2014 C7 Chevrolet Corvette

[zoomzoomers]

Completely agree!

Originally Posted by ZDan

There are about as many definitions for "sports car" as there are for "God", so obviously people will disagree.

To me, outright speed has little to do with it. IMO a Triumph Spitfire (slow in every direction) is 1,000,000 times more of a "sports car" than a GT-R.

"Sports Car" to me implies a small, minimalist, lightweight car with pure driving enjoyment being a larger priority than huge power and maximum speed around a track. The Corvette is, to me, more of a supercar.

There are those who consider a 4100 lb. Dodge Challenger to be a "sports car". But whatevs...

[Sbeezy]

Originally Posted by ZDan

There are about as many definitions for "sports car" as there are for "God", so obviously people will disagree.

To me, outright speed has little to do with it. IMO a Triumph Spitfire (slow in every direction) is 1,000,000 times more of a "sports car" than a GT-R.

"Sports Car" to me implies a small, minimalist, lightweight car with pure driving enjoyment being a larger priority than huge power and maximum speed around a track. The Corvette is, to me, more of a supercar.

There are those who consider a 4100 lb. Dodge Challenger to be a "sports car". But whatevs...

[chulooz]

By definition exhaust pressure isnt a parasitic loss, thats energy spent not consumed.

Tuning on the fly is much more than just changing boost. You can go from 300whp to 455whp with the push of a button.

[serialk11r]

Originally Posted by chulooz

Tuning on the fly is much more than just changing boost. You can go from 300whp to 455whp with the push of a button.

If you can go from 300hp to 455hp with the push of a button, that means your engine could have been making 455 hp but you limited it to 300hp. Same thing as boost limiting. It has a different "feel" when you drive but you can accomplish that with an accelerator pedal remap too.

[ZDan]

Originally Posted by chulooz

By definition exhaust pressure isnt a parasitic loss, thats energy spent not consumed.

It is a loss. It takes POWER to compress the intake charge. It's not free. The power that drives the turbo's impeller comes from the exhaust. That restricts the exhaust and consumes power. It is a net output power gain, but its also a net gain if the power comes from the crank.

There is increased exhaust restriction from the power required to spin the turbine to drive the impeller. It ain't free.

[chulooz]

Originally Posted by serialk11r

If you can go from 300hp to 455hp with the push of a button, that means your engine could have been making 455 hp but you limited it to 300hp. Same thing as boost limiting. It has a different "feel" when you drive but you can accomplish that with an accelerator pedal remap too.

Or you can have two maps for 400hp, both with different levels intensity. Either way the point is that the options are far greater and easier to implement than SC.

Originally Posted by ZDan

It is a loss. It takes POWER to compress the intake charge. It's not free. The power that drives the turbo's impeller comes from the exhaust. That restricts the exhaust and consumes power. It is a net output power gain, but its also a net gain if the power comes from the crank.

There is increased exhaust restriction from the power required to spin the turbine to drive the impeller. It ain't free.

Parasitic doesnt mean loss, it means consumption of power. Exhaust gases have already been made so using them consumes nothing, restrictive losses are not the same as parasitic losses. And plenty of setups have minimal restrictions.

[ZDan]

Originally Posted by chulooz

Parasitic doesnt mean loss, it means consumption of power.

The turbo consumes power. Compressing the intake charge more than offsets this, of course, just as in the crank-driven case.

Exhaust gases have already been made so using them consumes nothing,

No, that doesn't follow. Harnessing the exhaust gases absolutely does consume power. If you used the turbo to pressurize air in a chamber and *didn't* feed it into the intake, you would lose power in a big way.

restrictive losses are not the same as parasitic losses. And plenty of setups have minimal restrictions.

I never referred to the loss as "parasitic". The power required to compress the intake charge is not parasitic in either the crank-driven or exhaust-driven cases. The tiny portion of exhaust backpressure due to friction in the turbo bearings is parasitic, as are the larger frictional losses in the supercharged case. Both cases still consume power to make boost, and *that* power loss is non-parasitic.
Of course a good turbo setup will minimize exhaust restrictions to maximize the amount of power the turbine can consume to drive the impeller. Other exhaust restrictions will rob exhaust energy from the turbo and reduce the amount of work it can do, reducing boost.

