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.

So, in other news I'm a total idiot. I didn't know what D-4S mean, and found this thread:
http://www.ft86club.com/forums/showthread.php?t=100

Ok, the weekend is over, the hangovers have subsided and here we go.

***I haven't read through the thread as yet, but for the first post, so bear with me***

5 valve heads were designed that way principally for more flow and velocity. I distinctly remember a design study showed that 5 valves were the optimum configuration before reaching the point of diminishing returns. Good luck finding that, cause I certainly can't get my lazy ass to google it. sorry. Yes, you do have more flow inteference, but overall, you will have more volume and intake velocity from three slightly smaller intake valves than two large intake valves.

Now it goes further, the valves themselves can almost be smaller and more importantly, lighter, so you have less inertia and this is obviously better for high rpm motors.

Then you get into the interesting stuff. VAG in some of their 20v engines has the central valve opens at a slightly different time than the outside 2 intake valves. By doing this, the engineers can change how the intake charge swirls in the cylinder by having the intake streams from the valves collide differently. IIRC perhaps Honda does this as well with their engines, but you know, 2 valves open is better than one.

Due to new engine technologies such as intelligent valve lift systems, valvematic, direct injection and the like, the advantages of a 5VPC setup has decreased and since packaging would be extremely difficult to have all the technologies integrated at once (not to mention costly) the concept arguably wouldn't be advantageous in a modern engine, but IMHO it certainly is not overrated in the era which it was used.

:happy0180:

Post #10 has more detail, including about when a 5V will outperform a 4V.

The only way I can see a velocity increase, is momentarily if one of the valves opens first. But that is very, very brief. Otherwise, no velocity difference.

Not so much a tech question, but i come from the land of low-rpm torquey motors. What does Toyobaru mean with the talk of a "free-revving" motor? Sounds like PR talk to me, but maybe they are hinting at something that I don't know coming from V8s and Superchargers.

It's a weird term and even I'm a little stumped by what Toyota/Subaru mean or are hinting at. In my context I take it that maybe they do indeed intend on a production higher-rpm naturally aspirated boxer engine. As in a engine that has a higher rev limit and or produces more top end horsepower than low end torque.

I have a 2ZZ-GE; my engine is "free" to rev to a 8200rpm redline... (the FT86 Concept 1 had a 7500rpm redline I believe). It's all just speculation though, so if anyone has other thoughts I would be happy to hear and engage. I have half a mind to plug in some numbers to see what they need to change on the FB20 to what they've stated as a goal, if this is indeed the case.

Low internal inertia a la 4A-GE, 2ZZ and 1LR I suppose.

Yeah, got around to reading it, but having this discussion with a couple mechanical engineers really drives it home. Some of my memory cells are defunct right now, and I'm not in the mood to debate so I'd gladly let you have this one for now. However, I'll google around to see if I can find a valid argument anywhere on the interwebs, there must be, cause, you know... I'm right. :bellyroll:

"free-revving" means high rpm.

Renesis, F20C are two more, both Rev to 9k. Some of the Subaru STI in the 2.0l size rev to 8k, those could be called "free-revving." Also the Toyota Altezza free revs to 8k, maybe that is what they mean :iono:.

Good stuff :popcorn:. One note is that the CR-Z uses a lower cam that only partially opens the second valve until VTEC engagement. Is that what you referring to Matador? That is to help with swirl or low end torque for those who don't know ;).

Direct injection is a nice point of discussion too :thumbsup:. That and port fuel injection :hint: :hint:.

Yes, fuel port injection.

Anyone care to explain D-4S?

Here is my 4agze over size valve

http://i223.photobucket.com/albums/d...r/valve2-1.jpg

http://i223.photobucket.com/albums/d...r/valve1-1.jpg

http://i223.photobucket.com/albums/d...r/valve3-1.jpg

Multi-point: The fuel is injected just before the intake valve during the intake stroke of engine. The engine effectively sucks in a/air fuel ratio during the intake stroke like virtually any of the previous fuel systems including carburetors.

Direct Injection: The fuel is directly injected into the cylinder, leading to enhanced control of fuel delivery, timing, amount etc...

D-4S from my limited look through combines both in the form of a low pressure point injectors and high pressure direct injectors also known as twin injection system.

I do remember that multi-point had some sort of advantage over direct injection (there is a reason) but I can't recall off hand what it was. It might have been greater mixture of fuel and air at higher engine rpm due to the engine drawing in air at a higher velocity? Can't remember, anyone?

NVM it's in the D-4S thread down. It's actually greater mixture at idle and low rpm...

Interesting stuff. Both my current cars are VVT DOHC 4V cars. When that Ti-VCT kicks in on the 6S Duratec 30, its a kick in the seat. It'd be gutless before then had I not swapped a larger throttle body from the new Mustang Duratec 37 and a set of shorty headers onto it. Now it pulls hard from 2K to redline. :) It also has cams, so that might help a teensy bit.

