True; although isn't the IC more known as (colloquially) a heat pump?
Don't mean to parse words, I'm serious.
No matter, it's aside from the point.

And 3-stage more efficient than a 2 ad infinitum.
Nonetheless I've always beleived there's a price one pays for air-pump equipted motors, also.
Excessive heat & the subsequent wear, notwithstanding.

There is??
Hmmmmm perhaps employing a "supercharger", SD.
But is [that] true concerning turbos whatwith the dreaded turbo-lag?
The damnedable lag before a turboed IC spools-up are seconds wasted as the rear of the opposition pulls away.
That's the #1 reason why I've always held Chevrolet's LS series motors in such high regard, the engines performed fabulously without jazzy crap or evoking [/i]Pascal's Law[/i].

Well you're undoubtably correct, taking each criteria point-by-point.
I plead "No Contest".

Still isn't the whole design approach to most things a matter of "six of one half dozen of the other"?
Especially true when it comes to making HP with an IC?
Lots of variables insofar as design goes and most of those variables interestingly enough can be applied in an inverse proportion, all to arrive at the same place.
If that's true then personally I'll opt for simplicity (of design) every time over gagetry. (~have to beleive those who race, professionally, would have to agree, also.)

For example: Chevrolet (followed?) coventional engineering wisdom of the late 80s when the multi-valve/cam "experts" Mercury Marine were asked to build the 48 valve, 4 cam LT5 mill for the "King of the Hill" ZR-1.
If memory serves me correctly the "King" was dethroned when the design was (quickly) scrapped.
The power anticipated from the LT5 never quite materialized, failing to meet expectations, forget the incredible complexity of that motor (which left a LOT of Chevrolet service departments in a cold sweat).
Even though powerful the LT5 just didn't produce the immense power the numbers said it c/would, so it was bye-bye to that idea.

There was a better approach to making power than incorporating multi-valve/cam motors, that approach was the LS series..or so I'd thought.

Curiously enough shortly after the LT5 was discontinued sure enough Ford went right ahead with their multi-valve/cam designed high performce SVT engine for the Cobra, totally ignoring the lesson(s) GM learned with the LT5.
Surely Ford had to be watching GM's expereince?

Though Ford's product uses a multi-valve 2-cam design and on top of that uses an Eaton supercharger?
The LS series engines consistently whipped Ford's butt where it counted, on the track.

Now the way I'm seeing it GM's following of Ford visa vi supercharging their high performance engine(s) is nuts.
Cheap solution, yea.
But nuts, nonetheless.

Amen to that, SD!!
But given our expereince in this world wouldn't the operative word have to be, "when".
"When": the trickiest of all variables, trumping all.

Muchos gracias senior'.
Your expertise' & insights are both educational and entertaining.
Rare as hen's teeth, these days.

This Bud's for you!

 

Intercooling is a powerful tool for increasing dual stage compressor efficiency. Intercooling allows the second stage to see a much denser charge of air, which yields greater mass flow into the second stage compression chamber without expending extra mechanical work.

In a spark ignition engine, intercooling is also important to prevent detonation due to self-ignition of the fuel with the hot incoming air. (Diesels, and direct injection gas engines, don't have this problem, because fuel isn't introduced until the momment ignition is desired, but it is an important issue in conventional Otto cycle engines.)

But even without intercooling, you still get the advantage of greater air flow into the second stage. Rather than being pushed by merely atmospheric pressure, it is pushed by the interstage pressure. That means the high pressure stage can be smaller and still support design flow. Or, it can be somewhat larger than the minimum size and support the design flow at a lower RPM. Since parasitic losses are proportional to RPM squared, being able to support design flow at a lower RPM means better efficiency. (Most dual stage air compressors run about 1/3rd slower than single stage compressors with equivalent flow. That translates to a 2.25 times lowering of pumping losses.)

For an IC engine, horsepower is proportional to mass flow. The more air, the more fuel you can burn, and the more power you can make. So obviously, supercharging allows you to get more power from a given displacement engine. There are clear advantages in a vehicle to having a smaller and lighter engine for a given power output. Overall engine efficiency issues aside, better power to weight ratio alone translates to better vehicle dynamic performance.

As you mentioned, turbocharging has the additional benefit of reclaiming otherwise wasted exhaust heat. Roughly 1/3rd of the BTUs produced by burning fuel are lost as waste heat in the exhaust (roughly another third is lost to the engine coolant, leaving only one third to do useful work in the engine). Reclaiming any part of that lost heat to do useful work is a clear efficiency win.

As example, brake thermal efficiency of a good NA spark ignition engine is on the order of 13%. BTE of a compound cycle engine can reach 45% in large stationary installations (about 22% in vehicle applications). So the potential is there to nearly double the power output for the same fuel consumed, or double the MPG for the same vehicle performance, depending on what trade-offs the system designers chose. (In practice, we rarely see that much improvement. Designers have other criteria that they have to satisfy, so maximum power and/or efficiency are often lower than they could be in theory. Still, in any reasonably good design, they will be better for FI engines than the NA case.)

 

Proper turbo sizing and wastegate design can reduce turbo lag to negligible values. While this has plagued some aftermarket add-on kits, and some poorly executed factory designs, GM had this licked back in 1965 on the F85 Jetfire Olds. Drive a well done aftermarket twin turbo package like the one from APS and try to find the "turbo lag". You won't. It pulls like a freight train nearly from idle.

