4 valves. But, I would have to say that four valves would increase reliability.

 

Another way of having variable valve timing(5 valve setup). The center intake valve opens at a different time than the outside 2, ie;the postion of the center valve is a few degrees different from the 2 outside intakes. The newer engines had variable timing actuators so they didn't need the 3 intake concept. Regards, Vern

 

Technology constantly evolves. Too many concessions and compromises needed to be made for a 5 valve chamber and a way was found to make more power with 4 valve heads. F1 motors went that way a few years ago.

The center intake valve opened at a different time as a matter of need. There was no room for all to open at the same time.

The 4 valve pent roof chamber has been found to be about the best chamber shape devised and they went back to it.

 

A professional engineer once mentioned to me something like 'remember, each time the number of valves goes up, the turbulence increases'.

This might also explain why one wouldn't want 6 (Honda square piston bike notwithstanding) or 8 valves, etc... just because the engineering budget could afford it - might be worse.

Also explains why 2 valve engines can do surprisingly (though not up to competative racing standards) well - low turbulence to counteract the lack of swirl and overall area.

Hard to rev high with 2 valves, another prolem, and as Honda proved with motorcycles in the 60's, 4 valves is pretty hard to beat.

 

This might lead to some insight. I was just reading Motorcycle, and Yamaha went back to 4 valve heads (they used a genesis 5 valve cyl head since the 80's) because with the 5 valve cyl heads you had to run a lower compression and peak torque was much higher in the rev range and therefore almost unusable for racing and streetriding. This year they're heading back into racing. With the 4 valve head they were able to raise compression and the peak torque comes in a couple thousand rpms lower now.

 

20% off on valve jobs.

Especially after the timing belt breaks.

(Were the timing chain cars also the 5 valve cars?)

 

Beat me to it

Yamaha originally stated that for max performance 7 valves were required (4in, 3ex) but that the mechanical complexity of this setup meant 5 was a compromise which I would guess eventually became a marketing tool until they needed real performance. Which is now, because the teams have finally pushed the marketing people into letting them have the best engine as a basis for World/National Superbike series. It was intersting that Ferrari ran it in F1 and 355/F50 (didnt realise 360 was too)...shame the 355 isnt 4 valve, make the valve issue repair bill 20% cheaper in parts

Honda did make an engine with 8 valves per cylinder, but it was cheating as the cylinder/pistons were oval (2 conrods per piston) and it was effectively a V8 with some cylinder walls removed (NR750) - hard work sealing the rings I understand, click below and count the valves!

http://home.planet.nl/~motors-20th-century/drawing/Honda-NR750-1992-ghosted.jpg

 

Wow! Are there any examples of this bike ont hte street??

 

I don't get why you would need five valves for VVT - couldn't you just make one of the two intakes in a four-valve design with a different cam profile? I know you can, I have an engine like that. Also, what would be the real advantage unless you had a separate intake manifold (tuned runners, different injectors, etc.) for the differently timed valves?

It is also of interest to note that Mercedes seems to have given up on the three-valve heads and also gone back to four valves.

Maybe 4 valves and a central plug location really are the most practical answer.

 

Note that VW/Audi also went the 5 valve route, and it was also a design failure. They amortized the cost of development by selling their failure as a marketing excercise, and succeeded, by disguising the failure with a turbocharger. But as soon as they had made their money back they dropped it like a hot potato.

 

Reread my post. 5valve heads had different timing ONLY for the purpose of keeping the valves from crashing into one another. There is no performance advantage to timing them differently. It is a negative.

Mercedes lost a law suit by the inventor of that head design, a Californian by the name of Jim Feuling. His estate won an out of court settlement after his death by cancer. It was knowingly ripped off by them in a classic David and Goliath confrontation.

