Thursday - December 19, 2019

random turbo thoughts

It seems like more and more vehicles are moving to much smaller engines equipped with turbochargers. As long as they last 200,000 or more miles, I’m pretty much for it.

But I think there is a great application of turbocharging/supercharging that is going unused. Ok, perhaps it is slightly addressed by this HCCI engine that Mazda keeps teasing us with; that thing has a small supercharger on it that provides just a little boost, enough to give their 2.0 liter HCCI engine nearly the same power as their standard, normally aspirated 2.5 liter engine.

You see, any kind of piston driven internal combustion engine has to draw air into itself. Suck it in, add some fuel vapors, squeeze it up, light it off, take the power, then pump out the exhaust. If you provide just enough boost pressure, then the engine doesn’t have to waste energy ( pneumatic drag ) sucking the air in. Just open the valves, and in comes the appropriate standard amount. And the less energy you waste, the more efficient the engine becomes. So turbo engines should have an Economy mode.

Also, since just about every engine has a rev limiter on it these days, and all of them have fairly sensitive knock sensors, and most of them have touch screens, making a car with a 4 or even 5 mode turbo shouldn’t be that hard.

C   Concierge Mode: no boost at all, engine limited to 3000rpm. LeadFoot the parking lot boy can’t thrash your vehicle.


E   Economy Mode: just enough boost to let the engine breath freely, engine limited to 4500rpm. Adequate performance and maximum mpg.


N   Normal Mode: a few pounds of extra boot and the normal engine redline. Makes it a bit zippy but still gets decent mileage.


S   Sport Mode: even more boost, perhaps the standard redline or a bit higher. Probably hooked into the dynamic suspension control for a firmer ride for better handling.


R   Robust Mode (because the lawyers won’t let us say “Race"): maximum boost, maximum redline, firmest suspension settings.

All of these would be dominated by the knock sensor, which would back off the spark advance or even downgrade the mode if excessive knock happens. Obviously, you’d want to use high octane gas for the top 2 modes.

And I’d design it so that the touchscreen / joystick / voice recognition (with password?) would allow the modes to be changed while the car is moving, walking up or down the modes as necessary until the speed and rpm was within the proper limits. That way you couldn’t go from Robust Mode to Concierge Mode at 130mph and 8000rpm. You’d have to drop down through Sport and then Normal first, perhaps Economy too.

A little 1.6 or 2.0 liter engine can get you 40mpg or better on the highway, yet with a potent turbo those engines can churn out more than 300hp. But you can’t have it both ways. Why not?

Posted by Drew458     on 12/19/2019 at 02:36 PM   
Filed Under: • planes, trains, tanks, ships, machines, automobiles •  
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