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Algorithm for tuning a turbo engine for power

This is the process for designing a turbo engine for power in Automation. There’s several game quirks you must be aware of to get the most hp (which isn’t necessarily the best performance score.) One important thing to realize is that you are always fighting against limited octane. You have an octane budget, so to speak. You can’t use a lot of boost and high compression and high ignition timing. Other things that use up octane includes valvetrain type (SOHC 2V and better have the same level; DAOHC and pushrod use up more octane), cam profile (milder cams need more octane), bigger bores, forged vs cast pistons (forged use less octane), all the turbo sliders, fuel system (direct injection is obviously the best), intake (standard uses less octane, but it lowers performance), fuel type (sets up your designated octane budget), fuel mixture (richer mixture adds to your budget), and exhaust (but indirectly).

The following procedure will be demonstrated with a 1.6L I3 turbo engine, 79.8 bore and 106.4 stroke.

#1
What do you need to balance on the first screen?
You need to balance between being too oversquare, which makes valve float a problem and slightly digs into your octane budget, and being too undersquare, which reduces your max RPM and (I think) makes the head flow less well (I haven’t tuned for power for a long time so I’m not sure.)

You will want DOHC 5v/cyl, of course. Nothing else matters. Using 4v/cyl with VVL is not a good idea, because the game calculates minimum octane required from the first, milder cam profile, so that digs into your octane budget.

Magnesium block makes the engine’s smoothness score go down, and depending on how big your engine is already, that will lower your max RPM. Just use AlSi for all of them.

This game has major issues with decimal numbers and its user interface. For that reason, be aware that the when the bore is at most 4/3 the stroke, and the stroke is at most 4/3 the bore. Which means you need to make sure the bore or stroke need to be divisible by 3, if you’re operating at the limit. Otherwise, it doesn’t matter. For example, my engine is operating “at the limit” (stroke and bore are limiting each other). My bore is the smaller number. 798 divides by 3 into 266. You can tell if a number is divisible by 3 by adding all of its digits. 7+9+8= 24, 24 is divisible by 3, so 798 is divisible by 3.

#1.5
What engine configuration should you choose?
The max turbo size in this game is linked to the bore size. This means that I3/V6, I4/V8, I6/V12 with the same bore will all have the same max turbo size. This means that for a given max turbo size, you can choose between 3, 4, or 6 cylinders feeding from it.

Make no mistake. You want more turbo capacity per cylinder. This means going for I3s and V6s. I hope I’m making sense.

A 4L I3 will have the same max turbo size as a 5.4L I4 as a 8.1L I6.

An 8.1L I6 will have the same max turbo size as an 8.1L V6, but the V6 will have two of them. So that’s double the turbo. More peak power.

A 4580cc I6 with 90 bore and 120 stroke will have a smaller max turbo size compared to one with 108.8 bore and 82.1 stroke. 72.6 vs 90.2 max compressor (compressor is the limiting part of the turbo when it comes to power in Automation, it seems).

The other side to this, is, of course, the minimum turbo size. If you want boost (and thus torque and power) early, like at 1500 RPM or less, you’re gonna want more cylinders per turbo, and also a smaller bore, to decrease the minimum turbo size (much more goes into making boost early, but generally you want the smallest turbine size possible).

#2
Second screen is easy. Just use the best stuff, except for pistons–forged will handle much more torque (and thus boost) than lightweight forged.

#3
Start by lowering compression to 6 and cam profile to 100, we’ll deal with those later. Use VVT on all cams.

#4
Make sure to choose ball bearing. Max out the intercooler and compressor and the turbine and the AR ratio and the boost. We’ll deal with those later.

#5
Choose direct injection, per-cylinder throttle bodies, and race intakes. Fuel type would be 95, of course, and set fuel mixture to 12 and ignition timing to 100. RPM limit to 2000.

#6
Biggest exhaust diameter. Turbos do not like exhausts. I like to keep the catalytic converter on. Just because it’s fast and 5% efficient, doesn’t mean it needs to spew out unpleasant smelling products! No mufflers.


