I know i shouldn’t post this but I think this would help or not.(No , I don’t play this)
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Yeah, I’d love to compile a list of what is good stats year by year, but I think there’s too many variables to make a solid number. And even if we could, I don’t want to be the guy to spend all that time trying to make that list…
@Lorenztype While what you asked for was already in the guide, I’ve added some pictures to make it easier to understand
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No I don’t mean you should do it, I think we can all contribute to it on discord (because it’s easier), on what is an average stat for an 80’s economic car, etc… it would be a huge work but if several people contribute it’s less complicated 
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I understand all but i posted that for some new players that don’t know some things.
Part 2: Engine Families
First of all we have the engine family tab. Now this should serve as the base for multiple engines in different trims or even models, so you want to think about how you set up an engine here so it can be adapted for as many models as possible. Doing this saves money and engineering time.
On the left you can change the family name, and on the right the variant name (Like trims of a car).
In the top left of the screen we have the family year selector. This year has to be before the variant year.
First of all we have the configuration of the engine. At the time of writing we have 4 configurations, and a total of 13 different types of engine.
The configuration can change the way your car turns out drastically, so this choice is important.
I3 - This has the lowest costs, ET and PU of all the engine types. It is the second lightest engine type, and is generally good for budget cars that need to be produced cheaply and quickly. The downside to it is that it is very unsmooth, and also is unable to rev as high. This is available from the start of the game.
I4 - Basically a larger I3. A bit smoother, a bit more expensive, a bit higher ET and PU. This engine is most common in real life, especially in more normal and standard family cars. It is also available from the start of the game.
I5 - Between the I4 and I6 in everything. Unlocks in 1970
I6 - This is the second smoothest engine type, and currently the best engine to turbocharge because the six cylinders are all feeding into one turbo. Works well for lower end luxury or sports cars. Available from the start.
60 degree V6 - This is the lightest engine configuration, and is fairly good at everything. It is also very compact so it can fit in lots of bodies. This engine isn’t great of turbo charging, and has a much longer ET and PU than I6s, while being much less smooth. Still smoother than I4s unless you’re an idiot that makes silly I4s. Recommended for sports cars and track cars. Unlocks in 1960.
60 degree V8 - Slightly larger than a V6, and a bit heavier and smoother. Is available from the start of the game.
V12 - The largest, smoothest, most expensive, highest PU and ET engines. Very prestigious. Good for super and hypercars, and luxury cars. Available from the start.
90 degree V6 - Less smooth and reliable than a 60 degree V6. The only reason you would pick this over a 60 degree is if you have familiarity built up with 90 degree V8s. Unlocks in 1960
90 degree V8 - Smoother and more reliable than a 60 degree V8, as well as lower ET and PU. Slightly more expensive and heavier though. It can have the choice between a crossplane and flatplane crank. Available from the start.
V10 - Somewhere between a V12 and V8. Useful for when prestige matters but you can’t quite fit a V12 in an engine bay. Unlocks in 1985.
V16 - The biggest, heaviest, most prestigious engine currently in Automation. If smoothness and prestige are important, this is the one to go for, but beware that not many cars will be able to fit it at any size. Available from the start
Boxer 4 - Heavier, but a fair bit smoother than a I4. The other advantage of these is the low centre of mass they provide. This means you can usually improve handling with this engine option. Also can only have twin turbos, unlike the I4. Available from the beginning.
Boxer 6 - Less smooth and heavier than an I6, with slightly higher PU, but far smoother and with lower PU and ET than V6s. Lower centre of mass means it can improve handling. Available from the start.
Family Capacity is where you can set the maximum size of an engine family. Any variants of the engine you make can be smaller, but not larger. You can change capacity in two ways, changing bore, and changing stroke.
Bore - This is how wide the piston is. This increases weight quickly, but is also an easy way to increase capacity. A higher bore can also increase the chances of running into valve float. A lower bore lowers octane, increases smoothness, and reduces service and material costs.
