Stream-of-consciousness car build

I was thinking about the way that watching LPers has helped me figure out games like this, and while I don’t have good video recording software, I have a copy of Notepad and a willingness to blather endlessly. So I went through my car-building process and tried to document it as best as I could, in case that helps anyone else build better cars. It’s roughly broken up into eight steps, although they’re not of equal size.

I. Make a general plan of attack.

For this demo, I decided on a 2005 luxury sports saloon - competitor to the Jaguar, BMW, Lexus, etc.

II. Pick a reasonable body, style to taste.

I picked the 1995 26.5m/104.3" 4-door sedan body, stretched out the trunk as much as possible for easy loading of cargo, tried to equalize the front and rear doors (after all, a lot of our customers are going to be riding in the back typing on their PDAs), and generally fiddled with the body shell until I was bored with doing so.

I didn’t touch the wheel arches, though. That’s because I need to hit the next tab to know how much arch I need. I did put three points into quality, though - after all, this is going to be luxury.

III. Blueprint the chassis based on your plan.

Unless you need to make a very high-utility car, Monocoque is generally better. Also, I’m going straight to AHS steel - there’s no need to scrimp, but no need to be ridiculous, either. Thinking it over, I see no reason to move away from Front Longitudinal engine placement, either - a simple rear-wheel drive setup is the usual thing for this kind of car, and I don’t see a reason not to use it here.

Because, in the real world, some of our customers might want to armor-plate this beast, we’ll use a MacPherson Strut for the front suspension (higher load capacity) and we’ll go ahead and splurge on the MultiLink for the rear. MultiLink also has the advantage of allowing wider tyres to be fitted in there; I can easily flare the rear wheel arches to fit 255 mm tyres. I stop at making space for 225 mm tyres in the front, as the arches are already looking a bit silly.

For the panels, I’ll use aluminium, for a good compromise between safety, prestige, and weight. And I give the whole thing +3 quality for good measure.

IV. Decorate the car.

As long as you put reasonable fittings on the car, you’ll probably have enough cooling - so make it look good. A good trick is to use grilles and vents as decorative moldings, or to add some nice chrome accents. In many cases, you’ll want to have lips and/or wings for aerodynamics - I go with lips.

I used a couple tricks when I was making this - some more obvious than others, some more ubiquitous and standard than others:

[ol]]Putting grilles on top of grilles to add a more interesting chrome pattern./:m]
]Putting indicators and lights in grilles and vents./:m]
]Using a hood scoop as a roof vent for the cabin./:m]
]Using a lip as a spoiler on the trunk./:m]
]Using the round squarish grille on empty body molding mode to make a license plate holder./:m][/ol]

Finally, I once again added +3 quality. I really want this thing to stand out as a well-made vehicle.

V. Approximate Engine

I happen to know that V8 Crossplane engines are very smooth. An inline-6 might be smooth, too, but I put dual exhausts on the body, so I should actually use them. Also, short stroke engines have less vibration, so I build an oversquare 3.5 L (3498 cc) engine - 84.0 mm by 78.9 mm.

Aluminium block and heads is pretty standard in this era - I’ll just go with that. And a low friction DOHC setup seems like the thing to do, too. And given that this is a high-end vehicle, I should at least have the high-tech options, so I go with 4 valves per cylinder and VVL, too.

I then fill the bottom-end with forged parts - forged crank for smoothness, I-beam steel conrods and lightweight forged pistons for revving. I’ll probably add some quality later, too.

Compression I drop to 9.0 temporarily - compression is usually the first thing you drop for performance. Cam profiles I leave at default. In keeping with the high-tech, I put some VVT into it, too.

This engine I’ll make NA. Turbochargers are nice, but I don’t think they’ll be necessary here.

I go ahead and use multi-point EFI with a standard intake - might as well save a little money, and standard intakes mean less noise - and I push the RPM limit up to 8000 to see if I can get away with it.

For the exhaust system, long tubular header mean more production hours, but better airflow - and they’re actually a bit lighter for some reason. (Might be a bug?) I then fit a high flow cat and Conedodger240’s favorite muffler setup: reverse flow and straight through.

