Can you choose the idle RPM in the final version?
No, it is deemed reasonable that the optimum idle RPM is set automatically as it doesn’t add any gameplay value to decide on it yourself and as such would be a waste of time.
Also, wrong forum. 
Yeah, as it would change pretty much nothing about the engine there isn’t much point
i would deem it actually a very Important part of the game, Seeing as changing idle rpm can effect Alot of things in real life… Ontop of that what if for say you had a 12k redline engine and you needed 4k to keep it running in the winter before startup… Adding additional real-life variables is important to a realistic game… just consider that guys.
I can’t imagine any car stats that are going to be effected at all by idle speed, its not going to make a difference to performance, it’ll only make a minuscule difference to economy and engine wear. Its not going to change the cost of it. Peak loudness is usually at high throttle and revs so its not going to do that.
What extra interesting game play choices and decisions make this a worthwhile addition. Is it going to be something that has any use at all on most cars anyway?
Highly cammed engines already idle poorly, so that’s covered anyhow.
Whenever we add a new variable or option or gameplay mechanic in the engine designer we need to weigh up the negatives, and I’d say these are the three test it needs to pass.
It needs to be all these things.
A: A key technical part of real life engine design, the kind of thing that that is a major focus of real life engineers, not a small engineering chore. Full power and Cruise fuel mixtures: Yes. What temp the thermo fans switch on: No.
B: An interesting design compromise, there have to be disadvantages and advantages to each choice in the gameplay mechanic. If you’d only ever really want to leave it on one setting then its not an interesting mechanic.
C: A worthwhile tradeoff for the effort required to develop it, considering that there are a practically infinite amount of features we could add to Automation, they need to be weighed up against each other, for example would it the best use of our time redesigning the user interface to fit an idle speed slider, working out the best way to impliment the calculations, testing them, and then giving our test team a few weeks of work retesting every scenario to ensure that the scoring limits are still correct, even with the addition of a new variable in engine design. No, it probably wouldn’t that time would be much better spent working on Turbos, or the Car Designer. Both features that are likely to offer much more reward to the player for our work.
Hopefully this gives everyone a bit of an insight into why we don’t just implement every single aspect of engine and car design that comes to mind, or every single gameplay mechanic we could think of.
Will idle vacuum change based on the cam profile? It’s more eye-candy than anything else, but I think more compelling than an idle speed adjuster. It wouldn’t require any UI changes, and the calculations could be “simplified” just by having an inverse relationship to the cam profile (and not take into account the compression ratio, engine size etc.).
I know it’s a long shot, but I figured I’d ask anyway since we’re on the subject… 
Yeah, I think the vac gauge reflects it correctly 
Ohh, nice reply Andy, nailed it!
Don’t know how I missed that. The changes are subtle, but they’re there. That’s so cool!!! 