Remember the flow bench I mentioned in part 1? This is the first place where you can influence that. If your valves are restricting flow, a larger bore increases the size of the valves, so reduces the restriction.
Stroke - This is the distance the piston travels. This adds less weight than increasing bore, but quickly limits RPM in the bottom end components. A lower stroke allows you to rev higher, increases smoothness, and reduces service and material costs.
When an engine has a higher bore than stroke, it is called oversquare, and when the bore is smaller than stroke, it is undersquare. Oversquare engines are usually better at revving high, although can run into valve float issues, while undersquare engines are usually lighter and more compact.
The advantages of having more pistons is that you can have a lower bore and stroke without losing displacement, so you can rev higher without running into reliability issues. They are also usually smoother. The downside is more cylinders are usually more expensive, and have higher ET and PU.
Also bear in mind that having more cylinders means you can have the same stroke and just lower displacement, so there are times where you could have an equal displacement V6 and V8 with the same stroke, but because the V8 can have a much lower bore, it could be lighter.
A good idea is to try and make stroke as high as you can to reduce weight, but just low enough to not damage your internals from high RPMs. Also bear in mind that you may want to take into account that other variants of your engine families could require a higher redline, so it is all a balancing act to reduce weight while maintaining high RPMs.
There are 4 different block materials and 3 different head materials in Automation, which can make a significant difference in making a good car.
Cast Iron - This is very heavy, cheap, and simple. Also the most reliable out of all materials, and reduces loudness the most. Available from the beginning.
Aluminium - Far lighter, but in the early years has a massive reliability penalty compared to cast iron. By the 80s and 90s it becomes reliable enough to not be too much of an issue. Aluminium heads unlock in 1950, and the block in 1960.
AlSi - Short for aluminium silicon, basically a better aluminium. Lighter, more reliable, lower ET if you match materials for head and block, and the only real downside is that it is slightly more expensive. Also matches loudness with aluminium. Any familiarity with aluminium should also help you engineer this, so there’s no reason really not to pick it vs aluminium. Unlocks in 1996.
Magnesium - This is only available for block material. Lightest of all the materials, and doesn’t have too much of a negative effect on reliability. Second quietest block. Unlocks in 2005.
You can mix materials between head and block, but this isn’t really recommended. In real life it wasn’t uncommon to see a cast iron block with an aluminium head, and in game that does also improve reliability compared to an all aluminium engine. But anything else is basically pointless and reduces reliability, for example an aluminium block with a cast iron head reduces reliability as much as an AlSi head. Mixing materials also increases PU by a small amount.
Head and valves are also very important to your engine. These can change drastically the cost, ET and PU of an engine, along with how high it can rev and how fuel efficient it is. As a general rule as you run down the valvetrain options, parts can rev higher and are more efficient, but also a lot more expensive. All valvetrain options are available from the start, but not all valve numbers are.
Pushrod (OHV) - This is incredibly basic. Cheap, low revving, and will quickly run into valve float issues. Popular on muscle cars and trucks, and is still used today, most famously on Chevrolet and Dodge muscle cars. Very compact and light too. Also much shorter than other valvetrains.
Direct Acting Overhead Cam (DAOHC) - An upgrade from OHV, and allows for a decent bit higher RPM at a slightly higher cost, and is larger and heavier. This will also develop familiarity with DOHC.
Overhead Cam (OHC) - Common in the 80s and 90s, but less so today. This is fairly usable throughout the entire game. Also the same size as DAOHC, but a bit heavier.
Dual Overhead Cam (DOHC) - Double the fun of OHC. Rather expensive, but does allow for the best results. In real life this is the most commonly used type of valvetrain today. Very large and heavy.
The number of valves can also have a large effect on ET and PU.
2 - This is available for all valvetrains. Cheap and simple.
3 - This is exclusive to OHC. A nice middle ground between 2 and 4 valves.
