Turbo vs non-turbo: An Automation Experiment

If you haven’t heard about Automation the game, it’s essentially a simulation allowing you to build complete cars with an in depth engine designer.

I recently did some direct comparisons between turbo and non-turbo cars, to assess the advantages/disadvantages of each. I knew that adding a turbo obviously increases cost and engineering time, and makes the engine less responsive and possibly makes the car harder to handle due to turbo lag. On the plus side, you can increase power without increasing the block size or rpm limit and potentially it makes for a performance engine with good fuel economy. When would you opt for turbo vs naturally aspirated?

My challenge was simple: Make a mid-range premium performance/family car with three different engine setups, and compare the following:

1) A standard engine VS the same engine size and layout but with a turbo (obviously with the necessary adjustments on compression, cooling etc. to accommodate the turbo).

2) The turbo engine VS an engine with the same layout (e.g. Inline 4cyl vs Inline 4cyl) but bigger size so that it can match the turbo on torque and power.

Here are my results: I decided to go with a reasonably good chassis and suspension, with rear-wheel rather than front wheel drive so that the more powerful versions wouldn’t be at a disadvantage. I ended up with three 5 door hatchback 2015 model cars:

1) 2L I4 Naturally Aspirated (performance)

20160815220324_1
2) 2L I4 Turbo (performance turbo)

20160815220337_1
3) 2.9L I4 Naturally Aspirated (made with almost identical torque and power compared to 2L turbo)

20160815220418_1

I tried to change as little as possible about the car itself, with the exception of adjusting cooling and top speed to allow maximum speed and sufficient cooling for each car. Here’s what I found:

– The turbo engine was significantly more powerful compared to the standard 2L.
– The turbo engine added only about 600$ to the total cost of the car, which was very little compared to the substantial step up in power.
– The 2.9L might have matched the turbo on power, but was 1500$ more expensive compared to the base 2L. The increased cost was due to increased engine size and a better crank, con-rods and pistons which were required to keep good reliability.
– All three cars performed well in terms of market ratings, beating the competition in family sport and similar segments.
– All three cars were very similar in terms of most overall ratings, with the biggest difference being the turbo car scoring quite a bit lower on drivability.
– While the turbo engine might be cheaper to build given like for like performance, it will have higher service costs.

Here are some cost vs performance figures. Total cost excl markup; 0-100 kp/h times; and time around the game’s airfield (“Top Gear”) track:

1) 2L I4 Naturally Aspirated 15700$; 7.4; 1.31.64
2) 2L I4 Turbo 16300$; 5.9; 1.27.12
3) 2.9L I4 Naturally Aspirated 17200$; 5.9; 1.27.24

Conclusion:
If you want power at a lower cost, go for a turbo. If you’ve built a good turbo engine it’s unlikely that you can build a naturally aspirated engine that can produce the same power at the same cost. Just keep in mind that the reduced throttle response and uneven power curve of a performance turbo will make the car harder to handle. That said, the higher service cost will likely make the turbo car more expensive in the long run.

Which would I buy?
In this scenario probably the turbo car. There isn’t much separating the two high performance engines, but a much prefer the sound of the turbo given that the naturally aspirated I4 has a pretty boring noise for a performance car. Would it have been a V6 or V8, it would be a very different story.

If you have thoughts on this either form real life experience or experimenting in Automation, I’d love to hear for which kinds of cars and setups you found that having a turbo is better/worse.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s