8 replies to this topic

[Powersteer]

Why didn't it survived? Could it be because it didn't create a combustion chamber that is compact enough or did the valve pockets spoil turbulence by design. Seems that 5 valve have better intake area thus naturally contributing to better exaust area yet still it couldn't be competitive enough. I also wonder how will a 5 valve arrangement do with forced air induction, thereoreticly its sexy.

[marion5drsn]

We have been into this several times before. But here we go again. The way to solve this to yourself is to get a pair of dividers and draw a circle of the size you wish to use as a comparison. Draw a top view of a 5-valve cylinder and notice the cluttered look and the difficulty of putting 3 intake or exhaust valves into the combustion chamber, with an appropriate compression ratio. Then put in a centralized spark plug provide for some coolant etc. then you will see the problem. The only people who claim big advantages are Audi and I believe Yamaha. Remember we are talking about road cars or are you talking about F1 cars. I don’t believe that any F1 car has five valves per cylinders today.

I also believe that Audi and Yamaha do it for advertising purposes to have something the others just don’t have, and probably don’t need. It is an engineering nightmare. This is especially true of an engine with a D.O.H.C. system. If you put in rockers and so forth you lose even more of some simplicity and lose what Birkigt called “Direct Push”. Yours M.L. Anderson

[RTH]

Doesn't the Ferrari 355 and 360 have 5 valves per cylinder ?

[schuy]

The 355 used 5-valve, the 360 does, the F50 did and the Enzo does.
Ferrari sure think 5-valve per cylinder is the way to go.

[Bill Sherwood]

I have some information about four-valve Vs five valve engines here -> http://www.billzilla.org/2v4v.htm

[ZoRG]

I have seen the Enzo chamber and it only has a 4 valve arrangement, this is because combustion is better in a pent root type chamber than the 5 valve chamber.

[Bill Sherwood]

There's a lot more area for squish in a four-valve chamber. I don't have any actual values on-hand, but I have plenty of anecdotal evidence that says engines that make good power use very carefully shaped & clearanced squish areas.

[Powersteer]

For what i know and read Ferrari has the central intake valve opened 10 degrees earlier as an attemp to improve swirl. I guess 5 valve has too many valves close to each other so no flow for that 'next to' area like what signior Anderson described. This is probably why i saw an article that wrote the racing 5 valve needed more lift to valve size ratio than 4 valves and below. As for Ferrari, probably they paid rights to access the technology and might as well put it on road. Thier GT race cars aren't doing to bad and AUDI did well when they were racing BTCC. I don't think thier DTM V8s are 5valve/cylinder though.

[marion5drsn]

You people are bringing up S & Q and Swirl, something that I didn't consider when I drew the combustion chamber the first time! What you say just puts more nails into the coffin of the Five-Valve theory. M.L. Anderson