My FE/Performance Project

[theholycow]

Originally Posted by *************

If the exhaust wasn't "wasted", the exhaust would be at ambient temperature which it obviously is not.

Ah, but the turbo doesn't work on exhaust heat, it works on exhaust velocity. There have been discussions of scavenging exhaust heat too; to do so, you would change the exhaust gas's density, producing more pumping loss (though I don't recall if there was any data showing whether the recovered heat outweighs the increased pumping loss).

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.

Forcing more air into the engine requires you to put in more fuel. More air, more fuel, more power. Now you have to back off the throttle, introducing extra pumping loss at the intake (in addition to the turbo's pumping loss at the exhaust).

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

I wasn't talking about superchargers at all. I know someone else was, but I was just addressing turbochargers.

Originally Posted by pgfpro

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.

It is not my forum. My responsibilities beyond those of a regular user are mainly to keep out troublemakers and spammers; I do NOT direct discussions unless they are grossly misplaced.

It's not that I didn't want to discuss it, just that I didn't want to pollute your thread with a tangent off-topic discussion. I was trying not to step on your toes.

Where does the exhaust gas's movement come from? The pistons pushing it out. A turbocharger is driven by the pistons, using the exhaust as a linkage. It is not using free energy to do its job of shoving more air (and the resulting more fuel) into the engine.

Originally Posted by DRW

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?

This. Many factory turbocharged cars are more efficient because they have a more efficient, less powerful engine plus a turbocharger to provide the missing power only when needed.