Engine technology thread.

[xantonin]

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

[Matador]

Originally Posted by Dimman

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...

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:

[Dimman]

Originally Posted by MatadorRacing_F1

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.

[1GoZoom]

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.

[Exage]

Originally Posted by 1GoZoom

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.

[Matador]

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

[Matador]

Originally Posted by Dimman

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.

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.

[NESW20]

"free-revving" means high rpm.

[Allch Chcar]

Originally Posted by MatadorRacing_F1

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

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 .

Good stuff . 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 . That and port fuel injection :hint: :hint:.

[xantonin]

Yes, fuel port injection.

Anyone care to explain D-4S?

[4agze]

Originally Posted by Dimman

Visual aid time, 4AGEs:

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

Here is my 4agze over size valve

[Exage]

Originally Posted by xantonin

Yes, fuel port injection.

Anyone care to explain D-4S?

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...

[1GoZoom]

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.

[Allch Chcar]

Originally Posted by Exage

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...

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.