Hello, I thought you could integrate:
-Dual ignition, twin spark ^^ (reducing emissions and better performance)
-The old distribution system with side valves (Flathead engine en.wikipedia.org/wiki/Flathead_engine)
-ERG valve
-Different systems for recycling oil vapors
sorry for my english very poor … I am a bad student, but I improves!
forced air cooling or liquid cooling…
according to year of manufacture and the funding available
The game starts post war and side valve engines were pretty much dead at that point. I think we would get more utility from straight 8s than side valve. Twin spark has been discussed before and they say it doesn’t really add much right now so there is no point to it. EGR valves would be nice to improve emissions since right now that is all based on fuel delivery, tuning and what cats you use.
Yeah, we’re already at a level of complexity we’re happy with. Time to get the game finished 
I agree, these are just ideas that come to me.
I’m looking forward to see the sequel (I’m certainly not the only one 
)
And what do you think of variable intake tubes?
A crazy idea certainly, after I stop I promise (for engine)
What about “Race Gas” for the sandbox? 116? So we can really build some monster motor’s…
after all, mainstream is what filters down from racing.
Also how about VW VR5 and VR6 engine’s?
Race gas, that would be fun! 
we already have 100 octane, race gas is usually 110-120, e85 is pretty much alcohol so its unlimited octane.
more fuels could be useful if it ain’t to difficult to implement. USA usualy has a 87-90 octane fuel as regular, a 95 leaded is also useful, Germany has aral ultimate 102 at the pump. Also E85 has 105 rating, not unlimited and pure ethanol has 108.7, but has 3/4 energy content of gasoline. Diesel fuel has 15 octane . Toluene aka Paint thinner has 140 octane.
diesel is meassured in c-tane, not octane 
wasnt aware of the paint thinner, though im not gonna start running that in my engine. Did some research on propane last night and found it had octance rating of about 105 while also burning a little cooler than petrol.
diesel is measured in cetane, but also contains isoctane in lower concentrations. after all it’s still distilled from crude oil. also this octane ratings are RON and do not represent the real octane content, but is an indication to compression resistance
I know the developers are busy… And I respect them, but I have to argue in defense for Side Valves.
“Side Valves are Dead”
Yeah, in the 21st century, but the game starts in 1940, and SV was still well in use a decade and a half after that.
Its an higher performance alternative to OHV, because it benefits from almost unlimited compression, will never knock,
and a cheap alternative to OHC.
If side valves were a feature, it would be easier to create a early high performance engine. Side valves have their place.
I think it would be a necessary feature to have in the end.
On a side note, I’d like to see throttle per cylinder single-barrel carbs an option, it is a cheap alternative to DCOE and it would be available before DCOE is, with similar performance.
Also, 6 seat (front bench) option for more cars. Comfortable, and more seats.
Depends on the domestic market… after WW2 most manufactors, infact almost all, either used OHV or (D)OHC systems. The last European car with SV was the Ford Taunis 12M and that was using a slightly more powerful engine of the 1939 Taunus. I dont know where you got the “high performance” alternative to OHV from, but SV just have the advantange of being cheaper and more reliable. They have worse airflow, a horrible combustion chamber shape and thanks to that fuel mixture needs longer to combust, leading to low RPM, high fuel consumption and bad emission values.
Short: They are worse than OHV.
The game will start in 1946, although tech year goes down to 1940.
About the Individual Single Barrels: Could be an option although its not common on production cars, show me an example please.
From what I remember, the individual single barrel carbs were planned to be included in the extreme engine configurations (that is, V12s and V16s).
Yeah! Looking forward to the hexadeca-carb setup!
A vote for flatheads…
Not entirely true, flathead engines are still being developed, built and used in lawn mowers, motorcycles, chainsaws, (ultra-light-)airplanes etc. just not cars (that I know of)…
Though I wouldn’t say they “would be a necessary feature”, I hope to see them listed as “to be considered” in what’s in and out, since it’s the only engine configuration I could think of that isn’t there and had at least some relevance.
So don’t get me wrong, I still would rather see wankels, two strokes and whatnot before I’ll really miss flatheads…
Otherwise I completely agree whith the above.
edit: Biggest advantage is the compact design and low weight per power, and that’s why they survived until nowadays, so don’t just say OHV is simply better or even call SV “extinct”.
The SV engines you mention are being built, not developed. All of them use ancient technology, and are among the worst performing engines in existence.
Lawn mowers: Briggs & Stratton, the engine has looked the same for decades.
Motorcycles: Harley Davidson SV engine, the last time something new happened to that one was 50-60 years ago.
Chainsaws: No idea.
Edit: LOW WEIGHT ??!!!?? what are you smoking? More compact than a OHV design, i’ll give you that. But lower weight, no friggin way.