Then I start the test.

VI. Engine Refinement

I never expect my engines to be well-optimized to start with, and this is no exception. The two big things when refining your engine are octane rating and RPM rating. (Torque can also matter, but this is more rare.) If your engine is knocking badly, you drop compression; if your engine is spinning into pieces, you either fit better internals or lower the RPM limit. If your engine has a lot of fuel octane to spare, you figure out how to use that effectively.

In this case, I have valve float and I have a lot of surplus RON. I decide to go down to regular unleaded for now (surplus RON doesn’t have much effect on the engine at all - if your car needs regular, premium isn’t likely to make it last longer or drive faster), and take a look at the valvetrain to see if I can button that back down.

In the valvetrain window, I make the cam profile more aggressive and I add a little bit of quality. Not much, though, because I notice that quality is very expensive here - something like 7 production units per tick. Cam profile adds a lot of power and I notice the exhaust system is starting to choke the engine, so I jump over and open up the pipes a tick.

I notice Smoothness is at 69.0, so I jump back to the bottom end and add 2 points of quality - just enough to bump it over 70. (I like round numbers.)

Next, I roll down to the fuel tab again to adjust ignition timing. Timing is tricky, because sometimes you have weird drops in the curve, so I generally go by large leaps first, then play around a lot when I’m fine-tuning to make sure I’m hitting the optimal performance timing (or my octane limit, whichever comes first).

In the end, I’m jumping around between base cam profile (the lower cam profile determines knocking), compression, fuel mixture, and ignition timing, looking for a compromise between a torque curve I like, reasonable fuel efficiency, and optimal use of my available fuel octane. I ultimately decide I’m satisfied with 22.29% economy (345.0 g/kWh) on fuel burned and 330 hp at 7700 RPM. And the relatively close regular and VVL cam profiles make for an engine which, rather than beginning to blare once the aggressive cams kick in, simply and steadily grows louder from idle to 8000 RPM.

VII. Approximate Vehicle Design

First tab is the drivetrain. For this, I decide to splurge on a fancy six-speed sequential gearbox - much less driver effort than a manual, much better performance than an automatic with a torque converter. Given how generously I festooned this car with cooling vents, I don’t put too much stock in the “Est. Top Speed” line; for now, I’ll set the gearing up for 208 mph and see what happens. Finally, I give it a viscous limited-slip differential - a fairly good standard option, and much cheaper than a geared LSD. I give it two points of quality, but looking at the hovertext I can see that quality is expensive here, too.

Next, wheels. The car has looked pretty stupid up to now with its little wheels disappearing into the wheel wells - I enbiggen them and widen them up to use most of the wheel well, and fill the rest with offset - if I have to, I can push them to the limit later. Sports compound tyres are a probably necessary expense, and alloy wheels the obvious choice.

In a departure from my usual habit, I choose vented discs all around, with 3 pistons in the front; I’m thinking a smaller brake disc with more pistons will make for more comfortable braking. For the rear, I use 1 piston, as usual. Pad types are for later.

For aero, I skip immediately to Fully Clad and install Cooling Flaps for extra fuel economy. Wing angle I’ll look at later, when tuning the downforce from the front and rear lips. Extra Cooling Airflow makes for better reliability, but I figure that double the engine requirements will be sufficient for the vast majority of situations. I skip the brake airflow altogether. Also, I give it +3 Quality because I know aero quality is cheap.

For the fittings, I give it Luxury seats and Premium SatNav. I don’t see the need for Launch Control, but I give the driver power steering, ABS, TCS (traction control), and ESC (electronic stability). I expect to add some quality later - we want to have nice options for the TV presenters to drool over here. Advanced 00s safety seems like another good bet.

For suspension, I forgo the fancy stuff and use progressive springs, gas mono-tube dampers, and passive sway bars. I’ll start with a Sport setup and make it more to my liking later (although I reflexively raise the ride height to minimize bottoming out).

VIII. Vehicle Refinement

This is the part of the process that is most in flux for me. Between the following steps was a lot of playing around in tabs that I didn’t document.