4 - Available from the beginning for OHC and DOHC. An interesting thing to note here is that 4 valve OHC engine is better than a 2 valve DOHC, and cheaper too, but will encounter valve float earlier.
5 - Available from 1989 for DOHC only, and doesn’t allow VVL on the engine.
Increasing the number of valves can also reduces any flow restrictions the valves give in the flow bench.
Having VVL can be a major benefit as it allows you go adjust a low RPM and high RPM cam profile, allowing you to get power and still keep fuel economy. The most famous example of VVL is VTEC. In game it unlocks in 1994.
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Engine Design Guide: Part 3 - Bottom End
The bottom end (also known as internals) is the core of your engine. The components you pick here can change significantly how fuel efficient, environmentally friendly, or reliable your engine is. There are 3 components to pick from here, and your first quality slider.
The first component is a crankshaft. This is what transfers power to the gearbox from the engine. It can usually take more slightly more RPM than the other two components.
Cast Iron - This is cheap and simple. Nothing more.
Forged Steel - This is stronger, can take more torque and RPM and is lighter, but requires a factory with a forge works, which is expensive, and has a higher ET and PU. Cheaper in material costs than cast iron. Available from 1956.
Billet Steel - The strongest crankshaft available. Can take a lot of torque and RPM, and is light, with a bit more ET and PU, but requires your factory to have a CNC Shop. Even cheaper than forged steel in material costs. This unlocks in 1986.
Flat Plane vs Cross Plane Cranks
If you select a 90 degree V8, you’ll be able to choose between “regular” cranks (cross plane) and flat plane cranks. From the little I actually understand about these myself, a flat plane is similar to a crank you’ll find in an inline 4 engine, and has a different firing order to cross plane. This gives it a different sound, so if you care about that, awesome for you.
Cross plane V8s are smoother, a bit more reliable, and have very slightly lower production units.
Flat planes are slightly lighter, and very slightly cheaper. They also give a very minor boost to midrange power. From my testing you’ll usually gain about 1lb-ft of peak torque, at least on NA engines.
The next component is your conrods. This connects your pistons to the crankshaft. It usually has the same limits as the pistons in RPM and torque.
Cast Iron - Cheap and simple.
Heavy Duty Cast - Useful in the early years for powerful and low revving engines as it can take a lot of torque, but has a low RPM threshold and reduces smoothness. They are also slightly heavier. Available from the start.
Heavy Duty Forged - Like the cast version, but lighter, smoother, and can take RPMs equal to a cast iron crankshaft. Requires a forge works, and is available from 1956.
Lightweight Forged - This can take more torque than cast iron, and higher RPM than anything before it. Unlocks in 1967.
Lightweight Titanium - This can take as much torque as heavy duty forged, and more RPM than any other conrod, while also being smoother than any other. Requires a CNC shop and unlocks in 1997.
The final component is pistons. Changing these can drastically change your engine’s emissions and fuel economy.
Cast Iron - Cheap and simple.
Heavy Duty Cast - Useful in the early years for powerful and low revving engines as it can take a lot of torque, but has a low RPM threshold. Also slightly heavier and less smooth. Available from the start.
Forged - This can take as much torque has heavy duty forged conrods with a bit higher RPM, but can’t rev as high as lightweight forged conrods. Forged pistons also lower octane by one RON, but increase emissions and loudness… Requires a forgeworks and is available from 1956.
Hypereutectic Cast - These pistons are like cast, but lower emissions a lot. They are also the quietest pistons. Unlock in 1970.
Low Friction Cast - These are like cast, but improve fuel economy drastically and lower emissions by a lot, while also increasing smoothn. They are also slightly more limited in RPM. Unlock in 1992.
Lightweight Forged - These can take the most RPM and torque, and improve smoothness the most, but also increase emissions a lot. Forged pistons also lower octane by one RON. Unlocks in 1992.