Until rules changes designed to make them non-competitive were implemented, FI engines dominated many forms of racing. The venerable Offenhauser of Indy fame is a classic example, as were the FI engines used in Formula One. Put another way, anywhere the rules allow their use, super/turbo charged engines dominate racing.

The biggest problem with the LT5 was its complex valvetrain, and the size, weight, and maintenance issues associated with that. Super/turbocharging is much simpler. At base, only one additional moving part is added to the engine, the rotor/turbine of the unit. These are incredibly reliable, as testified by the millions of them in daily use on diesel engines.

 

Thanks. I've always known that 2 stage compression is better when intercooled because it reduces the area under the curve (takes less work) on a TS (temperature versus entropy) diagram because the constant pressure lines diverge. You are also right about a non-intercooled 2 stage being more efficient, but only at high pressure ratios. At lower pressure ratios (like a supercharged IC engine), using a two stage compressor versus a single stage really won't buy you any efficiency gain if it is not intercooled. That's why I asked the question, I could see that a turbo IC engine would be more efficient, but I had never heard that a supercharged IC engine was more efficient. I always believed (and still do) the only reason for supercharging an IC engine was for performance only.

Thanks,
Glenn

 

Yes the end result was performance for the aircraft industry. But remember the planes were flying at altitude where the air density is low and as is the temperature. In the early days of military air warface they toyed with using liquid O2 with their normal carbs as the planes would lean out horrible once they were at altitude and if lucky loose power only, but more often than not they would burn pistons. The planes were already carrying a limited supply of O2 for the crew to use so they thought they could just increase the volume they carried and use it to supliment the lack of air density. Two problems they found, one to carry enough 02 to make it worth while, they would decrease their payload and if they did not use all the 02, and the plane crashed or shot....use your imagination.

They had an engineer on board to monitor the engines EGT and either increase or decrease the fuel/air ratio as their carbs at the time could not do it well. The idea of S/C a plane engine is to use the S/C to increase the air density and since it was so cold anyway, they did not have to intercool it.

If I remember correctly wasn't the blower, like the 6/71 we all know, first used on big trucks and then adapted to cars. Look at top fuel cars today, they don't intercool because they fuel takes a lot of spark to ignite as well as they really don't care about detenation, as for efficency...............but the really good crew chiefs know how the mix the nitro depending on the air temp amoung other things.

As for Ford using the Eaton supercharger, I know the Lighting truck was water to air intercooled and the Magnacharger uses the same S/C and is also intercooled.

 

They have????
I'll be, obviously there've been quantum leaps in turbo technology unbeknownst to me.
Had no idea.
In fact your answer clearly demonstrates why Porsche (& a few other exotics) continue using turbochargers, something I've often wondered about.

Unbeleivable.
1965 you say.
Welcome to the future for me then, huh.
Now you've me wondering why turbos haven't appeared on more of GM's car lines, or, at least as an option.

I'll bet it would.
So the supercharger's almost obsoleted given the instant response of a turbo, then.
Apply a little Boye's P1T1=P2T2 & voila', pretty inexpensive and reliable performance v.s. internal mods.
I feel like a dork.

I drew a conclusion when I didn't see 'em being used, I guess.
Mybad.

Well one look at an exploded diagram of the LT5 by the casual observer clearly reveals the LT5 to be an extremely complex piece of machinery, so naturally I'm with you on that.
So could one conclude GM's LT5 [read: multi-valve/cam design] was the result of rules requirement(s) of the various racing venues GM engines competed?
If so, a facinating tale explaining an engineering/design direction GM felt compelled to take as opposed to a more direct route.

OK, I'm woefully not up to speed.
All I remember is Chrysler's turbocharged Mitsu 4 since I've honestly never had a close look at an exotic, per se.
Just knew because of incredibly high operating temps generated by turbos after the engine was turned off, allegedly an accumulation of mineral deposits from the gasoline would appear over time on the turbin blades. That in-turn could easily throw the whole turbocharger balance off rendering it nonfunctional. I'd always thought turbo fans -- due to the intense heat & incredible operating RPMs -- are in fact very finely balanced instruments. Screw-up the balance, screw-up the turbocharger so a "maintenance issue" went along with all turbos.
(Granted an after market gizmo became available for these engines that'd keep the turbin rotating for a few minutes following shut-down allowing the turbo fans to slowly cool off thereby eliminating the issue. However assuming it even if worked as advertised it wasn't available to Chrysler turbin owners for years after the engines had been on the market.)

Anyway most of what I know regarding turbos comes from the 80s, FWIW.

Here SD, have a case of Buds.

 

An issue with turbos was oil coking if not allowed to cool down before shutdown. But a few things have changed since that was a concern. Modern synthetic oils don't coke at the temperatures that conventional oils did. Modern turbos use water cooling and/or ball bearings which basically eliminate the issue of the oil trapped in bearing journals at shutdown getting so hot that coking is a concern.

 

Wow so all these years it wasn't how I envisioned it, it was "coking".
Overheated oil essentially being carbonized, that'd sure screw-up anything.

I was an elecrical guy (can you tell?), so something mechanical could've easily been lost in the translation when someone was trying to explain the issue.

That's the best thing about growing old for me, SD.
I listen more often, and, more carefully these days.

They say youth's wasted on the young.
Hell's bells I could've been the poster boy for that old tome.