While looking through Boost’s Engine Design Guide for the hundredth time, I noticed something peculiar that I perhaps should have noticed earlier:
Even though DOHC and multi-valve setups were basically restricted to race/super-GT/ultra-luxe cars back in the late-1940s (if even that; most American luxury/sports cars were still using sidevalve or overhead-valve valvetrains back in 1947, with side valves being especially common on V engines), we still can use just about any valvetrain setup we want (besides DOHC 5-valve) right from the beginning of the game. Almost every other aspect of vehicle and engine building in Automation is limited/de-limited with time and technological advancement (as it should), but not valvetrains.
And yes, I am aware that Alfa Romeo and Duesenberg were using DOHC 4-valve in the late-1920s (in fact, DOHC 4-valve was invented in 1911, with Georges Boilliot’s Peugeot racer dominating the 1911 French Grand Prix with this valvetrain setup), and that Bentley was using SOHC 4-valve on their 3-Litre four as early as 1922, but those were extremely-expensive (and complex) vehicles that would have been way out of reach of even the richest of average Joes. So, to keep valvetrains in line with everything else, I propose these revisions to the unlock dates of DOHC/multi-valve valvetrains (these are rough estimates based upon my (admittedly limited) knowledge of valvetrains throughout the years):
*No multivalve setups until about 1965-1970 (SOHC 3-valve) and/or 1970-1975 (SOHC/DOHC 4-valve) (Perhaps even later)
*No DOHC until about 1955-1965
I would greatly appreciate the time taken to balance out valvetrain unlock years to make them in-line with the rest of the car/engine part unlock years, as that will make the game a bit more realistic (and more challenging) than it is now, where I can make a DOHC 4-valve engine in 1954 and get over 300 horsepower from a 4-liter V12.
Just so you know, Ferraris of the time were getting higher hp per liter numbers that same exact year (> 75 hp/liter).
About the availability of the different valvetrain setups, the more complex of a valvetrain type you choose, the higher amount of Production Units (PU) and Engineering Time (ET) you’ll be getting, that’s how the game penalizes you for selecting those.
Whereas technologies like electronic fuel injection, radial tires, or self-leveling suspension were very truly technologically infeasible or if nothing else extremely uncommon to the point of being beyond trivia prior to certain years, the primary limiting factor for valvetrain technology was its complexity. Nothing about DOHC / multivalve design was impossible in the 1940s / 1950s (and in fact it surfaced in several significant production vehicles) unlike some of the other technologies I listed. That and there was little reason for it before emissions and fuel economy regulations.
So basically, use any valvetrain you want in any year because it was fully possible, unlike other stuff which was often literally impossible. But realize that the real world’s vendetta against complex expensive designs applies to Automation as well. And subsequently stick to OHV and/or 2 valve designs until the 1980s.
To add to this: ETs will be a lot longer with the LC V3 for the multivalve head designs. That way they only really become feasible when you have gained enough familiarity with their 2-valve counterparts.
Also, don’t forget that more complex designs do get a reliability penalty. That may have to be increased still though.
Alright, that sounds good enough (and it would make DOHC/multi-valve setups more realistic in the early years, as those were pretty much limited to race cars, fighter aircrafts, Depression-era MGs, the Jaguar XK120, and the Pegaso Z102 from '46-'55). Perhaps I was a bit overzealous in wanting to outright ban DOHC/multi-valve setups to keep it “equal” with the rest of the technologies, when (as @kmBlaine pointed out) twin-cam and multi-valve setups weren’t not used because they were completely infeasible, but because they just weren’t worth the development time, service costs, and reliability penalties in the early-postwar period. (It definitely was possible to build regular DOHC engines even before the war; MG used DOHC 2-valve on all their models from 1930-'35, right down to the tiniest 750-cc PA/PB Midget, which is why they broke so many hillclimb records back in the '30s. but as their owners learned again with the MGA Twin Cam, they were a right pain to service and were so unreliable that MG had to resort to OHV for the T-Series Midgets - which was better for the time than most engines, but not as good as twin cams for speed). So, I’m glad to hear that DOHC/multi-valve engines will be getting balanced a little more compared to OHV/DAOHC, as right now, it seems that they might be a little bit too powerful for the early years. (And this will also make DOHC/multi-valve a more challenging option for campaign, as the reliability/reputation penalties early on will be somewhat balanced out with higher performance and economy post-1990.)
