Some Questions about engines

[TanTan95]

Hello there, I consider myself an engine guy but i am under no illusion that i know everything lol, and so while playing the game and reading some of the forums, some questions started popping into my head, and hopefully i can get some answers!:)

1) What is a flat 4 or 6? I always thought it was just another name for an inline? And what is the difference between a flat and an inline?

2) What are some advantages in having an V-6 v.s. a inline-6? Does the design of the V allow for more power?

3) I always thought that a larger bore, shorter stroke engine resulted in a higher RPM, lower torque. And that a smaller bore, longer stroke resulted in a lower RPM, higher torque engine, but when i attempt this in the game, there is not much of a difference between the two?

4) Veritable Valve Timing & Veritable Valve Lift. Are these options computerized? Like if a engine had them, are they controlled by a computer? I only ask because i was creating an engine for a Muscle Car, so i would want to keep computers out of it.

5) Last but definitely not least, when talking in-terms of a old Muscle Car's engine i always heard that if break even on HP per cu in (300ci getting 300hp, 400ci getting 400hp) was considered good anything above that ration was excellent (Naturally Aspirated). My question is what is considered a good ration by today's standards?

p.s. And when adding a supercharger or turbocharger, what is considered good for a ratio? 2:1..? 3:1...?

[Der Bayer]

Hey,

1) Flat engines have two banks of cylinders, similar to V-engines. The cylinders in a flat engine have an angle of 180° between them (that's why "flat"). But there are also V-engines with an angle of 180°. The difference to that is the shape of the crankshaft and the way the conrods are mounted to it. In a flat engine, opposing pistons will in move in the opposite direction, that means if one moves inwards (closer to the crank), the opposing one does that too. In a V-engine, if one piston moves inwards, the opposing one moves outwards.

2) The most important things are, that V6 engines won't be as long as inline 6s, but wider. I6s will run ultra smooth, V6s are not that good. In first approximation there is no difference for power output between both engines. All that matters is engines capacity. Remember: There's no replacement for capacity. Well, just more capacity.

3) Basically, you are right. Maximum RPM is influenced by stroke. If you have lower stroke, bore is bigger (at given capacity). But this allows for bigger valves and better air flow, resulting in more torque. In the upcoming engine designer revamp this will be happening, so no worries.

4) "Variable" valve timing and lift can, as far as I know, work both with an hydraulic and with an electronic system (someone correct me if I'm wrong).

5) Power output is a difficult topic and I don't want to start a fight between tuners and non-tuners. You can achieve high power outputs with small engines (see racecars) and there are engines with huge capacity and low power (for examle trucks). In general, more power from a given capacity will raise the stress on the components of the engine, thus lower the lifetime. You just have to know, what kind of engine you want to build: long lasting with lower power or a powerful unreliable one.

Greets
Martin

[TanTan95]

Wow, that answered a lot lol thanks. And when you say capacity, is that the same as the displacement? And a lower stroke bigger bore, is that what allows for a bigger valve and more air flow?

[Der Bayer]

Both yes.

[TanTan95]

thanks again!

[T16]

1) Flat engines have two banks of cylinders, similar to V-engines. The cylinders in a flat engine have an angle of 180° between them (that's why "flat"). But there are also V-engines with an angle of 180°. The difference to that is the shape of the crankshaft and the way the conrods are mounted to it. In a flat engine, opposing pistons will in move in the opposite direction, that means if one moves inwards (closer to the crank), the opposing one does that too. In a V-engine, if one piston moves inwards, the opposing one moves outwards.

Since it's flat and no boxer engines it doesn't specify if it's 180 degree V or a opposing piston setup. For an example see flat 12s which are 180 degree V even in Porsches.

4) "Variable" valve timing and lift can, as far as I know, work both with an hydraulic and with an electronic system (someone correct me if I'm wrong).

All the systems I have seen are electronically controlled with either a hydraulic or electric actuator. If some one knows of a pure hydraulic system in a production car I would love to hear about (I'm a nerd like that).

[Der Bayer]

Ah okay, I thought "boxer" was "flat" in english... Translation problem

[Daffyflyer]

@T16, Flat in this case is referring to Boxer


Re VVT and VVL, both are usually computer controlled, and will either use oil pressure and a valve to change the cam position (VVT) or to lock an extra set of rockers into play, thus changing to a higher cam profile (VVL)

[TanTan95]

Can someone explain what boxer is to me? haha. and i just wanted to know about the VVT and VVL because when creating a Good Old Fashion Muscle Car Engine, i would like to keep computers out of it, so now i know, thank you!

[Killrob]

TanTan, you have been asking a massive amount of questions, and while we appreciate your enthusiasm, to me it starts to feel like you think we are Wikipedia. Most of your questions would be answered very quickly there if you just did a quick search (please do so in the future):
http://en.wikipedia.org/wiki/Boxer_engine
http://en.wikipedia.org/wiki/Variable_valve_timing
http://www.nissan-global.com/EN/TECHNOL ... /vvel.html

I spent just 2 minutes finding these, so I doubt you'd have any trouble doing so yourself.
/Killrob

[TanTan95]

Sorry! The boxer and flat i could have looked up i guess thinking about it, but VVT and VVL i looked at and i couldnt fine anything about it being computerized, just what it was. And there isn't necessarily a defiant answer for 5, so it was just people's thoughts, so everywhere i looked for 2, 3, & 5. It turned into people bickering about they're answers. Since i couldn't any solid answered for those ones, i just posted um all. I'll dig deeper next time when questioning!

[T16]

@T16, Flat in this case is referring to Boxer

That's kinda obvious since you only have listed flat 4 and 6 and for cool engines stuff a flat 8 those make more sense as boxers (no flat 12 btw?) but that still doesn't mean the term flat is the same as boxer.

[thereddaikon]

Technically flats and boxers are not the same, but in general conversation they are used almost interchangeably.


As for power it really depends on what your goals are. over 100HP per Liter is considered high output for an engine's displacement. But that isn't super common. The main reason being the higher specific output you have the higher wear you get on the components of the motor and the higher quality and thus more expensive components you need. Take the Honda S2000's motor for example, it is a 2.0L that produces 240HP and has a 9000 rpm redline. To have such a high output it needs to rev very high, but it is also a highly stressed motor. It's cam is very near race duration and if it wasn't for the VVT it would have a bad idle. You wont see output's this high from many other engines save for people like Porsche or Ferrari. More modern metallurgy techniques and advances such as direct injection, VVT and other things have improved the specific output while maintaining reliability and driveability so it isn't as one sided as it used to be. Back in the day if you wanted a high output you either had to go very big like Muscle car V8s or have a very high strung motor. The 302 in the Z28 Camaro made around 360hp which was great for back then, the 302 being close to a race spec motor but that is 73hp/L, a very respectable number still today but far from the 120hp/L in the S2000 or the 124hp/L of the Ferrari 458. You can also bet the newer motors make fewer emissions, are more reliable and also get better fuel econ. This is just the progression of technology.