The Saturn's LE5, like I said I think somewhere, is torquey. It has what is called DCVCP. Pulls hard in the low band and at 3900rpm, the VVT kicks in and it roars to life. Just wish it had more power to match the throaty sound. :/

I'm fascinated by VVT systems. A good set of cams on a VVT head sounds like the end of the world, even on a four-pot.

Direct Injection injects the fuel as the piston rises while the combustion chamber is under pressure and generating heat. This cools the combustion chamber. The disadvantages is that it doesn't allow enough time to mix the intake charge. And that is why Direct injection is better under moderate-heavy loads and high rpm, from my understanding. A throttle body injection system actually allows more time for fuel to mix with air but it's been abandoned for the most part. It was more common for engines that were converted from carburetors to EFI before multi-port EFI became common.

Wait if it doesn't have time to mix intake charge, why would it be better at higher speed, when there is less time to mix?
Hmmm but if it switches to port injection at higher speed, that would limit torque at higher rpm since you no longer have the cooling effect of introducing fuel in the compression stroke, which increases thermodynamic efficiency...and this is supposed to get higher max power right? Or maybe the gains are just from better flow.

Pet peeve of mine. All the automakers naming their systems differently. I have to research every automakers newly named system just to know what they are talking about.

If everybody just stuck to something more specifically descriptive like 'cam-phasing' (eg: VVT-i) and 'cam profile switching' (eg: VTEC), plus how they operate and which ones (eg: IS300's 2JZGE has 'hydraulic intake cam phasing') I would be a much happier person.

^So what is what on those ones?

Well I think for Valvetronic, Valvematic, and whatever valvetrain designs that allow phase, lift, and duration control it'd be a huge mouthful, so maybe acronyms and weird names aren't so bad :D

This is why I had originally thought that the multi-point was for high rpm, but I read the article and it stated that the intake manifold (on the 2GR-FSE) had "high tumble intake ports". But as stated above DI allows for chamber cooling on the compression stroke, and therefore allowing higher compression ratios.

DOHC eventually became standardized, when companies were using Twincam, and even Quadcam for some of their motors.

Variable lift with cam phasing, is how I would describe Toyota's application of Valvematic.

There's pretty much only the three mechanisms I can think of.

Variable Valve Lift (Valvematic).
Cam Phasing (VVT-i)
Cam profile switching (VTEC)

Most of the named systems like VVTL-i, iVTEC, Valvematic, etc... are just combinations of these.

It's just wishful thinking on my part...

You should look at the older VTEC, i-VTEC, MIVEC, and VVTL-i systems (among others). You want kick in the seat? Single cam-shift... There is nothing that will replicate those systems in the coming years with Variable Valve Lift mechanisms (see BWM Valvetronic, Toyota Valvematic, Fiat Multi-Air etc...) being implemented. An interesting fact is that BMW Valvetronic and Double VANOS systems control the intake and exhaust valve lift so well that they don't need a conventional throttle plate to control the engine.

VVTL is probably the best name for Valvematic and whatever, cuz the way they alter lift also shortens duration. And I think VVTi and VTEC have the same effect, so why not just call them both cam phasing lol.

VVT-i and VTEC are completely different.

VVT-i alters the cam's position, like you would tuning with cam gears (advance, retard, overlap), on the fly. The ecu has pretty much infinite control of position within the range limit of the system. eg: anywhere within 30 degrees.

VTEC changes the cam profile used, as if you were swapping a cam (or two) on the fly. VTEC can change to a pre-set new profile that has more lift, overlap, duration, but it's either one or the other.

iVTEC and VVTL-i are basically the same, and do both of the above.

Valvematic I'm not super familiar with how it changes to affect the lift part of it, but it is used in conjunction with VVT-i's cam phasing.

http://www.youtube.com/watch?v=RHNXbGGvOdc

Get familiar, they'll become the norm haha.

Like a rocker arm that can change it's ratio on the fly, sort of?

What bother's me is that this has been out for a few years in Europe, but why not in North America?

We are very slow to adapt. Just look at how many people we have on dial up still.

Has it? I think it's in some particular American models or something, but only a few.
The base model Lotus Elise (which they don't sell in America, because apparently Americans refuse to buy <1.8 liters lol) has an engine with it I think. Probably are some emissions tests that for some reason they haven't done or had trouble passing for some reason, or maybe they're just trying to squeeze more profits out of the American market by getting rid of the old engines here lol.

Valvematic should give pretty good fuel efficiency increases I'm guessing because if you look at the rocker thingy if the lift is low, the valve also closes very early, so they have a very low pumping loss strategy of throttling, since reducing lift introduces some restriction, but reduces the air taken in as well.