Why Small Turbo Engines Are Not Efficient

There's only ONE reason why my turbocharged 4 cylinder gets bad gas mileage.... REASON: It's because my foot's in it so far that the fan is clipping my toenails..

People forget - your right foot is connected to a valve. That valve drains your wallet ;)

so.......what you’re telling me....is that they ARE efficient , but idiots keep flooring it while expecting to get 40mpg.

My Alfa Giulia has the 2.0 turbo, and if I don't push it, the mileage is amazing. It really comes down to driver input.

I always looked at turbo'd engines as having the smaller displacement when driven softly and a larger displacement when driven hard. Therefore, you will only get good fuel economy when you drive very easily, but you have the option of way more power when you want it. You just have to sacrifice that fuel economy when you want power. Kind of like cylinder deactivation, only more reliable.

A turbo engine is great power when you kick it and eco when you don´t. Its that simple

in short : you're Jeremy Clarkson , or James May

You mean to say that when my engine is making more power, it's also using more fuel? Say it ain't so!

3:37 "as you floor it" well there is your problem right there. if you want fuel efficiency, why would you ever floor it, n/a or boosted?

The answer is more stickers

"You dont want that many cylinders" laughs in Italian

Not quite so simple as richer fuel mixture and retarding ignition timing to prevent pre-ignition (aka Detonation). Combustion chamber shape and piston top shape, detonation sensing, intake air temperatures and LOTs more factor into how good any turbocharged engine could be. To overly simplify turbo engines are less fuel efficient due to the need to enrich intake mixture does not factor in or account for how some manufactures have addressed these innate problems with turbo engines. Example: Saab-Scania's B234 & B204 turbo engines have a static compression rating of 9.2 to 1 and they achieve good fuel economy with balanced shafts (which consume power increasing fuel consumption). This is done by using a well designed pent roof cylinder head combustion chamber and a domed down piston top and intake/exhaust gas flow pattern control. These basic designed in factors work to prevent detonation with and without turbo boost. The more complete burn due to the afore mentioned design elements in the engine work to help the intake charge burn more complete which extracts more energy per intake charge, lowering emissions and resisting the potential for pre-ignition aka Detonation. To monitor pre-ignition at each cylinder burn cycle, Saab uses in cylinder ionic sensing of the burn in process via the spark plugs. Before and after the intake charge is ignited by the spark plug, the spark plug becomes a sensor to detect pre-ignition and alters when the spark plug is fired as needed, per intake cycle, per cylinder. To address intake charge temperature rise due to air compression by the turbo an intercooler is used to reduce the heat of the intake air. Intake air to the intake manifold is monitored for air temperature and air density. Both are figured and LOTs more factors are figured into the amount of fuel to be injected per cylinder. These factors work in conjunction with the ionic pre-ignition system using the spark plugs. The Saab-Scania turbo engine management system IS one of the most sophisticated out into production with with many technical features that are not recognized, appreciated or understood. Beyond Saab-Scania's turbo engine management system, the B234 & B204 engines are built really tough, durable and very strong to withstand the increase in torque of a turbo engine. It is also why a stock B234/B204 can be up boosted to 450 lb/ft of torque as delivered. Forged chrome-moly steel cranks with nitrided bearing surfaces, Forged chrome-moly steel con-rods, forged aluminum alloy pistons specifically designed for turbo engine duty made by Mahle with oil jets and additional oil cooling features. Stout main bearing and bottom end design, good coolant flow design to move the larger amount of heat produce by a turbo charged engine, oil cooler with thermostat to reduce the oil's operating temperature.... These are just a few technical reasons why Saab-Scania was able to produce a reliable-very durable turbo engine with good fuel efficiency for a given power requirement. These same turbo engines also features low emissions. Turbocharged engines are essentially a two stage pump system that recovers some of the heat energy that would have been lost via the exhaust to increase overall engine efficiency. The added plus of a turbocharge, lower exhaust noise due to conversion of that pulsed energy into rotational forces to drive the turbine.

All I heard was V8s are more efficient and I should drive my turbo car fast for better mileage. Don't correct me, this is the world I want to live in.

When my Firefly Turbo kicks in around 3000 rpm, it feels like an extra cylinder just started firing. My 3 cylinder, 1 litre suddenly becomes a fire breathing 1300. Hold onto your hats....!!!

In the case of extremely high boost pressures, I remember seeing twin-fuel systems being implemented. Check out the Ronin Exige, which uses a separate methanol system that is injected into the engine after reaching a certain boost threshold. The methanol increases the octane rating of the gas being burned, at the expense and complexity of two fuel systems in a single car.

Great video! It'd be interesting also to see how say an LS motor stacks up against a DOHC V8. It's interesting to compare how the E92 M3s compare to the Corvettes of the same era in terms of mileage, for example.

Not everyone drives at sea level. Turbocharging makes a huge difference when driving at higher altitudes. For the vast majority of the time, the engine is operating at only a limited throttle opening. Sure, if you smash down on the gas pedal all the time, your fuel mileage will decrease. The advantage of the turbo is that the extra power is there when you need it; entering onto a freeway or climbing steep grades or over-taking slower vehicles. You must factor in the effect of the intercooler in any discussion on engine efficiency.

I'm a proud owner of a 2018 Civic Si with the 1.5 L turbo that's pushing 20.6 psi from the factory. I get well over 30mpg under normal circumstances because I don't rev the crap out of it like some people do. They complain the mileage is bad; yeah it's gonna be bad when you're hammering the throttle all the time. These cars were built for the instances where you need power, but most of the time you want to save fuel. They're not supposed to be efficient when you're hammering on them

nice! would love to see more on superchargers. tons of available info on turbos, comparatively very little on blowers.

I’m surprised you didn’t mention the option of higher octane fuels to help reduce knock. Typically the factory turbo cars use a specific type of programming or ecu tuning called “adaptive octane logic” so the computer can tell how high of octane the fuel it’s using is. Most of the factory turbo cars tend to “recommend 91/93 octane” for this reason. Basically it allows you to use 87 if you want but once the adaptive octane logic sees the fuel is crap it can set a lower cap on the engine timing. So let’s say you use 87 octane. The adaptive octane logic may set the limit of the timing to 12 degrees(advanced) well once you throw 93 in the tank and the sensors sample that fuel it will increase the limit of the timing from 12 degrees to lets say 20 degrees (advanced) resulting in more power out of the same calibration all while keeping the engine safe.