From the Game at Launch thread, there are this many DLC packs and items planned:
• W8, W12, W16, W18
• Wankel Rotaries
• Flat 8
• Inline 8
• V4
• Two Strokes
• Diesels
• Hybrids
• Electric
I imagine this’ll all add up to $45 of DLC (at $5 each)? I’d buy all of them, hands down. Maybe there would even be a deal for that? Buy all 9 and get them for the price of 7 or 8? I don’t know, I’ll just buy it…
Of course we have no real idea about either pricing, if any DLC packs are going to happen at all, or when they would come out. To give you a bit of perspective on things though, here are my estimates for how much time it would take to develop the content with our current manpower and Automation 1.0 completely finished, focusing only on the listed feature:
• W8, W12, W16, W18 (3-4 months)
• Wankel Rotaries (4-6 months) (requires new Engine Designer)
• Boxer 8, Inline 8, Inline 2, V4 (2 months)
• Two Strokes (4-6 months) (requires new Engine Designer)
• Diesels (4-6 months) (requires new Engine Designer)
• Hybrids + Electric (6-8 months) (requires new Engine Designer)
That adds up to 23-32 months, i.e. 2-3 years, which is also why we want to smack people in da face (just in our thoughts of course) when they suggest it’s just changing a few values around. 
No… Don’t smack me in da face. D: Haha.
Killrob, I don’t mean to sound like the 1,000 other people who have asked about diesels, but why will it require a new engine designer? I see why it would be extremely hard, as you would have to change nearly every calculation, but the designer itself would be the same, right?
If I have understand right to change every calculation = new engine designer. There is also some different aspects that needs to be defined. You’ll have to change the user interface for diesel engine related controls and get rid of the things that only relates to petrol engines. So the only tabs in engine designer that doesn’t change are maybe the bottom end and exhaust… There’s not that much left from the engine designer we have at the moment.
Very true, almost everything changes, it’s not like you add a fuel type option “Diesel” and the rest stays the same. I’m not implying that this is what you said or meant. Most art assets could be removed, but the sheer amount of rewriting the calculations (also: turbos), testing them, balancing, getting them worked into the game, into the AI and all that… takes ages. :s