Especially at low rpm when it comes to pumping losses.

I had the perfect turbo setup before and I wanted more HP for when I race the car and just went to big on my last turbo choice.:mad:
The best I could do was only 68mpg with the last turbo setup.:(

My wife has a 88 Prelude SI. 4-Wheel steering makes it really cool but that isn't the reason she won't part with her beloved 'Baby Luv' for any reason. She just likes the car.
Anyway, eventually, I'll have to replace the oil-leaking head gasket because it smokes like it's on fire at stop lights and is embarrassing. What suggestions do you have to increase the performance a bit and push the mileage beyond 27?

If you rebuild the engine in that car to like new, and judging by how much she likes the car, I'd say it'd be worth it. To save some money, you could do the majority of the labor and then have a shop do the work to rebuild the head and bottom end, then you reassemble everything.

The energy of the exhaust's movement is not wasted. This has been thoroughly discussed so I don't feel like it's appropriate to fill up this thread with the same discussion, but you can search for turbo, waste, exhaust, and egv.

Of course it's wasted, that's how turbos work on the principle of scavenging the exhaust. If the exhaust wasn't "wasted", the exhaust would be at ambient temperature which it obviously is not. Just because we have headers and other exhaust tuning that takes advantage of exhaust pulses in NA engines which scavenge exhaust in order to improve power, it doesn't mean that a turbo doesn't take this a step further by using this energy to spin a turbine to force more air into the engine. There is a reason why turbo props are more efficient than supercharged ones...

https://en.wikipedia.org/wiki/Turboch..._supercharging

Turbo chargers are better than superchargers, especially for our application.

I'm sorry but I will have to disagree based on real life experimentation's and examples of over ten different engines that I have built and tuned on, from small four cylinders to large V-8 engines.

But this is your Forum and if you don't feel its necessary to have a discussion on why it works for me and several others(search yourself, outside this forum) then I'll just check out.

I'm not sure what he is really trying to say but in very simple terms, having a turbo charger on your car is like the difference between a single cycle power plant and a combined cycle power plant. Combined cycle natural gas power plants can have efficiencies of around 60% compared to the 35%-40% we currently see with single cycle natural gas power plants. Turbo chargers work on the exact same principle, the gasoline engine works on gasses at a higher potential and the turbo charger works on gasses at a lower potential, thereby more fully utilizing the energy of the gasoline. If you can understand these well established principles, not just based on theory but in actual practice, I don't see why he'd disagree with us.

One counterpoint is the issue of fitment. An inline 4 typically has plenty of room for a turbo system. A V8 usually doesn't since the exhaust headers on each bank of cylinders are far away from each other, so a supercharger usually makes a better choice.

The issue of low end power depends on the size of the turbo. A factory turbocharged vehicle typically has a small turbo that spools up at low rpm which makes peak torque at low rpm. The VW 1.8T and 2.0T engines come to mind, it makes peak torque at 1800 rpm. See https://buyersguide.caranddriver.com/...specs#features

That analogy might apply if turbo cars were driven nearly full throttle all the time.

If an engine has sufficient power without adding a turbo, would adding a turbo increase FE?

Increasing efficiency doesn't necessarily mean increasing fuel economy.. Hard to believe but it's true and the reason for this is because of how you use the increases in efficiency. A motorcycle can get better fuel economy than most cars but to call it efficient would be ridiculous. Also there are variable geometry turbo chargers so they provide boost as low as idle speeds, though they're not that common yet.