This time, I start off by getting rid of the rest of the bottoming out - I push up the ride height and stiffen the front springs (the rear doesn’t seem to be bottoming out, judging by the effect of stiffness there).

Next, I go down to the brake window and get rid of the Brake Fade by changing the rotors - the rears turn out to have some diameter to spare, but the fronts require a little enlargement.

Then I go over to the wheels. I don’t want to use the Quality slider here - judging from the forums, it’s seriously OP for competition purposes - so instead I just play with the sizes and the offsets. I end up putting much bigger tyres on the rear than the front to handle all the power coming out of the engine, but I notice that this makes for a very understeery car - I’ll probably want to see if I can do something about that later. (I think widening the front tyres again should probably be a last resort.)

For testing purposes, I go down into the Gearbox tab and set up the spacing to put the engine horsepower just at the limit of grip in second gear. I’ll want to adjust the top speed and spacing sliders again later for fuel economy, but I figure I need some basis to work with when tuning the aero and suspension.

Before I tune those, though, I need to have the total weight and weight distribution locked down. So I go into the fittings tab and giving it +1 quality on seats and +3 on electronics. Because this already has my safety at a 65, I decide that’s good enough I don’t need more safety quality. I do, however, add another point to the drivetrain and two to the suspension.

At this point, I decide I’m ready to set up the suspension. Generally speaking, my strategy is to look for a few things:

[ul]]Zero bottom out./:m]
]Very little bouncing in the bump test (left graph)./:m]
]My favorite numbers (sportiness, drivability, and occasionally comfort) to go green (up) instead of red (down)./:m][/ul]

…plus one more thing:

[ul]]High traction on the skid pad in the next tab./:m][/ul]

After playing with the dampers and roll bars (I end up putting extremely soft bars on the front and stiff on the rear), I start looking at camber. I know, intellectually, that for power you want minimal camber, but for cornering you want a substantial amount of negative camber, so that’s a thing that I play with. Given how understeery the car is - and given that the driven tyres are in the rear - I figure I’ll start pushing the front camber and see how much I can improve. I start off with 34.6 mph @ 20.0 m and 120.5 mph @ 250.0 m. By pushing the angle to a probably-excessive degree, I increase that to 34.9 mph @ 20.0 m and 121.8 mph @ 250.0 m.

Then I start playing with the wing angle. I end up starting out with maximum wing angle, front and rear, and then backing off to see where I lose grip in the 250 m circle. The car still has lift at that point, but it brings me up to 122.5 mph @ 250.0 m - nearly as many g’s of acceleration as I have at 20 m.

…at which point I discover, to my embarrassment, that the Downforce slider is not meaningless here. Playing with the slider in increments of 10, I find at 40 I get an improvement in 250 m g’s, at 70 another improvement, and at 100 still another.

74/100 wing angle then admits retreat back to 63/100 at 100 downforce without losing grip in the 250 m circle. 74/100 wing angle allows retreat to 94 downforce. The former proves more efficient aerodynamically. Having created this maximum-downforce arrangement - 123.3 mph @ 250.0 m - I go back to the transmission tab to optimize there.

Transmission optimization I begin with the Top Speed slider, looking for maximum fuel economy. Having found that, I adjust the spacing for 0-62 mph time again.

Finally, because I forgot earlier, I decide to soften the brakes a little. The brake tab has a perfect display for the purpose on the right, showing how much grip the front and rear tyres have and how much braking force the pads have. I adjust the brakes to just exceed the available grip, front and rear. (I have noticed, mind, that additional rear braking force reduces the stopping distance; however, the benefits of comfort I think are often worth this price.)

The end result?

A pretty decent executive saloon car. Total manufacturing costs of $16,326.76 probably corresponds to an MSRP between $32,500 and $50,000 - significantly cheaper than a Mercedes-Benz E-series - and for that, you get a highly comfortable vehicle with all the luxury options that does a sub-9-minute lap of the Nurburgring right off the showroom floor, and sub-1:30 at the Airfield Track.
Test Car (21.9 KB)