Now the numbers should be up. The game should also tell you if your proposed engine will fit into the car. Change the powertrain layout if need be. Notice that only the bore size affects block size (which isn’t realistic but whatever). More displacement, even if undersquare, is almost always better.

#a
First things first: Raise the RPM limiter until one of two things happen: Either the peak power occurs, or you reach the limit of the components. (Ignore knocking if necessary) I like to keep everything green.

#b
Then, fiddle with the cam profile until you find the number that gives you the most power. Sometimes there will be multiple options–in that case, choose the highest one. This gives you more octane to work with. I got 84.

#c1
This is where shit gets real. Time to fiddle with the turbo settings. Usually, max boost is unnecessary. You can lower it to the point where the numbers start changing. In the engine I’m tuning to test this procedure out, I lowered it from 43.5 psi to 22.0 psi.

After that, fiddle with the turbine size. Max turbine size is usually not the answer. In my example, I lowered it from 63.8 to 56.0.

Now try raising boost again. I raised boost from 22.0 psi to 27.6psi (at which point no more changes occured after that).

I lowered my compressor size from 63.0 to 54.0. The peak power did not change, and it is good to leave some room.

I raised boost some more. 27.6 to 28.6.

I reduced turbine size again, this time in accordance with the numbers on the left. The top number is your performance rating. I lowered my turbine size from 56.0 to 38.5. Any less, and the number turns red, indicating that performance rating is going down. The peak power did not change.

I raised boost again. 28.6 to 34.4.

I raised compressor size back up. From 54.0 to 55.0.

I dicked around with the turbine size, but it was fine where it was, so I didn’t change it.

I raised boost again. 34.4 to 34.8 for 1hp gain.

Now it’s time to change the intercooler size. Lower it until you get max power. Notice that your octane budget increases as you do this. It’s doing twice the benefit! I lowered my intercooler size from 12182 to 891. Keep track of the colours of the numbers on the left. They are very useful to know when to stop, when the HP numbers on the graph don’t change.

That seems to be about as much as you can do with the turbos for now. So enrichen the fuel mixture to 10.

Now is also a good time to fiddle with the cam profile. Sometimes, the initial cam profile is not tuned to the new turbo settings, but in our example, it seems to be doing fine. (It may stop being fine once compression is raised.)

There’s only one thing we haven’t touched left, and that would be compression. From 6 to 8.7.

I fiddled with the turbine size again. From 38.5 to 39.0 gives us 2hp.

Fiddling with the compressor and boost separately did nothing. But! If you raise the compressor from 55.0 to 55.5, and then raise the boost, you can get 1hp, from 34.8 psi to 36.4 psi.

Raising the turbine size again from 39.0 to 40.5 gives us another horsepower.

#c2

Now it’s time to spread the optimization beyond the turbo. We have to compromise between compression, boost, cam profile, and ignition timing.

I raise the compression by one point–8.7 to 8.8, which gives the engine knock. I remember the horsepower number, 428hp. I lower the boost until it stops knocking, from 36.4 to 34.3. Drat, the hp is still 428. I repeat the process. Nope, power goes down. 36.4 boost seems to be the answer for now. I lower compression back down to 8.8 from 8.9, and boost back up to 36.4. I fiddle with the timing.

Good stuff. Lowering timing from 100 to 97 gave us one hp.

I repeat that process until I get to 9.5 compression and 76 timing. Any more and the hp starts going back down.

It’s time to check on the turbos again. Nothing happens.

I check the exhaust last. Occasionally, lowering the exhaust boosts hp a bit. It doesn’t this time.


A couple tips. We didn’t max out the compressor size this time, but sometimes you need to. And if the size is not a multiple of 5, then it’ll occasionally reset to one that is. For example, in the 1000hp I6, the compressor size keeps changing from 76.6 to 76.5. That’s the difference between 999hp and 1000hp.

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