Engine technology thread.
 

Going to start a thread for people to ask and answer general questions about the various tech used in engines.

So if you want to know the differences for example between, TVIS, ITBs, VVT-i and VTEC (the list of acronyms goes on and on...), ask here. But try to go through any existing questions first to avoid repeats.

First off:

Why are 5 valves per cylinder designs not necessarily the best setup for cylinder heads? (even though they sound awesome)

Short answer: 5 VPC heads have more flow interference on the intake side so the flow benefit is not as big as would be expected, the combustion chamber is not favourable for good flame propagation, and they tend to create hot spots between the valves. Overall they do not have the flexibility of the 4 valve per cylinder's powerband.

That's a pretty basic answer. I may get into it a little more after Matador answers, pending his future hangover...

I would like to know regardless

i'm all for four valve heads. although i will admit, a 20V 4age would be fun. :D

You can also forget about having direct injection with 5 valves per cylinder... for some of the reasons Dimman posted above in regards to the valves taking up combustion chamber space problems.

I'll let you know I might become a bit pedantic on this thread (, you've now been warned). I'm studying to become a specialized engineer that is able to work on and repair engines that make the Veyron Super Sport W16 quad turbo engine look like the engine out of a zip-zap car in terms of power output and displacement.

I'll enjoy putting some insight in and I hope to help with some questions and understanding. I usually end up learning something too!

If anyone's up for a little crash course in engine "basics" I'll be glad to post up some stuff.

Yeah I got a question. Why has it taken so damn long to come up with electronically controlled valves?

I thought this idea up years ago...

Because to produce something that would work at average 25hz (3000 rpm average use but since valve works only half the time..) reliably for 200000km(guestimated life span before replacement) at a low cost is not and was not feasible.

I see. I thought Toyota had already implemented this in an engine? Looking for it now...

Found it: http://en.wikipedia.org/wiki/VVT-iE

Guess I was wrong it's not really the same thing as a camless engine..

Have a look at the valvematic ;) now that's fucking awesome

I always thought the Coates rotary valve was a cool idea. I don't think it ever actually worked though. LOL

They claim "extremely higher RPM's" a 30% increase in efficiency and oil changes every 50k miles.

http://www.coatesengine.com/images/graphics/product.jpg

Visual aid time, 4AGEs:

4 Valve: (This looks like it's been worked on a bit)

http://i821.photobucket.com/albums/z...4vcompared.jpg

5 Valve:

http://i821.photobucket.com/albums/z...oblemareas.jpg

Starting straight off, the 5 valve can out-flow the 4 valve at low lifts with the same valve area. This is partly to do with the circumference (at low lift flow is around the outside of the valves, so it's not the area that is most important). 3 smaller valves are lighter than 2 larger valves of the same area. These are the same reasons that 4 valves are better than 2 valves.

Now the problems.

The green lines are the (exaggerated) intake flow paths. The more direction changes of the 5 valve has 2 effects. First it hurts flow, a bit. Secondly because this is after fuel is injected, the direction changes have more of an effect on the flow of the heavier fuel droplets. The result is that 5 valves do not have as even fuel distribution. This hurts combustion, and efficiency.

The red A's are the areas where the intake air interferes with each other. It's been shown on flowbenches that the simultaneous flow of the intake valves is less than the total of them measured individually. So the problem is a bit more magnified as the number of valves increase.

The red B in the 5V head is a bit of a hump that interferes with the flame propagation, partly because the plug has to be deeper. It sort of splits the combustion chamber into two halves, and this hurts the burn process.

You can also see that there is less material between valves, and this can cause problems with hot spots as they will heat up faster. This can also cause valve seat distortion (Ferrari endurance motor problem).

A problem that can't be seen in this pic is the smaller shims and buckets. It is my understanding that for some reason Toyota chose to use a shim over bucket design on the 20V 4AGE (not uncommon though). The smaller diameter shims limit the amount of the cam's lift, as large lift with small shim usually ends up with the lobe catching the edge of the shim and spitting it off in a destructive manner. This is correctable though.

Now consider these issues and the extra cost of grinding the cams, the cost of 25% more valvetrain, and you can see that the costs are probably not offset by the restrictions.

I have read on the 'Net, that whereas NA 4V 4AGEs can hover around the 240hp mark for totally built motors, the top 5V 4AGES top out at around 220hp.

And as for the good numbers of the 20V, it had individual throttle bodies, cam phasing, and had a more modern port angle (not the 'G' traditional 45 degrees). See below for my awesome diagram, also used elsewhere on here. Honda did it with 16V and cam lobe switching. I think that the B16 did it with less, so...
http://i821.photobucket.com/albums/z...edsautocad.jpg
Part is what 70NYD mentioned, part is that the electric actuators can't create the rapid accelerations needed. Cams smack the valves open and closed REALLY FAST. Particularly at high rpm. I think BMW experimented with your idea, but there is an rpm limit on what they do. Who knows? They may end up on future diesels once the reliability issue gets solved.

^ great read.

So am I correct to assume that if I wanted say a 200hp factory (un-modified) motor a 20valve would be a better idea, but if I were to want an all out power motor (modified) than 16 would be a better choice. Hypothetically speaking.

Maybe. But if you are choosing between a 200hp 16V and a 200hp 20V, both stock why go with the more expensive 20V?

I would still go with a 16V. The 20V's combustion chamber 'hump' causes response issues, and they burn more fuel for the same amount of power typically. Not even considering the cost difference.

That's just me, though. Some people get car-boners when they hear '5 valve per cylinder' (I used to).

Thanks for the info.
Now I shall wait to see matadors input on the subject.

What about Direct Fuel Injection? IE: The same thing diesel's use. I've read that more and more cars will be using this as it results in better performance and MPG.