[serialk11r]

Semantics, whatever.

In theory you can have a turbo setup that is extremely laggy but has almost no exhaust restriction by having the turbine be gigantic, but that's not how it pans out in the real world where people don't want to feel like their foot is spooling up a plane engine, waiting multiple seconds for boost. What you get is quite a lot of power lost to backpressure.

[ZDan]

At least partly semantics. But no matter how big the turbine is, it takes a certain amount of power to drive the compressor to provide a given amount of boost at a given flow rate. The power is coming from the exhaust gas energy. *Some* of that could be considered "free" (the heated combusted gases will expand on their own, which would drive the turbine a small amount even if the piston didn't rise), but a lot of it is taking kinetic energy from the exhaust stream, basically plugging it up. I don't know what the typical pressure drop is across the turbine in a turbocharged engine, but that pressure drop is directly related to power lost/spent/consumed (not parasitic, mind you...), as the high pressure on the turbine inlet size is acting against the piston trying to move up in the exhaust stroke.
I suppose it's possible in theory to have a turbo big enough that all the mechanical energy is derived from the temperature drop across the turbine, but I would imagine such a turbo would be enormous, too big to fit in the engine bay, and with unbelievable lag as you mentioned. In the real world, the majority of the power has to be coming from the pressure drop. But I will have to study up on this!

[chulooz]

Yeah, what you said last...

[markr01000]

Yep...to each his own. To me, a true "Sports Car" in the traditional sense, is a two seater (or maybe 2+2) lightweight, toss able, short wheelbase, great handling car. These attributes make me want throw my FR-S around, with a big grin on my face. I loved my C6 experience, but it was completely different. The car didn't want to be thrown around, unlike its race derivative as pointed out here by some. It wanted stay planted an generate big acceleration and top speed numbers. It was a blast. But the FR-S is actually more fun to take through a turn. You feel every bit of the dynamics going on, which is amazing since its got electric power steering. The driver feedback is 911 like. My Corvette, although a great machine, felt numb by comparison. The C6 was always ready to blow you away (I actually beat a sport bike stoplight to stoplight!) but you aren't driving, the car is. There is (IMHO) a thick layer of technology between you and the road, and you feel it. It feels like you're dialing in requests to the engine room. The FR-S is far more transparent by comparison. **I** am driving once again.

Just my 2¢ worth

[LSxJunkie]

Yep...to each his own. To me, a true "Sports Car" in the traditional sense, is a two seater (or maybe 2+2) lightweight, toss able, short wheelbase, great handling car. These attributes make me want throw my FR-S around, with a big grin on my face. I loved my C6 experience, but it was completely different. The car didn't want to be thrown around, unlike its race derivative as pointed out here by some. It wanted stay planted an generate big acceleration and top speed numbers. It was a blast. But the FR-S is actually more fun to take through a turn. You feel every bit of the dynamics going on, which is amazing since its got electric power steering. The driver feedback is 911 like. My Corvette, although a great machine, felt numb by comparison. The C6 was always ready to blow you away (I actually beat a sport bike stoplight to stoplight!) but you aren't driving, the car is. There is (IMHO) a thick layer of technology between you and the road, and you feel it. It feels like you're dialing in requests to the engine room. The FR-S is far more transparent by comparison. **I** am driving once again.

Just my 2¢ worth

Was your car a Z51 or MSRC car?

[OrbitalEllipses]

FR-S/86/GT/BRZ/twin/thricies/wtf with a new LT1...I want to overpower the chassis on my short wheelbase and spin ALL day.

[serialk11r]

The reason there's "free" energy in the exhaust is because when the exhaust valve opens the exhaust gases are at 3-5 times the intake pressure, giving you a surge of exhaust gas. In theory you can capture 50% of that energy but there's always restriction and there's no perfect turbine that doesn't disrupt the flow.

A quick dirty estimate is exhaust backpressure vs. boost pressure. If exhaust backpressure is like 30-40% higher than boost pressure, then you might as well run a supercharger since the backpressure is sapping the same amount of energy as a belt driven supercharger. Having exhaust gases dammed up before the turbine can deliver over twice as much power to the shaft as having a completely unrestricted turbine, which is why turbos spool in a reasonable amount of time.