Brucemation on: The restrictiveness of the families system.

[Leonardo9613]

Yes, I have to say that would be very very good, Daffy.

[maffc]

Seconded

[Killrob]

Yes, it is planned to put this into the tool tip for the family bore and stroke sliders because it is tight in the UI

[Slim Jim]

The GM v-6 fitted into SAAB and Opel, was at 2.8l. The larger versions of this engine is at 3.6l, with a estimated max of 4.0l

http://en.wikipedia.org/wiki/GM_High_Feature_engine

In other words, it was designed with a 4.0-liter capacity in mind, first. Then downsized to a 2.8. The 3.6 version came out before the 2.8 - further making the point. Start with the largest capacity you intend to use for the engine - then downsize as needed.

Yes, it is planned to put this into the tool tip for the family bore and stroke sliders because it is tight in the UI

Awesome!

[FordManFromHell]

I'd be interested to know how alloy heads improve airflow though, as that should really only depend on the shape of the ports and valves.

I might be very wrong here, but could it be that the aluminium cast would result just slightly smoother surface in ports vs iron cast, therefore, giving a better airflow?

[TrackpadUser]

I tried searching google for that info and depending on the sources, they either say that both get similar finishes, or that aluminium gets a slightly better surface finish.

At least that's what I found for sand casting, but AFAIK it will also depend heavily on the alloy used and how viscous it is when melted.

Although from what I heard, you actually want your ports to have a slightly rough surface so the airflow doesn't stick to them, so I don't know if the surface finish really makes that much of a difference.

[MWisBest]

On the topic of increasing bore and stroke down the line instead of only decreasing:
The Chrysler SOHC V6 started out as a 3.5L with 96mm bore and 81mm stroke. A smaller, 3.2L, version was later introduced with a smaller bore (92mm) but the same stroke, as has been mentioned here, and this idea makes sense. However, a decade or so after the 3.5L's introduction, it was expanded to 4.0L, with the same 96mm bore but with a 91mm stroke. So while I agree with the points about increasing the bore as a not-gonna-happen sorta thing, increasing the stroke shouldn't necessarily be out of the question. There's been a few people who've taken the 3.5L blocks and stroked them to 4.0L without extensive modifications as well.

[Daffyflyer]

Yes, but the problem is if you let people make an engine bigger then you can exploit the system by designing a 3.5 and then boring/stroking it to 4.0, then you'd have an engine that'd be lighter and smaller than an engine designed as a 4.0, which is a bit silly.


It's simple enough with the current system, the bore and stroke on the first tab is setting the MAXIMUM possible bore and stroke that block could possibly fit, then the varient bore and stroke is setting how much of that available space you actually choose to use.

[MWisBest]

Yes, but the problem is if you let people make an engine bigger then you can exploit the system by designing a 3.5 and then boring/stroking it to 4.0, then you'd have an engine that'd be lighter and smaller than an engine designed as a 4.0, which is a bit silly.


It's simple enough with the current system, the bore and stroke on the first tab is setting the MAXIMUM possible bore and stroke that block could possibly fit, then the varient bore and stroke is setting how much of that available space you actually choose to use.

Ah, I see what you're saying. Balance is something that I tend to overlook a lot

[Sayonara]

My two cents about this engine family affair:

The best match between Automation's engine family system and a real-life engine family is probably the Honda K engine. Every single one is an all-aluminum 16-valve DOHC with VVL, with engine capacities ranging from 2.0 to 2.4 litres; the differences are mostly tune, cam profiles*, and MPFI vs DI. Even redlines range from 6500-7500 RPM.

With that said the 2.0 litre K block has a shorter deck height than the 2.3 and 2.4 litre block, so one could argue that they're actually two different engine families as far as Automation is concerned.

*Honda uses two entirely different VVT/VVL systems for performance and economy K engines, although both are marketed as i-VTEC.

Although from what I heard, you actually want your ports to have a slightly rough surface so the airflow doesn't stick to them, so I don't know if the surface finish really makes that much of a difference.

The primary benefit of a rough intake port is an improved rate of fuel evaporation off the intake walls.

[Daffyflyer]

My two cents about this engine family affair:

The best match between Automation's engine family system and a real-life engine family is probably the Honda K engine. Every single one is an all-aluminum 16-valve DOHC with VVL, with engine capacities ranging from 2.0 to 2.4 litres; the differences are mostly tune, cam profiles*, and MPFI vs DI. Even redlines range from 6500-7500 RPM.

With that said the 2.0 litre K block has a shorter deck height than the 2.3 and 2.4 litre block, so one could argue that they're actually two different engine families as far as Automation is concerned.

That's probably about right, yeah.

I think most of the LS V8 motors would be the same family too, as would the Honda B18 and B16. Every flavor of Nissan SR would be the same family too I think.. (I'm pretty sure they're all the same external size?)

[nialloftara]

If the family started in the middle rather than the largest possible couldn't you apply a reliability bonus or penalty due to the wall thickness between the bore holes? So you could build a light weight, overbored engine but it would suffer due to thin walled design, and contrastly a thick walled under bored version would be heavier but allow better oil and coolant passages and gsin reliability. You could sink quality points into the bottom end to counter the thined walled penalty which would probably be for higher end motors like the LS7, it has very thin walls but due to its higher quality design is quite reliable untill you start to boost it which is why the LS9 has a smaller bore for a tougher block to handle the supercharger.
The same can go gor stroke length ad a large increase will lead to ovaling the cylinder due to the angle of the taller crankshaft.

[Daffyflyer]

I really don't see why we'd want to have a complicated system like that though? What is the disadvantage to specifying the largest capacity that will fit in the block when you design the engine?

[nialloftara]

Nothing really, just exploring options.

[Daffyflyer]

Fair enough! That's quite alright, but I'm just trying to understand what issues people have with the current way of choosing capacity.