I am wondering what a turbocharger does for a car while it is driving 65 on the freeway.
I know it allows them to put a smaller engine in an suv for instance, but is it only helping during acceleration?
During freeway driving is it shutdown or active? Is it making the car use less gas and / or adding power?
A turbocharger is only in use when it’s needed, such as when you’re accelerating. That’s because it takes less power to maintain a steady speed than to accelerate. A turbocharger forces more air into the cylinders and that extra air requires extra fuel, so your mpg drops. When the turbocharger isn’t needed the exhaust that would otherwise drive the it is diverted by a valve called a “waste gate.” So it’s not adding power but it’s also not wasting gas. https://driving.ca/auto-news/news/how-it-works-turbocharging
Dave’s answer is better than mine, but I will say this. Engines with turbos use an entirely different design than do non-turbo cars. There are lots of differences. Stepping back from the original question, I will say that now that turbos have been completely sorted out, they are almost always my pick for the best engines in small crossovers. The Honda 1.5T and the Mazda 2.4T are both fantastic.
Turbocharged engines can be great but they’re not miraculous. Some years ago one of the automotive magazines–Car & Driver IIRC–evaluated standard pickups. They found that the F150 “Ecoboost” gave disappointing real world mpg because drivers who were used to conventional engines tended to mash the accelerator in order to get the same oomph. There’s no free lunch.
I was amazed at the mpgs my rental Jetta got on the freeway with its 1.4 L turbo gas engine - 45 mpg over hundreds of miles. And it was roomy, comfortable, smooth and peppy. Great engine!
Did you even read the article you cited.
The turbo is spinning (in use) anytime the engine is running.
The waste gate is between the turbo And the intake manifold to prevent too much boost. It does not divert the exhaust, it lets out excess boost.
If you don’t know there is nothing wrong with saying so.
If the turbo isn’t adding boost, then as far as I’m concerned it’s not “in use.” We can argue semantics another time. As for how the “waste gate” works, here’s what the article says:
“a valve called a waste gate opens up, diverting some of the exhaust gases away from the turbine.”
Dave , you don’t need to answer if you are not sure of the answer . We can all make mistakes but trying to actually give a correct answer is best . Besides the position of Forum guesser is filled .
I think there is a conflation of two different turbo system valves here.
The wastegate, mounted before the turbine inlet, does as Dave says and diverts exhaust gases from the turbine to regulate/limit boost. These wastegates can be external or internal (built into the turbo).
A blow-off valve (aka dump valve or compressor bypass valve), mounted between the compressor and throttle body, releases boost pressure when the throttle plate is closed, to prevent a sudden large pressure increase.
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Nobody is guessing except possibly PvtPublic. On a vehicle with hydraulic power steering the pump runs even when the car is going straight so it’s not “in use.” Same with a turbocharger. Again, semantics. PvtPublic accused me of not reading the source material, which I obviously had and he hadn’t. Like him, I was under the initial impression that the “waste gate” diverted air flow from the turbocharger but instead of going with that I did some basic research, which is the opposite of guessing and found out I was wrong, so I bowed to the superior knowledge of the article’s author and posted what I thought was a correct answer, which is what you wanted me to do. I’m out of this thread for now before a mod shuts it down but please stop making false accusations.
I’m not sure what you mean by this. It’s common to put a turbo on a naturally aspirated engine to make it more powerful. An entirely different engine design isn’t necessary.
I stand corrected, my apologies.
Just my 2 cents, but that little wheel won’t create much boost unless it’s really spinning. That’s one reason why little or no boost during easy driving.
When I worked for SAAB part of the PDI and every 30k miles a boost pressure test was required. The red/green gauge on the dash was not sufficient so a vacuum gauge had to mounted on the dash and plumbed in. The process was lengthy so I won’t go into it but boost only occurred when the foot was moderately planted and it came on gradually.
SAAB at one time used an adjustable waste gate which caused problems due to owners messing with it and blowing head gaskets or pulling head bolts out of the engine block. They got around this by using an electric overboost switch which detected too much boost and cut off the fuel pump temporarily.
The waste gate is set for a certain PSI and only opens to prevent overboost.
Many turbo and supercharger systems also use a bypass valve which allows naturally aspirated operation until the foot is planted. Ford, GM, etc, use or used a vacuum pod which holds a flap closed until the foot is planted. Manifold vacuum goes away, upper intake vacuum takes over and pulls the bypass flap closed, and boost is created. Back off the throttle; spring closes flap, back to natural breathing.
This is kind of what the bypass valve (GM) looks like and the pic below it can be seen on a Ford.
No worries. Misunderstandings happen.