A turbo does not boost fuel economy, MPG, it reduces it. However, when compared to a non-turbo engine of equivalent (boosted) HP, it does save gas.
In other words, a 200 HP engine with turbo (final HP of 250) will give you lower MPG than the same engine without turbo, but that same boosted 200HP engine will have lower MPG than an equivalent non-boosted 250 HP engine.
"Sure, a brand new turbo Honda will run fine. Itās new. Letās see how it runs in 10 yrs. ask ford how their eco boost trucks will run at 10 yrs. "
@Cavell
I agree. An entrepreneur could create a lucrative business, manufacturing and selling kits that would make a slot in a turboās grille, just big enough for the vehicleās tongue to hang out.
Driving by, you could spot a 10+ year-old turbo car or truck. Its tongue would be almost touching the pavement and thereād be a little puddle from the drooling.
Honda and many others have lots of geed experience building screaming little engines for race cars, ones that turn up unbelievable RPM and put out incredible horsepower! Theyāre quite reliable, no doubt. Iāve been to tracks where they fly by at 200mph. However, thereās a difference between designing an engine to run 3 hours and one that runs for 3 decades (as the NA will).
CSA
A 250hp turbo 2.5 motor will produce better overall fuel economy vs a 4.0L 250hp non-turbo motor. Smaller motor wins sitting at idle. Uses less gas. Part throttle cruise on highway. 2.5motor wins. I bet they use the same gas during a full power pull too.
I owned a supercharged Toyota Previa with a 2.4L four cylinder. It was an odd duck with a flat four mounted mid-ship under the seats. The supercharger oil got changed every 60,000 miles. I sold it with 220,000 miles and never had to repair the engine or transmission. The next owner had it for 6 more years and drove it over 300,000 miles with no engine or transmission issues. Super and turbo chargers can run reliably for very long times with proper lubrication.
The problem with horsepower numbers (a sales tool of sortsā¦) is that those numbers are for high RPMs and/or full boost situations.
How many people have normal driving habits of 6000 RPMs or their foot planted through the floor with the car under a load to acquire full boost.
Granted, Iām sure thereās a few out there who drive like thatā¦ 
A turbo does not boost fuel economy, MPG, it reduces it. However, when compared to a non-turbo engine of equivalent (boosted) HP, it does save gas.
Thatās somewhat true of spark ignition engines, however with diesels the opposite is true. With no throttle to restrict airflow into the cylinders, the boost turns the intake stroke into a second power stroke. The turbocharged diesel is essentially a combined cycle engine with a turbine scavenging leftover energy from the dieselās exhaust and returning it to the engine via manifold pressure. Itās why turbocharging has become almost universal in diesel engines, even farm tractors and stationary power plants.
agreed, which is why I donāt see buying a feature Iāll never (or rarely) use. But itās getting more and more difficult to find an auto with no turbo, no low profile tires, and good visibility.
From reading reviews on various Turboās, it also seems to depend on where in the RPM range the power delivery is. So overall, driving a V6 with the same HP as a Turbo I4 might give you more available power in all RPM ranges.
My question is how difficult or pricey a turbo repair would be. Is there a re-manufactured one cost effective to bolt on? I know on the transverse mount V6 engines, the rear plugs are always a pain, so there you have one negative for those.
As to the OP, I am with the majority in here; reluctant to be a beta tester, but now have ended up owning a direct injection engine. It sounds a bit like a diesel, but so far at 36K miles not burning oil, so we will see. Owning a turbo in the next 10 years might be inevitable.
db: Iām not clear exactly what those numbers mean. I realize they are percentage numbers but not how that translates to actual distance ground to metal wheel. And that latter number is the one I consider important. I see cars with that number at about one inch and regard that as dangerous.
My present car has ļæ¼P225/60R17 98H tires and I consider them marginally low profile. Ie, I can live with them, but not any lower.
225/60R17 . . .
225mm tread width
The sidewall is 60% as high as the width of the tread
Motors that were designed for a turbo last fine. Some manufacturers added turbo to existing motors with poor results. Pistons, crankshafts, and bearings need the design strength to handle the extra stress of a turboās boost. Turboās are nothing new to Honda engineering. Iād trust a new motor from Honda.
What do you consider low profile?
I donāt know that thereās a definitive āindustry standardā out there, is there?
As far as Iām concerned, 50 series and above are normal, āstandardā profile tires. 45 and lower are what I consider lo-pro tires.
A 250hp turbo 2.5 motor will produce better overall fuel economy vs a 4.0L 250hp non-turbo motor.Really? I once owned a Subaru WRX, and that thing was HORRIBLY inefficient for what it was. 227HP out of 2.0L...but FE numbers in the mid-teens. I think you could easily use a good 3.5L, NA V6, and get similar HP with better FE.
I agree with you
Iām just kind of surprised that @BillRussell considers 60 series to be marginally low profile
@db4690 Back when the family sedan came with 7.50X14 bias plys or even 195/75R14 tires I suppose that a 70 series tire might have been thought of as low profile, but things have changed over the last few decades. I doubt any new passenger cars have anything taller than a 65 these days.
I think we all may have fond memories of the way that 1973 Ford LTD drove, but compare one to a new car today and that feeling will soon disappear.
People donāt buy a WRX for excellent fuel economyāor for fuel economy at all. They buy them because they go fast.
@meanjoe75fan
Do you think your poor fuel economy was because of how you drove the car
Iāll be more wary about the CVT than the turbo engine. Millions of trucks take food from the farm to your local supermarket using turbo charged diesel engine.
Turbocharged engines do have lower thermal efficiency, especially those earlier ones such as the WRX. Generally, turbocharged gas engines have to use lower compression ratio to prevent detonation. Newer turbo engines with direct gas injection allows the engineers to increase compression ratio a bit because direct gas injection lowers the cylinder pressure by lower temperature.
From the systemās point of view, a turbo engine is lighter, which means the car isnāt lugging around as much weight. The smaller engine also has to open its throttle wider compared to a larger engine while cruising; this reduces pumping loss provided that the engine isnāt constantly boosted
Iām on my 4th car with a turbo and I have never had a problem and not one of them even used any oil between changes. Turbos been around a long time and yes I think they are reliable.