 

To clarify (in my opinion)

To paraphrase my patent attorney: "No one loses a patent lawsuit, they just decide not to pay the royalties"

Jay

 

How interesting...I guess that didn't make much of a splash in the motoring press. What I read about it was some blather that "maybe 4 valves were better all along, blah blah blah". This was after they went through all kind of reasoning on why 3 vavles were better than 4. I think a lot of the popular press are very subservient to their advertisers.

BTW, your post was indeed clear, but it was the one before it that I didn't understand.

 

Well stated and sadly very common in modern times.


The guy who invented time delay wipers got ripped by EVERY car maker. He won after years a suit against Ford and that money was being used to go after others. If there is any money left after the monumental legal battles it will go to his heirs.

 

Why do 4V engines seem to be less torquey than the 2V version on the bottom end of the rpm band (in general - not necessarly Ferrari). It seems that was how they felt to me back in the 80's.

 

http://www.eibis.com/eibis/eibiswww/eibisdoc/4007en.htm
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At the end of the development cycle of the 2v motors due to emission regs and what that required them to do to cam timing torque was all they could hope for. When 4v's became all the rage high RPM hp was again possible so thats what they went for.

If you want agood example of the torque that can be had from a 4v take a look at a Rolls Merlin from a P51 or drive a 550.

 

Dat be him.

Brilliant guy.


He forgot more about gas flow through a piston engine than most of the auto engineers in Detroit, Stuttgart, Munich, Maranello and all of Japan ever knew.

 

What the heck(scatching my head) I thought I read an article on the 5 valve concept being related to variable timing. Wow sorry about that guys I must be losin' my mind. Regards, Vern

 

I think Yamaha's original R&D and design plan was to make the biggest hole they could in the head to get as much fuel in. If you draw a large circle (cylinder) then try to fit circles (valves) inside it the 3 inlet valves give more port area than 2 hence potentially more fuel/air getting in. Problem as I see it is to then get the gases out through 2 exhaust valves...

The Honda NR750 was created for Grand Prix Racing, the oval piston design was a way to produce a V8 that was legal for Grand Prix regs that had max 4 cylinder 4 strokes. It was a V4 oval pistoned 750 that had 2 conrods, 2 spark plugs and 8 vavles per cylinder. Honda also produced (an expensive) road bike using the same technology. Came out around the same time as the Fireblade, I was sitting in a car at the British Motorcycle Grand Prix around '94/'95 and looked in the rear view mirror and there, parked amongst all the normal bikes was an NR750 complete with tatty helmet attached to its front wheel with a big chain, not seen one since though. The cut away photo on Google is of the road bike.

 

You were probably just reading an article written by a motorsports journalist (you know....those guys that know everything there is to know about cars?) that read too much into a statement or product info piece from Ferrari.

Reminds me of a statement by Sam Posey once when he was announcing (I think it was Indy car or a Cart race). He was describing the advantage of a turbocharger and said it was just like a bellows on a camp fire, it blows more air on it so the fire is hotter.

Sam couldnt explain how a rear view mirror worked, much less a turbocharger.

 

I think it is way simpler and the word is cost. The more valve, the more valve area, the more air can flow. But valves are expensive as are overhead cams. The US maker have stuck to 2 vavle engines because making hp with cubic inches is much cheaper than with technology.

The 5th valve adds something like 5% more flow area to the head and costs say $500. Adding 5% more displacement costs about $0.50 If I were the engineer asked to make the call, that 5th valve would be gone so fast your head would spin. Audi just increase the displacement of their 4 cylider engines...to make hp while saving money.

It does make sense if there goal is hp/liter. My race classes restrict displacement, so adding the 5th valve give a real advantage. I saw pictures of heads Yamaha was playing with about the time they released their 5 valve engines that had 7, 9, and 11 valves. I remember that the hp peaked at 9 valves, but the hp/lb peaked at...you guessed it 5 valves.

 

Yeah, your probably right I have read a few articles over the years that left me saying wtf was that! hahaha. Anyway it sounded logical to me, the 5 valve deal. I hate it when I read crap on here that isn't correct and I didn't/don't want to be one that spews the crap. Regards, Vern