Next you have variant capacity. This is where you can adjust the bore and stroke of this version of the engine.
Some reasons you may reduce the size of the engine:
-
To make your car get better fuel economy
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On a performance variant you may decrease the stroke to allow it rev higher reliably.
Reducing bore and stroke here will also reduce weight slightly, but not as much as on the family bore and stroke selector.
Next we have your first quality slider.
In simple terms, quality sliders change the year of a component, and also reduce or largely increase ET and PU depending on the direction you move the slider. On bottom end, increasing quality reduces weight, very slightly reduces cost, slightly increases reliability and largely improves smoothness. Applying lots of quality will quickly make your car very expensive, so carefully watch ET and PU when applying it.
Having tech pool in bottom end will also let you unlock engine family things such as block material earlier.
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Adding to the useful threads. I forgot to do it before.
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Engine Design Guide: Part 4 - Top End
The top end is where you can change the balance of power vs fuel economy the most, especially in naturally aspirated engines.
First we have compression.
This is usually best to leave for fine tuning after you’ve built your engine and are looking to maximise its potential. The most significant thing increasing compression does is increase your octane requirement. It will also improve power and fuel efficiency slightly, along with throttle response. Emissions will also increase.
I recommend using this to reduce your octane requirement first, then adjust to increase power and fuel economy as much you can. Never set compression at the beginning and tune your engine around it.
Cam profile is how wide the valves open to let air and fuel in.
A higher, or more aggressive cam profile, means the valves open wider so more fuel and air is let in the engine. Doing this means you make more power at a higher RPM, but this will quickly destroy fuel economy. It will also decrease emissions, and your engine’s octane rating. A higher cam profile will also reduce valve float.
Reducing cam profile, or making them milder, will give you a flatter, more drivable torque curve, will make your engine smoother and improve fuel efficiency up to a point. Cooling requirements will also decrease.
For more normal cars, a good guide is to aim for about 35 to 45 cam profile, and for sportier cars around 50 to 60, although don’t take this as law. Super and hypercars should go all out for power.
VVL profile is a secondary cam profile in the top end of the power band.
VVL cam profile can only be higher than the normal cam profile. Increasing it will have roughly the same effect as changing the regular cam profile, but will not affect fuel efficiency or octane requirement.
VVT (Variable Valve timing)
VVT is the main reason DOHC becomes great past the 90s. DOHC with any VVT massively improves fuel economy, and helps power. If you can afford to use it, there’s almost no negatives to using it.
VVT - Normal VVT on every valvetrain type but DOHC. It helps everywhere a bit. Only slightly increases ET but adds a couple onto PU, and reduces reliability slightly. This unlocks 1988.
VVT - Intake - This boosts fuel economy more than the fuel efficiency stat tells, while improving performance. Only available on DOHC valvetrain. Unlocks 1988.
VVT - All - A huge boost to fuel economy, with a bit of power increase. This is the main reason to use DOHC in the later years, because the bonus is so huge. Unlocks 1992.
Quality
Adding quality to top end massively increases PU and a bit to ET. It can also change how late you make peak power, and improve power higher up the rev range.
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Engine Design Guide: Part 5 - Turbo Tuning
Turbos in Automation currently aren’t fantastic right now. Currently, even in 2020, they are based on 80s tech and as such you can’t tune them like real turbos or make them spool as quickly as real turbos.
Turbos can massively increase power and fuel economy if setup right, which can be tricky if you don’t know the tricks.
This section will be kinda vague, since turbocharging is more and art than a science. Still, hopefully with this you’ll be on the right track.
Turbos unlock in 1975. Engines with two cylinder banks can only have two turbos, while inline engines currently only have single turbo options.
The more displacement per turbo, the quicker spooling the turbo will be. For single turbo engines this is pretty simple, but for twin turbo engines just half your displacement to get that. A 2L I4 and a 2L I6 will spool a turbo up in near enough the same time, so cylinder counts don’t really matter.
