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Family vs. Model VVL/Valves and throttle bodies


It’d be really nice and probably more realistic to move the number of valves and inclusion of VVL to the variant rather than the family.

Prior to DOHC 4V engines becoming ubiquitous it was pretty common for engines with long lineages (or even much less long) to be in the same family with varying numbers of valves. the more well known examples are probably the Ford modular V8 came in both single cam and twin cam varieties with valve counts from 2 to 4, as well as the various “quattrovalvole” models out of italy. Just picking the placement of the camshaft (block or head) might be the most freeing way of doing things and doesn’t allow for anything unheard of.

Would also be really nice to be able to base one family of engines off another, possibly with engineering time bonus/penalties depending on how similar the two are so you could, for example, cut a V8 in half to make an inline 4 or make a V12 from two V6s. This could possibly also accomplish the former as it isn’t very common to switch to fewer valves per cylinder, although Mercedes actually did for a bit in the early aughts.

Own little thing: For V10s, it would be nice to have the option of either odd or even firing crankshafts, basically like flat vs cross plane for V8s.

At the moment, particularly for single bank engines, throttle bodies have a giant jump from single to per cylinder. I recall a dev update on the subject of more options for induction, is that still being worked on? If it isn’t, a quick and dirty way reducing this jump might be to add a “big single” option of some sort.


This has been asked several times before, and (don’t quote me) it may even be in the FAQ. The devs have explained the reasoning behind the decision as something like (iirc):
You would be able to design a 1946 2-valve engine which would still be efficient and viable in 2015 by simply changing the number of valves.
Although it is done IRL, it isn’t compatible with the way the game is designed to be played, ie: “the way the factories work”


What problem does not allowing this prevent? I guess to put it another way, what is the game not simulating that makes this a bad idea? You can already build a four valve engine in 1946 and do exactly that. It’s not that uncommon for engine families to have persisted for decades, like the Miura V12 and rover V8.


As in, make a 4 valve, then 1952 same engine 2 valve, then '56 a 3 valve, all same block on same production line, et cetera, ad infinitum. Even though I’d like it (because IRL), it’s not my call. There are a great many posts on this topic, and you are welcome to search for them.


There’s also an aspect of engine families getting slightly better over time, mainly in terms of reliability and possibly production as time goes by, which isn’t implemented yet but is planned for the future campaign.

Letting people change the valve train would let you take advantages of bonuses by building a SOHC 2V engine for ever and then add valves as time goes by to make a super engine.


My opinion is that it would be great and immersive if head options could be changed within the same family. Many IRL engine families have done this.
However if that were to be allowed in game then engine families essentially become all about the block. I’ve said this before but I’d like to see the number of main bearings added to the block options. More bearing = more cost, engineering, weight & production, but also sees more reliability, perhaps higher rev limits on the crank & smoothness.

Also there would need to be more reasons give the player a reason to develop a replacement family instead of adding better heads. Perhaps some other values could be baked into the block based on it’s year of design. I imagine an alu block designed the 1960s would be inferior to one designed from scratch in the 1990s.
Perhaps upper limits on the improvement over time mentioned by trackpad, to emulate the idea you’ve taken this design as far as it will go.


Block strength and cooling system design are what comes to my mind. Let’s say that you have a 50s OHC design with 7:1 compression and making 80 hp, and you have a block designed to withstand some more pressure (let’s say, 10 atm) and with cooling ducts able to take some more heat (let’s say, enough to cool 140 hp). Now, a quick jump to the 80s, and you want to reuse that engine for your fancy new car, so you switch to a 4-valve DOHC head and add a turbocharger. By now, especially in such an advanced engine, your company would probably use MPI, thus leaving more octane for use - be it for compression, boost or other things. So now you have a 50s block with… hm, 8:1 compression with a 0.6 bar of boost on top of that, making 180 hp. It has to withstand 12.8 atm pressure and cool 40 hp more than it was designed for, so obviously it would overheat, warp, damage, fail - in short, die. But the game doesn’t emulate this in any way, instead limiting you by locking the head design within a family. I, being a perfectionist tinkerer-optimiser, would love to see this implemented, along with more advanced head design (flow, valve angle etc.) and more advanced block design (some cooling system sliders, bore spacing, walls thickness, main bearings, balance shafts…), but I understand why it wouldn’t really fit the game - in the end it’s a car company tycoon, not an engine design game.


It seems like they need to do something, in the current version you can already build an aluminum 4V (or 5V!?) engine in 1960 and the only technological advancement it can’t accept is VVL.


Aaand good luck with its reliability. Also I don’t know about the others, but I tend to optimise bore and stroke to the limits of the current tech, and that gives reasons for significant changes in 1967 (LWF pistons) and 1991 (LFC pistons and titanium rods) too.


I built two similar engines, one a DOHC 4V and one a SOHC 2 valves, 31 vs 38.

Oh wait I forgot changing the block material changes reliability. Those numbers are with iron block and heads.

Messing around with this I noticed a funny behavior on the dyno needles: losing power to valve float causes a drop on the manifold pressure gauge even if the flow bench doesn’t show any intake restriction.


This is not funny behavior, this is as intended.
Manifold restriction is things like throttle bodies and carbs causing resistance to airflow, thus the less air your engine moves, the less of an issue it becomes. Its expressed as a rough percentage of possible flow.
Valve float dramatically reduces an engines volumetric efficiency, that is the percentage of the stroked capacity that it refreshes each cycle (2 revolutions on a 4 stroke), thus for a given RPM your pumping less air, and your intake restriction percent will be less for a given sized carb or throttle body. Its not that the intake gets better at flowing air, its just not being tested as hard as your pulling less air though it. You can also see this in that often you won’t have any issues with a carbs intake restriction until after you open up a constraining exhaust, the engine is making more power and pumping more air, so limits that didn’t used to be binding, start to become so.

As for reliability, thats a very big difference, 22.5% more reliability for all other factors the same… but that gap gets even a little wider when you add into the fact not only does it cost less ($ and PU) which you can add back into the design in other ways (like carb quality), but quality on the SOHC 2v vavletrain itself is also cheaper AND once campaign mode is implemented you’ll likely have existing company wide tech points from previous familiarity with SOHC, while pre-1960 DOHC is very unlikely. Finally one of the big power benefits of DOHC or more valves is it experiences vale-float at higher RPM, but revving higher decreases reliability noticeably. All these things make the effective reliability gap for the given engine layouts even wider, and the power\emissions benefit smaller. Its not necessarily a bad choice still, especially if your wanting to go for a race car or hypermile, but its certainly not always a better choice to adopt high tech valvetrains early on. The game balance is pretty good in that regard.


Yup, I’ve recently found out that for early lazy engines the best choice is… OHV. Yes, taking efficiency into account.