Engine technology thread.

[xantonin]

Originally Posted by serialk11r

So sorry for the bump but did anyone notice this post? Dimman I know you were talking about Valvematic at some point.

Wouldn't the valves on a boxer engine be on the sides not the top? Thus not affecting the height at all?

[serialk11r]

Originally Posted by xantonin

Wouldn't the valves on a boxer engine be on the sides not the top? Thus not affecting the height at all?

Right, so you'd be adding a crapload of width to the engine. I remember width was the reason they kept the stroke so short on the EJ to give enough space for the front wheels right? The extra shaft on Valvematic goes between the valves and cam.

[Exage]

Originally Posted by serialk11r

If they reduce stroke to 75mm, and then increase compression ratio to say, 12:1, that would take off 32ish mm. If the width grows by a full 36mm, that would create some issues...and 75mm stroke is unlikely as people said. Rather disappointing since Valvematic reduces pumping loss by a ton (especially if the exhaust timing is right), and allows for better flowing ports.

It's unlikely that we'll see any cam-shift or variable lift mechanism on the engine. Subaru could implement i-AVLS, however all single cam-shift (lift) mechanisms are being replaced by the variable ones.

For the cost and simplicity sake of the engine I'd see them just running AVCS with the D4-S at high compression. 7Xmm stroke would work but not for production, depending on what the new WRX (and STI) cranks will be put in, I could see them squaring the FB up with stroke around 86mm.

Perhaps what should keep our eye out for is the aforementioned engines (WRX and STI), because I would be surprised if they kept the 90mm stroke as well (Dimman has eluded to this on more than one occasion). Has there been any word on the release of the new WRX/STI models? Or is it going to be a Toyota, Subaru launch fest at Tokyo?

[serialk11r]

Is there a chance that since the engine is shifted farther back (that's right isn't it?) that there is more room horizontally? That would leave more room for longer rods. But I guess they'd have to be planning on changing the rest of their cars as well to do this.

I don't think variable lift is much more complex than the current profile switching (at least not Valvematic). It basically adds a lever in between the cam and valves, and then an electric motor to control it, which I don't think is much more complicated than a camshaft with multiple profiles, a hydraulic locking system, and such.

I think we'll eventually see all cars have it since it is the simplest way to cut pumping loss at part load without compromising power. The problem with putting it on a boxer of course is the added height to the heads. A throttle is a pretty primitive device, it's like controlling an electric motor with a variable resistor instead of using voltage conversion. Valves are a pretty complex thing, but their presence allows precise control over a lot of things, which are starting to be taken advantage of.

[serialk11r]

Hey guys weirdish question, but does anyone know if there's a place where we can see EPA emission testing? More specifically, I'm interested in the Toyota 3ZR-FAE, which looks like an engine with a lot of potential that will be interesting to watch For whatever reason it's not okayed for the US or something...yet. I hope Lotus figures something out with them (or maybe the 2ZR to keep in line with their 1.8L lineup) for the future.

I find it a bit weird that these Toyota engines with A designation (Valvematic) aren't in the states while Nissan's 3.7L and just about every BMW engine has a similar mechanism...could it really be that hard to tune?

[Allch Chcar]

Originally Posted by serialk11r

Hey guys weirdish question, but does anyone know if there's a place where we can see EPA emission testing? More specifically, I'm interested in the Toyota 3ZR-FAE, which looks like an engine with a lot of potential that will be interesting to watch For whatever reason it's not okayed for the US or something...yet. I hope Lotus figures something out with them (or maybe the 2ZR to keep in line with their 1.8L lineup) for the future.

I find it a bit weird that these Toyota engines with A designation (Valvematic) aren't in the states while Nissan's 3.7L and just about every BMW engine has a similar mechanism...could it really be that hard to tune?

The fueleconomy.gov website has some basic emissions data below the MPG numbers and other stuff. They display the carbon dioxide output and the score on a 1-10 scale, pretty underwhelming. I'm sure there is probably a site out there with pages of emissions testing results if that's what you mean.

[serialk11r]

Hey guys this is something I don't quite understand, what is running rich for? Doesn't stoichiometric give you the most power theoretically?

[Dimman]

Originally Posted by serialk11r

Hey guys this is something I don't quite understand, what is running rich for? Doesn't stoichiometric give you the most power theoretically?

Remember that those numbers are theoretical averages throughout the chamber. Air and fuel are flying all over the place and not evenly distributed. Rich (excess fuel) ensures that more of the air gets used, whereas stoich can still have lean areas and is still a detonation risk.

[Exage]

Originally Posted by Dimman

Rich (excess fuel) ensures that more of the air gets used, whereas stoich can still have lean areas and is still a detonation risk.

My add on to your post!

Detonation can occur with to lean air fuel mixture because the burn is much hotter then the slightly rich mixture. This can cause localized hot spot/s within the chamber.

Get a spot hot enough and instead of the fuel air mixture being ignited by the spark plug it gets ignited by the hot spot throwing off and providing dangerously random ignition timing. It can be hot enough to melt the metal causing damage (think of a hole being burned through the piston crown for an example).

___________________

I was told that higher combustion temperatures will produce NOx. I'm not sure if this applies to near stoichiometric air/fuel ratios... I haven't researched it.

[serialk11r]

Wait that was also something I never understood, how does running lean create hotter temperatures? Shouldn't stoichiometric theoretically do that? If you run lean you have less fuel, and burning fuel adds more heat...

[Dimman]

Originally Posted by serialk11r

Wait that was also something I never understood, how does running lean create hotter temperatures? Shouldn't stoichiometric theoretically do that? If you run lean you have less fuel, and burning fuel adds more heat...

I thought you were the chemistry guy???

Something about the fuel absorbing heat? I failed chemistry in high school...

I just know if you want something hotter, you usually add more oxygen (cutting torches for example, acetylene by itself doesn't do much in the atmosphere, then it's mixed with oxygen in the torch, but you add the extra oxygen with the trigger for cutting and look out).

[serialk11r]

But the temperature after ignition is much higher than the temperature can ever get before ignition...sure before ignition the more fuel the cooler, after ignition up to stoichiometric the temperature is hotter the more fuel you add...there's no way to increase oxygen concentration since you pull air from the atmosphere, at least not without forced induction.

[Dimman]

Originally Posted by serialk11r

But the temperature after ignition is much higher than the temperature can ever get before ignition...sure before ignition the more fuel the cooler, after ignition up to stoichiometric the temperature is hotter the more fuel you add...there's no way to increase oxygen concentration since you pull air from the atmosphere, at least not without forced induction.

Are you forgetting about the compression?

[serialk11r]

Uh no...ignition is supposed to happen at maximum compression. The temperature is higher after ignition than before, otherwise your engine wouldn't make power.