Although for this reason, boxer 4s are terrible for turbocharging since a 2L boxer 4 has 1L per turbo, less than an I3 at 86/86 bore/stroke.
Journal Bearing vs Ball Bearing
If you can, don’t use journal bearings. End of story. Ball bearings cut down on turbo lag so much, without really having any negatives anywhere else.
Intercooler
Use the Flowbench for this. You never want to have your intercooler be restricting power. Set it to whatever gives you the most power, and simply lower compression if you need to.
Starting off
Ignore the presets and move straight to manually adjusting. Lower compressor and turbine to their minimums, while setting AR to its highest. This sounds wrong, but is the best way to tune turbos.
Eco tunes
- Usually 0.5 bar of boost or lower. The advantage of lower boost is it lowers octane requirement which you can spend on increased compression, leaned out fuel mixture, to improve efficiency.
- Almost always minimum turbine size.
- If turbine is at minimum size, you can then start lowering AR from 1.4.
- Compressor will be quite small, sand might also be at minimum size.
- The compressor and turbine will be very restricted.
If you want numbers to aim for, on the flow bench aim for a compressor about 0.82-0.86 and a turbine at about 0.6-0.75. I wouldn’t stick to these numbers though, adjust for yourself and it’s likely that range won’t work best for your car.
Sporty tunes
- You’ll need somewhere between 0.7-1.2 bar, depending on how extreme the performance needed is and the fuel you’re using.
- Everything will be more free flowing, probably spooling between 3-4K RPM depending on displacement and number of turbos.
- AR at 1.4 no matter what.
Again, numbers probably aren’t set in stone but if you want some numbers to aim for a compressor about 0.75-0.85 and a turbine at about 0.86-0.92. These aren’t strict rules, but tend to work.
Quality
Quality can help spool up the turbo quicker. It doesn’t affect PU as much as other places, but significantly increases ET. It can also make your engine much more reliable if you have lots of boost. For the most part though turbo quality is pretty useless.
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Engine Design Guide: Part 6 - Fuel system
Fuel systems can have a considerable impact on fuel effiency (duh), reliability, and performance. It’s probably the single most important tab after the engine family tab to get right for your car, and possibly even more important.
Carburettor vs Injection
In short, fuel injection is superior to carburettors. More reliable, lower octane requirements, more fuel efficient and generally more powerful. After single point injection unlocks, there’s very little reason to not use it for cheap cars, and after multipoint injection unlocks there’s very few reasons to go for carbs at all.
Carburettors (Carbs).
These will be your only option up until 1964. These are bad for reliability and throttle response, but cheap and simple to make. As a general rule, as you go down the list, they have better throttle response and are easier to get power from, but are more expensive and less reliable. They also don’t tend to work well with turbos.
(All fuel systems shown with a performance intake)
Single Barrel - This is cheap and basic. It works, but isn’t great past the very early years. Available from the beginning.
Single Barrel Eco - More fuel efficient, but way less powerful. Restricts the intakes a lot more than single barrel, so power is usually limited, and limits how rich your AFR can be while also increasing your octane anyway. Has the worst throttle response. The cheapest fuel system available. Available from the beginning.
2 Barrel - Slightly more fuel efficient than Single Barrel, with better flow so you can get more power. A bit more expensive and has higher ET, but along with DCOE is slightly smoother than single barrels. Unlocks in 1948.
DCOE - Also known as webber carbs in real life, or sidedraft carbs. These are for racing and sports cars, as reliability is lower and fuel efficiency is terrible, but you can easily get power using them. They can also only have performance and race intakes, so another reason to not use them with normal cars. Very expensive. Unlocks in 1954.
4 Barrel - The highest ET of any carb. The worst reliability, but good power and fuel efficiency. Also slightly smoother than other carbs. Unlocks in 1959.
Fuel Injection (FI).
