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Barebones Turbo Tutorial

Awhile ago I put together a video tutorial for tuning turbo engines. For those of you that don’t want to sit through that (don’t blame you, it’s hard to watch), I’m just leaving my notes here. They’re way better than the turbo tutorial I wrote in the engine guide, but to be honest I can’t be bothered to write these up properly for the guide. Hopefully this somewhat helps and is somewhat readable.

Advantages to turbos:

  • More power.
  • Better low end power, can lead to a flatter power curve. This in turn leads to better fuel economy.
  • Better efficiency.
  • Helps make an engine quieter.
  • Boosts prestige (especially in the early years, bonus wears off in late game).

General info:

  • Unlocks in 1975, with the only option being Journal bearing, (ball bearing unlocks in 1980).
  • Turbo quality is probably the weakest quality option. Can sometimes increase power, reduce turbo lag, and * helps a little, but for the most part doesn’t change much.
  • With enough boost, you can bypass the fuel mixture limits of your fuel type.
  • Carbs have issues with turbos, and after 0.7 bar of boost will get a serious reliability reduction with each 0.01 increase.
  • Increasing boost pressure will reduce reliability.

Reducing Turbo lag:

  • Your goal is to lower turbo lag as much as possible, while increasing power.
  • Smooth lines are also not good. You want a wall as soon as possible, this means there’s less lag and the power curve is wider.
  • Avoid boxer 4s, I3s, and boxer/V6s.
  • Displacement affects turbo lag more than cylinders per turbo.
  • Ignore the presets. They’re trash.
  • Having an all green turbo setup means that you’ve got something wrong. Compressor and turbine should always be limiting a little.
  • Low turbine, high AR setups work best. Otherwise, there’s more lag and it struggles to keep boost up at high RPM.
  • Intercooler should almost always be free flowing. Rarely a case otherwise. Usually you want to keep increasing size beyond free flowing, around 50% more than your actually max power to get the most out of the engine.
  • Always use ball bearing when available. (Unlocks 1980).
  • Your compressor should be more restricted than your turbine.
  • Boost pressure doesn’t directly affect turbo lag.

Eco Build

(For cars where performance isn’t needed):
  • Usually 0.5 bar of boost or lower. 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.
  • AR can then be reduced from 1.4 when turbine is at minimum size.
  • Compressor will be quite small, and usually very restricted.

Performance Build

(Usable performance levels without excessive lag):
  • Will probably run somewhere between 0.7-1.2 bar, depending on how extreme the performance needed is and the fuel you’re using.
  • More free flowing turbo setup, a bit more laggy but doesn’t have to be crazy late.
  • AR at 1.4.

Max Power Build

(Memes/getting the most out of an engine at the cost of being usable):
  • Ignore turbo lag. Probably want a max size compressor (or at least close).
  • Boost pressure definitely over 2 bar, might not want to go all out to 3 bar as you can actually lose power with really high boost.
  • Fuel mix can be set to 10.0 as long as you have enough boost.