Turbo Tuning

[DeltaForce]

I've designed several naturally aspirated engines, but turbos are proving to be more difficult to tune. It's not difficult to create power and torque, but my designs often end up with a very prominent S shaped power and torque curves, with the turbo massively boosting both in the space of a few hundred RPM. I would prefer a somewhat more gradual spooling up.

Also, I notice that there is an Eco setting for the turbos in game. Can you go about tuning a turbo to produce better fuel economy than the engine produces in naturally aspirated configuration (as with a turbo-diesel engine), or does the Eco setting simply mean the turbo is tuned to consume less fuel than the other settings?

[Daffyflyer]

Yeaaah, the turbo calcs are not great right now, you can basically just get realistic simulation of 1980s turbo technology at the moment

[VicVictory]

As for the "Economy" turbos... you can absolutely use them to get better fuel economy than a N/A engine. At least as far as gas engines go, this means being able to use a smaller engine (My 1.4L turbo gets slightly better economy and the exact same power as its 1.8L N/A equivalent in my real-world car)

The biggest issue, of course, is car design. You have to make sure you are maximizing the engine and transmission's potential for the car. So if a certain size N/A engine is too small and gutless and isn't giving good results, throwing on an Economy turbo will give better power and economy. But if the N/A is the perfect size and power, throwing that turbo on the same size engine will increase performance but eat fuel. Just like a real car.

[Daffyflyer]

Ahh, also don't forget that whilst a turbo won't necessarily increase efficency at full power (g/kwh).

It may increase economy by letting you reduce displacement, smaller displacement means greater throttle settings for cruise and better economy. The better low RPM power of a turbo motor could also allow higher gearing, thus less RPM at cruise and better economy again.

[DeltaForce]

Yeaaah, the turbo calcs are not great right now, you can basically just get realistic simulation of 1980s turbo technology at the moment

Will electric turbos be added later on? No turbo lag could be interesting.

[Daffyflyer]

Yeaaah, the turbo calcs are not great right now, you can basically just get realistic simulation of 1980s turbo technology at the moment

Will electric turbos be added later on? No turbo lag could be interesting.

Probably not, but I really do want both Twin Turbos and Twin Scroll turbo housings.

[vmo]

As for the "Economy" turbos... you can absolutely use them to get better fuel economy than a N/A engine. At least as far as gas engines go, this means being able to use a smaller engine (My 1.4L turbo gets slightly better economy and the exact same power as its 1.8L N/A equivalent in my real-world car)

In my case, I have better fuel economy in N/A engines than in the turbo.

This is a question: A tutorial about how I can make a smooth and powerful turbo engine (for example, 250hp at x rpm and 450 nm of torque at 1800-2000rpm in a 3.5l. engine)?.

[USDMFTW]

I get better fuel econ and power out of my turbos compared to N/A engines, but the graph in the aspiration section seems to be useless, unless i read it wrong. Also turbo engines dont follow any pattern, example is increasing the cam value higher will sometimes net lower horsepower.

[Daffyflyer]

I get better fuel econ and power out of my turbos compared to N/A engines, but the graph in the aspiration section seems to be useless, unless i read it wrong. Also turbo engines dont follow any pattern, example is increasing the cam value higher will sometimes net lower horsepower.

Yes, too higher cam profile doesn't work very well with turbo engines, that's correct.

Which parts of the turbo graph need explaining better? For me it's the single most useful bit of information for designing a turbo setup, as it shows you when it will spool up, how much boost it will make at what RPM, how effecient it is and if you're working the turbo too hard etc.

[USDMFTW]

I get better fuel econ and power out of my turbos compared to N/A engines, but the graph in the aspiration section seems to be useless, unless i read it wrong. Also turbo engines dont follow any pattern, example is increasing the cam value higher will sometimes net lower horsepower.

Yes, too higher cam profile doesn't work very well with turbo engines, that's correct.

Which parts of the turbo graph need explaining better? For me it's the single most useful bit of information for designing a turbo setup, as it shows you when it will spool up, how much boost it will make at what RPM, how effecient it is and if you're working the turbo too hard etc.

Thats what i assumed it is, so i do understand it, blue bar is best turbo possible, while red is the efficiency of the current setup, . Useless was an overstatement

[Sayonara]

Which parts of the turbo graph need explaining better? For me it's the single most useful bit of information for designing a turbo setup, as it shows you when it will spool up, how much boost it will make at what RPM, how effecient it is and if you're working the turbo too hard etc.

I do have one suggestion - would it be possible to crop the turbo graph off at (or somewhere slightly above) the engine's RPM limit? If you happen to be building an econobox with a 6000 RPM redline, for example, fully half of the turbo graph is useless information.

Also, I notice that there is an Eco setting for the turbos in game. Can you go about tuning a turbo to produce better fuel economy than the engine produces in naturally aspirated configuration (as with a turbo-diesel engine), or does the Eco setting simply mean the turbo is tuned to consume less fuel than the other settings?

Turbocharged engines actually can exceed the specific fuel efficiency of a naturally aspirated engine by a considerable margin, but this requires a lot of careful tuning. The trick is to use low boost (somewhere in the region of 7 PSI, or 0.5 Bar, seems to be ideal) and size the turbocharger to spool up just before your naturally aspirated engine reaches its most efficient RPM range.

Just as an example, I've built a naturally aspirated engine 2.2L engine which makes 134 hp and 197 Nm at ~35% efficiency. Adding a small intercooled turbocharger (38.5mm compressor, 31mm turbine) shoves this up to 227 Nm and close to 43% efficiency, while a 1.24 AR ratio allows it to make 198 horsepower despite the tiny turbine. And it still runs on the same octane fuel.

The Economy preset is a good starting point, but I always prefer to run a smaller turbine and a larger AR ratio as you gain a lot of top-end power with minimal effects on efficiency and responsiveness.

Because a picture is a thousand words, here.

[TheTom]

As a side note, increasing the compressor size will improve efficiency up to a certain point (max. size where this is possible varies depending on the engine capacity). I usually run 0.5-0.7 bars of maximum boost on my eco engines, with a A/R ratio above 1 and a very small turbine. Also, you can influence the power and torque curve not only with the cam profile, but also with the ignition timing: the higher the ignition timing, the earlier the engine will make its peak power (if you leave everything else as it is). In addition to that, if you lower the cam profile, the turbo might reach its maximum boost a little bit earlier and that's useful for economy cars.