This is what all modern cars use these days. Better than carbs in almost every way, but much more expensive and higher PU/ET. Electronic fuel injection doesn’t give a drivability penalty for having too high throttle response either.
Mechanical Fuel Injection - An early version of multipoint fuel injection. Fuel efficient, very reliable compared to carbs but heavier, with higher ET and PU while also being more expensive than most carb configurations. Unlocks in 1964.
Single Point EFI - The first option for electronic fuel injection (EFI). Generally pretty terrible, but better than using carbs for cheap cars. Far cheaper than mechanical FI in every way. Think of it like the single barrel eco but for FI. Unlocks in 1978.
Multi Point EFI - Wonderful technology that entirely replaces mechanical FI because it’s better in every way. Worse than single point FI cost wise, but far superior in terms of fuel efficiency and power. Can also have multiple throttles, unlike Single Point.
Direct Injection - Very expensive to design and produce, but is very good for power and fuel efficiency. Also lowers octane requirement significantly. Unlocks in 2001.
Configuration.
For carbs, you get to choose how many carbs you have, which can vary between 1 and 8 carbs depending on both your engine configuration and carb type. The more carbs you have, the better the airflow so you tend to get more power and fuel efficiency with a better throttle response at the cost of higher material and service costs, higher ET and PU.
For fuel injection, you get to choose how many throttles your car has. As with carbs, more means better air flow and throttle response, but is more expensive with higher PU and ET. With V and boxer engines, you get the option of twin throttles, which also adds weight. Throttle per cylinder reduces weight.
Intake
This is a simple way to increase power, at the cost of service costs and loudness. Standard intakes are quiet and cheap to service, while performance intakes are louder with a higher service costs. Race intakes destroy reliability, but can considerably increase power and airflow. They are also slightly lighter and cheaper.
Standard
Performance
Race
Fuel Type
This is the fuel grade that your car uses. Next to the type is a number. This is the fuel’s maximum octane.
On your stats you see your engine’s octane requirement number. This number should either match or be just under the maximum octane of your fuel choice. This means you’re maximising the potential of your fuel choice, which means more power and better fuel economy.
Leaded fuel (the first two options) have extremely high emissions, and eventually get banned in all countries meaning you cannot sell vehicles there.
Banned in Gasmea in 1982
Banned in Fruinia and Hetvesia in 1978
Banned in Archana in 1990
Banned in Dalluha in 1985
Fuel types:
Regular Leaded - 92 octane. Cheap and available everywhere. Available from the start.
Super Leaded - 98 octane. Expensive and has limited availability. Available from the start.
Low Quality - 85 octane. The first unleaded fuel. Tricky to use because it has such a low octane rating. Only even slightly possible to use in Archana. Available from the start.
Regular - 91 octane. The first usable unleaded fuel. Also the best fuel that Archana gets. Unlocks in 1965.
Premium - 95 octane. 100% available everywhere but Archana. Available from 1985.
Super - 98 octane. Available everywhere in Gasmea, Hetvesia and Dalluha, but is very limited in Fruinia. Available from 1985.
Ultimate - 100 octane. 100% available in Dalluha, either unavailable or quite limited everywhere else. Available from 1990.
Fuel Mixture
The number is the ratio of air to fuel you’re putting in at full throttle. A higher number (leaner mix) means less power, higher octane requirement, and a lower throttle response, but with a significant gain to fuel efficiency. A richer mixture does the opposite, but there is a limit to how rich you can go. To get around that, use a turbo. Higher boost turbos can let you go past your AFR limits (shown when you hover over the slider).
Ignition Timing
This should be used along with compression as final fine tuning to maximise the potential of your engine. Try and find the right timing to squeeze the most out of your engine. It is extremely unlikely that setting ignition timing to 100 is optimal, usually the range of 50-70 is about optimal, but it depends on many things about your engine such as where peak power is. The only consistent thing that happens when you adjust it is that a higher ignition timing improves throttle response.
RPM limit
This sets how high your RPM limit (redline) is. A higher redline means less reliable, but is usually better for sports cars. Use the right column of the RPM & Torque boxes to see how high you can rev reliably, but watch the torque curve. If you rev too far past peak power, you can lose out on performance. And never, ever set the redline at peak power. This means you’re wasting potential with your engine, as you can never take advantage of your peak power. Keep an eye on your performance index as that can help tell you where to put your redline at.
For an extreme example, here is an engine with peak power at redline. It’s making 244hp at peak power.
To the wheels, this is 224hp. On the gearing tab, we see the gear change between first to second brings power down to 182. 42hp down, which can hurt acceleration.
Now, if we increase the max RPM to 8200RPM, there’s little to no power increase, but now a wider range of power.
On the gearing graph, I set the max speed to be roughly the same as before. From the end of first gear, I have 220hp. On the change to second, I still have 204hp. A loss of 16hp between gears vs 42hp, so setting your max RPM to the correct
Even if I don’t adjust the gearing at all, you can see the benefit in terms of just having power between gears. Actually, there is a similar loss to the shorter final drive above.
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You don’t mention here that leaner fuel mixtures are more economical. The way you describe it here makes it seem like richer fuel mixtures are what you want at all times.
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Oops, that’s what you get when you don’t get others to read it for you.
Fixed it. Thanks for quoting the entire section, I wouldn’t have known where to look without it. 
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Thank you! Now I understand why my shit-boxes from APATI never sold as expected with RON80…
Lower centre of mass? Is this a hidden stat or something?
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Not necesarily, but if you compare roll angle between an I6 vs V6 vs B6 on the same suspension and body, the difference is quite clear.
It’s not a stat literally, and as far as I know there’s no way of seeing the centre of mass in game.
What this means is the engine is all set much lower than other types of engines, so there’s less weight up high. This helps cornering by reducing body roll, so you might see an improvement in cornering G and lower roll angle.
Great Guide, especially for beginners! 
Even after 200 hours of playing automation, I still got something out of it.
It’s very well researched
Update on the turbo tuning side: Something’s changed in turbos (actually I’m kind of late to that).
In short, the ideal range for the compressor is 0.6-0.75 roughly. Turbine can stay in the 0.82-0.86 sort of area, AR should be maxed out unless you’ve got a minimum sized turbine and need to restrict the turbine more. I’ve updated the guide to reflect that.
As usual, what I say isn’t law, but a good starting point. Obviously experiment and learn how your changes effect your engine.
Engine Design Guide: Part 7 - Exhaust systems
Finally, after all this time we get to the end of the combustion cycle. Just writing this, I feel exhausted.
Mandatory pun complete. Let’s go.
Exhausts are surprisingly important. Mostly for luxury cars, but the exhaust setup can help you make big gains in comfort, power, fuel economy and weight reduction.
Exhaust Headers
These are the first thing the exhaust gasses go through, you can make some significant gains here in power and weight reduction. Also they look pretty if you go for the expensive ones. This is only available to choose if your engine is naturally aspirated, since if it’s turbo you have to have Short Cast. All headers are available from 1946.
A thing to note is that you’ll likely not notice any real flow issues here until the late game. Or maybe just a quirk with the way I build engines. To improve flow here, you can either change the headers or make the engine bigger. Bear in mind with better flow means a louder engine, so it might not always be best to have a totally free flowing exhaust system. A turbo engine won’t ever have any flow restrictions here.
Cast Log - This is your cheap and nasty one. Only for use in the most cheap and mass produced cars, even the markets will usually go away from cars that use this. In the campaign, this is probably quite useful for getting the very maximum cars out of your factories. With this you’ll get serious flow issues.
Short Cast - What 90% of your cars will use. Your standard header for cars everywhere that aren’t totally cheap and garbage. Note that it’s slightly heavier than Cast Log, and with higher material costs.
Tubular - Slightly sporty and lighter than short cast, with better flow. Probably best to have on sporty cars that aren’t too high end. Lighter than Cast Log, but with slightly worse emissions. Interestingly is lower on material costs.
Long Tubular - This is getting to the expensive to manufacture point. Still usable on widely produced car, but I wouldn’t recommend it unless performance is needed. Somehow even cheaper on material costs, worse on emissions still.
Race Tubular - This is your custom built, perfectly shaped for your engine exhaust head to perfectly manage the gasses. It cannot be mass produced, so use only on low production and limited cars such as hypercars. A large jump in production units and it takes a month longer to engineer.
General Exhaust
Single - A single exhaust pipe. Nothing really to say here.
Dual - Two exhaust pipes, only available on V or Boxer engines. With this you can just double the maximum power possible with the engine, but bear in mind that it can get heavy quickly. Recommended for cars that need power and to be quiet, but where weight isn’t an issue.
Bypass Valves - A simple way of keeping a car quiet for comfort, but at the same time avoid a sportiness penalty for having a quiet car. You won’t get a bonus for loudness, but at least won’t lose sportiness. Unlocks in 1999.
Exhaust Diameter
This will help determine exhaust flow. A larger exhaust will help increase power if there’s a serious restriction, but if there isn’t a restriction you won’t see a power gain. This can also significantly affect loudness.
If your exhaust is too big you will actually reduce power and efficiency, while restricting the exhaust will lose power you will also gain efficiency as you improve low end power.
If you go from a single to dual exhaust it’s not as simple as just halving the size of the exhaust. You get bigger and bigger gains in flow the bigger your exhaust is.
Catalytic Converter
This is the main way you’ll reduce emissions. You cannot use one of these if your car is using leaded fuel. Right now in the game there doesn’t really seem to be a point in using them, since emissions are irrelevant to the markets as far as I can tell. For choosing one of these look at real cars and figure out what would make most sense.
None - No Catalytic Converter. Largely unrealistic for most cars. To be honest I recommend looking at real cars of the era you’re making an engine in and deciding for yourself if you need to have one or not.
Two-way - The worst possible option in this section. Bad at everything, ruins flow so you make no power. At least it makes the engine quieter. If you have to use one, upgrade to a three-way as soon as possible. Unlocks in 1972.
Three-way - Something actually decent. This is probably the best catalytic converter for most cars. Good flow, lowers emissions more than a two-way too, and at a decent price. Unlocks in 1978
High Flow Three-way - The best catalytic converter for performance engines where power matters, but you want realistic emissions equipment. It’s a little expensive in material costs and production units. Unlocks in 1984.
First Muffler
Choose the muffler you put here after the second muffler, since this one works less efficiently.
Here always put the muffler choice with the best flow out of the ones you’re using, so for example if you have a straight through and a reverse flow muffler, put the straight through in the first muffle position.
Second Muffler
Put the more restrictive muffler here, because it will work more effectively.
None - No muffler, nothing making the engine quieter. Use on cars where you don’t really care about comfort. If you’re using this in the second muffler position, have the first muffler also be none.
Baffled - Cheap way of making your car quieter. You’ll likely use this in a None/Baffled setup or a Baffled/Reverse Flow setup. Available from 1946.
Reverse Flow - The quietest but most restrictive exhaust. You’ll likely use this on a Reverse Flow/Reverse Flow setup or a Straight Through/Reverse Flow setup. Available from 1950.
Straight Through - Sporty loud muffler. Used to make the exhaust a little quieter without ruining flow too much. Used in a none/Straight Through setup. Unlocks in 1968.
Quality
Quality here can help reduce loudness and weight, lower emissions, and ever so slightly lowers material costs (by $0.1 per quality point).
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As of the current stable release (LCV3.73), this is no longer true - low quality unleaded is now 85 RON, not 80 RON as it was when you first posted your guide.
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